CA1125552A

CA1125552A - Image projection system

Info

Publication number: CA1125552A
Application number: CA349,693A
Authority: CA
Inventors: Friedbert Freitag; Walter Gutmann; Wilfried Hofmann; Traugott Liermann
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert AG
Priority date: 1979-04-17
Filing date: 1980-04-11
Publication date: 1982-06-15
Also published as: AT367553B; JPS55143569A; ATA185480A; EP0017904A1; DE2915512A1; EP0017904B1

Abstract

ABSTRACT OF THE DISCLOSURE

A projection system includes a pair of deflecting mirrors fixedly arranged on a support at right angles to each other for deflecting a light beam from an original on a light receiving surface. The support is pivotable at the point of intersection of the mirrors and is moved synchronously with the motion of the light receiving surface in a plane parallel to the original, and simultaneously is rotated about its pivot point so that the light beam always impinges on the light receiv-ing surface at right angles.

Description

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This invention relates to a projection system for scanning an original and for selectively projecting it onto a projection surface.
From the U.S.P.S. 3,663,101 a film prolection system is known for directing an image through a rotatable reflecting mir-ror and a projecting lens in selective paths. In the one path, an original, such as a microfilm is scanned by the rotatable mirror which is supported between the microfilm and the projecting lens and is reproduced on a rotatable drum of an electrophotographic copying device through the projecting lens and a further reflec-ting mirror. The other path is used to project the original onto a screen. Since the projecting beam impinges the copying drum at a right angle, it is necessary to provide the scanning angle also at a right angle in order to prevent distortions of the copied image. Consequently, it is proposed to arrange the microfilm in a curved manner around the pivotal axis of the mirror within the exposure area so that the scanning beam impinges the original at a right angle.
Although the reproduced images are developed in a dis-tortion-free manner, the principle according to the U.S.P.S.
3,663,101 is circumstantial due to the requirement of curving the original in the area of the scanning beam. Moreover, this re-quirement creates a considerable limitation of the apparatus since for example the use of microfiche tables of conventional type as employed in microfiche readers are foreclosed.
Accordingly, it is a general object of the invention to overcome the difficulty of the prior art.
More particularly, it is an object of the present in-vention to provide a projection system in which an original is arranged in a planar manner and a distortion-free projected image .~

ll~S~52 of the original is ob-tained nevertheless.
A concomi-tant object of the present invention is to provide a projection system which is simple in construction, reliable in operation and inexpensive to manufacture never-theless.
In keeping with these objects, and with others which will become apparent hereafter, one feature of the invention re-sides, briefly stated, in a projection system having a light source emitting a projecting course of beam and a stationary projecting lens wherein a stationary original is optically scanned in stripes and projected on a light receiving surface movable past a stationary exposure area, the system comprising means for reflecting the projected course of beam from the projecting lens to the light receiving surface, and means for removing the reflecting means synchronically to the light receiv-ing surface in a direction parallel to the original wherein the light receiving surface has a tangent plane parallel to the plane of the original.
According to a further feature of the invention, the reflecting means consists of two reflecting mirrors mounted on a reflector support wherein the mirrors are arranged at a right angle to each other and thus are reflecting the projecting beam twice from the projecting lens to the light receiving surface.
Therefore, the original is projected in a distortion-free manner onto the light receiving surface like for example on a rotatable drum wherein the reflector support is movable synchronically in linear direction with the rotatable drum. Thus a rotational movement of the mirror is synchronism wi-th the movement of the light receiving surface is avoided since the reflector support is carrying out a linear scanning movement. Consequently, it is ll'~S~ti~

