CA1185809A

CA1185809A - Apparatus for measuring the characteristics of an optical system

Info

Publication number: CA1185809A
Application number: CA000398453A
Authority: CA
Inventors: Hiroshi Tamaki
Original assignee: Tokyo Kogaku Kikai KK
Current assignee: Tokyo Kogaku Kikai KK
Priority date: 1981-06-03
Filing date: 1982-03-16
Publication date: 1985-04-23
Also published as: JPH0222328B2; JPS57199933A

Abstract

ABSTRACT OF THE DISCLOSURE

The disclosure describes an apparatus for measuring the optical characteristics of an optical system. It comprises a collimator for collimating a beam of light from a source of light, means for selecting part of the light beam from the collimator, means for holding an optical system to be tested between the colli-motor and the selecting means, means for detecting the selected light beam from the selecting means, and means for operating the optical characteristics of the optical system to be tested on the basis of the results detected in the detecting means. The select-ing means includes a beam selecting pattern comprising two groups of parallel linear lines, each of the groups consisting of at least two parallel linear lines, the parallel linear line groups being disposed such that they are oriented in different directions without any intersection.

Description

Jo TITLE OF TOE INVENTION
An Apparatus for Measuring the Characteristics of an Optical System BACKGROUND OF TEE INVENTION
The present invention relates to an apparatus for automatically measuring the characteristics of an optical system, such as the spherical refractive power, the cylindrical refractive power and the orientation of the cylinder assay and the prismatic refractive power and the orientation ox the prism base. The principle and the examples of the present invention will hereinafter ye described mainly with respect to a measurement for such characteristics of a spectacle lens.
However, this does not necessarily mean that the present invention it applicable only to a so-called lens meter which is Atwood to measure the above characteristics of a psychotically lens, but the present invention is broadly applicable for measurement of the characteristics of a lens optical Steele used in optical instruments in general.
In recent years, various proposals have been mace in thy id of automatic lens~et~rs for automatically measuring the. optical characteristics of a spectacle lens, such as the spherical retractive power, the cylindrical refractive vower and the. orientation of the cylinder axis and so on. For example, United States Patent 3,880,525 discloses an airports in which a parallel light beam is projected through a lens along the optical axis of the apparatus and the optical characteristics are determined by the deflection of the light which has passed through the lens. For the purpose, the apparatus includes a mask located behind the lens and having small apertures which are offset from the optical axis of the lens, and a detecting plane which is spaced apart by a predetermined distance along the optical axis from the mask so that the locations on the detecting plane of the projections of the apertures are detected.
The locations thus detected are compared with the locations ox the apertures on the mask to calculate the direction and the amount of deflection of the light beam which has passed through the lens. In order to obtain adequate information, the mask must be provided with at least three such apertures.
lo The apparatus as proposed by the US. Patent is considered as being disadvantageous in that it is required to determine exactly which one of the projections on the detecting plane corresponds to each specific one of the apertures in the mask. Further, the apertures in the mask must be in two-dimensional arrangement so that the light beams which have passed through . , .
thy apertures in the mask are not coplanar with each other.

Thus, a two-dimensional scanning is required at the detecting plane and the apparatus therefore becomes expensive as a whole.

Complicated and expensive operation circuits are required because it is necessary to solve five simultaneous equations to I
based on the infor~la-tions derived from the locations of at least three apertures. The apparatus has a further significant disadvantage in that the image detection and measurement are disenabled by foreign matters such as dust on the lens to be tested or the detecting plane since the images are detected in the form of a spot go image.
In order to solve the problems of processing bulky information inherent to such two-dimensional detection, the United States Patent 4,180,325 proposes to pass the light beam from the mask through a rotatable disc having a special pattern comprised of transparent and opaque portions. The disc pattern functions to intermittently interrupt the light beams so that the light beams arrive at the detecting plane respectively at different timings to thereby eliminate the necessity for disk criminatlng the light beams. Louvre, in this apparatus, tnepattern on the disc is very complicated and the dejection or the annular position of the disc is of a significant importance.
Therefore, serious problems are encountered in providing an accurate pattern on the disc and detecting the angular position of the disc.

SUP WRY OF THE INVENTION
It is tune first object of the present invention to provide an apparatus for measuring the optical characteristics of an optical system in itch detection and succeeding operations can relatively simply be performed.
The second object of the present invention is Jo provide an apparatus for measuring the optical characteristics of an optical system in which measurement can more precisely be made with operations therefrom being processed more rapidly.
The third object is to provide an apparatus for measuring the optical characteristics of an optical system which includes no movable mechanical part and can simply be asser.lbled and adjusted with less error inherent to aging.
The fourth object is to provide an apparatus Lo measuring the optical characteristics of an optical siesta in which the spherical refractive power, the cylindrical refractive power and the orientation of cylinder axis of an optical system to be tested can be measured and calculated simultaneously and independently of the prismatic refractive power and the oriental lion ox the prism hose of the same, thus, it higher measuring an processing speeds.
In accordance with the present invention, the apparatus is based on a principle of the optics on which planar light I beams passed through an optical system and selected by the use of a beam limiting Moscow having two linear pattern (said planar ll~ht beams being twisted if there is a cylindrical refractive vower) can be varied in spacing, orientation and inclination depending on the optical characteristics of tile optical system US hut never in flatness linearity in the projected image.

I

In one aspect of the present invention, an apparatus for measuring the optical characteristics of an optical system is provided which comprises collimator means for converting a bundle of rays from a source of light into a parallel pencil of rays, selection means for selecting part of the rays from said collimator means, means for holding an optical system to be tested between said collimator means and said selection means, detection means for detecting the selected rays from said selection means, and operation means for calculate 10 in information from said detection means to determine the optical characteristics of said optical system, said apparatus Boone characterized in that said selection means includes a beam selecting pattern consisting of two groups ox parallel linear lines arranged in different orientations without any 15 intersection, each of said Russ being comprised or at least two parallel linear lines.
In another aspect of the present invention, such an apparatus is further character~zq;l in that it comprises first optical path splitting means for dividing the fight beams from I said optical costume to be tested into at least two optical path, each owe which includes at least one of selection means Levine beam selecting pattern of at least two parallel linear lines, the linear lint patterns in said selection means being different in orientation from one to another.
In still another aspect of the present invention, ox such an apparatus is further characterized in that it comprises means for rotating a pencil of rays passed through said optical system to be tested relative to said selection means in a plane intersecting an optical axis for measurement, and that said selection means in-eludes a beam selecting pattern consisting of at least two parallel linear lines.
BRIEF DESCRIPTION OF THE DRAWINGS
The principle and embodiments of the present invent lion will now be described with reference to the accom-paying drawings, in which:
Figures 1 and 2 are perspective views of a project-in system for explaining the principle of the present invention, Figures pa, 3b and 3c are schematic views showing relationships between projected mask patterns and line sensors to prove that the optical characteristics can be measured in accordance with the present invention;
Figure 4 is a view showing a relationship between I perpendicular and oblique coordinate systems, Figure 5 is a view showing a relationship between a mask pattern and an imaginary parallelogram, Figure 6 is a schematic view of an optical system which is one embodiment of the present invention, Figures pa and 7b are front elevation Al views showing examples of the mask pattern, Figure 8 is a schematic view illustrating the project lion and detection of a mask pattern on line sensors;
Figures go - EM are timing charts showing relationships between outputs detected by line sensors and coordinate values;
S Figure 10 is an arrangement of line sensor elements for illustrating a process which determines coordinate values from the output detected by the line sensors;
Figures 11~ 12 and 13 are schematic views illustrating a measurement based on the principle of the present invention;
Figure 14 is a block diagram of an operational circuit;
Figure 15 is a schematic view of the second embodiment of the present invention;
Figure 16 is a view showing an arrangement of line sensors based on the third embodiment of the present invention;
Figure 17 is a fragmentary schematic view of an optical system which is the fourth embodiment of the present invention;
figure 18 is a fragn,ent..;y schematic view of an optical system which is the fifth embodiment of thy present inanition;
20 " Figure 19 is a view showincJ an optical arrangement which is the sixth embodiment of the present invention;
FicJ~Ire 20 is a view showing an optical arrangement which is the seventh embodiment of the present invention, Figure 21 is a view of an optical arrangement which is the eighth embodiment of the present invention;

