CA1071330A - Optical focussing read-out device - Google Patents
Optical focussing read-out deviceInfo
- Publication number
- CA1071330A CA1071330A CA251,476A CA251476A CA1071330A CA 1071330 A CA1071330 A CA 1071330A CA 251476 A CA251476 A CA 251476A CA 1071330 A CA1071330 A CA 1071330A
- Authority
- CA
- Canada
- Prior art keywords
- optical
- read
- displacement
- out device
- data carrier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
Landscapes
- Optical Recording Or Reproduction (AREA)
- Automatic Focus Adjustment (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
The present invention relates to an optical read-out device for reading data carrier, comprising an optical reading head capable of displacement parallel to its optical axis at low velocity and with high amplitude, giving rise to displace-ment of the focussing spot, and an optical light-weight element capable of displacement parallel to its optical axis at high velocity and with low amplitude, giving rise to a small displace-ment of the focussing spot. The corresponding displacements are respectively under the control of the low-frequency and high-frequency components of an error signal characteristic of the error interval between the focussing spot and the spot projected on to the data carrier.
The present invention relates to an optical read-out device for reading data carrier, comprising an optical reading head capable of displacement parallel to its optical axis at low velocity and with high amplitude, giving rise to displace-ment of the focussing spot, and an optical light-weight element capable of displacement parallel to its optical axis at high velocity and with low amplitude, giving rise to a small displace-ment of the focussing spot. The corresponding displacements are respectively under the control of the low-frequency and high-frequency components of an error signal characteristic of the error interval between the focussing spot and the spot projected on to the data carrier.
Description
133~
The present invention relates to -the optical xead-out of information recorded in a track carried by a moving data carrier in the form of disc o~ tape, and relates more particularly to an optical focussing read-out device.
The optical read-out of information recorded at high density, poses the problem of accurate focussing o~ the light beam on the track which latter has to be illuminated by a spot o very small dimensions.
It is well known to make the displacement of an element of the optical read-out device, with which element the vertical displacement of the focussing spot is associated, ` subject to an error signal characteristic of the vertical deviation between the track and the focussing spots. Optical ; readers of this kind make it possible to control the displace-ment of the focussing spot in accordance with slow variations in said error; however, their speed is too slow to compensate for spot de~ects when the error varies rapidly.
According to the invention, there is provided an optical read-out device adapted ~or reading data recorded along a track carried by a moving data carrier, said optical read-out device comprising an optical reading head having an optical axis and comprising a first and a second optical element which can be displaced along said optical axis, said reading head being adapted for projecting read-out radiation onto said track and for focussing said radiation at a focussing spot which is displaced by displacements of said first and second optical elements, said read out device ~urther comprising detection means adapted for detecting read out radiation emexging from said data carrier and for delivering an error signal representing distance between said focussing spot and said track, filtering means receiving said error signal and furnishing ~ first and a second control signal having - , .
IL33~
frequencies respectively lower and higher than a limiting frequency, and first and second displacement devices,adapted for respectively receiving said first and said second control signals, for respectively controlling said displacements of said first and second optical elements.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will be made to the following description and the attached drawing among which:
Fig. 1 illustrate a first embodiment of an optical read-out device in accordance with the invention;
Figs. 2, 3 and 4 illustrate variant embodiments of the optical reading head included in optical Lead-out device in accordance with the invention.
In Fig. 1, which represents a catGptric optical reader designed to read-out a track carried by a data carrier, by transmitting a read-out light beam, the beam 1 coming from a coherent light source is received by a mirror 2, the center of which, is located upon the optical axis of the beam 1. The mirror
The present invention relates to -the optical xead-out of information recorded in a track carried by a moving data carrier in the form of disc o~ tape, and relates more particularly to an optical focussing read-out device.
The optical read-out of information recorded at high density, poses the problem of accurate focussing o~ the light beam on the track which latter has to be illuminated by a spot o very small dimensions.
It is well known to make the displacement of an element of the optical read-out device, with which element the vertical displacement of the focussing spot is associated, ` subject to an error signal characteristic of the vertical deviation between the track and the focussing spots. Optical ; readers of this kind make it possible to control the displace-ment of the focussing spot in accordance with slow variations in said error; however, their speed is too slow to compensate for spot de~ects when the error varies rapidly.