preferable to couple the means for moving the reflector support with the movement of the light receiving surface.
According to yet another feature of the invention, the reflector support is pivotable around an axis which is the inter-section of the respective mirror planes and moreover, is connected to guide means to support the pivotal movement of the reflecting mirrors around -the axis. Therefore, it is possible to adapt the reflector support to each structural arrangement there-by achieving an especially compact device.
In comparison to copying devices having only one re-adjusting mirror, the copying device according to the invention has the advantage that no distortion occurs and a constant depth of focus is achieved. Consequently, the diaphragm of the imaging optics can have a larger aperture so that a better using of the present light intensity is possible.
Furthermore, the projection system is independent from different image scales and is suitable for using a rotating prism.
A further advantage of the projection system according to the invention is that the projection of the scanned original is not influenced by the movement of the reflecting mirrors around the pivoted axis. Therefore, vibrations of the reflecting mirrors do not have any negative impact on the sharpness of the original to be projected.
Yet another feature of the invention is that the pro-jection system consists of a projection copying device and a microfilm reader. Through the provision of the reflector support according to the invention, the micrographs can be supported in a plane manner so that a use of microfilm readers is possible having conventional and interchangeable platforms for different sizes of microfiche or microfilm. Accordingly, there is arranged a pivot-ll~SS5,'<;:

able surface mirror between the two reflecting mirrors for de-flecting the projecting course of beam onto a screen. This arrangement is especially of advantage since it requires only a limited amount of space.
Still another feature of the invention is the provision of a curtain which is connected to the surface mirror for shield-ing the interior of the system against the ambient light and for preventing the projecting light from being emitted outwardly through the screen during the copying process.
The novel features which are considered as character-istic for the invention are set forth in particular in the ap-pended claims. The invention itself, however, both as to its construction and to its method of operation, together with addi-tional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
FIG. 1 is a schematic illustration of a projection system according to the invention having a movable reflector support:
FIG. 2 iS a longitudinal cross-section showing a major part of projection system wherein the reading position is depic-ted; and FIGS. 3 and 4 are sectional views of the projection system according to FIG. 2, depicting respective copying positions of the reflector support.
Referring firstly to FIG. 1, there is shown a copyboard 1 containing for example a microfilm or microfiche which can be positioned manually or mechanically in a known manner relative to a projecting beam 2. The micrograph 1 to be projected is illu-minated by a light source 3 wherein the light rays pass a first ll'~SSt~2 condenser lens 4 directly ahead of the light source 3 and a sur-face mirror 6 which deflects the light rays so as to pass a sec-ond condenser lens 5 arranged at a right angle to the first con-denser lens 4. The light rays consequently impinging the micro-graph 1 pass through a projecting lens 12 which is projecting the beam 2 onto a copy drum 8 by means of a reflecting mirror 7. The reflecting mirror 7 has two planes which are arranged at a right angle to each other so that the course of beam 2 is reflected twice until impingings on the light receiving surface of the drum 8 which is rotating in direction of arrow A. The reflecting mirror 7 is moved in the direction of arrow B synchronously with the rotational speed of the drum 8. In order to achieve that only a strip-shaped area of the scanned micrograph is projected on the light receiving surface, the drum 8 has an exposure area 11 which is defined by a light shield 9 having a slot aperture.
As already mentioned, the reflecting mirror 7 is mov-able in direction of the arrow B along a motion path 10 when the drum is rotating, and the micrograph 1 has a plane which is parallel to the tangent plane of the rotatable drum in the ex-posure area 11. The sliding speed of the reflecting mirror 7 along the motion path 10 is half the rotational speed of the photosensitive surface of the copying drum 8. By moving the reflecting mirror 7 synchronously relative to the copying drum 8 between two end positions, the entire micrograph 1 to be projected is scanned in strips and projected onto the copying drum 8 in the same manner, i.e., in form of successive strips.
As can be seen by dotted lines, the reflecting mirror 7 can be pivoted around an axis which is the intersection of the mirror planes. The projecting beam 2 is, however, not influenced when pivoting the mirror. The total length as well as the posi-ll~ZS55Z