Figure 22 is an optical arrangement of the ninth embodiment of the present invention, Figure 23 is a view showing a relationship between the mask pattern of the ninth embodiment and line sensors, and Figure 24 is a schematic view of a relationship between the mask pattern in the tenth embodiment of the present invention and line sensors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
When a parallel pencil of rays is incident on the spherical lens, cylindrical lens or astigmatic lens, the rays are refracted depending on the refractive kirk-teristics of the lens. It is well known that the sphere teal lens termed herein is one comprised of two spherical faces. The cylindrical lens intends to include at least one cylindrical face. The astigmatic lens means that it includes at least one towardly face. The towardly face used herein includes principal meridians having maximum and minimum radiuses of curvature which intersect with each other. The spherical face is considered to have two curved surfaces of the same radius of curvature which in-tersest with each other. On the other hand, the Solon-Dracula face is recognized to have two curved surfaces in-tersecting with each other, one of the curved surfaces I having infinite radius of curvature. Therefore, the spherical and cylindrical faces can be considered to be specific examples in the towardly face. The principle of the present invention will be described with respect -to an astigmatic lens including the towardly fuse, and will be explained to deal with the spherical and cyllntlrlcal lenses as specific cases.
Where a parallel pencil ox rays is incident on an astigmatic lens to be tested and if tile incident beam is a S circular bundle of rays, it is Nemo that the emitted beam is an elliptical bundle of rays. If the incident beam is a linear bundle of rays, the emitted beam becomes a planar beam (the latter being twisted if there is a cylindrical refractive power). The planar beam can be varied in orientation and inclination depending on the optical characteristics of the optical system, but has a basic property in that an image projected onto a plane perpendicular to said incident parallel rays is maintained linear at all times. The refractive character-is tics used herein includes refractive powers of two principal meridians having maximum and minimum radiuses of quarter which form the towardly face of a lens to be tested, angles Ox said two principal meridians relative to a predetermined reference line, and a prismatic amount representing an offset between the geometric and optical centers ox the lens to be on Tut or an offset of the lens to be tested in setting.
However, where. various limited pencils of rays are incident on and pass throucJh a mask disposed just forwardly ox a lens to be tested, other refractive characteristics, that is, two shape factors in both the refractive directions are added.

_ 9 _ 5 ~C,f~3 These additional retractive characteristics mean that the relationship between the incident and omitted pencil of rays can be varied by changing at least one of the radius of curvature in the first face, the central thickness, and the refractive index of a lens to be tested. The shape factors provide a useless unreliability to the refractive characteristics to be measured according to the present invention. The add-tonal shape factors can be avoided ho limiting the refracted pencil of rays after passed through the lens to be tested.
Namely, this can be accomplished by causing a general circular bundle of parallel rays to be incident on a lens to be tested and causing an elliptical bundle of rays refracted depending on the refractive characteristics ox the lens to pass and iota through a certain aperture pattern. my detecting the limited bundle ox rays, one can know the refractive characteristics independently ox the shape factors. In the present invention, therefore, mask means having an ap-rtured pattern must be located rearwardly of a lens to tested.
Referring to Figure 1, a beam of light 1 emitted from a source of light LO it converted into a parallel pencil ox rays by means of a collimator lens CAL. A lens to be tested T
ha a Jurist principal meridian R1 having minimum radius of curvature and a second principal meridian X2 haven McCoy radius of curvature. The lens T is disposed in a plane X
I per~enc1icl1lar to an optical measuring axis such that the optical axis O' of the lens is positioned at a locution offset by Eve along Y-axis an EN along X-axis from the optical measuring axis O in the same plane X - Y and that the meridian R2 is inclined relative to X-axis by an angle I. Further, a mask MA is disposed on the optical measuring axis O rearwardly of the lens T at a distance ad with the center thereof being coincide with the optical axis o.
This mask PA is formed with such an opening that a group of at least two parallel linear lines L with a pitch P
intersects X-axis with an angle m.
The pencil of rays, which has passed through the lens T and been refracted dependent on the refractive characteristics thereof, is limited by the mask to form a limited light beam which has passed only through the opening pattern. This limited iota beam is converged on positions corresponding respectively to the focal lines F1, F2 I the first and second principal meridians R1~ R2 in the lens to be tested T. There is a detect lion plane X - Y between the owl line F1 and the mask I.
the group ox parallel linear lines 1, which corresponds to the opening pattern of the mask MA is changed to a group of parallel linear lines If' projected with a pitch P', the ankle thereof relative to x-axis being changed to M. This angle M is represented by the felon equation:

{1 din ox eye do _ 1 )sin~coS~

I = -- . ....
md(1 _ z1)sin~cos~ do z H + swoons e) 1 Further, the pitch P' is represented by the following equations:

¦ {d~z1 + z1,) _ zdz _ 1}

p. = 1 1 2 2 up (22 z1)sin~-cosa _ d(c + sin-e) ........... I

In the above equations, Z1 is a distance prom the mask MA to the first focal line F1 and Z2 is a distance US therefrom to the second vocal line F2.
On analyzing the changes in the group of parallel linear lines only with respect to eye inclination and pitch prom the above equations (1), (2). it is understood that such change are related only by the refractive vowers of the Tao I meridians and the inclination angle thereof, but not by the prismatic amount relatlncJ to the offsets Eel and Eve This means that the prismatic amount can be calculated by operation means completely different prom that of the refractive power in the lens to be tested, resulting in simplified calculation and reduced time required Jo operate.

, I
In practically measuring the refractive characteristics of a lens to be tested T from changes in inclination an pitch of the parallel linear line group based on the equations (1) and (2), it in understood that the equations cannot be solved only by the changes in one of two parallel linear line group since there are three unknown quantities Z1' Z2 and in the equations (1) and (2). It is actually required also to know changes in inclination and pitch of the other parallel linear line group. A construction for attaining such requirement is shown in Figure JO Mast MA shown in Figure 2 has a opening pattern which includes a group of two parallel linear lines Lo sloped by an ankle my with a pitch Pi and another group of two parallel linear lines Lo inclined by an ankle my with a pitch Pi. After passed throusil the openings on the mask r the bundle of rays is imaged on a detection plane D to form a group Of two projected parallel linear lines Lo' slanted ho an ankle my' with a pitch Pi' and another group of two projected parallel linear lines Lo' sloped by an ankle my' with a pitch Pi'. From these two groups of projected parallel linear lines are obtained equations corresponding to the above equations (1) and (2) with , ..
the total number of equations beincJ equal to your. accordingly, said unknown quantities Al Z1 and Z2 can be calculated. If to solve the quadratic equations I and (2) for obtaining the value Z1~ Z2 and leads to a complicated and expensive process-ivy mechanism and an increased processing time, an intermediate operation process may be mace a will be described hereinafter.
inure pa shows pattern openings Lo and Lo which are wormed in the mask MA shim in Figure 2. It is the same as in Figure 2 that the opening group Lo is sloped by the angle my with the pitch Pi while the opening group Lo is inclined by the angle my with the pitch Pi. It is now supposed that there are a fine W spaced apart from and parallel to one linear opening L11 of the parallel linear line group Lo by a distance eye and another line OW spaced apart from and parallel to the same opening by a distance Pi It is further assumed that there are a line ~,~ spaced away prom and parallel to one linear opening L21 I the parallel linear line group Lo by a distance gP2 and another line Us spayed away from and puerilely to the same linear line L21 by a distance hP2. These parallel lines W , Queue, ~^~ and Us defines an imacJinary parallelogram I having four corners which are positioned in zoo coordinate system at imaginary coordinates (O 1' OWE)' VEX' YO-YO)' ~0~3~ YO-YO) and Quacks, Owe).
Figure 3b shows groups of parallel linear lines Lo', It which are protected onto the detection plane by the bundle ox rays ~assecl through the parallel linear line group Lo, Lo that are shown in Figure pa as opening pattern. It is the same us in Figure 2 that the group Lo' is inclined by the angle my' with the pitch Pi' while the group Lo' its sloped my the angle my' with the pitch Pi'. Assuming that these projected parallel I

linear line groups are detected by linear sensors So and so intersecting with each other at an ancJle and Helen it origin O" which is spaced apart from and parallel to an origin O' ox zoo' coordinate by a distance along taxis and by a distance n alonc3 yuccas, the linear sensor So would detect the projected parallel linear line groups at detection joints DP1, DP2, DP3 and DP4 while the linear sensor So would detect the projected parallel linear line groups at detection points DP5, DO DP7 and DP3.. Results obtained at the detection points DP2 and DP6 are used to calculate the equations with respect to one linear line L11' of the projected parallel linear line groups while results from the detection points DP3 and DP7 are utilized to operate the equations with reference to one linear fine L21' Similarly, results obtained respective-US lye at the detection points DP1~ DP5 and DP4, Pi are respectivel.yen~ployed to calculate the equations with respect to the respective linear lines I,12' and L22'. At the same time, the pitches Pi' and Pi' can be calculated with respect to the respective linear 11 12 ~21 L22 . Furthermore, there can be supposed a line Uvula spaced apart from and parallel to the linear line ~11' with a pitch eP1' which is obtained by multiplying the pitch Pi' by the same macJnification e as in Faker pa. There can similarly be assumed a line WOW' spaced away from and parallel to the linear line L11' with a pitch fP1'. There can I be also derive lines VOW' and US spaced away from and parallel to the linear lint L21' with the respectl~e pitches gP2' and hP2'. These parallel lines US QUEUE', 17'~ll and UIQi defines an imaginary parallelogram U'V'~'Q'. Assign that the imaginary parallelogram has four corners located respectively it imaginary coordinates U'(x1, Yo-yo V'(X2l I
Woks, ye) and Q'(x4~ It) in zoo coordinate system, this imaginary parallelogram U'V'W'QI ox Figure 3b corresponds to the imaginary parallelogram UVWQ shown in Figure pa. Such a change relates directly to that of the refractive characteristics of a lens to be tested.
Now, the following coefficients and equations are defined with respect to the imaginary corners of tune parallel-grams.
it (ox _ xi) (~j Ye Ail (ox xi) (ox Ok) BLj = (owe Yip j Bit (owe Yip (ok Ye) (pa) Siege = ox ox Seiko = ox ox it owe oYj ' it o i o k where or lo is taken with respect to a reference rum these imaginary corners there can be derived twelve com~inalions.
By the us of thy above equation (pa), the values land Z2 relating to the refractive powers of two principal meridians can be represented my the following quadratic equatioi7:

