JPS5814163A - Regulating device for exposure in copying machine - Google Patents

Abstract

PURPOSE:To prevent the malfunction occuring in the state of an original picture in a copying machine that can correct exposure automatically by providing a limiter that limits the rate of correction. CONSTITUTION:Photodetector arrays 33, 35 are disposed near a photosensitive drum 32 as means of controlling the light emission voltage of a light source 22 for copying the aperture card 19 on an original platen 21. When the outputs of said arrays are inputted to a photometric control part 26 for quantity of light, said outputs are compared with a reference voltage and a lamp control part 24 controls the applied voltage upon a lamp so that no photographic fogs are generated in the min. output parts. A limiter is provided for said comparison means with the reference voltage, and since the quantity of the light of the lamp is controlled to the extent that copying is at least assured despite the wrong recognition of the drop-out part as a background part, no wasteful copies are made even with the originals of peculiar ratios between the bright and dark parts.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure adjustment device for a copying machine that copies images recorded on microfilm.

2. Description of the Related Art As an apparatus for enlarging and copying an image recorded on a microfilm, there is, for example, a microcopying machine using an electrostatic photograph method. Micro copying machine (hereinafter simply referred to as copying machine)
In this method, an aperture card or a microfilm itself is fixed to a document table, and an optical image of an image portion is formed on a sensitive material such as a photosensitive drum to create a copy image.

Adjustment of the exposure amount for microfilm in such copying machines has conventionally been performed by relying on the intuition of the operator. In other words, the operator takes into account the density (fog density) of the background portion of the microfilm and the copying magnification and adjusts the aperture of the lens and the voltage applied to the irradiation lamp while performing copying work. However, with this method, it is extremely difficult to determine the optimal exposure amount for the individual fog density of the microfilm and the set copying magnification, and it is difficult to determine the optimal exposure amount for each microfilm's fog density and set copying magnification. It was usually possible to obtain a copy. For this reason, recently, automated devices have been proposed that automatically determine the exposure amount in consideration of the fog density and copying magnification of the microfilm.

FIG. 1 shows the principle of such an automated copying machine. A light beam emitted from a light source lamp 1 of this copying machine is focused on a document surface 3 by a condenser lens 2. As a result, the image information on the document surface 3 is slit-exposed onto the light receiving drum 6 via the copying lens 4 and the slit exposure device 5.

A plurality of sensors 7 are arranged in the slit exposure device 5 to receive a portion of the optical image.

When an operator sets a copying magnification after setting a document such as an aperture card in this copying machine, a predetermined voltage is applied to the light source lamp 1, and the document surface 3 is irradiated with a specified illuminance.

Along with this, the light beam of a predetermined portion of the optical image is incident on the sensor 7.

FIG. 2 shows an exposure adjustment device for adjusting the amount of exposure based on the light beams incident on, for example, three sensors 71 to 73. In this device, the outputs of the valley sensors 7, to 73 are connected to amplifiers 8. ~83
After being amplified by , the signal is input to the minimum value detection circuit 9 . The minimum value detection circuit 9 detects each sensor 7, to 7. Detection signal 11 after being output and amplified from. ~113 are compared using the built-in comparator. Then, the detection signal with the lowest level is supplied to the comparator 13 as the minimum value signal 12. The comparator 13 compares this minimum value signal 12 with the reference value signal 15 output from the reference value circuit 14 and supplies the result to the exposure adjustment circuit 17 as a comparison signal 16. The exposure adjustment circuit 17 controls the voltage applied to the aperture of the copying lens 4 (FIG. 1) or the light source lamp 1 based on this comparison signal, and determines the exposure amount completely automatically.

By the way, in such a proposed copying machine, the minimum value detection circuit 9 employs the detection signal of the sensor corresponding to the background part of the image, and based on this, the exposure amount corresponding to the copying magnification and fog density of the image is determined. decisions are being made. In microfilm recording drawings or documents, the background area usually occupies 97% or more of the total area of the image. Therefore, if a plurality of sensors 7 are arranged in the slit exposure device 5,
The probability that any one of the sensors will receive light from the background portion of the image is extremely high, and there is little possibility that a problem will occur in determining the exposure amount. However, on microfilm that records printed circuit board patterns or ordinary photographs, the white areas are 10
% or even 50% or more, and there are many cases in which none of the sensors 7 receives light from the background portion of the image. In such a case, the exposure adjustment circuit 17 will mistakenly set the exposure amount for the white part of the image as the background part.
This method has the disadvantage that completely inappropriate exposure is performed, resulting in unnecessary copying.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an exposure adjustment device that can always perform proper copying regardless of the copying magnification in a copying machine that copies images recorded on microfilm. With the goal.