According to the invention, there is provided an optical read-out device adapted ~or reading data recorded along a track carried by a moving data carrier, said optical read-out device comprising an optical reading head having an optical axis and comprising a first and a second optical element which can be displaced along said optical axis, said reading head being adapted for projecting read-out radiation onto said track and for focussing said radiation at a focussing spot which is displaced by displacements of said first and second optical elements, said read out device ~urther comprising detection means adapted for detecting read out radiation emexging from said data carrier and for delivering an error signal representing distance between said focussing spot and said track, filtering means receiving said error signal and furnishing ~ first and a second control signal having - , .
IL33~
frequencies respectively lower and higher than a limiting frequency, and first and second displacement devices,adapted for respectively receiving said first and said second control signals, for respectively controlling said displacements of said first and second optical elements.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will be made to the following description and the attached drawing among which:
Fig. 1 illustrate a first embodiment of an optical read-out device in accordance with the invention;
Figs. 2, 3 and 4 illustrate variant embodiments of the optical reading head included in optical Lead-out device in accordance with the invention.
In Fig. 1, which represents a catGptric optical reader designed to read-out a track carried by a data carrier, by transmitting a read-out light beam, the beam 1 coming from a coherent light source is received by a mirror 2, the center of which, is located upon the optical axis of the beam 1. The mirror
2, which is of low weight, can be displaced by means of a piezoelectric element 3 to which it is attached, the piezo-electric element being capable of developing vibrations under the control of an alternating electrical signal of high frequency which causes the mirror 2 to perform rapid movements of low amplitude, less than some tens of mlcrons. The light rays received by the mirror 2 are reflected towards a mlrror 4 containing a circular orifice to pass the incident beam 1.
The mirror 4, also centered on the optical axis of the beam 1, ~ reflects the light rays which it receives~ The radii of curva-- 30 ture of the mirrors 2 and 4 are such that in the rest sta~e, the rays reflected by the mirror 4 converge at a point 0 upon the optical axis of the incident beam 1. The data carrier 6, - ~ .
L331~
carrying the track 7, is arranged in such a fashion that at ~he time of origin, the point 0 is located on the track 7.
The mirror 4 is attached to a mounting 5. The radiation diffracted by the track 7 and transmitted by the data carrier 6 is picked up ~y two photoelectric detectors 8 and 9 arranged symmetrically in relation to the optical axis of the system, one in front of said axis in the direction of motion of the track, the other behind said axis~
Known devices make it possible, from electrical signals furnished by these two detectors, to obtain a focussing error signal which is characteristic of the interval between the focussing spot 0 of the beam and the track being read out.
Such a device is for example a phase comparator 10.
The Eocussing error signal is applied to filters 11 and 12, the first being a low-pass filter whose cut-off frequency if fc and the other being a high-pass filter whose cut-off frequency is equal to that of the filter 11, namely fc~ The output signal from the filter 11 therefore represents the slow variations in the focussing error whilst the output signal from the filter 12 represents the rapid variations therein. The first is applied to an electrodynamic coil 13 and the second to the piezoelectric crystal 3. The common frequency fc to the bands of the two filters 11 and 12, is imposed by the dynamic range of the slow device and the phase-shift in said device at the corresponding frequency. It may be of the order of 150 Hz for example.
The range of the fast control is deliberately restricted to a zone which does not include the saturation zone, so that said control reacts rapidly when the amplitude of the control signal comes into the pull in range of the system.
Thus, for displacements of the focussing spot which take place at ~igh frequency, this corresponding to substantial L3~
acceleration, only a light-weight optical element is displaced.
This device ma~es it possible also to reduce the acoustic noise generated by the displacement of a substantial volume within the range of the audible frequencies spectrum.
This optical device, as also the devices described hereinafter, is designed for a pair of well-defined object and image points. The displacements of one or more elements of the device introduce aberrations which impair the readout spot. This device must therefore be a high-grade device, and limited by diffraction. The introduction of small aberrations, the displacements always being less than some few tenths of a millimetre, has the effect of reducing the intensity of the radiation at the center of the diffraction spot and of increasing the intensity of the diffraction rings. It is reasonable to assume that the ~iffraction spot is not too severely distorted by the aberratlons if the intensity at the spot center experi--ences a drop of less than 20 % of the maximum intensity.
The elements of the optical device are therefore designed so that the focussing spot is of "good" quality within a ~olume determined by the variations in the vertical positioning of the data carrier and by the deformation of the data carrier tra~ks.