1C Dip CijDik)(z) + aged BlkCij it Jo ' ' ' i - BijCik)(z) (AikBi~ Air it .... (3b) where the Tories encoded by parentheses in the above equation are defined as hollows:

I - PijCIik qijPik CUP/ I Pi If p and q in such a definition are respectively derived either of A, I, C or D, the equation (3b) can be replated by:
C, do + {[B, I - [I (z) Car = ... (3c~
where d is a distance between the mask and the direction plane D as shown in Figure l, and z is a distance between the Newsweek I and the focal line of the lets lo> be tested.
Thus, by detecting the respective pitches Pi', Pi' and inclinations my', my' in two groups of projected parallel linear lines It and Lo' to term eye ir~acJinar~ parallelogram us shown irk Figure 3b and solving the quadratic equation (3) based on information to the four corners of said parallelo~rarl1, two roots x1 and Z2 can be obtained. eased on these roots Al and I the r~fractlve powers Do and Do of the first and second principal meridians Al and R2 in the lens T to be tested can be calculated respectively as follows:

TV
l / Z 2 Do do Do 3 do -I

Further, an angle of the cylinder axis I placed in a relation with the angle which is included between the first principal meridian I and the taxis + 90. This angle can be obtained from the felon equation:

-1 LID - I, C3:

2 tan { - - -} + 90 (5) AUDI BY

Although the imaginary parallelograms have been obtained by multiplvin~ the respective pitches Pi, Pi Pi and Pi' by the optional magnifications e, f, g and h in figures pa and 3b, the calculating process can be simplified actually by the us of lmayinarv parallelograms UOVoWo~ and UolVo~Jo~QI when the magnification e and g are set to be equal to one, respectively.
Although the coordinates of the respective corners on the imaginary parallelograms have been explained with rocket to the per~nclicular coordinate systems yo-yo and x-y, there can be taken an oblique coordinate system yo-yo' along the disposition of the linear sensors So and So. This oblique coordinate Costume zoo' is shifted prom the perpendicular coordinate system yo-yo such that x-axis end y-axis are inter-sooted respectively by taxis and foxes with the respective annul a and and that the origill 2 of Y' coordinate system.

is offset from the origin Al of zoo coronet stem by distanc08 and along the s- and yucca, respectively as shown in Figure 4.
Such coordinate shift from the zoo' system to the x-y system can be represented by the following equations:

x - x'sina + y'.sln~ +
} OWE. (6) y = yokes - x'cosa + n There it known the following equation from the above equation group (3):
it (ox Xi) (ox - xj) Substituting the equation I for the last-mentioned equation, A j = {( x'~sina Ox Isis x i Y
- {(Ox'ysina + Owe join +~) - (x'jsina - y!.jsin~
I) }
- sine{ Fox ' i x it _ (ox + Sweeney i) (MY j jsina B'ijsin~ .... (pa) Further, there is Nemo:
B i j ( ox i Y i MY
Jo Similarly, the following equation is obtained:

By; = c05~3{ Joy L Y i) ox j -cost{ ox - Zoo) - ox X'j)}

a Bit jco.5~3 AlijCOS0~ .... (7b) Similarly, the following equations are also obtained:

Siege - C'ijsina D'ijsin~ ............... (7c):

Dip D ijco.s~ - C'ijcosa .... (Ed) Obtaining Do I I, Do; PA, Biro the elusions aye) - (Ed), arc Do a Of j Disk Do j Seiko = (C'ijslna + D'ijsin~) (Dick - C ikCOS) S - Discos - C'ijcosc~)~C'jksina + D'~ksin~) = (Swenson + cosasin ) [C ', D 'I
Similarly, BY = (Swenson + sin~cos~)~A',B']
AND] = sincos~[A',D'~ - sinr~cosa[A',C'J
sin~cos~ Do sln~cosaLB',C']
AHAB = (sinacos~ + cossln~)[A',B'3 and I 'c] [AUDI = (sinacos~ cosr~sin~{[~',C'~ - Do I, Therefore, the equation (3c) is changed as follows:
Sweeney) x {[C',D'J (z) Do - [DOW) [AHAB} = o .... (8) In this equation (8), the term enclosed by a brace it a quadratic equation of the same type as the equation (3c). It is therefore unrlr3rstood that the quadratic eciuation (3c) is an invariable I actuation independently ox all of the coordinate systems. This means that two linear sensors used as detectors can he disposed with very large freedom Namely two linear sensors can be located on the zoo' coordinate system rather than the zoo I, coordinate system and the perpendicularly intersecting coordinate axes. Accordln~ly, such a disposition or location can he made independently of accuracy in measurement oven if no attention is drawn to the precise intersections and optical axis alignment of the linear sensors. In actual measurements, the patterns ox parallel linear lines Lo and Lo prior to the insertion of a lens S to be tested into the optical measuring system are previously detected by the use of the linear sensors So and So located respectively on the x'- and yuccas in the obliquely intersecting coordinate system xl-yl. Thought resultintJ iTnat~inary parallelogram US is used as a reference imaginary ~arallelogra~... Thereafter, a lens to be tested is inserted into the optical misarrange system to form a projected imaginary parallelogram U'V'W'Q'. Dye co~.parin~
the projected imaginary parallelo~Jra~ Whitehall the reference imaginary parallelogram, the refractive characteristics of the lens Jo be tested can be obtained. At this time, both the parallelocTr~ms are considered only in the oblique coordinate systeTn zoo' icky it an invariable equation independently of the other equatiorls for calculating the refractive vower among; the retractive chafe-cteristlcs of the lens, a .1es-ribed herein before. In accortlance with the present invention, therefore, the linear sensors So and So can be positioned with no adjustment in assembling and . ..
m~lntenance.
The orientation ox cylinder axis in Thea lens to be teGttd con be given by the-e~uation (5) which is llSed in the perpendicular coordinate system. Ivory, err the sensors art disposed in tile oblique coordinate system I the - Al -orientation is first obtained by the fulling eq~la~ion ~7itn respect to the ohllque coordinate system with the result Boolean used to calculate the cylinder axis in the perpendicular coordinate system:
= 2 tan CS2~[B'~D']-CO5(a~ rod ~',C'~)~cos2arA~C~
Sin2atB',D']~sin(a~ Do +~B',C'])-sin2~A',C'~

.... (9) The cylinder axis can be obtained from the aforementioned equation:

Measurement of prism power will now be described with reference to Figure 5.
US Prism values in the perpendicular coordinate systems yo-yo and x-y are calculated such that an imaginary parallelogram UV~IQ is defined by linear lines V, W Q, V W, U Q which are drawn at the respective distances en f'pl~ glP2 and h'P2 prom the respective linear llnës L11 and L21 of the parallel linear line groups Lo and Lo which are disposed symmetrically .
relative to yuccas by the same ankle with the respective itches Pi and Pi, the four corner ox the above imaginax~
parallelogram Heinz placed on the Jo- and yokes Namely, if the imaginary parallelogram it located symmetrically relative to the optical measuring axis 0, the center thereof corresponds to the optical measuring axis O. Subsequently, a Lyon to be tested is measured to detect projected groups of parallel linear line Lo' and Lo' with linear lines U' V', W' Q', V' I
and U',Q''being similarly drawn at the respective distances e'P1', f'P1', fop and h'P2' from the respective linear lines L11' and L21' to form an imaginary parallelogram U'V'W'Q'.
This imaginary parallelogram includes four corners which are positioned at the respective coordinates U'(x1, Yo-yo, Vex Yore tx3, ye) and Q'(x4, ye) of the x-y coordinate system. By thy use of these coordinates of the four corner, a horizontal prism quantity and vertical prism quantity PI are represented by the following equations:

p = i _. X 1 ox yip ............................... ~10) PI = i "I x 1~2 where d is a distance between it direction plane and the Silas of the Newsweek.
For measurements in the oblique coordinate system ..
x' y', based on the principle owe symmetry as in the perpendicular coordlnat~ Sistine, original i~na~Jed points (owe owe)' (ox' owe)' (ox3r owe) and (Ox, owe) may be set to fulfill the ~ollo~in~;
conditions:

owe + ox ox ox - (12) owe owe owe owe Since the horizontal and vertical prism quantities end PI
are respectively obtained from the equation (10), the equation (6) can be used to chancre the equation (12) as follows:

ion is Ozone I = 0 .... I
ivy icon ~Ox~icosa I = o The equation (6) can be also used to change the equation (10) as follows:

