JPH01280746A - Exposure method in variable magnification copying machine - Google Patents

Abstract

PURPOSE:To change the cutoff amount of exposure luminous flux and to uniformize exposure amount distribution in a longitudinal direction by providing lens edge surface parts with light shielding plates and displacing the light shielding plate perpendicular to a lens optical axis and in a direction corresponding to the longitudinal direction of a slit-shaped exposure part. CONSTITUTION:The two light shielding plates 10 and 11 are provided on the lens edge surface parts 3A and 3B. The light shielding plates 10 and 11 are provided on a lens holding member 3-1 holding an image-formation lens system 3 and displaced integrally with the system 3. That is, when the system 3 is displaced, the light shielding plates 10 and 11 are also displaced. Every time a copying magnification is changed, the light shielding plate 10 is displaced perpendicular to the lens optical axis in the direction in response to the longitudinal direction of the slit-shaped exposure part. Therefore, the cutoff amount of the exposure luminous flux is changed based on the displacement of the light shielding plates 10 and 11 so as to uniformize the exposure amount distribution. Thus, irrespective of the changing of the copying magnification, slit exposure can be achieved always with the appropriate exposure amount distribution.

Description

[Detailed description of the invention] The present invention relates to an exposure method in a variable magnification type copying machine.

2. Description of the Related Art A copying method in which an electrophotographic photoreceptor formed in the shape of a drum, belt, or sheet is subjected to slit exposure to form an electrostatic latent image is well known. The slit exposure method is an exposure method in which a document is generally scanned by a slit-shaped illumination section, and a photoconductor is exposed and scanned using an image of the illumination section by an imaging lens system. This is achieved by physical movement. The most well-known slit exposure methods include a method that uses relative movement between an original, a set of photoreceptors, and an exposure optical system, or a method that uses two plane mirrors on the object side of an imaging lens system. There is a method in which the document is slit-scanned by moving sK, an image of the scanned part is formed at a fixed position in the apparatus space, this position is used as an exposure part, and the surface of the photoreceptor is moved with respect to this exposure sK.

As shown in FIG. 1, the original 0 placed on the original placing plate 1 is slit-scanned in the direction of the arrow by the lamp 2, and at the same time, the imaging lens thread 5 is moved from the position shown by the solid line to the position shown by the broken line. and move the image of the illuminated area of document 0 to the exposed area P.
As shown in FIG.
The two plane mirrors 6 and 7 on the image side of the imaging lens are moved together or separately to form an image of the illuminated area on the exposed area P, and the photoreceptor 4 is moved with respect to this exposed area P. Methods of moving surfaces are known. In order to avoid clutter, the same symbols are used in Figures 1 and 2 for the same equipment. Additionally, in these figures, the number 5 indicates a plate that has the function of cutting off a part of the imaging light beam in order to regulate the slit width in the exposure section, but in order to distinguish it from the light shielding plate described later, this is , called a slit plate.

Now, in FIGS. 1 and 2, the original O is illuminated by the lamp 2 and exposed by the light image, but the shape of the exposed area is a slit shape regulated by the slit plate 5. In FIGS. 1 and 2, the direction perpendicular to the drawing is referred to as the longitudinal direction of the slit-shaped exposure section P. The direction of movement of the surface of the photoconductor 4 is perpendicular to the longitudinal direction of the exposure section P, but when the surface of the photoconductor 4 is associated with the document placement surface, the direction of movement of the surface of the photoconductor 4 is in a plane parallel to the document placement surface. The direction fr corresponding to the moving direction of the surface of the photoreceptor in the exposure part P is called the exposure direction. In FIGS. 1 and 2, the left and right direction is the exposure direction. In FIGS. 1 and 2, the incident angle of the exposure light flux entering the imaging lens system 5 is continuous in the exposure direction during slit exposure. change.

Furthermore, in the example shown in FIG. 1, the imaging lens system moves perpendicular to the optical axis in the exposure direction.

The illumination of the document 0 may be performed by slit scanning as described above, or the entire surface may be illuminated at the same time.

Now, in order to form a good electrostatic latent image on the photoreceptor, the surface of the photoreceptor must be exposed under uniform conditions. This means that the exposure amount distribution in the longitudinal direction in the exposed portion of the shape must be uniform.

