JPH04299331A - Scanner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device such as a microreader printer.

0002

[Prior Art] Microreader printers generally enlarge a photographic image on a microfilm so that it can be observed externally on a display device such as a screen or CRT, and also display the enlarged image on a photoreceptor. A copy image is formed by projecting the image onto a photosensitive drum or a light receiving sensor such as a CCD. To form this copy image, a scanning system as shown in FIG. 5 has conventionally been used. That is, a photographic image on a microfilm F illuminated by an illumination system (not shown) is enlarged and projected by a projection lens 1, reflected by a scan mirror 2, and then
The image passes through the slit S and is projected onto the belt photoreceptor 7 at intervals of a predetermined width. The scan mirror 2 rotates in the direction of the arrow (clockwise in the figure) about its rotation axis 2a in synchronization with the movement of the belt photoreceptor 7. When the scan mirror 2 is at the rotation position 2b indicated by the solid line, a portion of the microfilm F shown by a1 is projected onto the belt photoreceptor 7, and the scan mirror 2 is at the rotation position 2c indicated by the dashed line and the rotation position 2d indicated by the dashed line. At this time, portions a2 and a3 of the microfilm F are projected onto the belt photoreceptor 7. In this way, by rotating the scan mirror 2 between 2b and 2d and changing the inclination angle, the entire image between a1 and a3 of the microfilm F is scanned, and this is scanned by the belt photoreceptor that moves at a constant speed of V0. An enlarged full image is formed on 7.

The optically scanned image is subjected to slit exposure in synchronization with the belt photoreceptor 7 moving at a speed V0 to form a latent image, and this latent image is then visualized by colored charged particles in the developing unit 21. The image is then transferred to copy paper (not shown) by a transfer charger 22. Thereafter, the remaining colored charged particles that could not be transferred are removed by the cleaner unit 23, the non-uniform potential remaining on the belt photoreceptor 7 is removed by the static elimination lamp 24, and the primary charger 25 is applied to the belt photoreceptor 7. A different potential is applied to prepare for the next optical scan. These series of operations are known as a general electrophotographic copying process.

0004

However, in the conventional scanning system described above, the rotation axis 2a of the scanning mirror 2
is disposed at a fixed position, so when the scan mirror 2 is tilted to a position other than position 2c in Fig. 5, the focus position shifts and a magnification error occurs, resulting in defocus and barrel-shaped image distortion of the copied image. There was a problem. This is because, as shown in FIG. 5, the equivalent projection surface C is a curved surface, and this equivalent projection surface C is separated from the equivalent focal plane H for the projection lens 1. For example, the points on the equivalent projection plane C of the portions a1 and a3 of the microfilm F are C1 and C3, and the distances between them and the equivalent focal plane H are ΔC1 and ΔC3.
A dimensional difference occurs, which causes defocus and barrel-shaped image distortion in the copied image. One way to solve this problem is to make the conjugate length sufficiently long to reduce the rotation angle of the scan mirror 2, thereby reducing ΔC1 and ΔC3 to a level that poses no problem in practice. There is a tendency for microreader printers to become larger.

There is also a method of correcting the optical path length by slightly displacing the position of an optical path changing mirror provided in the middle of the optical path from the scan mirror 2 to the belt photoreceptor 7. However, in reality, it is very difficult to displace the mirror without changing its inclination so as not to disturb the scanning optical path, and the vibrations that occur during the displacement greatly shake the projected image and tend to cause synchronization blur. Furthermore, there is a way to correct barrel distortion by imparting pincushion aberration to the lens in advance, but there are still problems such as pincushion distortion remaining in the reader system and the inability of zoom lenses to handle all magnifications. SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a scanning device free from distortion caused by optical scanning.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a reader printer equipped with a scanning mirror that rotates and scans, and a photoreceptor arranged in a band shape that reads a desired image on an image recording medium. A positioning member is provided to displace a part of the photoreceptor in the optical axis direction in synchronization with the rotational position of the scan mirror, and one part of the photoreceptor is positioned so that the light-receiving surface of the photoreceptor is always equal to the equivalent focal plane. This is to adjust the position of the part.