4PHc1~10 2 x'isina + ~y'isin~ + 4 4Pvdx10 = yo-yo = MY icon ix i a n cause there is a difference between the coordinate ox owe') I ox tile oricJinal (ox, owe) in the oblique coordinate system when a lens to be tested is absent and the coorclinat~ (zoo', Yip of the measurement in the oblique coordinate system when the e 'o s lens is inserted in the measuring system, the oiling kiwi joy;, can be outlined from the previous equations (13) and (1~3;

I

sin ox i) Sweeney i ox i 2 PI = - x 10 Casey i) COSSACKS 1 ox) 2 Ed these equations represents the prism values.
AccordincJ to the present invention, the refractive power of a lens to be tested can be calculated from the invariable equation independently of all of the coordinate systems. However, any coordinate change between the 0'.31 pique and perpendic~ r coordinate systems is required to obtain the cylinder axis and prism value of the lens to be tested Jo that any chancre in the equations l12~ and (15) will also be required If there is a complicated o2eration.^mechanism, measured coordinates (x', y') in the oblique coordinate system ma be changed to those ox the perpendlcu].ar coordinate system my the use of the equation I Thereafter astigmatic axis anywhere prism value can be calculated by utilizing the equations I (S) and (10) which can be used in the perpendicular coordinate stem.
According to the present invention thus, an imaginary p~ralleloyram loch is disposed symmetrically relative to the optical axis O it previously wormed based on the parallel linear fine years Lo and Lo on the mask when no lens to be tested is I
inserted in the optical measuring system. Thereafter, a lens to be tested is inserted in the optical measuring system so that the parallel linear images will be projected to form a similar projected imaginary parallelogram. Consequently, prism values can ye calculated. This means that such a calculation can sorely be made independently of the refractive powers and inclinations of the first and second principal meridians in the lens to be tested. This is very advantageous over the prior art lens meter in which the prism values cannot be calculated without knowing the refractive characteristics of a lens to be tested.
In such a manner, the present invention provides very reduced time required to operate the refractive characteristics and prism values of the lens to be tested since both the steps for calculating them are simultaneously and independently made .
The present invention is not limited to a so-called lens meter or measuring the characteristics of spectacle lenses, buy broadly applicable to any apparatus for measuring the optima characteristics of optical systems.
Although a process has been described which forms an imaginary parallelogram by drawing imaginary lines spaced apart from and parallel to the linear lines ~11 and L21 of the linear line group h a pitch which is obtained by the pitch in said groups multiplied by n, the present invention is not limited to such a method and can be accomplished also by such a method as seen from Figure 3c in which imaginary leerier lines l11 and 1~1 are defined to have the respective angles and relative to the respective linear lines l.11 and L21. Based on the so formed imaginary linear lines l11 and l21, then my be formed an imaginary parallelogram uvwq. This does no S depart from the principle of measurement according to the present invention Embodiments of an apparatus for measuring the rerractiv~
power of an optical lens which is constructed based on the adore-mentioned principle of measurement of the present invention Jill now be described with reference to the accompanying drawings.
inure 6 shows the arrangement of an optical system constructed accordinc3 to the present invention. In this figure, pa and 2b designate sources of light which are alternately driven by a drive circle 1 to respectively emit lights having di~Perent wavelengths, such as LID and the like A team of light emitted from the source of light pa are reflected by a wavelength selecting reflective-transmissive film pa in a dichroic prism 3 and then incident on a relay lens 4. On the outwore hand, a beam of light from the light source 2b I it transmitted through the same reElective-transmissive- film pa . .
in the dichroic lent 3 and then incident on the relay lens I.
The licJht beams incident on the relay lens 4 and condensed to a pin-hole 5. This pin-hole S serves to provide appropriate dimensions of apparent lookout sources in consideration with light quantity and diffraction in measuring. The diameter of the plainly is in the order of 0.1 to 0.3 mm. The beam of light emitted from the pin-hole S is converted into a parallel pencil of rays by means of a collimator lens 6 and then reflected downwardly at a reflective mirror 7 to be incident on a lens to be tested 8 which is held by any suitable holding means (not shown). The light beam from the lens 8 is reflected by a reflective mirror 9 to be incident on a relay lens 10. The light beam from the relay lens 10 is then incident on a dichroic prism 11 including a wavelength selecting reflective-transmissive film aye which serves to reflect or transmit the light beam there through appending on the wavelength of the incident beam.
For example, the transmitted light beam is reflected by a reflection mirror 12 and then incident Oil a beam limiting Miss 13b whereat information required to detect the optical character-is tics of the lens 8 is selected. Thereafter, the light beam is incident on a beam splitting means having a semi-transmissive film aye, or example, a half-mirror 14 with part of the beam being reflected by the semi-trans~issive film aye to be incident on line sensor 15 for detection. The other part of the beam us transmitted through the semi transmisslve film aye to by incident on a line sensor 16 for detection. On the other hand, tho fight beam reflected by the reflective--transmissive film aye of the dichrolc prism 11 isrreflected ho the reflective mirror 17 to be incident on a beam limiting mask aye whereat information required to detect the optical characteristics of the lens 8 is - I

I

selected. Thereafter, the light beam is incident on a half-mirror 14 with part of the incident beam being reflected by the semi-transmissive film aye to be incident on the line sensor 16 for detection. The other part of the incident beam is transmitted through the semi-transmissive film aye to be incident on the line sensor 15 for detection. In the illustrated embodiment, the beam limiting masks aye and 13b are disposed at the rest pective positions conjugate with a position MA through the relay lens 10 as if the masks are disposed on the position MA spaced apart from the lens 8 by a distance d. Similarly the line sensors 15 and 16 are also located respectively at the positions conjugate with that of a detection plane D through the relay lens 10.
Each of the line sensors 15 and 16 may include a linear type charge-coupled device, COD solid-state pickup eye-mint or the like.
the line sensors 15 and 16 are disposed to intersect with each other in their conjugate plane D.
In the illustrated embodiment, the light beam emitted from the source of light pa forms the first opt tidal path for measurement defined as follows: the dip chronic prism Thea relay lens the pin-hole I the collimator lens 6 the reflection mirror 7 the lens to be tested the reflective mirror I the relay lens 10~ the dichroic mirror lithe reflective mirror 17 the mask aye the half-mirror Thea line sensors 15 and 16. On the other hand, the beam of light emitted from the light source 2b forms the second original path for measurement I
defined as follows; the dichrolc prism 3 the relay lens 4 the pin-hole S the collimator lens 6 the reflective mirror 7 the lens to be tested 8 the reflective mirror 9 -I the relay lens 10 the dichroic prism 11 the reactive mirror 12 the mask 13b -I the half-mirror 14 the line sensors 15 and 16.
Figures pa and 7b show the mask patterns in the aforementioned beam limiting masks aye and 13b, respectively.
The mask aye includes a group 20 consisting of plural linear lines sloped my an angle my and spaced away from and parallel to each other with a pitch p. At least one linear line of the parallel linear lint group 20 includes a reference linear pattern 22 having a different dimension such that it can be d~stlnguish~d from the other linear patterns. Similarly, the mask 13b includes a group 21 consisting of plural linear fines inclined by an angle my and spaced apart from and parallel to each other with a pitch p, said group having a similar reverence linear pattern 23.
Although the illustrated embodiment of the present invention his been described with respect to the reference linear patterns 22 and 23 having different thicknesses ton distingllishing them Prom the other linear patterns, the presort invention is not limited to sun an arrangement. For exhume t the reference linear patterns may have different transmission factors or transmissive wavelerlyth characteristics for to distinguishing them from the other linear patterns. Alternatively, all ox the linear fine groups are identical with one another except that a pitch is varied it a specific area in the part-cuter group to provide the same function as the reference linear lingo The parallel linear line groups 20 and 21 on the asks aye and 13b are arranged such that they intersect by an angle in the common conjugate plane of the masks aye and 13b through the relay lens 10 shown in Figure 6, the bisector 24 of said angle being intersected by a reference axis 25 with an angle In the illustrated embodiment, the angles 0 and equal to 30.
Although the pitch has been selectee to be eta to P in both of the parallel linear line groups 20 and 21, this is attained only for more easily manufacturing the masks aye an 13b. The masks aye and 13b may have parallel linear line groups having die rent pitches from each other. Alternatively, one parallel linear line group may include linear patterns having clif~erent pitches from each o'er. Furthermore, the angles and E can also be selected optionally.
I Figure 8 is a view showing the projection of the mask pattern images onto the line sensors when the mask pattern :Lrnages are Dakota by the line sensors. us shown in Figure 8, the line sensors 15 and 16 of Figure 6 are disposed such that they intersect with each other my an angle in the Canaan So conjugate plane or detection plane D through the relay lens 10.

