JPS63115123A - Scanning device - Google Patents

Abstract

PURPOSE:To simplify a scanning mechanism by moving one scanning mirror linearly under specific conditions and scanning luminous flux passed through a projection optical system. CONSTITUTION:The luminous flux passed through the optical system 1 is scanned by the scanning mirror 5 provided between the projection optical system 1 and a plane ideal image plane 3 and guided successively onto a drum type rotatable photosensitive body 4 which has curvature linearly. In this case, the mirror 5 is moved on a vertical bisector connecting respective points on an image plane 3 and a reference point 40 on the surface of the photosensitive body 4 and a straight line 52 cross a track formed of intersections 51 of the main luminous flux of luminous flux incident on respective points on the image plane 3 or a straight line 52 nearby the track, thereby scanning the luminous flux. Thus the system which scans the luminous flux by moving one mirror 5 linearly on the specified straight line 52 is employed to simplify the scanning mechanism.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a scanning device suitable for copying machines, microfilm reader/printer devices, etc. The present invention relates to a scanning device suitable for projecting and forming an image on a photosensitive surface by sequentially scanning an image using a scanning mirror disposed on the image field side of a projection optical system.

(Prior Art) Conventionally, in copying machines, microfilm radar printers, etc., a light beam from an original that has passed through a projection optical system is sequentially scanned by a scanning mirror to form a projected image on the surface of a drum-shaped photoreceptor that rotates once. I'm letting you do it. At this time, a scanning device that scans two or more mirrors in a predetermined relationship, as proposed in JP-A No. 52-69616, has a relatively high optical precision. Although scanning is possible, there are drawbacks such as the overall complexity of the device and the difficulty of high-speed scanning.

On the other hand, a scanning device has been proposed, for example, in Japanese Patent Application Laid-open No. 126258/1983, which uses a single scanning mirror to guide the light flux that has passed through the projection optical system onto the surface of a photoreceptor.

In the scanning device disclosed in the same publication, the scanning mirror is moved while changing the inclination of the mirror so that the distance from the reflection point of the light beam on the scanning mirror surface to the ideal image surface and the distance to the reference point of the photoreceptor are both equal. Scanning is done by moving. Although this scanning method can maintain good optical performance of the projected image formed on the surface of the photoreceptor, the scanning locus of the scanning mirror tends to be non-linear and the scanning mechanism tends to become very complicated.

In addition, there is a method of placing one scanning mirror between the projection optical system and the ideal image surface and scanning by rotating the mirror, and a projection method as proposed in Japanese Patent Laid-Open No. 52-69616. There is a method in which the rotation center of a scanning mirror is provided outside the optical axis of the optical system and scanning is performed.

However, in all of these scanning methods, it is not possible to keep the above-mentioned two distances constant at each scanning position, and a difference in optical path length occurs, causing the reproduced image on the photoreceptor surface to become distorted unless some kind of correction means is used. It has the drawback of causing distortions such as shape and trapezoidal shapes.

(Problems to be Solved by the Invention) The present invention uses a single scanning mirror to scan a light beam that has passed through a projection optical system, and projects an image onto a drum-shaped photoreceptor surface having a curvature in one dimension. It is an object of the present invention to provide a scanning device having a simple configuration, which can obtain a high-quality image output with small distortion of 0, for example, about 1% or less even when a scanning mirror is linearly scanned when forming an image.

(Means for solving the problem)) A scanning mirror provided between the projection optical system and a planar ideal image surface scans the light beam passing through the projection optical system,
When guiding light sequentially onto a rotatable drum-shaped photoreceptor surface having a curvature in one dimension, the scanning mirror is connected to a vertical 2-axis connecting each point on the ideal image surface and a reference point on the photoreceptor surface. A straight line that intersects at least two points of intersection with a locus 1 formed from the intersections with the chief ray of the luminous flux incident on each point on the ideal image plane that is on the equisector, or a straight line that is tangent to the locus 1. This means that the image was scanned by moving the image.