[0007]

[Operation] The scanning device with the above configuration displaces the light-receiving surface of the band-shaped photoreceptor in the optical axis direction in synchronization with the scan mirror, eliminating defocus and image distortion caused by optical scanning, resulting in clear and accurate copied images. is obtained. Furthermore, even if minute vibrations occur when displacing the band-shaped photoreceptor in the optical axis direction, the influence on synchronization blur will be much smaller than in a method in which an optical path changing mirror provided in the middle of the optical path is displaced. This is because when the direction of microvibration is decomposed into a vector component parallel to the optical axis and a vector component perpendicular to the optical axis, the optical axis is deflected for both the vertical and parallel vectors because there is a reflection angle when correcting with a mirror. However, in the case of the present invention, it is only necessary to pay attention to the vector component perpendicular to the optical axis. Furthermore, in the case of correction using a mirror, if the reflection angle deviates by Δθ due to the influence of minute vibrations, the synchronization blur will be affected by the product of double Δθ and the remaining optical path length, but in the present invention, synchronization due to angular deviation There is no effect of blur.

[0008]

Embodiment A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of this embodiment, and FIG. 2 is a cross-sectional view of the main parts thereof, in which 1, 2, 2a, 7, F, and S indicate the same parts as in FIG. 8 is a tension roller 1 biased by a pair of tension springs 9 against the belt photoreceptor 7;
0 is the same guide roller, 11 is an optical path length correction cam disposed between the tension roller 8 and the guide roller 10 and below the belt photoreceptor 7, and 12 is an optical path length correction cam 11.
and a driven timing pulley connected by a camshaft 11a,
13 is a drive timing pulley, and a plurality of idler timing pulleys 1 are connected between the drive timing pulley 12 and the drive timing pulley 12.
A timing belt 14 is stretched through the belt 5. 16 is a scanning motor, one output shaft of which is connected to the rotating shaft 2a of the scan mirror 2 via a reduction gear 17a, and the other output shaft is communicatively coupled to a reduction gear 17b coaxial with the drive timing pulley 13. There is. A guide plate 18 is provided between the belt photoreceptor 7 and the optical path length correction cam 11 so as to be slidable in the vertical direction. Note that the driving device for the belt photoreceptor 7, the primary charger, the developing unit, etc. necessary for the electrophotographic process, that is, the reference numeral 21 in FIG.
25 are omitted from illustration to make the explanation easier to understand.

In this embodiment having the above configuration, the belt photoreceptor 7 is pressed against the guide plate 18 by a tension roller 8 biased by a tension spring 9, so that the optical path length can be corrected more stably. The profile of the correction cam 11 is accurately traced, and the slack in the belt photoreceptor 7 is taken up when the slit exposure section is displaced. The radius ratio of the drive pulley 13 and the driven pulley 12 is determined by the scanning angle of the scan mirror 2 and the optical path length correction cam 1.
For example, if the scanning angle of the scan mirror 2 is 10 degrees and the cam profile has one period of 60 degrees, the pitch diameter ratio of the driving pulley 13 and the driven pulley 12 is 6:1.

Therefore, FIG. 2 shows the optical path length correction cam 1 when the scan mirror 2 is in a neutral position, that is, in a position where the equivalent projection plane C and the equivalent focal plane H are projecting the center of the optical axis.
It represents the cam angle of 1. As shown in FIG. 5, if the exposure position of the belt photoreceptor 7 is set based on the optical path length at the center of the optical axis, the equivalent focal plane H becomes farther away from the equivalent projection plane C toward the edge of the image. The exposed portion of the photoreceptor 7 must be separated from the film F surface. In other words, the guide plate 18 that determines the exposure position of the belt photoreceptor 7 when the scan mirror 2 is projecting a certain image end is in contact with the optical path length correction cam 11 on the base circle, and is directed toward the center of the optical axis. As the scan mirror 2 rotates, the exposed portion of the belt photoreceptor 7 is lifted by the optical path length correction cam 11, and reaches the maximum lift amount at the center of the optical axis. Then, as the optical scanning further progresses and moves away from the optical axis center, the cam lift amount approaches the base circle of the optical path length correction cam 11, and when reaching the image end of the optical scanning type, the guide plate 18 again moves to the base circle of the optical path length correction cam 11. Tangent to the circle. This optical path length correction cam 11
The cam profile of can be determined by optical drawing and arbitrary cam rotation angle.