The light beam including information to the refractlv~
characteristics OX the lens to be tested 8 passes through the masks aye and 13b Jo that the parallel linear line group 20 on the mask aye will be projected onto the line sensors 15 and 16 as linear pattern images aye, 20'b .... 22l ,... 20'h.
Similarly, the parallel linear line group 21 on the other Newsweek 13b are projected onto the line sensors as linear pattern images aye, 21'b ... 23' ... 21'i. After projected, these linear pattern images have pitches p' and I" and intersectln~
ankle I' and ankle I' by which the bisector 24' thereon inter--sects a reference axis 25'.
On measuring, the light source pa is first energized to form the first Missourian optical path so that the linear pattern images aye, 20'h ... 22' ... 20'h are projected onto the line sensors 15 and I through the mask 1 Tao The line sensor 15 detects the linear pattern images aye, 20'b 020'h as the respective detection points eye, eye - eye. Similarly, the line sensor 16 detects the Respective detection joints ~12 -- ~19-Subsequently, the light source 2b is ener~iz2~l~ to form the second measuring optical path so that the linear pattern issue aye, 21'b ... 23' ... 21'i will be projected onto the line sensors 15 and 16 through the mask 13b. The line sensor 15 detects the linear pattern iamb aye, 21'b ... 23' ... 21'i as the respective detection points eye, eye I eye Similarly, the fine sensor 16 detects the respective detection points f21~ f I f 26~
Figures PA to EM are timing chats for illustrating the outputs from the line sensors when the linear pattern images are detected by the line sensors and the subsequent calculation thereof. figure PA shows a series of pulses for reading and driving ye detecting outputs of the line sensor As these pulses are input to the line sensor, the latter entice detection outputs in sequence. Figure 9B shows waveforms (envelope curves) of detection outputs from the line sensor 15 when the linear patterns aye, 20'~ ... 22' ... 20'h are projected onto the line sensor 15. The output waveforms ox Figure 9B
have their leading edges ox output levels which correspond to the respective detection points eye, eye ... eye. Similarly, Figure 9C shows Ol1tput waveforms of -the linear pattern images aye, 20'b ... 20'h detected ho the line sensor 16l Pharaoh ED
shows output waveforms of the linear pattern images aye, 21'b ... I ... 21'i detected by e line sensor 15, Figure YE
owe output waveforms ox the linear pattern images aye, 21'b I ... 23' .... 21'i detected by the line sensor 16. Figure OF -. ., I show rectallgular output waveforms shaped prom the a~oremen~.io~ed ~et~ct~d output.~clveorrns (B) - (~) by the use of a 5chmltt trigger circuit, with the waveforms (I (I) corresponding to the worms (B) - (E), respectively. The central positions of the so obtained rectangular output waveforms (I (I) are determined and positioned by utilizlnc3 the number of the sensor elements in the line sensor.
Namely, if a line sensor LENS consists of sensor elements of N in number, En, En, ... EN 1 and En a shim in Figure 10 and when the sensor elements En to E on of this line sensor LENS generate a rectangular waveform output eta and the sensor elements En to Em of the same produce a rectangular waveform outpllt ebb the width PA of the rectangular waveform output eta corresponds to the sensor elements of n in number while the width A of the rectangular waveform output en cores-ponds to the sensor elements of m in number. It is therefore understood that the center 1 of the rectangular waveform output eta corresponds to the sensor element of En I n/2 = E
in number which us offset from the sensor element En by n/2.
~irnilarly, the center I of the rectangular waveform output en corresponds to the solacer element En m/2 = ESSAY In order to increase the accuracy in detection, it is wrecker to provide any interpolation between the pitches of the sensor eleTnents.
This can be accomplished by waveform shaping the leading and trailing edcJe~ of an output signal precisely at an appropriate slick level attics an envelope curve has been detected, end then clekecttng the center of the output signal ho the use or clock pulses having a Erroneous sufficiently higher than that of the pulse series for driving the line sensors.
In such a manner, the linear pattern lames can be I -I

positioned by thy number ox the sensor elements in the line sensors when the center of the rectangular output waveform obtained by the line sensors at detection points is Nemo.
Namely, these images can be obtained as coordinate values in a coordinate system defined by the line sensors.
Figure 9J to Al show the respective detection joints as coordinates on the line sensors according to the above method.
Coordinate values e 3 1 1 eye I.. eye correspond to the detection points eye, eye ... eye respectively. Coordinate values f~11 I f'19 correspond to the detection points f11 f19~ respectively.
Further, coordinate values eye - eye correspond to the detect lion points eye eye, respectively. Still further cord Nate values f'2~- f'26 correspond to the detection points f21 f26 respectively .
US erring again to Figure 10, the number m ox sensor elements for generating the rectangular waveform output en is different from the number n of sensor elements or producing -thy other rectangular waveform ought en. Since the number m is larger than the number n, it is apparent that the rectancJular waveform output en is a detection output of linear pattern ir,la~e~, from such a reference linear pattern as shown in Figure pa and 7b. In the illustrated embodiment, -the detection points eye, eye, eye and f23 correspond to those of reference linear pattern images 22' and 23, and have the respective reference I cordiality values e 15~ f 16' 25 ant 23 Brie Thus, an equation or the reference linear pattern image 22' can be determined from the reference coordinate values eye and f'16, and an equation for the reference linear pattern image 23' can be established from the reference coordinate values eye and ~'23 Equations for the other linear pattern images can be determined from the respective coordinate values ordered by the reference coordinate values e 15' f 16' e 25 and f 23- For example, by the use of a coordinate value eye next to the reference coordinate value eye and a coordinate value f'17 of the reference coordinate value f'16, an equation for a linear petrol image 20'f can be determined. In such a manner, a plurality of equations for linear pattern images can be established by the use of the respective coordinate values. Since the linear pattern images are maintained parallel in the same parallel linear line croup, these linear equations can be averaged resulting in more precise detection. Furthermore, the obtained equations can be used to determine the respective pitches l' which are in turn averaged resulting in more accurate value for the pitch P'. This is an important feature of the present invention.
e~errLng to Fakers 11 to 13, there isle now be described a method in which imaginary linear lines are formed from equations for linear pattern images detected by the line sensors and used to establish any your points on the same plane azalea plane onto which the linear pattern images are projected, variations ox these joints being utilized to measure the retractive characteristics of a lens to be tested. E'Lgure 11 shows the projection of the linear pattern 20 and 21 onto the line sensors 15 and 16 when the lens 8 is not inserted in the measuring optical path. it this time the linear pattern images 20" and 21" only the reference linear pattern images 22", 23" and linear patterns eye, 20"f, 21"d, eye are shown in Figure 11) have their ox equations and pitch P which are determined by the aforementioned method.
Subsequently, for example, an imaginary linear line 30 can be produced with an angle f x my at a position spaced away from the linear pattern image eye by a distance e x P. An imaginary linear line I can be formed with an ankle f x my at a position spaced away From the opposite side of said linear pattern image eye by a distance x Pi Similarly, an imaginary linear line 32 can be formed with an angle f x my at a position spaced apart from the linear pattern image 21"d by a distance h x P, and an i.ma~in~ry linear line 33 con be produce with an angle x Mel it a piston spaced away by a distance i x P. The coefficients e, f, I, h and i can optionally he selected.
Mormall~, thy coefficient f is equal to one. Tamely, imaginary liner fines will ye formed with the same ankles as the angles my and my in the linear pattern image equations. Furthermore, the coe~icients e, g, h, and i are selected such that inter US sections 36, 37, 38 and 39 of the formed imaginary linear lines are located symmetrically relative to thy center 24 of the mast. Figure 11 shows the so formed imaginary linear lines which can be used to more easily calculate the prism refractive power of a lens to be tested as descried hereinbe~ore tlith the principle of the present invention.
Subsequently a lens to be tested is inserted in the measuring optical path. linear pattern ima~2s formed my a beam of light which has been changed by the refractive character-is tics of the lens to be tested are detected by the line sensors to obtain imaginary linear lines. This is Sheehan in Figure 12.
As aforementioned, there are first detected inure pattern imacJes 20' and 21' which have been changed respectively to pitches P' and I" and to angles my' an my' so that equatiorls therefore Jill be calculated. Subsequently, an ima~lnary linear line 30' it formed at a position space away fryer the linear pattern image eye corresponding to the linear pattern image eye used in figure 11 as a reference, by a distance e x P" in which e is the same coefficient a used to form the im~inary linear line 30 in FicJure 11. This imaginary linear line 30' is sloped with an angle f x my' in which the coefficient f is eel to one in the same manner that ho coefficient f in the annul E x my I the lma~inary linear line 30 in Figure 11 is equal to one. Similarly, an imaginary linear line 31' is formed at a position spaced away from the linear pattern image eye Lay I a distance g x P", an imaginary linear line 32' is formed at a position spaced away prom the linear pattern iron 21'd my a distance h x P', and an ima~lnary linear line 33' is donned at a position i x P', Intersections 36', 37', 38' and 39' can be obtained from these imaginary linear fines 30', 31', 32' and 33' and used to obtain the center 34' relating to these four intersections.
Thus, the four intersections 36 to 39 are shifted to the other four intersections 36' to 39' under the refractive characteristics of a lens to be tested in the detection plane D. This is shown in Figure 13. the amount ox such a shirt can be utilized to calculate the refractive characteristics of the lens to be tested by the use of the aforementioned equations I to I In accordance with such a method as suggested on the illustrated embodiment in which four intersection of imac3lnary linear lines when a lens to be tested is not insert.-in the measuring optical path are used as refer2nc2 points, and the amount ox shift in said intersections when the lens is inserted in the measuring Ol~tlcal path, the aforementioned rations (3) will completely be invariable for the coordinate system wormed by two line sensors. Accordingly, there is very . .
advantage in that no control of intersectln~ alleles and positions ox the line sensors will be required in assembling Figure I shows a simple bloc diagram of an example ox a processing circuit or effecting such a calculation as c1escribed above. The line sensors 15 and 16 are driven my fine sensor drivers 100 and 101 and detect images which are wormed by projecting a beam of light from the Lowe source pa driven by the drive circuit 1 through the beam limiting mask having the linear pattern openings. Such detection produces output signals as shown in Figures I 9C which are transmitted from the lone sensors to signal lines 102 and 103. 104 is a analog switch controlled by a microprocessor 105. Inn the microprocessor 105 is in~erruFted by a scan start pulse 105 from the driver 100 for the line sensor 15, it is operated to control the analog switch so that the output of the line sensor 15 will he couplec1 with the input of an AND converter 107. The A/D converter 107 is adapted to convert an annul output from each element of the line sensors which is read out from the driver circuit 100 by reading pulses as Sheehan in Figure I
to a doughtily value itch. is in turn supplied to the microprocessor, The A/D converter 107 is selected such that it has a resolving power in the order of bits (1/256) and a conversion time smaller than the scan frequency or the line sensors. The micro-processor 105 is adapted to rend the outputs of the line sensor 15 that have been converted into de~Jltal values at each element and to store them successively in a data memory 109 which is . . .
composed of RAM tranclom access memory) or the live. Conseq~lentl~, the outputs of the line sensor 15 are stored in the data Mueller 109 in the form of doughtily values proceeding from tune first element ox the line sensor to the subsequent elements thereof I rather than pr~c~e~termined locations (addresses. or eagle -- ago --I