In the present invention, a reasonable exposure amount at normal fog density is set for each individually set copying magnification, and the exposure amount is corrected based on the light image received by the light receiving sensor using these exposure amounts as a reference. At the same time, the range of correction is limited by a limiter, and even if correction is made by mistake, it is possible to reproduce the recording surface, thereby achieving the above-mentioned object.

The present invention will be described in detail with reference to Examples below.

FIG. 3 schematically shows a copying machine equipped with an exposure adjustment device. Document table 21 on which aperture card 19 is placed
A light source lamp 22 and a condenser lens 23 for condensing light beams emitted from the light source lamp 22 onto the document surface of the aperture card 19 are arranged above the light source lamp 22 . A lamp control section 24 is connected to the light source lamp 22, and the applied voltage is controlled by voltage control from a light amount photometry sub-side 1 section 26 connected to an operation panel 25. A copying lens unit 27 is provided below the document table 21 in which a low magnification lens 27A and a high magnification lens 27B are movably arranged vertically and horizontally. Below the copying lens unit 27, fourth mirrors 28 to 31 are arranged to successively reflect the light beams that have passed through the copying lens unit 27.

The fourth mirror 31 is disposed directly above the exposure surface 32A of the photosensitive drum 32, and among the light beams reflected by this mirror, only the light beams that have passed through the slit 34 provided in the slit exposure device 33 are directed to the exposure surface. It is designed to be irradiated with 32A. A plurality of exposure sensors 35 are arranged on both sides of the narrow gap 34 . The output of the exposure amount sensor 35 is supplied to the light amount photometry control section 26.

This copying machine can set copy magnification in 16 steps from 984x to 24x. The operator first operates the operation panel 25 to set a desired magnification. The light intensity metering control unit 26 adjusts the set magnification from 94 times to 16 times (9,
In the case of low magnification (4, 10, 11, 12 degrees, 13.14, 15.16 times), the low magnification lens 27A is placed directly under the aperture card 19 as shown in the figure, and the low magnification is adjusted based on the copying magnification. lens 27A and aperture card 19
distance to the original direction, and the distance between this lens and the exposure surface 3] A
Calculate the optical distance to. Based on this, the drive mechanism (not shown) is fully controlled to move the copying lens unit 27 in the direction of arrow 39, adjust its flange hack, and move the second and third mirrors 29, 30 i arrow 4
Adjust the optical path length by moving them integrally in one direction. I cut it,
The magnification set by the operation panel 25 is from 17x to 24x (17°1.8, 19, 20, 2], 22, 23.2
In the case of a high magnification (4 times), the high magnification lens 27 is moved directly below the Bi aperture card 19, and the above-mentioned flange bank adjustment and optical path length adjustment are performed based on the subject magnification.

The light amount photometry control circuit 26 determines the initial value of the lamp voltage applied to the light source lamp 22 in addition to these adjustment operations.

The light amount photometry control circuit 26 is equipped with a memory that stores the relationship between copying magnification and lamp voltage. FIG. 4 shows an example of the relationship between lamp voltage and copying magnification stored in this memory. The lamp voltage for each copying magnification is based on the case where the density of the background part of the microfilm is 10.

Now, when the operator presses a start button (not shown) on the operation panel 25, the exposure adjustment device in the light intensity metering control section 26 starts operating. FIG. 5 specifically shows the exposure adjustment device. When the start button is pressed, the timer 26A starts counting for 2 seconds, and at the same time, the initial value for the lamp voltage read from the memory (not shown) is sent to the lamp control unit as the voltage control signal 42 (FIG. 3). 24. The lamp control unit 24 adjusts the voltage supplied from the lamp power source 43, and applies a voltage of 70 V to the light source lamp 22 when the copying magnification is 94 times, for example.

When the light source lamp 22 is turned on, the light beam that has passed through a predetermined portion of the aperture card 19 enters the exposure sensor 35 . The detection output of each exposure sensor 35 is input to the amplification and minimum value construction circuit 26B, where each amplification is amplified to a predetermined level and then compared, and the minimum level detection signal 44 is selected. The selected detection signal 44 is compared with a reference voltage E45 output from the reference voltage generation circuit 26C in the reference voltage comparison circuit 26D. When the copying machine is set to automatic exposure mode, the reference voltage generating circuit 26C generates a voltage of 0.3 based on the operation control wholesale signal 46 output from the operation panel 25.
Generates a DC voltage of V. The reference voltage comparison circuit 26D changes the voltage control signal 42 so that the voltage (direction) of the detection signal 44 becomes equal to the reference voltage 45. Based on this, the lamp control unit 24 increases or decreases the lamp voltage.

By the way, the reference voltage comparison circuit 26D is equipped with a limiter, which outputs a voltage division control signal 42 that regulates the lamp voltage within a maximum range of +2V with respect to the initial value read from the memory. There is. ±2v at this lamp voltage means that the density of the background part of the microfilm is from 05.