In practice, the output signals from the filters ll and 12 are amplified so that the voltages respectively applied to the electrodynamic coil and to the piezoelectric element give rise to a resultant displacement compensating for that measured by means of the error signal. Thus, the voltages to be applied to the piezoelectric element are of the order of several -; ; h~ndreds of volts for a displacement of some few microns.
Fig. 2 illustrates the optical section of a dioptric optical reader in accordance with the invention.
Similar elements are designated by similar references ~7~33~
in all the figures.
The light beam 1 is focussed at a point 0 upon a track 7 carried by a data carrier 6, using a read-out head comprising a convergent lens 1~, a second convergent lens 15, a convergent meniscus 16 and a second meniscus 17.
The elements 14, 16 and 17 are secured to a frame 18 capable oE being displaced a-t low frequencies parallel to the optical axis o-~ the system, by rneans of an electrodynamic device such as that shown in E`ig. 1.
10~lhe convergent lens 15 is also carried by the mounting 18 but it can displaced parallel to the optical axis of the system relatively to said mounting. To do this, an annular piezoelectric element 19 is secured to -the lens 15 in order to cause -the latter to follow its own motion when an electrical signal is applied to it.
When the frame and the lens 15 displace together, the ; resultant displacement as ar as the focussing spot is concerned, is equal to the resultant of the displacements due respectively to the displacement of the frame and that of the lens 15. It is well k~own that for an optical device having a transverse magnification of G - ~ , where p is the distance of the object from the center of the lens and p' the image interval, the corresponding axial magniEication for a pair of object and image points is equal to G2. Since the radiation source is fixed~
if the optical device is displaced along its optical axis by ~x, the corresponding displacement of the image point will be equal to ~x - ~x/G2.
~ he assembly o~ the optical device described herein-before, can be split down into two elements, the first having a magnification G' which is high, and being constituted by the assembly of the read-out head with the exception of the low-weight element 15, this giving an lmage point I, and the other, . --- ~ --~73L33~
the lens 15, having a magnific~tion G' which is less than unity. A displacement a x of the frame 18, gives rise to a displacement d in the image point I by the first element, sub- -stantially equal to ~ x. The low-weight element also being displaced by ~ x since it is attached to the frame, the relative distant between the image point I~ this bein~ the object as far as the lens 15 is concerned, and the center of said lens is constant in the absence of any displacement of the lens, and the corresponding displacement of the focussiny spot is substantially equal to Qx since ~ x/G2 is negligible. If, in addition, the lens 15 is simulkaneously displaced by ~x', the corresponding displacement of the focussing spot 0 will be sub-stantially equal to ~X2 , ~x' being negligible. The displace-ment which is the ~esultant of the two simultaneous displacements is therefore substantially equal to d = ~ x ~ ~ 2 G' being considered as constant within the range of variations. ~ x can reach some tenths of a millimetre and ~ 2 is limited to some G' tens of microns as indicated earlier, so that the focussing spot retains good quality Fi~. 3 illustrates the optical section of a catadiop-tric optical reader in accordance with the invention.
The read-out light beam 1 is focussed at the point 0 on the track 7 carried by the data carri.er 6, by means of an optical device comprising a splitter plate 20, a convergent lens 21 and a~light.-weight mirror 22 which reflects the incident radiationl the reflected radiation which passes back through the convergent lens 21 and the splitter plate 20, being focussed .~ : at O by an objective lens 23.
The mirror 22 is secured to a piezoelectric element .
.
24 capable of performing low-amplitude displacements along the . optical axis of the system.
The mounting for the piezoelectric element, the lens : .
. ~ _ 7 _ :
. . .
21, the spitter pla~e 20 and the objective lens 23 are assembled in a frame 25 capable oE displacement at low frequenciec parallel to the optical axis of the beam reflected by the mirror 22, this, for example, with the help of an electrodynamic system such as that shown in Fig. 1.
'rhe displacement ~x of this frame gives rise to a displacement ~x on the part of the focussing spot 0. A
displacement ~x' on the part of the mirror 22, which may be a flat mirror or a spherical mirror, gives rise to a displace-ment of 0 which is a function of the focal lengths of the lens21 and the objective lens 23. In other words, the displacement of this mirror corresponds to the displacement of an object, which is the spot formed upon the mirror, relatively to said two lenses. This displacement is equal to K ~ x' where K is a constant which is a function of the local lengths. The resultant displacement of the focal spot 0 is a x ~ K a x~. :
In Fig~ 4, the optical section of an optical reader in accordance with the invention has been shown, in which the high frequency displacement of the focussing spot is pxoduced by varying the convergence of a dioptric element of the optical device.
