JPS61175634A - Controller for optimum quantity of exposure of copying machine - Google Patents

Abstract

PURPOSE:To set the quantity of exposure speedily and to hold the quantity of exposure at an invariably optimum value by providing a reference reflecting plate nearby an original scanning area and an exposure quantity detector at the final stage of an original scanning optical system, and controlling a voltage applied to a lamp continuously according to variation in the quantity of exposure during scanning operation. CONSTITUTION:The reference reflecting plate 6 is arranged where a light beam lwhich illuminates an original is not cut off and also partitioned by a side reflector 5 from an original side part. The reference reflecting plate 6 and side reflector 5 both move forth and back right under a platen together with the lamp. The exposure quantity detector 7 is arranged where it photodetects only a reflected light beam m' from the reference reflecting plate 6. Consequently, variance in the quantity of the reflected light is detected directly, so detection precision is improved and settled fast, so that only about 0.5sec is required to start copying operation. Further, the quantity of exposure is detected continuously in one scan and corrected speedily to the optimum value.

Description

[Detailed Description of the Invention] [Industrial Application Field] By controlling the light intensity of a light source in a copying machine, the present invention can always obtain stable copied images without being affected by dirt in the optical system. The present invention relates to an optimum exposure amount control device for a copying machine.

[Conventional technology]

As a conventional optimum exposure amount control device for a copying machine, for example, as disclosed in Japanese Patent Laid-Open No. 58-24170,
A method of increasing the voltage applied to the lamp in stages until the light emission amount of the lamp (light source) reaches the optimum light emission amount corresponding to the copying conditions, and Japanese Patent Application Laid-Open Nos. 52-119328 and 58
As disclosed in Japanese Patent No. 172642, a light receiving element for detecting variations in exposure amount and a slit for adjusting the exposure amount are arranged in the path from the light source to the photoreceptor,
There is a device that automatically adjusts the opening amount (aperture) of the slit in order to correct the exposure amount detected by the light receiving element to an optimal value. However, in the former method, it takes time for the light intensity of the lamp to reach the optimum value, and in the latter method, the sight settings must be adjusted due to the time required to operate the mechanical parts for opening and closing the slit. There is a problem in that the time required to complete the process increases, and as a result, the copying time increases. In order to improve this point, methods have been implemented in which the exposure amount is set only when the power is turned on or only when copying the first sheet during continuous copying.
The problem of increased copying time due to increased light amount setting time still remains. In particular, when a halogen lamp used as a light source is turned on continuously, the light amount fluctuates by about 5% during continuous lighting, so methods such as setting the exposure amount only when scanning the first sheet in continuous copying as described above are not recommended. It has been impossible to prevent the occurrence of image defects (blurring of copies due to deviation from the appropriate exposure range) in copies after the first copy.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. 57-6871, the reflected light from the reference density plate is placed directly below the reference density plate provided at the front end of the platen glass in the optical scanning direction. A first light-receiving element that receives light is fixed, and a second light-receiving element that detects the amount of exposure in the vicinity of the photoreceptor is disposed near the photoreceptor, and the output from the first light-receiving element is detected prior to each copying operation. Find a ratio between the signal and the output signal from the second light receiving element, correct the output signal from the second light receiving element based on this ratio, and obtain the amount of light emission corresponding to the corrected value. There is a device configured to apply the necessary voltage to the light source for this purpose.

[Problem that the invention seeks to solve]

However, the exposure amount detection method described in the above-mentioned Japanese Patent Application Laid-Open No. 57-6871 has the disadvantage that the circuit becomes complicated and expensive. Furthermore, if there is a variation in the exposure amount during one copy scan, this cannot be corrected.