FIG. 3 shows a second embodiment of the invention. In order to simplify the explanation, the same parts as in the first embodiment are given the same reference numerals, and only the different points will be explained. In the first embodiment described above, power is extracted from the scanning motor 16 that drives the scan mirror 2 through belt transmission to correct the position of the belt photoreceptor 7, but in this embodiment, the position of the belt photoreceptor 7 is corrected.
A cam drive motor 31 is connected to the cam shaft 11a of the optical path length correction cam 11 separately from the scan motor 16, and the scan mirror 2 and the optical path length correction cam 11 are electrically synchronized and driven by separate motors. It is. The other configurations are the same as those of the first embodiment described above. In this embodiment with the above configuration, a more compact scanning device can be achieved by using electrical synchronization means such as a pulse motor and a rotary encoder.

FIG. 4 shows a third embodiment of the present invention. In both the first and second embodiments described above, a cam 11 that converts rotation into a slide is used to correct the optical path using a motor as a power source, whereas in this embodiment, the rotation axis 2a of the scan mirror 2 is used. A rotary encoder 41 is provided at the bottom of the guide plate 18, and a piezoelectric element 42 is provided at the bottom of the guide plate 18, so that the output of the encoder 41 is inputted to the piezoelectric element 42 via a piezoelectric element control circuit 43. Note that 3 is a reflecting mirror, 4 is a lamp, and 5 is a condensing lens, forming an illumination optical system for the microfilm F. The other configurations are the same as those of the first embodiment described above. In this embodiment with the above configuration, the rotation angle of the scan mirror 2 is read by the rotary encoder 41, and the scanning motor 16 is driven in synchronization with the belt photoreceptor 7 by feedback control.
Furthermore, the piezoelectric element 42 is activated to correct the optical path length. In this way, in this embodiment, since direct displacement by the piezoelectric element 42 is used, the driving device itself can be made very small in size, and has the advantage that it does not produce noise unlike a motor. However, since the amount of displacement of the piezoelectric element itself is extremely small, ranging from several tens of microns to several hundred microns, it must be used in a stacked state as shown in the figure, or by amplifying the displacement like a lever. is required.

[0013]

Effects of the Invention As explained above, the present invention adjusts the position of the exposed portion of the belt photoreceptor using the positioning member according to the rotational position of the scan mirror, so that the light receiving surface of the belt photoreceptor is always equal to the equivalent focal plane. By doing so, there is an effect that the scanning device can be made inexpensive and free from distortion caused by optical scanning.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of a scanning device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the optical path length correction cam portion.

FIG. 3 is a schematic perspective view of a scanning device according to a second embodiment of the present invention.

FIG. 4 is a side view of main parts of a scanning device according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram illustrating a conventional scanning device.

[Explanation of symbols]

F Micro film 1 Imaging lens 2 Scan mirror 6. Optical path changing mirror 7 Belt photoreceptor 8 Tension roller 10 Guide roller 11 Optical path length correction cam 12 Driven timing pulley 13 Drive timing pulley 14 Timing belt 16　Scanning motor 18 Guide plate 31 Cam drive motor 41 Rotary encoder 42 Piezoelectric element

Claims (1)

[Claims] 1. A reader printer equipped with a scanning mirror that rotates and scans and a photoreceptor arranged in a band shape for reading a desired image on an image recording medium, including a positioning member that displaces a part of the photoreceptor, A scanning device characterized in that the positioning member controls the position of a part of the photoreceptor in synchronization with the rotational position of the scan mirror so that the light receiving surface of the photoreceptor is always equal to the image forming surface.