Cosine fourth law and aperture characteristics in imaging lens systems? Considering this, in order to achieve a uniform distribution of the exposure light 11, the light intensity distribution of the illumination in the document placement section should be set in the direction corresponding to the longitudinal direction of the exposure section, and in the direction perpendicular to the drawing in FIGS. 1 and 2. It must be low in the center and high at both ends. In general, the illumination of a document is done in this way.

However, if the copying magnification is fixed, this is not a problem, but if you use a variable-magnification type copying machine, that is, if you move the imaging lens system according to the switching of the copying magnification, even at a certain copying magnification, the exposure part Even if the exposure amount distribution in the hand direction becomes uniform, the exposure amount distribution will not be uniform at other copying magnifications.

Here, we will explain the displacement of the imaging lens system accompanying switching of the copying magnification. The above-mentioned displacement includes displacement based on the center and displacement based on one side.

In FIGS. 5 and 4, reference numeral 1-1 indicates a document placement surface, and reference numeral 4-1 indicates a photoreceptor surface. The left and right direction in the figure corresponds to the longitudinal direction of the exposure section, and points k, 8, 0, and D are the ends of the effective copy area on the document placement surface 1-1 and the photoreceptor surface 4-1. It shows. When the imaging lens system 5 is at the position indicated by the solid line, the copying magnification is equal to the same magnification, and the k point and the 8 point correspond to the 0 point and the D point, respectively. When the imaging lens system 5 is at the position indicated by the broken line, the W image magnification is a reduction magnification. At this time, in the case of the displacement shown in FIG. 5, point k and point 8 correspond to point 7 and point 87, respectively, on the photoreceptor surface 4-1. However, point A on the document placement surface 1-1, the center point q of the eight points, is the 0 point on the photoreceptor surface 4-1,
It corresponds to point q' at the center of point D. Displacement of the imaging lens system that provides such correspondence is called center-based displacement. On the other hand, in FIG. 4, in the case of the reduction magnification, the 8-point cutoff point corresponds to the point, but the point A' corresponding to the point A coincides with the 0 point as in the case of the same magnification. The displacement of the imaging lens system that provides such correspondence is called one-sided reference displacement. Although the reduction magnification has been described, the same applies to the enlargement magnification.

However, in general, when changing the magnification, the optical path length between the document placement surface 1-1 and the photosensitive surface 4-1 must also be changed. being ignored.

Now, let's return to the above-mentioned problem of exposure distribution.

For example, in the case shown in Fig. 5, if the light intensity distribution in document illumination is properly determined for the vI copy at the same magnification, when the reduction magnification is used, the exposure 1 distribution in the longitudinal direction of the exposure length is q With respect to point ', points 5' and B' become excessive. Father, if we consider the same case shown in FIG. 4, the exposure distribution gradually becomes excessive as it approaches the 8-point side. In the case shown in FIG. 4, as a method for correcting the exposure amount distribution at the time of reduction magnification, as shown in FIG. The slit width is
A method is known in which the trap is gradually trapped as it moves from the 0 point side to the B' point side. In addition, in FIG. 5, the broken line indicates the attitude of the slit plate 5 at the same magnification.

This method can be used only when the slit width of the exposed part is about 15101 mm or more. Although it is somewhat effective if you have high quality images these days? It is not uncommon for the above-mentioned slit width to be set as narrow as about 5 mm in order to obtain the desired result, and it is difficult to apply this in such a case. Also, when the exposure light intensity is not uniform in the width direction of the slit,
That is, if there is a mountain-shaped distribution of the exposure light intensity in the width direction, it is difficult to equalize the exposure light amount using such a correction method. Furthermore, it is practically impossible to change the illumination light intensity distribution of the document every time the copying magnification is changed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure method for a variable magnification type copying machine that performs slit exposure, which allows slit exposure to be performed with an appropriate exposure distribution at all times, regardless of the change in copying magnification.

The present invention will be explained below.

The features of the present invention are as follows.

That is, at least one light shielding plate is provided at the lens end face. This shielding plate is integral with the imaging lens system with respect to its displacement. That is, when the imaging lens system is displaced, the light shielding plate is also displaced. Each time the copying magnification is switched, the light shielding plate is displaced perpendicularly to the lens optical axis in a direction corresponding to the longitudinal direction of the exposure section. This displacement is carried out using known displacement means as appropriate. Based on the displacement of the light-shielding plate, the exposure light flux blocking it changes, thereby realizing a uniform exposure amount distribution.

By the way, providing a light shielding plate on the lens end face of the imaging lens system means the following.

