JPH06100772B2 - Exposure compensation mechanism for copiers - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exposure amount correction mechanism of a copying machine, and more specifically, achieves flattening of image illuminance over a wide range from enlargement copying to reduction copying. The present invention relates to an exposure amount correction mechanism.

<Background Art> A lens has an incident characteristic of the amount of light expressed by multiplying the cos 4th power law and the aperture efficiency, and an original image is formed on a photoconductor through an optical system including the lens. In the machine, the illuminance distribution on the light source side is set so that the image illuminance on the photoconductor side becomes flat during enlargement copying.
Therefore, the image illuminance on the photoconductor side is not flat at the same size copying and reduction copying, and if any of the flat state of the image illuminance exceeds the allowable range, some correction is required.

<Prior Art> Conventionally, in order to achieve a flat image illuminance over a wide range from enlarged copying to reduced copying, a light blocking member is attached to a lens that moves according to the copying magnification, and a predetermined size of the copying machine main body is attached. By engaging with a fixed cam attached to the position, it operates in synchronism with the movement of the lens and cuts the peripheral light amount at the time of reduction copying.The lens that moves according to the copy magnification has an opening with a narrow central part. The light-shielding hood is fixedly mounted to cancel out the incident angle characteristics as a whole, and other corrections are not performed.A lens with a relatively long focal length is used, and the magnification range for zooming is kept small. By setting so that the image illuminance on the photoconductor is flat during equal-magnification copying, the deviation from the flat state of the image illuminance during magnified copying and reduced copying is within the allowable range. A fixed light-shielding member is fixed to a predetermined position of the main body of the copying machine, and a suitable image illuminance is corrected according to the position of the lens that moves according to the copy magnification (Japanese Patent Laid-open No. 59-59). -44037 gazette), etc.

However, the above structure has a complicated mechanism, the above structure wastes a large amount of light, and a large-diameter lens is required.The above structure has a large amount of light on the image depending on the type of document. As unevenness appears, the optical path from the light source to the photoconductor has to be lengthened, and the size of the copying machine as a whole becomes large.
As shown in the figure, the mounting position of the light shielding member (5 ') is such that the reflecting mirrors (23') (24 ') and the lens (25') which constitute the optical system.
Must be in a position where it does not come in contact with any of the above, that is, the reflecting mirrors (23 ') (24') at the time of copying at the same size and at the time of reducing copying.
The maximum movement position of the lens (25 ') does not come into contact with the reflecting mirrors (23') and (24 ') at the maximum movement position (see the two-dot broken line in the figure), and the maximum movement position of the lens (25') during magnified copying. In (25E ') (see the two-dot broken line in the figure), the light-shielding member (5') must be in a position where it does not come into contact with the lens (25 '), and the distance from the light source (21') to the photoconductor (1 ') The optical path must be lengthened and the size of the copying machine as a whole must be increased, so that any of the configurations was not sufficiently satisfactory.

<Purpose> The present invention has been made in view of the above problems,
It is an object of the present invention to provide an exposure amount correction mechanism of a copying machine which has a simple structure, has little loss of light amount, and can perform good image illuminance correction.

<Structure> In order to achieve the above object, the exposure amount correction mechanism of the present invention has a variable-magnification copying function by displacing a lens for irradiating the image carrier with an original image along a predetermined optical path. In an exposure amount correction mechanism provided in a copying machine and having a light blocking member capable of changing a light blocking amount according to a displacement when the magnification of the lens is changed, in the light blocking member, the lens serves as a light blocking member with respect to an optical path when the magnification is changed. A lens position corresponding to the same-magnification copy, which allows relative displacement and allows the lens to pass by opening the optical path directly driven by the lens when the lens moves to the magnifying copy position. The image is illuminated by a light-shielding member to cut the amount of light during equal-magnification copying and reduction copying when it is composed of a movable member that is close to The possible flat, yet without any disturbing movement of the reflector during scanning exposure operation of the document can be downsized as a whole copier.

However, as the light-shielding member, various types such as a rotating type and a sliding type can be used, but the one that operates in a double-opening shape (may be a double-opening shape that opens in any direction such as vertical or horizontal) by a lens Are preferable from the viewpoint of simplifying the configuration.

<Examples> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating examples.

