JPS62220944A - Automatic focus controller for copying machine - Google Patents

Abstract

PURPOSE:To eliminate the need to vary the shape of an image plane when an original in a solid shape is copied and to form a sharp copy image by providing a lens for focus correction, a focal length measuring means, and a moving means for a lens for focal length correction. CONSTITUTION:This controller is provided with the lens 7 for focus correction which is movable in an optical-axis direction independently of a lens for copying, the focal length measuring means 44 which measures the distance between an original surface and a fixed point on the optical axis, and the focal length correcting lens moving means 7a which moves the lens 7 for focal length correction according to the measurement result of the focal length measuring means 44. Consequently, the distance between the lens and the image surface of the original mounted on table glass constituting an original platen is measured by the focal length measuring means 44 to move the focal length correcting lens 7 in the optical axis direction on the basis of the measurement result of the focal length measuring means 44 and also vary the focal length of the lens according to the distance between the image surface of the original and the lens.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an automatic focus adjustment device that is installed in a copying machine using electrophotography and changes the focal length of a lens according to the distance to an image.

<Summary of the Invention> In summary, the automatic focus adjustment device for a copying machine according to the present invention uses a focal length measuring means for measuring the distance between a focus correction lens that is movable in the optical axis direction and a document surface. By moving the apparatus using a moving means according to the result, it is possible to form a clear copy image even for an original having a three-dimensional image plane.

<Prior Art and Its Disadvantages> In a copying machine using electrophotography, an image of an original is scanned by light from a light source, and reflected light from the original is passed through a lens and distributed onto the surface of a photoreceptor. Lenses used in such copying machines must satisfy a wide angle of view, a high resolution, and a short focal length, and the depth of field and depth of focus are usually extremely shallow, about 1 yen. Therefore, in order to obtain a clear copy image, it is necessary to place the image surface of the document in close contact with the table glass that makes up the document table, and the image surface is uneven, such as on a double-page spread. In the case of an original having a 3D image, the parts raised from the table glass surface will be copied black, or only a blurred copy image will be obtained.

For this reason, in conventional copying machines, a book spread in two pages is loaded into the device, and a table glass is brought into close contact with the image surface under a constant pressure to make the image surface of the document as close to a flat shape as possible. was there. However, it takes a long time to take the original into the device, and a complicated mechanism is required to move the original and press the table glass, which reduces work efficiency, increases the size of the device, and increases costs. There was a drawback. Further, there is a drawback that the original document may be destroyed by repeated pressure bonding of the table glass, and furthermore, the effect cannot be obtained with a rigid document whose image plane does not deform into a flat surface even by the pressure bonding of the table glass.

<Object of the Invention> In view of the above-mentioned drawbacks of the conventional art, the object of the present invention is to change the focal length of the lens according to the change in the distance between the lens and the image plane, and to improve the image quality when copying an original having a three-dimensional image plane. An object of the present invention is to provide an automatic focus adjustment device that eliminates the need to change the shape of an image plane and can obtain clear copied images without reducing work efficiency, increasing the size of the device, increasing costs, and causing damage to the original. .

<Configuration and Effects of the Invention> The automatic focus adjustment installation of the copying machine of the present invention includes a focus correction lens that is movable in the optical axis direction independently of the copying lens, and a fixed point between the document surface and the optical axis. The present invention is characterized in that it includes a focal length measuring means for measuring a distance, and a focal length correcting lens moving means for moving a focal length correcting lens based on the measurement result of the focal length measuring means.

According to the present invention with the above configuration, the distance between the image plane of the document placed on the table glass constituting the document table and the lens is measured by the focal length measuring means, and the measurement result of the focal length measuring means is Based on this, the focal length correction lens can be moved in the optical axis direction. Thereby, the focal length of the lens can be changed depending on the distance between the image plane of the document and the lens. Therefore, even if the image surface is not in close contact with the table glass, the reflected light from the image can be clearly formed on the surface of the photoreceptor, and when copying an original whose image surface has a three-dimensional shape, the image There is no need to change the shape of the surface, and there is no need for operations or equipment related to changing the shape of the image surface, reducing work efficiency, increasing the size of the device,
A clear copy image can be formed without increasing costs or damaging the original. In addition, a clear copy image can be obtained even for an original whose image surface shape cannot be changed.