if the line sensor is comprised of 1728 elements, the micro-processor 105 ceases further data lathering when 1728 data is totally gathered, and welts to receive an interruption by a scan start pulse 110 driving the line sensor 16. As interrupted, S the microprocessor 105 begins to control the analog swish 104 to successively store the outputs of the line sensor 16 read out by line sensor reading Pulses 111 in the data memory 109 as digital values. Subsequently, thy microprocessor 105 controls the drive circuit 1 to turn off the light source pa now in action and to turn on the light source 2b. In the same manner, detention outputs shown in Figures ED and I are stored in the data emery 109 as doughtily values Thus, all of the measurement data will be stored in the data memory 109. Aster this, an operational circuit 112 in the microprocessor 105 will achieve the ~ollow..n~
processes bass on the Dwight in the data memory 109:
(l) Detectinc3 which element of the lint sensor the center of a line sensor output waveform produced form the projected imps ox linear pattern of the beam limiting mast is located at.
I . I Obtaining equations or the respective linear triune images in the coordinate system wormed by two line tensors.

3) E'ormincJ equations of such imaginary linear lines as shown by 30' - 33' in Figure 12 according to the aforementioned Matthew and obtain~n~J coordinate positions or four intersections 36~-39~ of the imaginary linear lines as shown in Figure 13 to determine its central position 34'.

(4) Determining the spherical refractive power S, Cylindrical refractive power C, orientation of astigmatic axis Ax and prism refractive powers Pox, Pry of a lens to be tested by the aforementioned equations (3) - (5) based on the four reference positions 36 - 39 with no lens to be tested, the coordinate position of the center 34 and the coordinate positions of the points 36' - 39' and 34' obtained by the aforementioned equation (3).
Further, in this case, the spherical refractive power S is obtained by value Do of the equation (4) when Do Do, or is obtained by value Do of the equation (4) when Do Do. And cylindrical refractive power C is obtained by value Do - Do¦ of the equation (4). Gore further, the orientation of astigmatic axis Ax is equal to of the equation (5). Prism refractive powers Pox, Pry are equal to Phi Pi of the equation (10), respectively.
The values thus obtained are output to an i~l~icator 113 end printer 114 As Sloan in Figure 14. The above processes are trade all accordions to programs which are recorder in a program memory 115. Such processes due to the microprocessor con easily be attained by those skilled in the art.
The present invention is not limited to the above embodiments, but includes many nnodifications a few examples of - I -which will be disclosed hereinafter.
Although the first embodiment chasm in Figure 6 has been described with respect to the formation of two measuring optical paths by the use of a dichroic prism which Sirius to selectively reflect or transmit two light beams having different wavelengths from two sources of light, the two light sources may be replaced by a mechanical chopper shown in Figure 15 for selecting the measuring optical paths.
In Figure 15, I

I

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- I -so the same components as in the first embodiment of Figure 6 are designated by the same numerals with the explanation whereof being omitted. A beam splitting means 150 such as half-mirror is disposed beyond the relay lens 10 for dividing S the light beam from the relay lens 10 into two bundles or rays.
One of the bundles of rays passes through a semitransparent mirror face 151 in the half-mirror 150 and follows the first measuring optical path 152 in which the first chopper aye it disposed. On the other hand, the other bundle of rays is reflected at the semitransparent mirror race 151 of the half-mirror 150 and then follows the second measuring optical path 154 in which the second chopper 153b is located. these first and second choppers are connected with and controlled by a chopper drive circuit 155 . Roy control is made such that it the first chopper 1 aye is inserter in the first measuring optical path 152, the second chopper 153b is out Ox the second measuring optical path 154 to permit the light beam passing through thy second measuring optical path to be incident only on the mask aye. The light beam pasted through this mask aye 20 it divided ho the hal~-mlrror 14 into two parts which are proejctec~ onto the line sensors 15 and 16, respectively.
Suhse~uentl~l~, the chopper drive circuit causes the first chopper aye to be out ox the first measuring optical path and at the same time inserts the second chopper 153b into the second measuring optical path 15~ to shut owe -the light Jo beam proceeding to the second measuring optical path. Accordin~Jl~, only the light beau proceeding to the first measuring optical path is reflected by the mask 13b and passes through the same to be divided by the half-mirror 14 into two parts itch are projected onto the line sensors, respectively.
Faker 16 shows another embodiment of the arrangement of line sensors. Although the first embodiment of Figure 6 has been described with respect to the line sensors 15 and 16 being disposed to intersect with each other in the optically conjugate detection plane D through the relay lens 10, the present invent Shea not limited to such an arrangement. The line sensors may be intersected with each other at their imaginary extensions.
us can seen from the principle of the present invention, it includes the first measuring step in which linear equations for projected imacJes of linear pattern wormed on the beam splitting mast.; are obtained. The linear ecIuat~ons can be obtained by measuring at least two points on the linear lines Therefore, the line sensors for detecting the linear pattern images Call ~xecly be located unless they become parallel to the linear pattern imac3es. FicJure 16 shows an example of such an arran~3emellt . .
in which two line sensors 160 and 161 are disposed parallel to each other in the detection plane D. More particularly, the line sensors 160 and 161 are located parallel to equine other in the detection plane D such that the lint sensor 160 is placed in the same plane that the line sensor 15 of Figure 6 is disposed I