FIG. 4 is a schematic view of a main part of a copying machine of a type in which an optical system moves, in which a photoconductor drum is used as a photoconductor to clearly show an internal mechanism.

Reference numeral (1) is an original placing table located on the upper surface of a copying machine main body (not shown), and a light source (21), reflecting mirrors (22), (23) and (24), and a light shielding member (5) are provided at predetermined positions below the original placing table. ), Lens (2
5) and an optical section (2) composed of a reflecting mirror (26), and by moving the light source (21) and the reflecting mirrors (22) (23) (24) in the direction of arrow A, the original ( D) can be sequentially scanned and exposed. Then, the light source (21) and the plane reflecting mirror (22) move integrally, and the plane reflecting mirrors (23) (24) also move integrally, so that the moving speed of the former is twice that of the latter. Is set to be Then, below the optical unit (2), the photosensitive drum (31) that rotates in the direction of arrow B for each copying operation, the charge eliminating lamp (32), the charger (33), the developing device (34), A copy processing section (3) including a transfer charger (35), a separation charger (36), and a cleaner (37);
An electrostatic latent image is formed by irradiating the surface of the photosensitive drum (31) uniformly charged by the charging charger (33) with the reflected light from the document (D), and the electrostatic latent image is developed by the developing device. The toner image can be visualized by (34), and the toner image can be transferred onto the copy paper (P) by the transfer charger (35). Further, reference numeral (41) is a registration roller which constitutes a part of the copy paper feeding section, and can feed the copy paper (P) at a speed substantially equal to the peripheral speed of the photosensitive drum (31). Reference numeral (10) is a document retainer mounted so as to cover the upper surface of the document placing table (1) so as to be vertically rotatable by a hinge mechanism or the like (not shown). Further, (25E) (see FIG. 5), (25N) and (25R) indicate the positions of the lens (25) at the time of magnified copying, copying at the same size and reduction copying, respectively.

FIG. 1 is a perspective view showing the relationship between the lens (25) and the light shielding member (5). A pair of flat plate members (51) are attached to each other so as to face each other, and the flat plate members (51) are provided at the central portions on the opposite end side. A triangular notch (52) is formed. And the flat plate material (51)
Is always flush with the biasing member (not shown) such as a spring as shown by the solid line in the figure, and when the lens (25) moves to the magnifying copy position (25E), As indicated by the two-dot broken line, the outer end portion is the center of rotation so as to come into contact with the lens (25) and rotate in a double-opening manner. The cutout portion (52) is shown in FIG. 2 (the left side of FIG. 2 is the original,
As shown in Fig. 3 showing the photoconductor on the right side), and as shown in Fig. 3, the optimum light amount is cut according to the position (25N) (25R) of the lens (25) during equal-magnification copying and reduction copying. A shape that can demonstrate its performance (for example, the maximum use magnification is Xmax, and the ratio of the edge of the document to the center of the required illuminance on the document surface is AX
When the ratio of the required illuminance of the document surface to the center at the maximum magnification x is set to AX, the cut ratio L of the amount of light entering the lens (25) from the edge of the document surface at the magnification X
Is set to L = (AXmax−AX) / AXmax). It should be noted that N in FIG. 3 shows a light amount cut state at the time of equal-magnification copying, and R in the same figure shows a light amount cut state at the time of reduced copying. As for the mounting position of the light shielding member (5), the scanning exposure distance is the longest, and the reflection mirror (23) (2
4) is the position closest to the reflecting mirrors (23) and (24) in the state in which 4) has moved to the most exposure end side (see the two-dot broken line in FIG. 4), and the lens (25) is The position is set to be close to the position (25N).
Incidentally, L in FIG. 1 indicates reflected light.

With the above configuration, during enlargement copying, the lens (25) moves to the exposure start side to open the light blocking member (5) in a double-opening manner, and the light amount correction by the light blocking member (5) is not performed. Therefore, for example, if an optical system with a lens (25) having a focal length of 150 mm, a manuscript, and an image width of 300 mm is used and the image illuminance is flat when the magnification is 1.13 times, As shown in Fig. 6, the deviation of the image illuminance from the flat state is small at the time of magnified copying (the magnification is 1.41 times, the deviation is about -5%, and even if the magnification is 1.00 times, the deviation is about +5).
%), Which is within the allowable range, and a good copy can be obtained.

Further, during reduction copying, the light shielding member (5) becomes flush with the light shielding property according to the distance between the lens (25) and the light shielding member (5), the image illuminance is flattened, and a good copy is obtained. Can be obtained.

Therefore, as shown in FIG. 7, when the light amount is not corrected by the light shielding member (5) at all, the scaling factor is 1.
In the case of using a light source (21) where the image illuminance becomes flat when it is set to 00 times, the magnification is 1.41 times and the deviation is about -8%, and the magnification is 0.50 times and the deviation is about + 27%. However, in the above-mentioned embodiment, it is within ± 5%, and the flatness of the image illuminance has sufficiently reached the permissible level as a product.

Then, structurally, as shown by the two-dot broken line in FIG. 5,
Since the light blocking member (5) only operates following the movement of the lens (25) to the exposure start position side at the time of magnified copying without performing full scan, simplification is possible and at the same time, the light blocking member (5) ) Is mounted in close proximity to the movement position of the reflecting mirrors (23) and (24) at the most exposure end side (full scan position at the time of copying at equal magnification and reduction copying), and at the time of magnifying copying, as shown in FIG. As shown, the lens (25) is configured to move from the light blocking member (5) to the exposure start side by operating the light blocking member (5) in a double-opening manner. Become.

The present invention is not limited to the one using the right-angled mirror shown in the above-mentioned embodiment, but if the original is scanned and exposed by moving the light source (21), the right-angled mirror is not used. The present invention can also be applied to the above, and various design changes can be made within a range that does not change the gist of the present invention.

<Effects> As described above, according to the present invention, the light blocking member is attached in proximity to the lens position corresponding to copying at the same size, and the light blocking member is moved to the non-light blocking state following the movement of the lens to the magnifying copying position. Since it is composed of members, a sufficient light amount correction effect can be exhibited. In addition, the light blocking member is closely driven to the corresponding lens position during equal-magnification copying so that when the lens moves to the magnifying copy position, the lens is directly driven to open the optical path to allow the lens to pass. Therefore, the light blocking member opens the optical path according to the displacement of the lens, and becomes the non-light blocking state when the lens moves to the maximum expansion position. On this occasion,
Since the lens and the light blocking member are relatively displaced with respect to the optical path, and the light blocking member allows passage of the lens at the time of enlarging, compared to the case where the light blocking member and the lens are maintained at a fixed position with respect to the optical path. The optical path length can be shortened to contribute to downsizing of the copying machine. Further, since the lens can directly drive the light blocking member, it is possible to adopt a simple configuration.

As described above, the present invention has a unique effect that the structure can be simplified and the size can be reduced when the sufficient light amount correction is performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing the relationship between the lens (25) and the light shielding member (5), and FIG. 2 is a schematic view showing the relationship between the light shielding member (5), the lens (25), and the optical path. FIG. 4 is a schematic diagram showing a light quantity cut state by a light shielding member (5), FIG. 4 is a schematic diagram showing a main part of a copying machine, FIG. 5 is a schematic diagram showing an enlarged copying state, and FIG. 6 is a position of the invention. FIG. 7 is a diagram showing light amount correction data according to the embodiment, FIG. 7 is a diagram showing data when light amount correction is not performed, and FIG. 8 is a schematic diagram showing a main part of a conventional copying machine. (5) …… Shade member, (25) …… Lens, (51) …… Flat plate material, (52) …… Notch

Claims (2)

[Claims] 1. A lens for irradiating an image carrier with an original image,
An exposure amount correction mechanism provided in a copying machine having a variable magnification copying function by displacing along a predetermined optical path, and having a light blocking member capable of changing the light blocking amount according to the displacement when the magnification of the lens is changed. In the above, the light blocking member allows the lens to be displaced relative to the light blocking member with respect to the optical path when the magnification is changed, and when the lens is moved to the magnifying copy position, the lens is directly driven to open the optical path. An exposure amount correction mechanism for a copying machine, which is configured by a movable member which is close to a lens position corresponding to a normal magnification copy so as to allow the lens to pass therethrough. 2. The exposure amount correction mechanism for a copying machine according to claim 1, wherein the light blocking member operates in a double-opening manner to be in a non-light blocking state.