[Means and effects for solving the problems] The present invention has the following features:
This was done in consideration of the above, and it aims to shorten copying time by setting the exposure amount in the shortest possible time, and also maintains the exposure amount at the optimum value during each copy scan, and furthermore, it is optimized for a long period of time. In order to reduce the number of maintenance operations by maintaining the exposure amount, a reference reflector is provided near the document scanning area to reflect the light irradiated by the exposure light source, and an exposure amount detector is provided at the final stage of the document scanning optical system. , the optimum exposure regime for a copying machine that continuously adjusts the voltage applied to the lamp in response to changes in the exposure amount during scanning? 1 device.

〔Example〕

The optimum exposure amount control device for a copying machine according to the present invention will be explained below.

1, 2(a), 3(o), and 3 show one embodiment of the present invention, and this device includes a platen glass 1 for placing an original, a photosensitive drum 4, and an optical system. The optical system 10 includes a lamp (light source) 2, a mirror 3, a final mirror 3a, a reference reflector 6, an exposure detector 7, a lens 8, and a reflector 9. . FIGS. 2(a) and 2(o) show examples showing the positional relationship between the lamp and the reference reflector, respectively, and the reference reflector 6 illuminates the original with light '4IA7! It is arranged in a position where it does not block the document side and is partitioned off from the document side portion by a side reflector 5. The reference reflector 6 and the side reflector 5 reciprocate directly below the platen together with the lamp. As the reference reflector 6, for example, one having a specular reflection surface or a diffuse reflection surface is used, and its inclination angle can be set to a desired angle as shown in FIGS. 2(A) and 2(U). FIG. 3 shows an embodiment showing the positional relationship between the final mirror 3a and the exposure amount detector 7, and the exposure amount detector 7 is positioned so that it can always receive only the reflected light beam m° from the reference reflector 6. has been set. code 7a
indicates the light receiving surface. Note that in a copying machine in which the platen glass 1 moves to perform scanning, the optical system is fixed.

FIGS. 4(a) and 4(0) show a second embodiment of the present invention, which differs from the one in FIG. There is. That is,
In FIG. 4, only the final mirror 3a corresponding to the light-receiving surface 7a of the detector 7 is configured to transmit light without being coated with a reflective film, or the final mirror 3a is configured to transmit light without being coated with a reflective film.
It is necessary to make a dichroic. n is a mirror reflective surface, n'' is a non-reflective film surface, m is a reflected light beam from an original, and m'' is a reflected light beam from a reference reflector.

The exposure amount control device shown in FIG. a width section 12; an A/D converter 13 that A/D converts the output signal from the widening section 12 and outputs it to the microcomputer 14;
The trigger circuit 15 is actuated by a trigger circuit 15 driven by a control signal output from a microcomputer 14, and a tritic 16 controls the voltage applied to the exposure lamp 2. The microcomputer 14 has an input interface for inputting sensor signals from various sensors in the copying machine (including the exposure amount detector 7) and operation command signals from a console (not shown), and a ROM for storing programs necessary for arithmetic processing of input signals. A CPU that performs predetermined calculations based on the program, a RAM that temporarily stores calculation results and data, and a CPU that controls various control objects (including trigger circuits) of the copying machine based on the calculation results. It has an output interface that outputs a signal. The ROM stores control information regarding the optimal amount of light emitted by the light source (the amount of light received by the detector 7) under various copying conditions (magnification, density, etc.) and the voltage control required to obtain the optimal amount of exposure.

In the above configuration, the optical system (lamp 2, mirror 3.3a, reference reflector 6, etc.) may be contaminated by dust, toner, paper dust, etc. in the air, and the amount of exposure to the photoconductor may be reduced due to fluctuations in the power supply voltage, etc. When it fluctuates, a light amount different from the optimum value is incident on the detector 7.