The light beam 1 is focussed at 0 on the track 7 carried by a data carrier 6, using two lenses 26 and 27 and a read-out objecti~e lens 28 capable of being displaced at low ; frequencies. The two lenses 26 and 27 are arranged in a zone in which the read-out beam has a small diameter, and the interval between them e, is capable of variation by means of an annular - piezoelectric element 29 attached to the lens 27.
This piezoelectric element is excited by the high frequency electrical signal obtained from the focussing error signal. The low frequency displacement of the objective lens 28 produ~es a substantially identical displacement of the focal : ' ' ; :-~3~33~
spot since the magnification of the objective lens 28 i~ high.
A variation ~e in the interval between the two lenses 26 and 27 is equivalent to a displacement on the part of the virt,ual object point in the case of the read-out objective lens 28, and gives rise to a displacement ~ x' on the par-t oE the focussing spot. The beam incident upon the ob]ective lens 28 has a narrow angle so that the axial magnifi~ation ( _~_ ,)2 is high, and it is -therefore necessary that a small variation in th,e interval e between the two lenses should give rise to a large displacement in the virtual object, the latter being the source of the incident beam upon the objective lens 28, so that the displacement a x~
of the focussing spot is perceptibleO
The invention is not limited to the embodiments described and illustrated. In particular, the high Erequency movement in order to displace the light-weight element, can be ~' achieved by means of a small high-speed electrodynamic system replacing the piezoelectric element.
Moreover, any optical read-out head capable of being displaced slowly and comprising an optical element which can be displaced rapidly, or to which it is possible to add an ; optical element capable of rapid displacement, can be used to ,~ form the optical device in the controlled variable focus optical reader in accordance with the invention.
, Finally, the optical readers illustrated have been applied to the read-out~oE data carriers which are read by ~
transmission. ~' This illustration is by no means limitative of the , scope of the invention and the various embodiments of the optical~reader in accordance with the invention can be applied ,~ .
~ ~ 30 to the read-out of data carriers which are read by reflexion. '
The mirror 4, also centered on the optical axis of the beam 1, ~ reflects the light rays which it receives~ The radii of curva-- 30 ture of the mirrors 2 and 4 are such that in the rest sta~e, the rays reflected by the mirror 4 converge at a point 0 upon the optical axis of the incident beam 1. The data carrier 6, - ~ .
L331~
carrying the track 7, is arranged in such a fashion that at ~he time of origin, the point 0 is located on the track 7.
The mirror 4 is attached to a mounting 5. The radiation diffracted by the track 7 and transmitted by the data carrier 6 is picked up ~y two photoelectric detectors 8 and 9 arranged symmetrically in relation to the optical axis of the system, one in front of said axis in the direction of motion of the track, the other behind said axis~
Known devices make it possible, from electrical signals furnished by these two detectors, to obtain a focussing error signal which is characteristic of the interval between the focussing spot 0 of the beam and the track being read out.
Such a device is for example a phase comparator 10.
The Eocussing error signal is applied to filters 11 and 12, the first being a low-pass filter whose cut-off frequency if fc and the other being a high-pass filter whose cut-off frequency is equal to that of the filter 11, namely fc~ The output signal from the filter 11 therefore represents the slow variations in the focussing error whilst the output signal from the filter 12 represents the rapid variations therein. The first is applied to an electrodynamic coil 13 and the second to the piezoelectric crystal 3. The common frequency fc to the bands of the two filters 11 and 12, is imposed by the dynamic range of the slow device and the phase-shift in said device at the corresponding frequency. It may be of the order of 150 Hz for example.
The range of the fast control is deliberately restricted to a zone which does not include the saturation zone, so that said control reacts rapidly when the amplitude of the control signal comes into the pull in range of the system.
Thus, for displacements of the focussing spot which take place at ~igh frequency, this corresponding to substantial L3~
acceleration, only a light-weight optical element is displaced.
This device ma~es it possible also to reduce the acoustic noise generated by the displacement of a substantial volume within the range of the audible frequencies spectrum.