(Embodiment) FIG. 1 is a schematic diagram of an embodiment of the present invention. In the figure, 1 is a projection optical system, 2 is an original image as a projection surface, 3 is a flat ideal image surface, 4 is a drum-shaped photoreceptor having curvature in one direction, and 41 is the rotation center of the photoreceptor 4. , 5 is a scanning mirror, and 6 is a slit portion having a slit opening in a direction perpendicular to the direction of curvature of the photoreceptor 4.

In this embodiment, the original image 2 is illuminated by an illumination system (not shown). The scanning mirror 5 has a perpendicular bisector shape connecting each point on the ideal image surface 3 and the reference point 40 of the photoreceptor 4, and each intersection with the principal ray incident on each point on the ideal image surface. For locus 1 formed by 51.

The object is moved along a straight line that intersects with at least two points of intersection, or a straight line that is tangent to the locus 1, for example, a straight line 52 shown by a dotted line.

As a result, instead of converging the light beam from the original image 2 that has passed through the projection optical system 1 onto the ideal image surface 3, it is scanned by the scanning mirror 5 and passes through the slit section 6 to the reference point 40 on the surface of the photoreceptor 4.
The light is guided sequentially.

Further, in this embodiment, when the distance from the ideal image surface 3 to the exit pupil of the projection optical system 1 is b, each point on the ideal image surface 3 is moved to an image forming position on the photoreceptor 4 surface by the scanning of the scanning mirror 5. Each element is configured so that the angle fits within a circle with a radius of b/Zoo, thereby further reducing distortion. If the radius exceeds b/100, distortion due to optical path length deviation increases and some kind of correction means is required, which is not good.

In this way, in this embodiment, the scanning mechanism is simplified by adopting a method in which one scanning mirror 5 is moved linearly on the straight line 52 specified as described above for scanning.

In addition, the distortion of the projected image formed on the surface of the photoreceptor 4 is reduced. For example, by specifying each element such as the coordinate points described later, the distortion of the projected image on the four surfaces of the photoreceptor can be reduced to 1.
% or less.

As shown in FIG. 1, the optical axis direction of the projection optical system 1 is the Y axis,
Let the scanning direction on the ideal image plane 3 be the X axis, and let the intersection 31 on the ideal image plane 3 with the optical axis 11 of the projection optical system 1 be the origin (0,0). Then, the coordinates of the exit pupil position 10 of the projection optical system 1 are (
o, b), the coordinates of the reflection point 51 of the scanning mirror 5 on the optical axis 11 of the projection optical system 1 are (0, a), and the coordinates of the reference point 40 of the photoreceptor 4 are (c, d).

At this time, when the coordinate points of each element are set for five types from I to ■ as shown in Table 1 below, the equation of the above-mentioned straight line 52 is found to be the linear trajectory equation shown by IV in Table 2.

At this time, the difference between the distance from the reflection point 51 of the scanning mirror 5 to the ideal image surface 3 and the distance to the reference point 40 of the photoreceptor 4, that is, the optical path length difference Δ, is calculated as shown in FIG. Become.

As shown in curves I to V in FIG. 2, in each of the examples, the optical path length difference Δ is about 1 (mm) at maximum. This is~b
/1ooo, and the amount of distortion in this embodiment is 0.1% or less. Therefore, in this embodiment, no correction for distortion is required.

This level of optical path length difference is such that the depth of focus of a projection optical system used in, for example, a microfilm reader/printer is one order of magnitude larger, so that sufficiently good optical performance can be obtained.

Table-1 Table-2 In this example, the scanning mirror is set relative to the trajectory l! It is preferable to move on a straight line obtained by performing the following regression because an image with less distortion can be obtained.

FIG. 3 is a schematic diagram of an embodiment for driving the scanning mirror 5 in the present invention. In the figure, 30 corresponds to the exit pupil point of the projection optical system, 31 corresponds to a reference point on the surface of the photoreceptor, and 40 corresponds to the origin on the ideal image.