In FIG. 6, the left-right direction in the drawing corresponds to the longitudinal direction of the exposure section. Regarding the imaging lens system 5 whose cut end surface state is shown, providing a light shielding plate at the lens end surface means that the light shielding plate is provided at the entrance side end of the casing 5-1 of the lens cell.
This means that the portion 5B is provided at the end portions 5G and 5D on the emission side.

First, let us consider the case where the displacement of the imaging lens system 5 is based on the center. In this case, since the exposure light beam is symmetrical with respect to the lens optical axis in the direction corresponding to the longitudinal direction of the exposure section, the shielding plate must also shield light symmetrically with respect to the exposure light beam and the lens optical axis. K to realize this is two light shielding plates T as shown in FIG. 7 (11).
o, ++ f (, disposed at the 5-in part, 5B part of the lens end face, or as shown in FIG. 7(n), the light shielding plate 10 i
It is only necessary to place the light shielding plate 11 at the i site K and the 5B site. In the method shown in FIG. 7(1) K, the light shielding plate 10. I+
are symmetrical with respect to the lens optical axis LIC, and are displaced symmetrically with respect to the lens optical axis in a direction corresponding to the longitudinal direction of the exposure section, that is, in the left-right direction in FIG. In the case shown in FIG. 7 (TI), the light shielding plate 10.
I+ is on the same side with respect to the lens optical axis LIC, and both are integrally displaced in the left-right direction to symmetrically block the exposure light flux. In order to block light symmetrically, the light shielding plate 10
and 11 must be the same.

If it is possible to switch the magnification between enlargement, equal magnification, and reduction using the center reference method, then the document illumination light intensity distribution will be determined based on the enlargement magnification and an appropriate distribution. The light shielding by the plates IQ and I+ is prevented, and the amount of light shielding by the light shielding plates 10° and 11 increases as the copying magnification decreases at equal magnification and reduction magnification.

Next, consider the case where the displacement of the imaging lens system is based on one side.

First, consider a case as shown in FIG. 4 in which the magnification can be switched between the same magnification and the reduced magnification. In this case, one light shielding plate 10 or 11 may be provided at the 9th or 50th position of the section 5A in FIG. An appropriate original illumination light intensity distribution is determined based on the same magnification, and at this time, the amount of light shielded by the light shielding plate is set to 0, and as the magnification decreases, the amount of light shielded may be increased. On the other hand, if the magnification can be switched between the same magnification and the enlarged magnification, one light shielding plate may be provided at the portion 5B or the portion D in FIG. An appropriate original illumination light intensity distribution is determined based on the same magnification. At this time, the amount of light shielded by the light shielding plate is set to 0, and as the magnification increases, the amount of light shielded is increased.

Furthermore, when it is possible to convert the magnification between enlargement magnification, equal magnification, and reduction magnification with displacement based on one side, two light shielding plates 10
．． Arrange the I+ as shown in Figure 7 (1) or (If), determine the original illumination light intensity based on the same magnification, set the amount of light blocking at the same magnification to 0, and block the light when the magnification becomes small. The amount of light shielded by the plate 10 may be increased, and when the magnification increases, the amount of light shielded by the light shielding plate opening may be increased. In this case, the light shielding plate 10 and the mouth are not the same.

The displacements of the light shielding plates IO and I+ are different from each other K.

In addition, regardless of whether the center reference or one side reference is used, the arrangement shown in FIG. In FIG. 7(n), the light shielding plate 10 i
Even if the light shielding plate 11 is placed in the 50th part and the 5B part, the 7th
This has the same effect as the arrangement shown in Figure (n).

In addition, the shape of the edge of the light-shielding plate that intervenes into the exposure light beam is semicircular (see (1) in Figure 8), as illustrated in Figure 8.
), a triangular shape ((It) in the same figure), a pointless shape ((m) in the same figure), a trapezoidal shape ((■) in the same figure), and other so-called chevron shapes are preferable.

Of course, the present invention can also be applied when magnification conversion is performed continuously.

Furthermore, the present invention is particularly effective in the case of the exposure method shown in FIGS. 1 and 2 among the slit exposure methods. In such an exposure method, the angle of incidence of the exposure light beam on the imaging lens system changes continuously, but in the present invention, since the light shielding plate is disposed at the end face of the lens, the change in the angle of incidence changes continuously. This is because regardless of the weather, it will surely block out the light. Furthermore, since the light shielding plate is provided on the imaging lens thread, in the case of the exposure method as shown in FIG. .