This optical device, as also the devices described hereinafter, is designed for a pair of well-defined object and image points. The displacements of one or more elements of the device introduce aberrations which impair the readout spot. This device must therefore be a high-grade device, and limited by diffraction. The introduction of small aberrations, the displacements always being less than some few tenths of a millimetre, has the effect of reducing the intensity of the radiation at the center of the diffraction spot and of increasing the intensity of the diffraction rings. It is reasonable to assume that the ~iffraction spot is not too severely distorted by the aberratlons if the intensity at the spot center experi--ences a drop of less than 20 % of the maximum intensity.
The elements of the optical device are therefore designed so that the focussing spot is of "good" quality within a ~olume determined by the variations in the vertical positioning of the data carrier and by the deformation of the data carrier tra~ks.
In practice, the output signals from the filters ll and 12 are amplified so that the voltages respectively applied to the electrodynamic coil and to the piezoelectric element give rise to a resultant displacement compensating for that measured by means of the error signal. Thus, the voltages to be applied to the piezoelectric element are of the order of several -; ; h~ndreds of volts for a displacement of some few microns.
Fig. 2 illustrates the optical section of a dioptric optical reader in accordance with the invention.
Similar elements are designated by similar references ~7~33~
in all the figures.
The light beam 1 is focussed at a point 0 upon a track 7 carried by a data carrier 6, using a read-out head comprising a convergent lens 1~, a second convergent lens 15, a convergent meniscus 16 and a second meniscus 17.
The elements 14, 16 and 17 are secured to a frame 18 capable oE being displaced a-t low frequencies parallel to the optical axis o-~ the system, by rneans of an electrodynamic device such as that shown in E`ig. 1.
10~lhe convergent lens 15 is also carried by the mounting 18 but it can displaced parallel to the optical axis of the system relatively to said mounting. To do this, an annular piezoelectric element 19 is secured to -the lens 15 in order to cause -the latter to follow its own motion when an electrical signal is applied to it.
When the frame and the lens 15 displace together, the ; resultant displacement as ar as the focussing spot is concerned, is equal to the resultant of the displacements due respectively to the displacement of the frame and that of the lens 15. It is well k~own that for an optical device having a transverse magnification of G - ~ , where p is the distance of the object from the center of the lens and p' the image interval, the corresponding axial magniEication for a pair of object and image points is equal to G2. Since the radiation source is fixed~
if the optical device is displaced along its optical axis by ~x, the corresponding displacement of the image point will be equal to ~x - ~x/G2.
~ he assembly o~ the optical device described herein-before, can be split down into two elements, the first having a magnification G' which is high, and being constituted by the assembly of the read-out head with the exception of the low-weight element 15, this giving an lmage point I, and the other, . --- ~ --~73L33~
the lens 15, having a magnific~tion G' which is less than unity. A displacement a x of the frame 18, gives rise to a displacement d in the image point I by the first element, sub- -stantially equal to ~ x. The low-weight element also being displaced by ~ x since it is attached to the frame, the relative distant between the image point I~ this bein~ the object as far as the lens 15 is concerned, and the center of said lens is constant in the absence of any displacement of the lens, and the corresponding displacement of the focussiny spot is substantially equal to Qx since ~ x/G2 is negligible. If, in addition, the lens 15 is simulkaneously displaced by ~x', the corresponding displacement of the focussing spot 0 will be sub-stantially equal to ~X2 , ~x' being negligible. The displace-ment which is the ~esultant of the two simultaneous displacements is therefore substantially equal to d = ~ x ~ ~ 2 G' being considered as constant within the range of variations. ~ x can reach some tenths of a millimetre and ~ 2 is limited to some G' tens of microns as indicated earlier, so that the focussing spot retains good quality Fi~. 3 illustrates the optical section of a catadiop-tric optical reader in accordance with the invention.
The read-out light beam 1 is focussed at the point 0 on the track 7 carried by the data carri.er 6, by means of an optical device comprising a splitter plate 20, a convergent lens 21 and a~light.-weight mirror 22 which reflects the incident radiationl the reflected radiation which passes back through the convergent lens 21 and the splitter plate 20, being focussed .~ : at O by an objective lens 23.
The mirror 22 is secured to a piezoelectric element .
.
24 capable of performing low-amplitude displacements along the . optical axis of the system.
The mounting for the piezoelectric element, the lens : .
. ~ _ 7 _ :
. . .
21, the spitter pla~e 20 and the objective lens 23 are assembled in a frame 25 capable oE displacement at low frequenciec parallel to the optical axis of the beam reflected by the mirror 22, this, for example, with the help of an electrodynamic system such as that shown in Fig. 1.