tion of the projecting beam which is twice reflected, remain un-changed.
Turning now to FIG. 2, there is shown a microfilm reader and copying apparatus having a lower housing portion 12 in which a copying unit is incorporated. The eopying unit is pro-vided with a photosensitive copy drum 21 which is mounted on a shaft to rotate in the direction indeated by arrow B, to cause the drum surface sequentially to pass a plurality of processing stations.
At first, the surface of the drum 21 is applied with an electrostatic charge by a corona charging device 34 extending transversely across the drum surface. After being applied with the electrostatic charge, the surface is subjected to an exposure station in its path of motion through which a copy image is pro-jected onto the drum surfaee from the stationary original, i.e., the mierograph, by an illumination assembly whieh is arranged in a desk-like housing portion 20a. The desk portion 20a projeets from the lower portion 20 in direetion to an operator. The il-lumination assembly is provided with a light souree 38 behind whieh a eoneave shaped refleetor 39 is disposed for reflecting light rays emitting rearwardly also in direction to a first con-denser lens 14 located ahead of the light source 38. The light rays are then passing a heat protection glass 42 and are imping-ing a deflecting mirror 43. Through the deflecting mirror 43, the light rays are deflected so as to impinge on the micrograph 37. A second condenser 41 is additionally arranged in the projecting course of beam between the deflecting surface mirror 43 and the micrograph 37. The beam 50 is then projected onto the drum surface in a manner described further below.
In order to protect the drum 21 from extraneous llght, 11~555;~

a light shield 35 is arranged having a slot aperture through which an exposure area 36 is defined. The exposure area 36 ex-tends parallel to the axis of the copying drum 21. Adjacent to the exposure area 36 is a developing station 22 in which the charge image located on the drum surface is developed by depos-iting toner particles on the drum to form a powder image.
Next subsequent thereto is the image transfer station which includes a corona transfer device 26 extending transversely across the drum surface. In the area of the corona transfer de-vice 26, the charge image is transferred on a transfer material, fed from a sheet feeding mechanism onto the rotating drum 21 in copying tact. The sheet feeding mechanism includes a sheet pile 25 in which a plurality of copying sheets are located in super-posing manner. The top sheet is in contact with a separating roller 23 through which the top sheet is taken and fed to the drum surface via a pair of feed rollers 24.
In the path of motion, a pick-off device 27 is arranged adjacent to the corona transfer device 26 for facilitating the removal of the transfer material from the drum 21. Consequently, the transfer material provided with the powder image is directed onto an endless conveyor 28 and subsequently to a fixing device 29 via which the developed and transferred powder image is fused on the sheet.
After fusing has taken place, the finished copy is gui-ded between a pair of discharging rollers 30 by which the copy is discharged into a bin 31.
Behind the pick-off device 27, in the path of motion of the drum as indicated by the arrow B, is a corona cleaning device 32 and subsequently a cleaning unit 33 for cleaning the drum sur-face by removing residual toner particles therefrom.

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As can be seen from FIG. 2, there is shown a microfiche platform 44 on the top side of the desk portion 20a which plat-form is provided with two transparent plates carrying the micro-fiche 37 in between. The pla-tform 44 is supported in a known manner for being movable in two axes. Above the platform 44 is a projecting lens 45 which is preferably supported in a floating manner. The projecting lens 45 projects the micrograph 37 onto a projection surface 49 by means of a pair of deflecting surface mirrors 47, 48 arranged in the interior of an upper housing portion 46. Thus, a magnified image is visible on the projection surface 49. The projecting beam is indicated by the dotted line 50.
The deflecting mirror 47 located above and adjacent to the projecting lens 45 is pivotable around an axis 51 of a rock-ing lever 53 into two end positions, each of which is respec-tively illustrated in FIG. 2 and FIG. 3. The pivoting motion of the surface mirror 47 is caused by the rocking lever 43 which is fixed in rigid relationship to the deflecting mirror 47 and con-nected to a rotating wheel 52 via a crank drive 54. The free end of the lever 53 remote to the axis 51 is supporting a guide roller 58 around which a cable line 55 is guided which is further stretched over guide rollers 56 and 57. The cable line 55 has one end attached to the housing portion 46 at a point 49 and another end fixed to a roll-up curtain 60. The curtain 60 is wound up on a take-up device 61 when in a position shown in FIG. 2.
As can be further seen from the FIGS. 2 to 4, the upper housing portion 46 is provided with a reflector support 62 having two mirrors 63, 64 arranged at a distance and at a right angle to each other. The support 62 is supported on a sliding carriage 65 which is movable into two end positions indicated by arrows C-D

