JPH0731359B2 - Scanning device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a scanning device suitable for a copying machine, a microfilm reader printer device, and the like, and more particularly to a drum shape having a curvature in a one-dimensional direction that is rotating or rotationally vibrating. The present invention relates to a scanning device suitable for projecting an image on the surface of a photoconductor by sequentially scanning the image using a scanning mirror arranged on the image field side of the projection optical system.

(Prior Art) Conventionally, in a copying machine, a microfilm reader printer, etc., a light beam from an original that has passed through a projection optical system is sequentially scanned by a scanning mirror to project an image on a rotating drum-shaped photoreceptor surface. I am letting you. At this time, as a scanning mirror, for example, a scanning device of a method of scanning two or more mirrors with a predetermined relationship as proposed in Japanese Patent Application Laid-Open No. 52-69616 has a relatively high precision in optical scanning. Although it is possible to scan, it has drawbacks such as making the entire device complicated and making high-speed scanning difficult.

On the other hand, for example, Japanese Patent Application Laid-Open No. 55-126258 proposes a scanning device that guides a light beam, which has passed through a projection optical system, onto a surface of a photosensitive member by using one scanning mirror.

In the scanning device of the publication, while changing the tilt of the scanning mirror so that both 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 photoconductor become equal. Scanning by moving. This scanning method can maintain good optical performance of the projected image formed on the surface of the photoconductor, but the scanning locus of the scanning mirror is non-linear, and the scanning mechanism tends to be very complicated.

In addition to this, one scanning mirror is arranged between the projection optical system and the ideal image plane, and scanning is performed by rotating the mirror, or the projection is performed as proposed in JP-A-52-69616. There is a method of scanning by setting the rotation center of the scanning mirror outside the optical axis of the optical system.

However, none of these scanning methods can make the above-mentioned distances constant at each scanning position, and the optical path length difference causes the reproduced image on the surface of the photoconductor to be barreled unless some correction means is used. There was a defect that distortion such as a mold or a trapezoid was generated.

(Problems to be Solved by the Invention) The present invention scans a light flux passing through a projection optical system using one scanning mirror to project an image on a drum-shaped photosensitive body surface having a curvature in a one-dimensional direction. It is an object of the present invention to provide a scanning device having a simple configuration in which distortion is small and a high-quality image output of, for example, about 1% or less can be obtained even if the scanning mirror is linearly scanned during image formation.

(Means for Solving Problems)) A light beam that has passed through the projection optical system is scanned by a scanning mirror provided between the projection optical system and a plane ideal image plane.
When sequentially guiding light onto the drum-shaped rotatable photoconductor surface having a curvature in the dimensional direction, the scanning mirror is a line segment connecting each point on the ideal image plane and the reference point on the photoconductor surface. With respect to the locus formed by the intersection of the perpendicular bisector and the principal ray of the light beam incident on each point on the ideal image plane, move on a straight line intersecting at least two intersections or a line in contact with the locus. It was scanned.

(Example) FIG. 1 is a schematic view of an example of the present invention. In the figure, 1 is a projection optical system, 2 is an original image which is a projection surface, 3 is a plane ideal image surface, 4 is a drum-shaped photoconductor having a curvature in one direction, and 41 is a rotation center of the photoconductor 4. Reference numeral 5 denotes a scanning mirror, and 6 has a slit opening in a direction orthogonal to the curvature direction of the photoconductor 4 which is a slit portion.

In this embodiment, the original image 2 is illuminated by an illumination system (not shown). The scanning mirror 5 is an intersection of a perpendicular bisector of a line segment connecting each point on the ideal image plane 3 and the reference point 40 of the photoconductor 4 and a principal ray incident on each point on the ideal image plane. The locus formed by 51 is moved on a straight line intersecting at least two intersection points or a straight line corresponding to the locus, for example, a straight line 52 indicated by a dotted line.

As a result, the light beam from the original image 2 that has passed through the projection optical system 1 is scanned by the scanning mirror 5 instead of being converged on the ideal image plane 3, and the reference point 40 on the surface of the photoconductor 4 is sequentially passed through the slit portion 6. It is guiding light.

Further, in the present embodiment, when the distance from the ideal image plane 3 to the exit pupil of the projection optical system 1 is b, each point on the ideal image plane 3 is imaged on the surface of the photoconductor 4 by the scanning of the scanning mirror 5. Each element is configured so that is contained within a circle with radius b / 100, thereby reducing distortion. If the radius is more than b / 100, the distortion due to the optical path length shift increases and some correction means is required, which is not preferable.

As described above, in the present embodiment, the scanning mechanism is simplified by adopting the system in which one scanning mirror 5 is moved by linearly moving on the straight line 52 specified as described above. The distortion of the projected image formed on the surface of the photoconductor 4 is reduced. For example, the distortion of the projected image on the surface of the photoconductor 4 is reduced by 1% by specifying each element such as the coordinate point described later.
It is as follows.