'rhe displacement ~x of this frame gives rise to a displacement ~x on the part of the focussing spot 0. A
displacement ~x' on the part of the mirror 22, which may be a flat mirror or a spherical mirror, gives rise to a displace-ment of 0 which is a function of the focal lengths of the lens21 and the objective lens 23. In other words, the displacement of this mirror corresponds to the displacement of an object, which is the spot formed upon the mirror, relatively to said two lenses. This displacement is equal to K ~ x' where K is a constant which is a function of the local lengths. The resultant displacement of the focal spot 0 is a x ~ K a x~. :
In Fig~ 4, the optical section of an optical reader in accordance with the invention has been shown, in which the high frequency displacement of the focussing spot is pxoduced by varying the convergence of a dioptric element of the optical device.
The light beam 1 is focussed at 0 on the track 7 carried by a data carrier 6, using two lenses 26 and 27 and a read-out objecti~e lens 28 capable of being displaced at low ; frequencies. The two lenses 26 and 27 are arranged in a zone in which the read-out beam has a small diameter, and the interval between them e, is capable of variation by means of an annular - piezoelectric element 29 attached to the lens 27.
This piezoelectric element is excited by the high frequency electrical signal obtained from the focussing error signal. The low frequency displacement of the objective lens 28 produ~es a substantially identical displacement of the focal : ' ' ; :-~3~33~
spot since the magnification of the objective lens 28 i~ high.
A variation ~e in the interval between the two lenses 26 and 27 is equivalent to a displacement on the part of the virt,ual object point in the case of the read-out objective lens 28, and gives rise to a displacement ~ x' on the par-t oE the focussing spot. The beam incident upon the ob]ective lens 28 has a narrow angle so that the axial magnifi~ation ( _~_ ,)2 is high, and it is -therefore necessary that a small variation in th,e interval e between the two lenses should give rise to a large displacement in the virtual object, the latter being the source of the incident beam upon the objective lens 28, so that the displacement a x~
of the focussing spot is perceptibleO
The invention is not limited to the embodiments described and illustrated. In particular, the high Erequency movement in order to displace the light-weight element, can be ~' achieved by means of a small high-speed electrodynamic system replacing the piezoelectric element.
Moreover, any optical read-out head capable of being displaced slowly and comprising an optical element which can be displaced rapidly, or to which it is possible to add an ; optical element capable of rapid displacement, can be used to ,~ form the optical device in the controlled variable focus optical reader in accordance with the invention.
, Finally, the optical readers illustrated have been applied to the read-out~oE data carriers which are read by ~
transmission. ~' This illustration is by no means limitative of the , scope of the invention and the various embodiments of the optical~reader in accordance with the invention can be applied ,~ .
~ ~ 30 to the read-out of data carriers which are read by reflexion. '
Claims (8)
1. An optical read-out device adapted for reading data recorded along a track carried by a moving data carrier, said optical read-out device comprising an optical reading head having an optical axis and comprising a first and a second optical element which can be displaced along said optical axis, said reading head being adapted for projecting read-out radiation onto said track and for focussing said radiation at a focussing spot which is displaced by displacements of said first and second optical elements, said read-out device further comprising detection means adapted for detecting read out radiation emerging from said data carrier and for delivering an error signal representing distance between said focussing spot and said track, filtering means receiving said error signal and furnish-ing a first and a second control signal having frequencies respectively lower and higher than a limiting frequency and first and second displacement devices, adapted for respectively receiving said first and said second control signals, for respectively controlling said displacements of said first and second optical elements.
2. An optical read-out device as claimed in claim 1, wherein said first optical element is said optical reading head itself, said second element being a light-weight component part of said reading head.
3. An optical read-out device as claimed in claim 1, wherein said first element is said optical reading head itself, with the exception of one of its component parts which can be displaced in an independent fashion and which constitutes said second optical element.
4. An optical read-out device as claimed in claim 1, wherein said displacement devices are electrodynamic systems.
5. An optical read-out device as claimed in claim 1, wherein said first displacement device is an electrodynamic system and said second displacement device is a piozoelectric element rixed to said second optical element producing the displacement of said second optical element.
6. An optical read-out device as claimed in claim 5 wherein said filtering means are two filters having the same cut-off frequency equal to said limiting frequency, the first being a low-pass filter and furnishing said first signal to said first displacement device, and the second being a filter which passes the frequencies which are higher than the limiting frequency and fursnishes said second signal to said second displacement device.