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along a plane parallel to the plane of the micrograph 37. The carriage 65 is provided with rollers 66, 67, 68 in such a manner that the roller 66 and 67 are sliding along the upper face or bottom face respectively of the sliding bar 69 while the roller 68 is connected to the reflector support 62. The motion of the carriage 65 is achieved by a conveyor belt 70 fixed to the car-riage 65 and having one end wound on a drum 71 and another end rollable on a drum 72. The drums 71 and 72 are coupled with pinions 75 and 76 via magnetic couplings 73, 74. The pinions 75, 76 are driven by a tooth belt 77 which is stretched over the pinions 75 and 76 as well as over guide pulleys 78, 79 and over a gear belt pulley 80. The gear belt pulley 80 is connected to a gear wheel 81 on a common shaft in such a manner that the gear belt pulley 80 does not execute any rotation relative to the gear wheel 81. The gear wheel 81 is meshing with a gear wheel 82 which is rotating with the copying drum 21.
The reflector support 62 is pivotable around an axis 83 which is the intersection of the planes of the mirrors 63 and 64. Furthermore, the reflector support 62 has two side faces each of which is provided with a protruding guide pin 84 adjacent to the reflecting mirror 64 wherein each guide pin is guided in guide slots 85.
The mode of operation is as follows:
Due to the force exerted by the curtain 60 onto the cable line 55, the deflecting mirror 47 is kept in a position according to FIG. 2 whereby the micrograph 37 is projected onto the projecting surface 49 for permitting a reading of the micro-graph 37. Consequently, the reflector support 62 is in such a position that the beam 50 emitted by the illumination unit is not influenced by arranging the support 62 with an open upper area.

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The position of the support G2 is shown in FIG. 2. In the read-ing position, the curtain is thus wound on the drum 61 so that the projection surface 49 is impinged by the beam 50.
If it is designed to reproduce the micrograph 37 lo-cated in the projecting beam, a button (not shown) is actuated, thereby initiating operation of the copying unit. Accordingly, the copying drum 21 is caused to rotate and consequently the drum 76is driven via the tooth belt 77. Via the drum 76 and the crank drive 54 connected thereto, the surface mirror 47 is pivoted downwardly into the position shown in FIG. 3 so that the cable line 55 is pulled downwardly. Therefore, the curtain 60 is moved in a position shown in FIG. 4, thereby shielding the interior of the system against ambient light.
Simultaneously with the initiation of the copying unit, the magnetic coupling 74 is actuated until the sliding carriage 65 occupies the initial position shown in FIG. 3. The sliding motion of the carriage 65 is caused by winding the conveyor belt 70 on the drum 72. When the carriage 65 is in the initial posi-tion, the magnetic coupling 74 is released and the magnetic coupling 73 is actuated so that the conveyor belt 70 is wound on the drum 71. Consequently, the carriage 65 is moved in the direction of the arrow C into the end position shown in FIG. 4 by a constant speed.
Upon sliding of the reflector support 63 from the position shown in FIG. 3 into the position illustrated in FIG. 4, the micrograph 37 is scanned in strips onto and projected in similar strip-shaped portions onto the rotating copying drum 21, the beam 50 being deflected twice on the respective mirrors 63 and 64. As can be seen from FIG. 2, the projecting beam 50 is directed through a light tunnel 86 defined by a pedestal 87 ~l~ZS55Z