Finally, specific experimental examples conducted by the present inventors will be described.

A copying apparatus was prototyped in which the slit exposure method was as shown in FIG. 1, and the displacement of the imaging lens system accompanying magnification conversion was based on one side, and the present invention was applied to this apparatus. The aspect of the one-sided reference is as shown in FIG. Note that the magnification can be switched between five types: 1x, 0.82x, and 0.65x, and the 1x magnification was set as the appropriate distribution of the original illumination light intensity distribution.

In FIG. 7, one light shielding plate having a trapezoidal edge portion,
It was placed at the site 5. In FIG. 9, the code +00 is
This light shielding board? It shows. In the same figure, reference numeral 9-1 indicates an imaging lens system, and reference numeral 9-2 indicates a pupil of which the aperture is 55 mm.

The length of the light shielding plate 100 indicated by the symbol 9-4 is 1°.
, the angle indicated by the symbol θ is 45 degrees. distance 9-5 is 18
This is the distance between the optical axis and the light shielding plate when the magnification is 0.65 times. Distance 9-5 is the distance between the two when the magnification is 0.82 times, and is set to 281 m111C. of course,
The amount of light interruption at the same magnification is 0. First, the light shielding plate +oo
Slit exposure is performed without correction by K, and the unevenness in the exposure distribution, that is, the maximum exposure light amount of the difference between the maximum exposure light amount and the minimum exposure light D in the exposed area/longitudinal direction. We investigated the ratio to As a result, the above-mentioned unevenness was 1.5% at the same magnification, 12% at the magnification of 0.82, and 20% at the magnification of 0.65. When correction was performed using the light shielding plate 100, the above unevenness was reduced to 5% for a magnification of 0.82K.
, it was possible to reduce the magnification to 7% for a magnification of 0.65.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams for explaining two examples of the slit H light system, and FIGS. 5 and 4 are diagrams for explaining the displacement of the imaging lens system accompanying switching of copying magnification. Is Figure 5 the conventional technology? FIG. 6 is a diagram for explaining the lens end face portion, and FIGS. 7 to 9 are diagrams for explaining the present invention. 5... Imaging lens, 5A, 5B, 5c, 5D... Lens end face portion, To, eye, 100... Light shielding plate procedure correction band (divisional application of Patent Application No. 149011 of 1980) 7,
Name of the invention: Exposure method 3 in a variable-magnification copying machine, and its relationship to the amended case Patent applicant address: 1-3-6 Nakamagome, Ota-ku, Tokyo Name (678) Ricoh Co., Ltd. 4, Agent address: Tokyo 4-5-4 Kyodo, Setagaya-ku "Claims" in the specification "Details of the invention" (1) The claims are amended as shown in the attached sheet. (2) "At the beginning of line 8 on page 7 of the specification"" is followed by "
Add the 7 characters ``photosensitive surface, i.e.''. (3) “Photoconductor surface” in line 11 of page 8 of the same page is “photoconductor surface”
and correct it. (4) "Light surface" at the beginning of line 14 on page 8 is corrected to "light surface." (5) “Photoconductor surface” in page 8, line 20 of the same page is “photoconductor surface”
and correct it. (6) “Photoconductor surface” at the end of the second line on page 9 is “photoconductor surface”
and correct it. (7) Correct "B" in the third line of page 10 to "B'". (8) In the 11th line of the 11th page of the same page, [The light shielding plate is provided on the lens holding member that holds the imaging lens system] from after J to before the ``shank'' at the end of the 12th line of the same page. "It is displaced integrally with the imaging lens system." (9) Add the six characters ``slit-like'' in front of ``exposure section'' on page 11, line 15. (10) At the beginning of page 11, line 17 of the same page, add the six characters "J," such as "power mechanism," before "publicly known." Add the 12 characters "that is, the imaging lens system holding member". (12) Correct the text after "etc." in the 10th line of the 15th page to the end of the 11th line of the same page to read "A tapered shape is better." (13) Add the following sentence after "Dekiru." at the end of the fourth line on page 16. ``As a technology for changing the amount of light shielding that blocks the exposure light beam in accordance with the conversion of the copying magnification, there has been a
The method described in Publication No. 39 is known. However, with this method, since the light shielding plate is located far from the lens end face of the imaging lens system, the amount of movement of the light shielding plate increases as the amount of light shielding changes, making it difficult to effectively utilize the space within the copying machine and to downsize the copying machine. . However, in the present invention, since the light shielding plate is provided on the imaging lens system holding member at the end face of the lens, the amount of movement of the light shielding plate for correcting the exposure amount can be extremely small. Therefore, it is possible to effectively utilize the space within the copying machine, and it is also possible to downsize the copying machine. (Claim 1) A photosensitive surface is exposed using a slit exposure method, and an image forming lens system is displaced in accordance with switching of copying magnification to selectively apply an original image to the photosensitive surface at different magnifications. In a variable magnification type copying machine that projects, a light shielding plate for regulating the exposure light flux is provided on the imaging lens system holding member at the end face of the imaging lens, and as the imaging lens system is displaced in accordance with switching of the copying magnification, The light shielding plate is moved in a direction corresponding to the longitudinal direction of the slit-shaped exposure part, and the light shielding plate is attached to the imaging lens holding member so that as the copying magnification decreases, the amount of exposure light flux blocked by the light shielding plate increases. 7. An exposure method in a variable magnification type copying machine, characterized in that the distal end portion of the light shielding plate in the moving direction has a tapered shape. Exposure method for double copying machines.