5~9 and that the line sensor 161 is located in the same plane as the line sensor 16 of Figure 6 is positioned Figure 17 shows further embodintent ox the present invention in which the two parallel line sensors are replaced by a single line sensor which is combined with image shifting optical means to provide substantially the same advantage as the two fine sensors are used. In Figure 17, the optical arrangement forwardly of the reply lens 10 is the same as that of Figure 6 and therefore omitted. The same components as in the first embodiment of Figure 6 are denoted by the same numerals with the explanation thereof being eliminated.
Por~lardly ox a single line sensor 162 is located image shifting optical means 170 such as plane-parallel which is perpendicular to the incident optical axis and includes a rotating axis parallel to a direction in which the sensor elements of the line sensor are c1isposed. The plane-parallels 170 are rotated by a drive circuit 172 around said rotating axis ho an angle in a direction shown byway an awry ~73, these plane parallels being moved in synchronism with each other.
Assuming that the lane parallel 170 are positioned perpendicular to the incident optical axis 175 as shim by a solid line in Figure 17, a beam ox light, which has been passed through the mask aye in the second measuring optical path and transmitted through the semitransparent mirror racy of the half mirror 14, is projected onto the line sensor 1~2 as a - I -projection light beam which has a projection optical axis 177 coccal of the incident axis ~75. When the driver circuit 172 is then energized, the plane-parallel 170 is rotated by an ankle to a position 170' so that the projected light beau will be shifted under the refractive action of the plane-parallel and projected onto the line sensor 162 as a projected light beau which has the second projection optical axis' offset parallel from the projection optical axis 177. It is of course that the light beam passed through the mask 13b in the first Missourian optical path is similarly processed after it has been reflected by the half mirror 14. If a twa-dimensional sensor is used in place of the line sensors shown in Figures lo and 17, the nuder of detection point may be increased.
Figure 13 Schloss still further embodiment of the present invention in itch a single line sensor may be moved in the detection plane rather than stationary line sensors as in the previous er~odiments. The same component as those ox the Reeves embodiments are designated but two tame numerals with the ey~planatlon thereof ~elng omitted.
A ll~ht beam passed through the mast 13b in the first Myron optical. aye 152 it reflected by a reflective film 211 Ox a clockwork prism 210 which causes the light beam to a select vilely reflect or transmit depending on its r,~ave]enyth and then incident on a line sensor 212. Tl1is line solacer 212 it Noel set at an ankle by a motor 214 in accordance with a command signal -- I -from a sensor rotational ankle controlling circuit 213. it this set angler the sensor effects the first detection. Aster the line sensor has teen rotated to another angle, the second detection is carried out by the sensor. At subsequent annular positions, the respective detections are effected. These results detected are used to calculate projected images of the linear pattern ox the ask 13b. Next, the source of light is exchanged to the other source of light to cause the Missourian beam to pass through the mask aye in the second measuring optical path 154. The fight beam passed through the mask aye is caused to be transmitted through a reflective film 212 of a dichroic prism 210 and then to be incident on the line sensor 212 for detection as in the previous embodiments.
The single line sensor may be parallel moved continuous y or stops in a plane rather than rotated. Alternatively, the single lint sensor may be stationary, but the projected light beams may he rotated or parallel-moved continuously or stops by rotating the conventional optical image rotator or continuously rotating the plane-~arallels. At this case, the image rotator I or plane-~arallels must be located beautician the ask and the line tensor dimensional plane sensor may be used in place ox the line sensors. Thus, more detection points pity be detected to improve the accuracy in measuring.
Figures 19, 20 and 21 show other embodiment ox the present invention in which a single group of parallel linear line pattern is formed on a single mask means which is diseased rearwardly of a lens to be tested, a Lotte beam passe through the lens being caused to be incident on the mask means such thought the orientation of the linear pattern group is changed relative to itself at at least two placed so that the same advantages as in the previous embodiments will be provided, although the embodiments in Figures 6, 7 and 8 have been described with reference to the groups of parallel linear patterns which are disposed on separate mask means such that the orientations of the linear pattern groups are different from each other.
Figure 19 shows an example in which mask means is adapted to be rotated relative to a fight beam passed through a lens to ye tested. In Figure 19, a light beam passed thrower a lens to be tested is incident on Moscow means through the relay lens 10. Such task means includes a plurality of parallel Texans as in the mask aye shim in FicJure pa which are Aryan along a sunnily orientation. Russ mask means aye is located it the optical path to provide a predetermined orientation. The light beam passed through this mask means 13~ its divided by the ho mirror I Unto two parts which are in turn incident on toe line sensors US and 16 for detection as in the previous embodiments. Subsequently, the Moscow aye is rotated around the measuring optical axis 0 by A predetermine d angle by means of a use motor 216 which can be controlled ho a motor drive controller 215. Thereafter, another light beam from the lens 8 is caused to be again incident on this mask aye and then similarly detected by the line sensors 15 and 16.
Figure 20 shows other embodiment of the present invention inch mask means is fixed whereas a light beam passed through a lens to be tested is rotated around a measuring optical axis 0. For this end, the passed light beau is incident on any beam notating means such as the conventional image rotator 220 which may be rotated. The light beam passed through the lens 8 passes through the relay lens 10 and then is rotated through the image rotator which has been disposed with a pro-determined angle. Thereafter, the passed light beam passes through the stationary mask aye and then is detected similarly by the line sensors 15 and 16. Subsequently, the image rotator is rotated over a predetermined ankle a which another light beam passed through the lens passes through the rotated image rotator and is rotated over another angle different from the previous angle to be incldenk on eye mask aye. The incident licJht beam is detected my the fine sensors 15 and 16.
There is probability that accuracy in measurement . .
ma be reduced since such movable parts as the mask means and image rotator are used as in the sixth and seventh embodiments This can be overcome by the use ox such a construction as in the eighth embodiment shown in Figure I In the eta embodiment the first and second relay lenses 10c and God are located behind - I

t,j~3~,3~3 the lens 8 to be jested Jo cooperate with each other for relaying an incident beam of light. Between the relay lenses 10c and God there are disposed two dichroic prisms 223 and 224 or selectively reflecting or transmitting the incident fight beam dip ending on its wavelength, and reflective mirrors 221 and 222. Thus, the first measuring optical path 225 it defined by the relay lens 10c, the dichroic prism 223, -the reflective mirror 221, the dichr.oic prism 224 and the relay lens God. In the first measuring optical path is disposed an optical length compensation lens 227.
Further, the second measuring optical path 226 is defined by the relay lens lock the dichroic prism 223, the reflective mirror 222, the dichroic prism 224, and the relay lens God. Between the reflective mirror 222 and dichroic prism 224 of the second measuring optical path 226 there is fixedly located an image rotator 220 having its reflective surface aye which has previously been rotated around the measuring optical awls o by a predetermined angle.
beam of light emitted from the source of iota 2b is first transmitted through the dichroic prism 3 and then passes through a lens to be tested 8 to be incident on the relay lens lock the light beam from the relay lens 10c passes through the prism 223 and follows said first optical path 225 to be incident on the mask aye. The light beam from the mask aye is detected by the inn sensors 15 and 16. Subsequently, the light source 2b it switched to the other light source pa having different .
wavelength of light from that of the light source 2b. A heat of fight omitted from the lookout source pa is reflected by the prism 3 and then incident on the lens 8 to be tested. The light beam from the lens 8 passes throuc3h the relay lens lo and then is reflected by the prism 223 so that it will follow said second measuring optical path 226 to be incident on the mask aye. The light beam incident on the mask aye is rotated by a predetermined angle under the action of the image rotator 220. Thereafter, the light beam from the mask aye is detected by the line sensors 15 and 16 in the same Menorahs in the previous embodiments.
Figure 22 shows the ninth embodiment of the present invention on which both the first and second parallel linear line groups are formed on the same mask the same components as in the first embodiment of Figure 6 are denoted by the same numerals with the explanation thereof being eliminated. Behind the lens to be tested 8 there is disposed a mask 13 including the lust and second parallel linear line groups 20 and 21 which are formed on the mask to have different orientations without any intersection as shown in Figure 23. The line sensors 15 and 16 are located to intersect with each other in the conjugate detection plane D shown in Figure 22 through the relay lens 10 end the half-mirror 11, respectively. The processes for obtaining the detection ox the line sensors 15 and 16 and for calculating I the optical characteristics of a lens to be tested from the so - 51; -to 3 obtained results ore similar to those of the previously described embodiments. In the ninth embodiment, however, the patterns corresponding to the first and second parallel linear Len groups 20, 21 are simultaneously projected on the line sensors 15 and 16. This is advantageous in that each of thy line sensors 15 and 16 may be scanned and detected only once. ire the mask show in Figure 23 is utilized to use the parallel disposed line sensors or the beam shifting means as in Figures 16 and 17, four line sensors 15, 15', 16 Rand I should be disposed parallel to one another as shown in Figure 24, or ours two line sensors 15 and 16 should be located parallel to the beam shifting means 170 (sex Figure 17).
Although the present invention has been described loath respect to the embalmments thereof all of josh utilize COD as line sensors, it is not limited to such COD, buy applicable to such techniques that a pickup tube is utilized to optically scan or that a linear scanning is optically or mechanically made by the use OX a photoelectric light emitting element.
Although the present invention has been described with . . .
resect to the mask means having a transmissive pattern ~7hichserves to selectively transmit the light beam passed through a lens to be tested, as means for selecting the light means, it is not limited to such an arrangement. According to the present invention there can be formed a reflective pattern for selectively reflecting the passed light beam to detect it by - the detectors.
The present invention us not limited to the construct Sheehan of the ~mbodlments thereof, but can be crawled out in many con~iguratiolls and arrangements including various csmbina-5 lions of each of the embodiments and various replacement ox components with other equivalent, without departing from the spirit and scope of the invention defined in the appended clowns.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An apparatus for measuring the optical charac-teristics of an optical system, comprising collimator means for collimating a beam of light from a source of light, means for selecting part of the light beam from said collimator means, means for holding an optical system to be tested between said collimator means and said selecting means, means for detecting the selected light beam from said selecting means, and means for calculating the optical characteristics of said optical system to be tested on the basis of the results detected by said detecting means, characterized in that said selecting means includes a beam selecting pattern com-prising two groups of parallel linear lines, each of said groups consisting of at least two parallel linear lines, said parallel linear line groups being disposed such that they are oriented in different directions without any intersection.

2. An apparatus as defined in claim 1 charac-terized in that each of said parallel linear line groups includes at least one linear line which can be discrimi-nated from the other linear lines.

3. An apparatus as defined in claim 2 charac-terized in that each of said parallel linear line groups comprises a transmissive pattern through which the light beam from said optical system to be tested is transmitted.

4. An apparatus as defined in claim 1 charac-terized in that said detecting means includes at least one line sensor and that said apparatus comprises drive means for producing a relative movement between the selected light beam from said selecting means and said line sensor in a plane perpendicular to the measuring optical axis.