At the exit pupil point 30 and the reference point 31, rotatable and internally slidable rod-shaped bodies 32, 33 are arranged, and the scanning mirror 5 is rotated at the intersection 34 with these rod-shaped bodies 32, 33. It is possible. A guide rod 35 is fixed to the scanning mirror 5 in the vertical direction, and a slider 36 is attached to the guide rod 35.
is fitted.

The vibrator 36 has a drive link 37 so that the guide rod 35 moves in a bisector of the angle formed by the two rod-shaped bodies 32 and 33.
．． 38 are provided. Of these, the drive link 37 moves the rod-shaped body 32 from the exit pupil point 30 to the drive section 40 that slides within a drive guide groove 39 provided on the ideal image plane.

At this time, the direction in which the rod-shaped body 32 is located corresponds to the direction of the principal ray that emerges from the projection optical system and enters the scanning mirror 5,
The direction in which the rod-shaped body 33 is located corresponds to the direction of the principal ray reflected from the scanning mirror 5.

This allows the linear trajectory 4 to change while changing the inclination of the scanning mirror 5.
Scanning of the light beam is performed by moving the light beam over the light beam.

In this embodiment, in order to reduce the size of the entire device, a slider 50 and a drive guide groove 51 are provided as shown in the broken line frame A, and a vertical drive guide groove is provided as shown in the broken line frame B. 61 may be provided with a slider 62, and a cam 63 may synchronize the vertical driving. The cam shape at this time is determined by synchronizing the image area μ from the origin 31 on the ideal image surface 3 using the coordinate system shown in FIG. 1, with the guide groove 61 in FIG. =px+q
If expressed as, the y coordinate on x=e is given by a function of μ. This may be synchronized with the rotation angle of the cam 63 to determine its shape. This results in:

According to this, the light beam reflected by the scanning mirror 5 can be reflected by a fixed mirror at any time thereafter, so that the space for a long rod-shaped body is unnecessary, and the entire apparatus can be miniaturized.

In addition, the scanning mirror 5 is controlled to change its inclination along the guide groove, so that the normal line of the scanning mirror can move along the guide groove while maintaining an angle of the formula with respect to the trajectory at each scanning position. You can also set the trajectory to .

(Effects of the Invention) According to the present invention, the light beam passing through the projection optical system is scanned by moving one scanning mirror linearly so as to satisfy the above-mentioned conditions. By guiding light onto the surface of the photoreceptor and forming one image, the distortion of the reproduced image with a small difference in optical path length was reduced. Furthermore, it is possible to achieve a scanning device that is simpler and more compact as a whole.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of optical path length differences in scanning mirrors of each embodiment of the present invention, and FIG. 3 is a method of driving a scanning mirror according to the present invention. FIG. 2 is an explanatory diagram of one embodiment of the invention. In the figure, 1 is a projection optical system, 2 is an original image, 3 is an ideal image surface, 4 is a photoreceptor, 5 is a scanning mirror, 6 is a slit section, 11 is an optical axis, 52 is a scanning locus, 40 is a reference point, 41 , 39, 51.
61 is a sliding guide groove. 3B, 62.50 is a slider, 32.33 is a rod-shaped body, 63
is a cam. Patent applicant Canon Co., Ltd. Figure 2

Claims (2)

[Claims] (1) A scanning mirror provided between the projection optical system and a planar ideal image surface scans the light flux that has passed through the projection optical system, and a drum-shaped rotatable mirror with curvature in one dimension is scanned. When sequentially guiding light onto the photosensitive surface, the scanning mirror is placed in the shape of a perpendicular bisector connecting each point on the ideal image surface and a reference point on the photosensitive surface, and each point on the ideal image surface is A scanning device characterized by scanning by moving on a straight line that intersects at least two points of intersection with a locus l formed by the intersection of a principal ray of a luminous flux incident on a point or on a straight line that is tangent to the locus l. . (2) The scanning device according to claim 1, wherein the scanning mirror is moved on a straight line obtained by performing linear regression with respect to the trajectory l.