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

At this time, when the coordinate points of each element are set for five types up to IV as shown in the following Table-1, the equation of the above-mentioned straight line 52 is obtained and the linear trajectory equation shown by IV in Table-2 is obtained.

Then, when the difference between the distance from the reflection point 51 of the scanning mirror 5 to the ideal image plane 3 and the distance to the reference point 40 of the photoconductor 4 at this time, that is, the optical path length difference Δ is obtained, as shown in FIG. Become.

As shown by the curves I to V in FIG. 2, the optical path length difference Δ is about 1 (mm) at maximum in each of the examples. This is ~ b / 1000
The strain amount in this example is 0.1%.
It becomes the following. Therefore, no correction for distortion is required in this embodiment.

The optical path length difference to this extent is a value at which sufficiently good optical performance can be obtained because the depth of focus of the projection optical system used in, for example, a microfilm reader printer is one digit larger.

In the present embodiment, the scanning mirror is set to 1 with respect to the locus.
Moving on the straight line obtained by performing the secondary regression is preferable because an image with less distortion can be obtained.

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

Rotating and slidable rod-shaped bodies 32 and 33 are stretched at the exit pupil point 30 and the reference point 31, respectively, and the scanning mirror 5 is rotated at an intersection 34 with these rod-shaped bodies 32 and 33. It is possible. A guide rod 35 is fixed in the vertical direction of the scanning mirror 5, and a slider 36 is fitted in the guide rod 35.

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

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

As a result, the linear trajectory 41 is changed while changing the inclination of the scanning mirror 5.
The light beam is scanned by moving it upward.

In this embodiment, in order to reduce the size of the apparatus as a whole, a slider 50 and a full drive guide 51 are provided as shown in a broken line frame A, and a vertical drive guide groove is shown as shown in a broken line frame B.
The slider 62 may be provided on the 61, and the cam 63 may perform the vertical driving in synchronization with each other. The cam shape at this time is the origin 31 on the ideal image plane 3 using the coordinate system of FIG.
3 in synchronization with the image part μ from
If 61 is expressed as x = e and the linear trajectory 41 is expressed as y = px + q, the y coordinate on x = e is given by the function of μ. The shape may be determined in synchronization with the rotation angle of the cam 63. This Is obtained.

According to this, since the light flux reflected by the scanning mirror 5 can be arbitrarily reflected by the fixed mirror thereafter, the space of the long rod-shaped body is unnecessary, and the overall size of the apparatus can be reduced.

In addition, the scanning mirror 5 is controlled so as to change the inclination along the guide groove, and the normal of the scanning mirror to this guide groove is expressed by the equation π / 4-ten ^-1 p with respect to the trajectory at each scanning position. You may set the locus so that you can move while maintaining an angle of +1/2 (ten ^-1 (px + qd) / (xc) + ten ^-1 (by) / x).

(Effects of the Invention) According to the present invention, a light beam passing through the projection optical system is scanned by linearly moving one scanning mirror so as to satisfy the above-mentioned condition, and scanning is performed to form a drum shape having a curvature in one-dimensional direction By guiding the light onto the surface of the photoconductor to form an image, it is possible to achieve an operating device in which the distortion of a reproduced image having a small optical path length difference is reduced, and the scanning device as a whole is simplified and downsized.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention, FIG. 2 is an explanatory view of an optical path length difference in the scanning mirror of each embodiment of the present invention, and FIG. 3 is a driving method of the scanning mirror according to the present invention. It is explanatory drawing of one Example. In the figure, 1 is a projection optical system, 2 is an original image, 3 is an ideal image plane, 4 is a photoconductor, 5
Is a scanning mirror, 6 is a slit portion, 11 is an optical axis, 52 is a scanning locus, 40 is a reference point, 41, 39, 51 and 61 are sliding guide grooves, 36, 62 and 50.
Is a slider, 32 and 33 are rods, and 63 is a cam.

Claims (2)

[Claims] 1. A drum-shaped rotation having a curvature in a one-dimensional direction by scanning a light flux passing through the projection optical system by a scanning mirror provided between the projection optical system and a planar ideal image plane. When the light is sequentially guided onto a possible photosensitive body surface, the scanning mirror is provided on the ideal image surface and a perpendicular bisector of a line segment connecting each point on the ideal image surface and a reference point on the photosensitive body surface. For the locus formed by the intersection of the chief ray of the light beam entering each point of
A scanning device characterized in that scanning is performed by moving on a straight line intersecting at least two intersections or a straight line in contact with the locus. 2. The scanning device according to claim 1, wherein the scanning mirror is moved on a straight line obtained by performing linear regression on the locus.