For example, when the amount of exposure decreases, a detection signal that detects the low amount of light is input from the A/D converter 13 to the microcomputer 14 (sampling of the amount of exposure). The CPU reads the optimal exposure value under the current copying conditions from the ROM and compares it with the input actual exposure value, and also stores the control information necessary to correct the decrease in light amount to an appropriate value from the ROM.
, and outputs the control information to the trigger circuit 15 as a control signal. This control information relates to a voltage value for adjusting the exposure amount to an optimal value by increasing or decreasing the voltage output from the power supply 11, and the optimal voltage value read from this control information is used as a control signal. When the voltage is output to the trigger circuit 15, the trigger circuit 15 triggers the triac 16, and the voltage output from the power source 11 to the lamp 2 is controlled. FIG. 6 is a flowchart regarding the above operation.

Unlike the conventional method of detecting variations in power consumption from output voltage and current consumption, the present invention directly detects variations in the amount of reflected light, so the detection accuracy is high and it settles quickly, in about 0.5 seconds. It has the advantage that it can be transferred to a copying operation. Moreover, it is possible to continuously detect the exposure amount during scanning and quickly correct it to the optimum value.

In addition, since the exposure amount detector 7 is installed near the photoreceptor in the optical path, it can detect a decrease in the exposure amount due to contamination of the optical system due to dust, toner, and paper dust in the air, and can maintain the optimum exposure amount over a long period of time. Can be maintained. Detection surface 7a of exposure amount detector 7
Since the dirt on the detection surface 7a is always the same as that on the final mirror 3a, there is no need to install a cleaning device or the like to remove dirt on the detection surface 7a, and even if the optical system and detection surface 7a are cleaned, the optimum exposure amount cannot be set. There is no need to fix it at all.

〔Effect of the invention〕

As described above, according to the optimum exposure amount control device for a copying machine of the present invention, a reference reflector is provided near the document scanning area to reflect the irradiation light from the exposure light source, and the exposure light source is provided at the final stage of the document scanning optical system. An amount detector is installed to continuously adjust the voltage applied to the lamp in response to fluctuations in the exposure amount during scanning, thereby reducing copying time by setting the exposure amount in the shortest possible time. The number of maintenance operations can be reduced by always maintaining the exposure amount at an optimum value during each copying scan and by maintaining the optimum exposure amount for a long period of time.

[Brief explanation of drawings]

Figures 1 to 3 show one embodiment of the present invention, with Figure 1 being an explanatory diagram of the overall configuration, and Figures 2 (A) and (El) being explanatory diagrams of the configuration near the reference reflector and modifications thereof. (C4) (I
I) is an explanatory diagram of the configuration of another embodiment of the present invention, FIG. 5 is an explanatory diagram of the configuration of an exposure amount control section, and FIG. 6 is a flowchart showing the operation of the present invention. Explanation of symbols 1---Platen glass 2---Lamp (light source) 3---Mirror 3a-
・-Final mirror 4・---m-Photosensitive drum 5・
・−・−Side reflector 6-111・−Reference reflector 7・−−−−1 Exposure amount detector 8−・−−～−−
Lens 9--------・Reflector 10-
・-Optical system 11--・AC power supply 12-・・
-Width increasing part 13-・-A/D converter 14-
--------Microcomputer 15-----Trigger circuit 16--Triac patent Applicant Agent for Fuji Xerox Co., Ltd.
Patent Attorney Shin Matsubara 2 Same as Seiji Muraki Same Same as Tadao Hirata Same Same as Atsushi Ueshima - I M

Claims (2)

[Claims] (1) In the optimum exposure amount control device of a copying machine that controls the exposure amount of the photoreceptor to the optimum value, there is a reference reflector plate placed near the document scanning area that reflects the irradiation light from the exposure light source, and an optical system end. an exposure amount detector disposed on the optical member of the step and receiving the reflected light from the reference reflector; and a light amount detector that compares the amount of light received by the exposure amount detector with a reference value and continuously determines the exposure value during the copying operation. An optimal exposure amount control device for a copying machine, comprising a control section that controls an applied voltage to a light source. (2) The optimum exposure amount control device for a copying machine according to claim 1, wherein the exposure amount detector is attached to the back surface of a final mirror constituting the optical system.