This corresponds to the variation range of the lamp applied voltage in the case of 1.5.

The voltage launch circuit 26F is supplied with the voltage control signal 42, and holds the signal by a launch signal 47 outputted when the timer 26A completes the timing operation. This voltage control signal 42 is a signal that ensures the optimum exposure amount when any one of the exposure amount sensors 35 receives the light beam from the background portion of the microfilm; If not, the signal is subject to restrictions to ensure copying. This voltage control signal 42 is continuously supplied to the lamp control section 24 to cause the light source lamp 22 to emit light with a predetermined amount of light. In this state, exposure is performed on the exposure surface 32A, and a copy image is created. When the exposure is completed, the voltage latch circuit 26E is restored, and the lamp control section 24 preheats the light source lamp 22 in preparation for the next object operation.

If the operator is not satisfied with the obtained copy image, that is, if the operator inputs a copy image that has been overexposed or underexposed due to the limited voltage control signal 42, the operator must readjust the exposure amount according to the degree of exposure. I can do it. In this case, the operator operates the operation panel 25 to switch the copying machine to manual mode. Then, by adjusting the operation control signal 46 as appropriate and changing the reference voltage 45, a copy image is created. Since a copy image is created in automatic exposure mode, it is easy to readjust the exposure amount.
You can easily get the best copy.

In this way, according to the present invention, an appropriate exposure amount at a normal fog density is determined for the set copying magnification and the exposure amount is limitedly corrected. In the field of microcopying, which has variable conditions such as fog density, image density, image pattern, and contamination of the optical system, the occurrence of copy errors can be significantly reduced. Furthermore, since the minimum value detection circuit can be used to determine the optimum exposure amount for most original documents, the probability of obtaining an optimum copy image is extremely high. In addition, by manually setting the reference voltage based on the initial value read from memory for the copying magnification, the initial value for the lamp voltage can be set at the center of the image density, and the image density can be easily adjusted.

In the example, the operation of the exposure adjustment device was explained on the assumption that there is no dirt on the optical system, but if it is assumed that dirt will occur on the optical system, an aperture card should be placed on the document table. The change in the amount of light received by the exposure amount sensor 35 before and after is determined, the initial value for the lamp voltage read from the memory is corrected by an amount corresponding to this amount of change, and this is used as the initially set value for the amount of exposure. Of course, by doing so, it is possible to obtain an optimum exposure amount that is independent of contamination of the optical system.

Further, in the embodiment, different initial values for the lamp voltage are set for each of the 16 levels of copying magnification, but it goes without saying that one initial value may be set for each of several types of copying magnification. In particular, in a copying machine that uses two types of lenses, one for high magnification and one for low magnification, as shown in the embodiment, two types of initial values may be selected in conjunction with switching of these lenses. By reducing the number of initial values for the lamp voltage relative to the copying magnification in this way, it is possible to determine the exposure amount even if the copying machine is not equipped with a μm CPU (microcomputer). .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventionally proposed copying machine equipped with an exposure adjustment function, FIG. 2 is a block diagram of an exposure adjustment device of this copying machine, and FIGS. 3 to 5 are an embodiment of the present invention. Figure 3 is a schematic diagram of the copying machine;
FIG. 4 is a relationship diagram showing an example of the relationship between copying magnification and lamp voltage, and FIG. 5 is a block diagram of the exposure adjustment device. 22...Light source lamp 24...Lamp control unit 25...Operation panel 26...Light amount photometry control unit 26B...Amplification and minimum value detection Circuit 26C...Reference voltage generation circuit 26D...Reference voltage comparison circuit 26E...Voltage latch circuit 35...Exposure sensor applicant: Fuji Xerox Representative Patent Attorney Co., Ltd. Yuji Ume 4 Figure 5

Claims (1)

[Claims] 1. Setting means for setting an initial value of a voltage applied to a light source lamp for copying according to a set copying magnification, and a microfilm projected by the light source lamp turned on at the initial value. A minimum value detection circuit detects the minimum value of illuminance at multiple locations in the optical image, and the detected value of the minimum value detection circuit is assumed to be a value corresponding to the fog density of the background part of the microfilm, and this detected value is set as a predetermined standard. an exposure amount adjusting means for adjusting the voltage applied to the light source lamp so that the voltage applied to the light source lamp converges to a value; and a limiter for limiting the adjustment range of the exposure amount adjusting means to a range that can ensure the reproduction of the copied image on the microfilm; An exposure adjustment device for a copying machine, characterized in that the voltage adjusted by the amount adjustment means is applied to the light source lamp to copy a microfilm. 2. Exposure adjustment of a copying machine according to claim 1, characterized in that the exposure adjustment of a copying machine is provided with manual operation means for completely manually varying a reference value, which is a reference value of the detection value of the minimum value detection circuit, within a predetermined range. Device.