5. An apparatus as defined in claim 1 charac-terized in that said detecting means includes two line sensors, one of said line sensors being disposed in a plane perpendicular to the measuring optical axis and the second line sensor being located in a plane per-pendicular to an optical axis changed by an optical path changing member which is arranged between the first line sensor and said selecting means, and the first and second line sensors intersecting optically.

6. An apparatus as defined in claim 1 charac-terized in that said calculating means is adapted to calculate an equation for projected linear lines of a projected pattern corresponding to said pattern on the basis of the results obtained by said detecting means, said equation being used to determine changes in the inclination and pitch of said projected parallel linear line groups for obtaining the optical characteristics of said optical system to be tested.

7. An apparatus as defined in claim 6 charac-terized in that said calculating means is adapted to form an imaginary parallelogram based on the inclination and pitch of said projected parallel linear line groups, whereby the optical characteristics of said optical system to be tested are calculated from a change of said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.

8. An apparatus as defined in claim 1 charac-terized in that said parallel linear line groups are disposed symmetrically relative to each other with res-pect to a plane including the measuring optical axis.

9. An apparatus for measuring the optical char-acteristics of an optical system, comprising collimator means for collimating a beam of light from a source of light, means for selecting part of said collimated beam of light from said collimator means, means for holding an optical system to be tested between said collimator means and said selecting means, means for detecting the light beam selected in said selecting means, and means for calculating the optical charac-teristics of said optical system to be tested on the basis of the results detected by said detecting means, characterized in that said apparatus further comprises first beam splitting means for dividing the light beam from said optical system to be tested into at least two optical paths each of which includes at least one of said selecting means having a beam selecting pattern consisting of at least two parallel linear lines, said selecting means being disposed to have different orien-tation of said linear patterns in the respective select-ing means.

10. An apparatus as defined in claim 9 charac-terized in that said beam selecting pattern comprises a transmissive pattern through which the light beam from said optical system to be tested is transmitted and said linear pattern group of said selecting means includes at least one linear pattern which can be dis-criminated from the other linear patterns.

11. An apparatus as defined in claim 9 charac-terized in that the second beam splitting means is disposed behind each of said selecting means, said second beam splitting means being adapted to divide the light beam passed through said selecting means into at least two parts which are in turn incident on the cor-responding detecting means. I

12. An apparatus as defined in claim 9 charac-terized in that said detecting means comprises at least two line sensors for linearly scanning and detecting light information.

13. An apparatus as defined in claim 12 charac-terized in that at least two of said line sensors intersect in a detection plane which is defined by a relay optical system located between said optical system to be tested and said first beam splitting means and which is optically conjugate with said line sensors.

14. An apparatus as defined in claim 12 charac-terized in that said line sensors are located parallel to each other in a detection plane which is defined by a relay optical system disposed between said optical system to be tested and said first beam splitting means and which is optically conjugate with said line sensors.

15. An apparatus as defined in claim 9 charac-terized in that said detecting means includes a two-dimensional sensor.

16. An apparatus as defined in claim 9 charac-terized in that said light source means comprising at least two sources of light having different wavelengths of emitting light from each other and said first beam splitting means being adapted to selectively reflect or transmit the light beam from said light source depending on its wavelength.

17. An apparatus as defined in claim 9 charac-terized in that each optical path split by said first beam splitting means includes means for blocking the beam of light oppositely and alternately.

18. An apparatus as defined in claim 9 charac-terized in that said detecting means is adapted to detect at least two points on the respective projected image of said linear pattern, and said calculating means is adapted to derive a linear equation for the projected image of said linear pattern from the results detected by said detecting means, said equation being utilized to calculate changes in the inclination and pitch of the projected image to obtain the optical char-acteristics of said optical system to be tested.

19. An apparatus as defined in claim 18 charac-terized in that said calculating means is adapted to form an imaginary parallelogram on the basis of the inclination and pitch of said projected image and said imaginary parallelogram being utilized to calculate the optical characteristics of said optical system to be tested on the basis of a change in said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.

20. An apparatus as defined in claim 19 charac-terized in that each of said line sensors consists of a charge-coupled device.

21. An apparatus as defined in claim 17 charac-terized in that said detecting means is adapted to detect at least two points on the respective projected image of said linear pattern and said calculating means is adapted to derive a linear equation for the projected image of said linear pattern from the results detected by said detecting means, said equation being utilized to calculate change in the inclination and pitch of the projected image to obtain the optical characteristics of said optical system to be tested.

22. An apparatus as defined in claim 21 charac-terized in that said calculating means is adapted to form an imaginary parallelogram on the basis of the inclination and pitch of said projected image, said imaginary parallelogram being utilized to calculate the optical characteristics of said optical system to be tested on the basis of a change in said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.

23. An apparatus as defined in claim 22 charac-terized in that each of said line sensors consists of a charge-coupled device.

24. An apparatus as defined in claim 15 charac-terized in that said light source means comprises at least two sources of light having different wavelengths of emitting light from each other and said first beam splitting means being adapted to selectively reflect or transmit the light beam from said light source depending on its wavelength.

25. An apparatus as defined in claim 15 charac-terized in that each optical path split by said first beam splitting means includes means for blocking light oppositely and alternately.

26. An apparatus as defined in claim 24 charac-terized in that said detecting means is adapted to detect at least two points on the respective projected image of said linear pattern and said calculating means is adapted to derive a linear equation for the projected image of said linear pattern from the results detected by said detecting means, said equation being utilized to calculate change in the inclination and pitch of the projected image to obtain the optical characteris-tics of said optical system to be tested.

27. An apparatus as defined in claim 26 charac-terized in that calculating means is adapted to form an imaginary parallelogram on the basis of the inclination and pitch of said projected image, said imaginary parallelogram being utilized to calculate the optical characteristics of said optical system to be tested on the basis of a change in said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.

28. An apparatus as defined in claim 27 charac-terized in that said two-dimensional sensor consists of a charge-coupled device.

29. An apparatus as defined in claim 25 charac-terized in that said detecting means is adapted to detect at least two points on the respective projected image of said linear pattern and said calculating means is adapted to derive a linear equation for the projected image of said linear pattern from the results detected by said detecting means, said equation being utilized to calculate change in the inclination and pitch of the projected image to obtain the optical characteristics of said optical system to be tested.

30. An apparatus as defined in claim 29 charac-terized in that said calculating means is adapted to form an imaginary parallelogram on the basis of the in-clination and pitch of said projected image, said ima-ginary parallelogram being utilized to calculate the optical characteristics of said optical system to be tested on the basis of a change in said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.

31. An apparatus as defined in claim 30 charac-terized in that each of said two-dimensional sensors consists of a charge-coupled device.

32. An apparatus for measuring the optical charac-teristics of an optical system, comprising collimator means for collimating a beam of light from a source of light, means for selecting part of said light beam from said collimator means, means for holding an optical system to be tested between said collimator means and said selecting means, means for detecting the selected light beam from said selecting means, and means for calculating the optical characteristics of said optical system to be tested on the basis of the results detected by said detecting means, said apparatus further comprising:
means for producing a relative rotation between said light beam emitted from said optical system to be tested and said selecting means in a plane intersecting the measuring optical path, said selecting means including a beam selecting pattern consisting of at least two parallel linear lines for selecting part of said light beam passed through said optical system to be tested to project a pattern which corresponds to said selecting pattern, said projected pattern being deformed by the optical charac-teristics of said optical system to he tested as projected on said detecting means;

said detecting means including position detector means located between said selecting means and a convergent point of said optical system to be tested for detecting a projected position of said projected pattern;
said calculating means including means for calculating the optical characteristics of said optical system to be tested based on the position, inclination and pitch of said projected pattern detected by said detecting means.

33. An apparatus as defined in claim 32 charac-terized in that said beam selecting means includes a transmissive pattern through which the light beam from said optical system to be tested is transmitted and said parallel linear lines include at least one linear line which can be discriminated from the other linear lines.

34. An apparatus as defined in claim 33 charac-terized in that said relative rotation producing means is adapted to rotate said selecting means around the measuring optical axis.

35. An apparatus as defined in claim 33 charac-terized in that said relative rotation producing means is adapted to optically rotate the light beam emitted from said optical system to be tested around said measuring optical axis.

36. An apparatus as defined in claim 35 charac-terized in that the light beam emitted from said optical system to be tested is split into at least two optical paths, at least one of said optical paths including said beam rotating means disposed therein.

37. An apparatus as defined in claim 32 charac-terized in that said detecting means includes at least two line sensors for linearly scanning and detecting light information.

38. An apparatus as defined in claim 37 charac-terized in that said detecting means is adapted to detect at least two points on the respective projected image of said linear pattern, the so obtained results being utilized to derive a linear equation relating to said linear pattern projected image, said equation being used to obtain changes in the inclination and pitch of the projected image for calculating the optical charac-teristics of said optical system to be tested.

39. An apparatus as defined in claim 38 charac-terized in that said calculating means is adapted to form an imaginary parallelogram on the basis of the inclination and pitch of projected image of said linear pattern, said imaginary parallelogram being utilized to calculate the optical characteristics of said optical system to be tested on the basis of a change of said imaginary parallelogram depending on the presence or absence of said optical system to be tested in the measuring optical path.