connecting the upper housing portion 46 with the lower housing portion 20.
The speed of the sliding carriage 65 along its path of motion during copying of the micrograph 37 is half of the rota-tional speed of the surface of the copying drum 21. In addition to the sliding motion in direction of -the arrow C-D, the reflec-tor support 62 is pivoted along the guide slot 85 through the provision of the guide pins 84 so that the space requirement for the reflector support is kept at a minimum.
As soon as the copying process has terminated, the reflector support 62 is returned into the initial position shown in FIG. 2 by actuating the magnetic coupling 74 instead of the magnetic coupling 73. Simultaneously, the lever 53 is released so that the curtain 60 is wound on the drum 61, thereby clearing the projection surface 49 again, the mirror 47 is thus pivoted to its initial position.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of projection systems differing from the type described above.
; While the invention has been illustrated and described as embodied in a projection system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Claims

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

1. A projection system having a light source generating a projecting beam and a stationary projecting lens wherein a stationary original is optically scanned in strips and is projected on a light receiving surface moving past a stationary exposure area, said system comprising means for reflecting the projecting beam from the projecting lens onto the light receiving surface, the reflecting means being a reflector support provided with two reflecting mirrors and the one mirror and the other mirror of the reflecting means having respective planes fixedly arranged at a right angle to each other, the reflecting means being pivotable about an axis defined by the intersection of the respective planes of the two reflecting mirrors, and the reflecting mirrors having edges spaced from the axis; means for moving the reflecting means synchronously with the motion of the light receiving surface between two end positions in a direction parallel to the original, the axis defined by the intersection of the respective planes of the two reflecting mirrors being connected with the moving means, the light receiving surface having a tangent plane parallel to a plane of the original and the projecting lens being positioned between the original and the reflecting means; and guide means for pivoting the reflecting means about its pivoting axis during movement of the reflecting means in the direction parallel to the original and so that the spaced edges of the reflecting mirrors move in a direction which is substantially normal to the plane of the original and the tangent plane of the light-receiving surface.

2. A projection system as defined in claim 1, wherein the speed of motion of the reflecting means is half that of the speed of motion of the light receiving surface.

3. A projection system as defined in claim 1, wherein the beam is reflected twice intermediate the project-ing lens and the light receiving surface.

4. A projection system as defined in claim 1, wherein the reflecting means has two side faces each provided with a guide pin adjacent the one reflecting mirror, the pins being in engagement with a guide slot for guiding the pivotal movement of the reflecting means.

5. A projection system as defined in claim 1, wherein the system further comprises a deflecting mirror pivotable into the projecting beam for deflecting the beam onto a projection surface.

6. A projection system as defined in claim 5, wherein the edges of the reflecting mirrors of the reflecting means spaced from the axis extend in an edge plane, the de-floating mirror being arranged so that when it is pivoted into the projecting beam the deflecting mirror extends sub-stantially in the edge plane of the reflecting mirrors between the spaced edges.

7. A projection system as defined in claim 5, wherein the deflecting mirror cooperates with a fixed second deflecting mirror at a distance thereto for projecting the beam onto the projection surface.

8. A projection system as defined in claim 5, wherein the deflecting mirror is rigidly connected to a rocking lever having one end around which the deflecting mirror is pivotable and another end connected to a curtain, the lever being pivotable upon rotation of the light receiving surface.

9. A projection system as defined in claim 10, wherein the deflecting mirror is arranged between the two reflecting mirrors.

10. A projection system as defined in claim 10, wherein the curtain is movable from a first position in which it is wound on a drum thereby clearing the projection surface, into a second position upon rotation of the light receiving surface for shielding the system against ambient light.

11. A projection system as defined in claim 1, wherein the system is further provided with an upper housing portion in which the reflector means is incorporated and a lower housing portion wherein the reflecting means project the light rays through a light tunnel onto the light receiv-ing surface, the light tunnel being defined by a pedestal connecting the upper housing portion and the lower housing portion.