Claims (1)

[Scope of Claims] 1. In a variable magnification copying machine that exposes a photoreceptor using a slit exposure method and displaces an imaging lens system in accordance with switching of copying magnification, at least one lens is provided at the end surface of the lens. A light shielding plate is provided, and this light shielding plate is integrated with the imaging lens system with respect to the displacement of the imaging lens system, and each time the copying magnification is switched, the light shielding plate is moved in the longitudinal direction of the slit-shaped exposed part. An exposure method, comprising displacing the lens in a direction corresponding to the direction perpendicular to the optical axis of the lens to change the amount of exposure light flux blocked, thereby making the exposure amount distribution in the longitudinal direction of the exposure section uniform. 2. A variable magnification type copying machine according to claim 1, characterized in that the displacement of the imaging lens system accompanying switching of the copying magnification is performed with reference to the center, and two light shielding plates are provided. exposure method. 3. A variable magnification type copying machine according to claim 2, characterized in that the two light shielding plates are arranged symmetrically with respect to the lens optical axis in a direction corresponding to the longitudinal direction of the exposure section. exposure method. 4. In claim 2, one of the two light-shielding plates is disposed on the entrance end face side of the imaging lens system, and the other one is disposed on the output end face side, and these light-shielding plates: An exposure method for a variable magnification type copying machine, characterized in that the exposure sections are arranged on the same side with respect to the optical axis in a direction corresponding to the longitudinal direction of the exposure sections. 5. In claim 1, the displacement of the imaging lens system accompanying the switching of the copying magnification is performed on a one-sided basis, and the switching of the copying magnification is between the same magnification and the reduction magnification, or between the same magnification and the enlargement. An exposure method for a variable magnification type copying machine, characterized in that exposure is performed between magnifications, and the number of light shielding plates is one. 6. In claim 1, the displacement of the imaging lens system accompanying switching of the copying magnification is performed on a one-sided basis, and the switching of the copying magnification is performed between enlargement magnification, equal magnification, and reduction magnification, An exposure method for a variable magnification type copying machine, characterized in that two light shielding plates are provided, one light shielding plate blocks light during enlargement magnification, and the other light shielding plate blocks light during reduction magnification. 7. In claim 6, the variable magnification is characterized in that the two light shielding plates are disposed opposite to each other across the lens optical axis in a direction corresponding to the longitudinal direction of the exposure section. Exposure method for copying machines. 8. In claim 6, one of the two light-shielding plates is provided on the incident end face side of the imaging lens system, and the other one is provided on the output end face side, and these light-shielding plates: An exposure method for a variable magnification type copying machine, characterized in that the exposure sections are arranged on the same side with respect to the optical axis in a direction corresponding to the longitudinal direction of the exposure sections. 9. In any one of claims 1, 2, 5, and 6, the angle of incidence of the exposure light beam onto the imaging lens system is continuous in the exposure direction during exposure. An exposure method for a variable magnification type copying machine characterized by a change in exposure. 10. Claim 9 is characterized in that the change in the angle of incidence of the exposure light beam onto the imaging lens system during exposure is caused by movement of the imaging lens system perpendicular to the optical axis in the exposure direction. An exposure method for a variable magnification copying machine.