<Embodiment> FIG. 2 is a schematic front sectional view showing the configuration of a copying machine equipped with an automatic focus adjustment device according to an embodiment of the present invention.

A photosensitive drum 2 is located approximately in the center of the copying machine main body 21.
2 is provided, and constitutes a copying process section 33 together with a charging charger 23, a developing device 24, a transfer charger 25, a cleaner 26, and a static elimination charger 27 on the outer periphery. The sheets fed one by one from the paper feed section 29 are discharged to the stray paper section 30 via the copying process section 33. During this time, the image is transferred to the paper by the transfer charger 25,
The fixing device 31 applies heat and pressure to fix the image.

A document table 32 made of hard transparent glass is formed on the upper surface of the copying machine main body 21 . An optical system including a light source 1, mirrors 2a to 2d, and a lens unit 3 is provided between the document table 32 and the copying process section 33. The lens unit 3 is movable in the direction of arrow A or B. The light source 1 scans an image of a document placed on a document table 32. This light reflected from the original is reflected from the mirror 2a~
2d, an image is formed on the photosensitive drum 22 via the lens 3, as shown by the dashed line in the figure. Photosensitive drum 22
The surface of the document is charged with a single polarity by a charger 23 before being exposed to light from the original. Exposure to light from the original forms a latent image of the original image;
This latent image is visualized by the developer supplied from the developing device 24.

FIG. 1 is a front sectional view showing the configuration of an optical system included in the copying machine.

The optical system provided on the lower surface of the document table 32 includes a first scanner 4, a second scanner 5, and a lens unit 3. The first scanner 4 includes a light source 1, a reflector la, a first mirror 2a, and a filter 6. This filter 6 cuts the far infrared region of the light from the light source 1. The second scanner 5 includes a second mirror 2b and a third mirror 2.
C is attached. Reflector 3 has body 1
A copying lens 8 fixed to body lla, a focus correction lens 7 attached to body llb, a pulse motor 7a for moving body 11b in the optical axis direction relative to body lla,
A light receiving element 9, a light emitting element 10, a pulse motor 10a for rotating the light emitting element 10, a pulse motor 3a for moving the body Ila in the optical axis direction, and a fourth mirror 2d are provided.

The first scanner 4 and the second scanner 5 are provided so that they can be horizontally reciprocated on the lower surface of the document table 32 in the direction of arrow A or B. The first scanner 4 operates at twice the moving speed as the second scanner 5. by this,
The first scanner 4 scans the entire image surface of the original placed on the original platen 32, and the light reflected from the original by the light source 1 is reflected from the first mirror 2a to the first mirror 2a as shown by the dashed line in the figure. The light is reflected by the three mirrors 2C and reaches the focal length correction lens 7 and the copying lens 8. The light passing through these lenses 7.8 is reflected by the mirror 2d, and the light is reflected by the photoreceptor drum 22.
light is distributed over the surface of the The pulse motor 3a rotates according to the copying magnification and moves the body 11a in the optical axis direction. Further, the pulse motor 7a rotates in response to changes in focal length caused by irregularities on the image surface of the original, and moves the body llb in the optical axis direction.

The light receiving element 9 is composed of a three-part photocell.

Each cell has a slit to split the incident light. Further, the light emitting element 10 is constituted by a far-infrared semiconductor laser diode, and irradiates the third mirror 2C with highly directional infrared rays. This infrared rays reach the original placed on the original platen 32 through the mirrors 20 to 2a, and the reflected light reaches the light receiving element 9 through the mirrors 2a to 2C.

FIG. 3 is a block diagram of the control section of the copying machine.