7. An optical read-out device as claimed in claim 6, wherein, said data carrier being adapted for read-out by transmission, said detection means detect the radiation trans-mitted by said data carrier.
8. An optical read-out device as claimed in claim 6, wherein, said data carrier being adapted for read out by reflection, said detection means detect the radiation reflected by said data carrier.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7513620A FR2309888A1 (en) | 1975-04-30 | 1975-04-30 | OPTICAL PROJECTION DEVICE AND OPTICAL READER INCLUDING SUCH A DEVICE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071330A true CA1071330A (en) | 1980-02-05 |
Family
ID=9154695
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,476A Expired CA1071330A (en) | 1975-04-30 | 1976-04-29 | Optical focussing read-out device |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5931776B2 (en) |
| CA (1) | CA1071330A (en) |
| DE (1) | DE2619232A1 (en) |
| FR (1) | FR2309888A1 (en) |
| GB (1) | GB1541596A (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4302830A (en) * | 1978-05-10 | 1981-11-24 | Olympus Optical Company Ltd. | Optical information reading-out apparatus |
| NL8003729A (en) * | 1980-06-27 | 1982-01-18 | Philips Nv | DEVICE FOR OPTICAL FOCUSING. |
| NL8004969A (en) * | 1980-09-02 | 1982-04-01 | Philips Nv | DEVICE FOR OPTICAL FOCUSING. |
| DE3039425A1 (en) * | 1980-10-18 | 1982-05-19 | Ernst Leitz Wetzlar Gmbh, 6330 Wetzlar | DEVICE FOR PHOTOELECTRICALLY DETERMINING THE POSITION OF AT LEAST ONE FOCUS OF AN IMAGE |
| JPS59168835U (en) * | 1983-04-27 | 1984-11-12 | パイオニア株式会社 | Optical recording information reading device |
| JPS6022743A (en) * | 1984-04-24 | 1985-02-05 | Olympus Optical Co Ltd | Pickup for disk reproducer containing information recorded optically |
| DE3544771A1 (en) * | 1985-12-18 | 1987-06-19 | Messerschmitt Boelkow Blohm | Method and device for imaging an object on a detector having radiation-sensitive regions separated from one another by dead spaces |
| JPS62163978U (en) * | 1986-04-08 | 1987-10-17 | ||
| US4835380A (en) * | 1987-06-11 | 1989-05-30 | U. S. Philips Corporation | Scanning device for an optical recording and/or reproducing apparatus |
| JP2676371B2 (en) * | 1988-07-04 | 1997-11-12 | パイオニア株式会社 | Pickup height adjuster |
| NL8803055A (en) * | 1988-12-13 | 1990-07-02 | Philips Nv | OPTICAL SCANNER, MIRROR-LIKE SUITABLE FOR APPLICATION THEREIN, AND OPTICAL REGISTER AND / OR READER EQUIPPED WITH THIS SCANNER. |
| NL8803048A (en) * | 1988-12-13 | 1990-07-02 | Philips Nv | OPTICAL SCANNING DEVICE, MIRROR-LIKE SUITABLE FOR USE THEREIN, AND OPTICAL ENTRY AND / OR READING EQUIPMENT PROVIDED WITH THE SCANNING DEVICE. |
| DE4213556C2 (en) * | 1992-04-24 | 1994-04-28 | Max Planck Gesellschaft | Device for the optical scanning of a record carrier, in particular a phosphor storage disk |
| CN109782962A (en) * | 2018-12-11 | 2019-05-21 | 中国科学院深圳先进技术研究院 | A kind of projection interactive method, device, system and terminal device |
-
1975
- 1975-04-30 FR FR7513620A patent/FR2309888A1/en active Granted
-
1976
- 1976-04-26 JP JP51047616A patent/JPS5931776B2/en not_active Expired
- 1976-04-27 GB GB1711576A patent/GB1541596A/en not_active Expired
- 1976-04-29 CA CA251,476A patent/CA1071330A/en not_active Expired
- 1976-04-30 DE DE19762619232 patent/DE2619232A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| DE2619232A1 (en) | 1976-11-11 |
| JPS5931776B2 (en) | 1984-08-04 |
| FR2309888B1 (en) | 1977-11-10 |
| GB1541596A (en) | 1979-03-07 |
| JPS51134604A (en) | 1976-11-22 |
| FR2309888A1 (en) | 1976-11-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |