JPS60164773A - Automatic exposure adjusting device - Google Patents

Abstract

PURPOSE:To execute an optimum exposure adjustment corresponding to a variable density of an original, executing a picture read operation, by constituting so that a shutter shape can be set to an optimum shape by feeding back an output signal of a sensor which receives a reflected light by a scanning exposure of the original, to a liquid crystal shutter. CONSTITUTION:A liquid crystal shutter 55 is provided on light irradiating part of a light source 21, and also a feedback control system is constituted by focusing a light which transmitts through a half mirror 25', in a reflected light from an original 18, by a lens 51, photodetecting it by a CCD area sensor 52, and impressing an output signal of the CCD area sensor 52 to each segment 56 of the liquid crystal shutter 55 through a control circuit 53 and a driving circuit 54, by which an exposure adjustment corresponding to a kind of the original 18 can be executed. Also, a light reflected by the half mirror 25' is focused by a lens 26, an output signal of a CCD line sensor 61 is binary-coded, and also it can be impressed to a memory, etc. 63.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an automatic exposure adjustment device, and more particularly, to an automatic exposure adjustment device that changes the amount of exposure using a liquid crystal shutter provided on an exposure optical path.

<Prior Art> Conventionally, in image reading apparatuses, the exposure amount for exposing a document is set by changing the voltage applied to a light source. However, when a fluorescent lamp is used as a light source, there is a problem in that the amount of exposure cannot be changed even if the applied voltage is changed.

In view of these problems, a copying machine was invented in which exposure is adjusted using an exposure illuminance correction liquid crystal plate, as shown in Japanese Patent Laid-Open No. 57-78058. The exposure illuminance correction liquid crystal plate used in this copying machine has -2- a plurality of illuminance control segments arranged in parallel in the longitudinal direction, each of which can be controlled independently of the other; By changing the light transmission rate or the reflection rate, the amount of exposure of the document by the light source is adjusted in whole or in part. However, in a copying machine with this configuration, the light transmission ratio of each illuminance control segment of the exposure illuminance correction liquid crystal plate is adjusted in advance so that the charge distribution on the photoreceptor becomes uniform in accordance with the type of light source and the type of optical system. It is a function to set the reflection ratio, and it is possible to perform the optimal exposure adjustment for each copying machine, and it is possible to adjust the exposure to the optimum level for each copying machine, and it is possible to adjust the exposure by adjusting the light and shade of characters, lines, etc. on the document during the scanning exposure operation of the document, or the paper of the document. It is not possible to automatically adjust the exposure according to the density of the image itself, and copying operations can only be performed using a preset exposure amount by manual operation. Therefore, there is a problem in that it is not possible to obtain an optimal copy image for each document.

<Purpose> This invention was made in view of the above problems.
- An object of the present invention is to provide an automatic exposure adjustment device that can perform optimal exposure adjustment corresponding to the density of a document while performing an image reading operation.

Structure> The structure of an automatic exposure adjustment device to achieve such a purpose includes an image reading device that exposes a document to light using a light source and forms an electrostatic latent image on a photoreceptor using light reflected from the document.
A liquid crystal shutter with many segments arranged in parallel in the length and width directions is provided on the exposure optical path, and a sensor is provided to detect the reflected light from the scanning exposure of the document. It is characterized by the provision of a drive circuit that drives the segments and changes the shutter shape.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a schematic diagram showing the internal mechanism of a copying machine equipped with an automatic exposure adjustment device of the present invention.

(1) is the main body of the copying machine, with the document presser plate -4 on the top.
- In addition to being equipped with a document loading table (11), two paper feed cassettes (12) and (13) are removably installed at the lower part of the right side, and the copying is completed at a predetermined position on the left side. The receiver 11 [1 (
14) is provided. Then, place the partition plate (
15), the upper chamber (16) and the lower chamber (
17), and an optical system (2) that can reciprocate in the upper chamber (16), and a lower chamber (17).
A copy processing section (4) and a copy paper transport section (3) are provided inside.

The optical system (2) includes a light source (21), a first reflecting mirror (2'2) having a curved reflecting surface, a second reflecting mirror (23),
3rd anti! 1) 11! (24), fourth reflecting mirror (25)
, a lens (26), and a fifth reflecting mirror (27), among which the light source (21) and the first reflecting mirror (22) reciprocate once for each copying operation. The original on the original placing table (11) can be sequentially scanned and exposed, and the reflected light from the original is reflected by the light 11M (21) and the second reflecting mirror (23) which moves following the movement of the first reflecting mirror (22). ) to fourth reflecting mirror (25), lens (26)-5
-1 Fifth counter@ (27) The light is irradiated onto the surface of a photoreceptor drum (41), which will be described later, through a slit (28) formed at a predetermined position of the partition plate (15).

The copy paper transport section (3) carries each cassette (12) (1
Paper feed rollers (31) and (32) take out one sheet of copy paper (P) from 3) and feed it to the registration rollers (33) (34), and the copy paper (P) from the registration roller (34).
) to the copy processing unit (4), a belt (36) that transports the copy paper (P) peeled off from the copy processing unit (4), and a belt (36) that transports the copy paper (P) peeled from the copy processing unit (4), It consists of a heating fixing roller (37) that heats and fixes the toner image, and a delivery roller (38) that sends out the heated and fixed copy paper (P) toward the receiver (14). Paper roller (3
1) By selectively driving (32), copy sheets (P) in the desired cassette (12) or (13) can be fed one by one.

The copy processing section (4) is provided approximately at the center of the lower chamber (17) and is operated in one direction (direction of arrow A1 in the figure) for each copying operation.
A photoreceptor drum (41) that rotates is provided, and a charger (42), a developing device (43), and a transfer charger (41) are arranged around the photoreceptor drum (41).
44), stripper V-jar (45), and cleaner (4
6) are provided in this order. Therefore, after the photoreceptor layer of the photoreceptor drum (41) is uniformly charged by the charger (42), the fi? An electrostatic latent image is formed, toner is adsorbed by a developing device (43) to form a toner image, and then a transfer charger (44) transfers the toner onto copy paper (P) fed from a conveyance roller (35). The image is transferred, the copy paper (P) is peeled off from the photosensitive drum (41) by a peeling charger (45), and finally a cleaner (46)
) to collect the toner remaining on the photoreceptor drum (41).

FIG. 2 is a block diagram showing the automatic exposure adjustment device of the present invention, in which a liquid crystal shutter (5
5), and the half mirror (25') (corresponding to the fourth reflecting mirror (25) in Fig. 1) out of the reflected light from the original (18). The transmitted light is focused by a lens (51) and received by a COD area sensor (52).
A feedback control system is configured by applying the output signal of the area sensor (52) to each segment (56) of the liquid crystal shutter (55) through the control circuit (53) and the drive circuit (54). It is possible to adjust the fog light according to the type of light.

In addition, the light reflected by the half mirror (25') is focused by the lens (26) and the COD line sensor +J (
61), the output signal of the CCD line sensor (61) is binarized by a binarization circuit (62), and can be further applied to a memory etc. (63).

Figure 3 shows a segment (56) of a liquid crystal shutter (55), in which a liquid crystal (59) is sealed in a cell (58) having transparent electrodes (57) on both sides. A segment (56) is formed by applying an operating voltage between the liquid crystal (59) from a transparent state to a reflective state, or vice versa. 56),
As shown in FIG. 4, a liquid crystal shutter (55) is constructed by arranging a plurality of shutters in a dot matrix shape in the arm direction and the width direction. However, one cell (58) is formed, and many pairs of transparent electrodes (57) (5
7) can also be used to configure a liquid crystal shutter (
(See Figure 5).

Therefore, the control circuit (53) and the drive circuit (54)
By driving each segment (56) independently of each other through the CCO area sensor (52), the liquid crystal shutter (55) is controlled into a light-shut area and a light-transmissive area with shapes corresponding to the output signals of each part of the CCO area sensor (52). The optimum exposure state corresponding to the density of the original (18) can be obtained.

More specifically, the CCD line sensor (61) receives only the reflected light corresponding to an extremely narrow range of document area in the scanning exposure direction of the document (18). If a black line is drawn on the entire main scanning line, the CCD line sensor (61) outputs a signal indicating that the entire main scanning line is black, and a white line is drawn on the entire main scanning line of the document (18). If it is drawn, the CCD line sensor (61) outputs a signal indicating that the entire area is white. Also COD area sensor (5
2) is a sensor that receives reflected light corresponding to a wider document area than the CCD line sensor (61), and for example, a black line is detected over a specific main scanning line of the document (18). Even if the image is drawn, if there is a white area around it, a signal corresponding to the overall average illuminance is output.

Therefore, by receiving the reflected light from a fairly wide area of the original (18) and driving the liquid crystal shutter (55), it is possible to always maintain the original exposure amount at the optimum value, and also to The reflected light is received and binarized, and the electrostatic latent image can be developed in an optimal state.

However, the same effect as the CCO area sensor can also be achieved by providing the CCD line sensor at a position shifted from the imaging position by the lens (51).

FIG. 6 is a block diagram showing an exposure adjustment device for correcting the light source, in which a liquid crystal shutter (55) is provided in the light irradiation section of the light source (21), and a device for scanning exposure of the original (18) is provided. The reflected light from the reference plate (19) of a predetermined color such as white, which is formed at a position preceding
(corresponding to the fourth mirror (25) in Fig. 1) and the CCD through the lens (26).
The output signal of the CCD sensor (64) is applied to each segment (56) of the liquid crystal shutter (55) through a control circuit (53') and a drive circuit (54'). The output signal of the CCD sensor (64) is also applied to a binarization circuit (62), and the binarized signal is applied to a memory etc. (63). .

More specifically, in this example, the manuscript (18
), the reference plate (19) is exposed to light, the reflected light is detected by the CCD sensor (64), and the control circuit (5
3') and the drive circuit (54') to each segment (56) of the liquid crystal shutter (55).
Therefore, until the scanning exposure of the original (18) is performed, not only the correction (shading correction) of the illuminance pattern in the longitudinal direction for light II (21) but also changes over time, environmental changes such as temperature, etc. , changes in the voltage applied to the light source, etc. can be effectively compensated for.

Furthermore, by changing the constants of the control circuit (53) by external operation, it is possible to make a part or the entire area of the copied image bright and dark.Furthermore, by using a fluorescent lamp as the light source (21) and changing the applied voltage, Even if only a constant illuminance is obtained, shading correction etc. can be performed using the liquid crystal shutter (55).

Therefore, by receiving the reflected light from a fairly wide area of the original (18) and driving the liquid crystal shutter (55), it is possible to always maintain the original exposure amount at the optimum value, and also to The reflected light is received and binarized, and the electrostatic latent image can be developed in an optimal state.

In particular, the exposure adjustment device shown in FIG. 6 performs shading correction, temporal changes in the light source (21),
After making corrections for changes in the environment such as temperature, changes in applied voltage, etc., the exposure amount is then adjusted using the exposure adjustment device shown in Fig. 2 in accordance with the density of the original during the scanning exposure operation of the original. , it is possible to obtain an optimal copy image and is the most preferred implementation.

The present invention is not limited to the above-described embodiments; for example, instead of using a liquid crystal shutter configured to change light transmission characteristics, it is possible to use a liquid crystal shutter configured to change light reflection characteristics. , CC as a sensor
A photodiode array or the like can be used instead of the D sensor, and it can also be applied to various fence image III reading devices such as facsimile machines in addition to copying machines, within the scope of otherwise changing the gist of the invention. It is possible to make various design changes.

Effect> As described above, the present invention is configured so that the shutter shape is set to the optimum shape by feeding back the output signal of the sensor that receives the reflected light from the scanning exposure of the original to the liquid crystal shutter. This has the unique effect of automatically adjusting the exposure amount in response to the density of the document during the scanning exposure operation, thereby achieving optimal image reading.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing the internal mechanism of the copying machine, Fig. 2 is a block diagram showing the automatic exposure adjustment device, Fig. 3 is a longitudinal sectional view of the liquid crystal shutter, Fig. 4 is a front view of the same as above, and Fig. 5 is a longitudinal sectional view showing the internal mechanism of the copying machine. The figure is a longitudinal sectional view showing another embodiment of the liquid crystal shutter, and FIG. 6 is a block diagram showing an exposure adjustment device. (18)...Original, (21)...Light source, (52)...
...CCD area sensor as a sensor, (54)...
・Drive circuit, (55)...Liquid crystal shutter, (56)・
··segment. Patent applicant: Sanda Kogyo Co., Ltd. -14-

Claims (1)

[Claims] 1. In an image reading device that exposes a document to light using a light source and forms an electrostatic latent image on a photoreceptor using light reflected from the document, a large number of light beams are arranged on the exposure optical path in the length direction and the width direction. A liquid crystal shutter with segments arranged side by side is provided, a sensor is provided to detect the reflected light from scanning exposure of the document, and a drive circuit is provided which uses the output signal of the sensor as input to drive each segment of the liquid crystal shutter and change the shape of the shutter. An automatic exposure adjustment device characterized by being provided. 2. The automatic exposure adjustment device according to claim 1, wherein the segments of the liquid crystal shutter are arranged side by side in a dot matrix. 3. The automatic exposure adjustment device according to claim 1, wherein the sensor is a CCD sensor and outputs a signal corresponding to each segment of the liquid crystal display.