The light emitting circuit 41 includes a light emitting element 10. Light emitting element 1
The reflected infrared light irradiated onto the document surface from the light receiving element 9
The light is received by the light receiving circuit 42 having a
is output to. Pulse motor feedback control circuit 4
3 drives the pulse motor loa according to the light reception signal to rotate the light emitting element 10 of the light emitting circuit 41. In this way, the pulse motor 10a is feedback-controlled by the pulse motor feedback control circuit 43 so that the light receiving state of the light receiving element 9 is appropriate. The amount of rotation of the pulse motor 10a is manually input to the distance calculation circuit 44. Distance calculation circuit 44
calculates the amount of movement of the focal length correction lens 7 from the amount of rotation of the pulse motor 10a, and drives the pulse motor 7a accordingly, while inputting copy data from the operation board 57 to the main body CPU 45 via the I10 ink face 46. be done. The CPU 45 uses the magnification calculation circuit 50 to calculate the copy magnification based on the input size data of the paper and the original. The magnification calculation circuit 50 outputs a drive signal for the pulse motor 3a according to the calculated copy magnification, and the body tia
moves in the optical axis direction. Motor control data corresponding to the copy magnification is output from the CPU 45 to the motor drive section 48 via the I10 ink face 47. Motor drive section 4
8 outputs a drive signal to the mirror motor 51 and main motor 52 based on the control data.

When the automatic focus adjustment mode is selected from the operation board 57, an on signal is output to the distance calculation circuit 44, and the distance calculation circuit 44 calculates the moving distance of the focal length correction lens 7.

FIG. 4 is a plan view showing the operation of the automatic focus adjustment device of the copying machine.

When the document surface is at the intermediate position 32b, the reflected far-infrared light from the light emitting element 10 is incident on the photocell 9b at the center of the light receiving element 9. If the focal length correction lens is at the reference position when the reflected far-infrared light enters the photocell 9b in the center, the pulse motor loa causes the reflected far-infrared light to enter the photocell 9b in the middle. Light emitting element 1
Operate 0. That is, when the document surface is in the state 32a, the reflected far-infrared light is incident on the photocell 9a. The light receiving circuit 42 outputs the light receiving signal of the photocell 9a to the pulse motor feedback control circuit 43, and the pulse motor 10a rotates the light emitting element 10 in the direction of arrow C. This rotation continues until reflected light is incident on the photocell 9b.

When the photocell 9b receives the reflected far-infrared light, the driving of the pulse motor 10a is stopped, and the rotation angle from the reference position is input to the distance calculation circuit 44.

The interval ΔL between the intermediate state 32b and the state 32a of the original is defined by the rotation angle of the light emitting element 10 being β, the angle from the direction perpendicular to the optical axis in the reference state of the light emitting element 10 being α, and the distance ΔL from the light emitting element 10 to the reference state of the original. distance between the optical axis and the light emitting element 10.
Let S be the distance from ΔL=S (muan(α+β)
−tanα). Therefore, the distance calculation circuit 44 uses the above equation to calculate ΔL based on the rotation angle β. Since there is a unique relationship between this displacement amount ΔL and the movement amount Δl in the optical axis direction necessary for correcting the focal length correction lens 7, the pulse motor 7a is controlled based on the displacement amount ΔL obtained by calculation. This makes it possible to correct errors in the focal length of the copying lens 8 caused by displacement of the image plane of the original.

Note that when the document is in state 32c and the photocell 9C receives reflected far-infrared light, the pulse motor 10
A can be driven in the opposite direction to move the light emitting element 10 in the direction indicated by the arrow, and the displacement amount ΔL can be determined.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view showing the configuration of an optical system of a copying machine equipped with an automatic focus adjustment device according to an embodiment of the present invention, FIG. 2 is a schematic front cross-sectional view showing the configuration of the same copier, and FIG. 4 is a block diagram of the control section of the copying machine, and FIG. 4 is a plan view showing the operation of the automatic focus adjustment device. 7 - Focal length correction lens, 7a - Pulse motor, 8 - Copying lens, 9 - Light receiving element, 10 - Light emitting element, 10a - Pulse motor.

Claims (1)

[Claims] (1) A focus correction lens that is movable in the optical axis direction independently of the copying lens, a focal length measuring means for measuring the distance between the document surface and a fixed point on the optical axis, and measurement of the focal length measuring means An automatic focus adjustment device for a copying machine, comprising: focal length correction lens moving means for moving the focal length correction lens based on the result.