JPS60437A - Exposure quantity control device for copying machine - Google Patents

Abstract

PURPOSE:To prevent the drop of an exposure quantity by using a recessed form diffusion surface reflector for an illuminating system, scattering the radiant light of a light source, averaging it, detecting only its diffusion light quantity, and controlling a light quantity of the light source so that it always holds an optimum value. CONSTITUTION:A radiant light from a lamp 1 is reflected irregularly by a reflecting surface of a diffusion surface reflector 2 and averaged. The lamp 1 is positioned in the vicinity of the bottom surface of the reflector 2, and the greater part of a light for irradiating the scanning part of an original 7 is a diffused light arriving from an opening part 2a and a reflector 3. The direct light which is made incident to the vicinity of an opening part 4a of a light detecting hole 4 does not reach an optical sensor 5 either because the wall surface is painted in black, and the magnitude of a detecting light is proportional to the average value of intensity of illumination of an original surface. The output of the optical sensor 5 is inputted to a controlling circuit 10, brought to voltage conversion, and thereafter, compared with the reference voltage. In accordance with its difference, a phase control type power source 14 is driven and the voltage of the lamp 1 is controlled, by which an irradiating light quantity is held at a constant value.

Description

[Detailed Description of the Invention] [Technical Field] The present invention detects the exposure amount and controls the original illumination light amount to prevent the exposure amount from changing over time due to contamination of the illumination system. The present invention relates to an exposure amount control device for a copying machine.

[Prior art]

As a conventional exposure amount stabilizing device for a copying machine, for example, there is one that uses a stabilized power source as a power source for a light source and maintains the amount of illumination light constant by absorbing fluctuations in the supplied voltage.

However, with this equipment, equivalent measures have not been taken for factors other than fluctuations in line voltage, so when using the copier for a long period of time, dust may accumulate in the lighting system such as the light source 2 lamp and 7 rectifier. There was a drawback that the exposure amount was reduced due to the adhesion of the film.

Additionally, most stabilized power supplies rectify the output voltage, compare it with a smoothed (averaged) DC voltage and a standard voltage, and control the difference so that the difference is zero. ,
If there is waveform distortion in the supply voltage, its effective value (which directly affects the light intensity of the light source) and the average value of the rectified voltage (so-called pulsating current) will not match, and the ratio of the two will also change due to waveform distortion. However, there was a drawback that it was not possible to rationally control the amount of light.

[Object and structure of the invention]

The present invention has been made in view of the above-mentioned problems, and it detects the average value of the actual exposure amount by a simple means, and uses the illumination light source (lamp) in order to compensate for the decrease in the exposure amount due to contamination of the illumination system. The reflector is configured with a light-diffusing reflective surface having a concave shape to diffuse and average the direct light from the light source, and the optical sensor is placed at a position where the direct light from the light source does not enter to diffuse the light. An object of the present invention is to provide an exposure control device for a copying machine that detects only the amount of light, compares the output with a standard voltage, and controls the amount of irradiated light so that the difference becomes zero.

Hereinafter, the exposure amount control device for a copying machine according to the present invention will be explained in detail.

(Example) Figure 1 shows an example of the present invention, and l is a rung (light source).
, 2 is a diffuser reflector whose reflective surface is the aperture surface 2a.
It is about 3 to 4 times the size of the original, and has a large depression on the inside. The reflective surface of the diffuser reflector has light diffusing properties (the property that each point on the reflective surface reflects incident light uniformly in all directions).
It is white and has fine irregular irregularities. Reference numeral 4 denotes a light amount detection hole, which has a certain depth (4a is an opening), faces in a direction where direct light from the light source 1 cannot enter, and the wall surface of the hole is painted black. Reference numeral 5 denotes an optical sensor disposed at the bottom of the light amount detection hole 4, for example, a phototransistor can be used. Reference numeral 3 denotes a mirror auxiliary reflector, which detects the light scattered from the diffuser reflector 2. It serves to reflect the light toward the original 7 placed on the platen glass 6. Reference numeral 8 denotes a first mirror located directly below the scanning part of the document surface, and has the role of reflecting light reflected from the document surface toward an optical system fixed to the main body. Reference numeral 9 indicates a light source 1 and reflectors 2 and 3.
This is a carriage that carries a first 8ft height and moves while irradiating the original 7. 1O is a control circuit mainly composed of an operational amplifier, and has functions such as charging current detection, voltage conversion, amplification, and voltage comparison.

In the above configuration, the light radiated from the lamp 1 is repeatedly reflected diffusely by the reflective surface of the diffuser reflector 2, and is diffused and averaged within the space surrounded by the reflective surface. Therefore,
Even if there is local contamination due to dust adhesion on the light source or reflective surface, the effect will be averaged out and will not have a direct effect on the amount of diffused light (the amount of light that has been repeatedly reflected diffusely) near the contamination point. do not have.

In addition, since the lamp 1 is located near the bottom of the diffuser reflector P-2, most of the light that irradiates the scanning part of the original 7 (the part directly above the first mirror 2-8) is from the reflector 2. This is diffused light coming from the opening 2a and the mirror auxiliary reflector 3.

Furthermore, the optical sensor 5 is arranged in a position where direct light from the lamp 1 does not enter, and the wall surface of the hole 4 is painted black so that direct light entering from the opening 4 & the vicinity of the light detection hole 4 from the 2 lamps is also prevented. Therefore, it cannot reach the optical sensor 5. Therefore, the amount of light incident on the optical sensor 5 is only the diffused light, and its magnitude is proportional to the average value of the illuminance on the document surface (in other words, the amount of exposure of the photosensitive drum).

The output of the optical sensor 5 is input to a control circuit 10, converted into a voltage, amplified, and then compared with a reference voltage. According to the difference, the sliding transformer 14 is driven to control the voltage of the lamp. Let the difference be zero.

〔Effect of the invention〕

As explained above, according to the exposure amount control device for a copying machine according to the present invention, a concave diffusion surface reflector is used in the illumination system to scatter and average the radiant light from the light source. Since only the amount of diffused light is detected and the light amount of the light source is controlled so that it is always the optimum value, even if the illumination system becomes dirty due to dust adhesion, this is compensated for and the document surface illuminance is adjusted accordingly. By keeping the value at an optimum value, it is possible to eliminate a decrease in the exposure amount even when the copying machine is used for a long period of time.

Further, even if the bus voltage includes waveform distortion, no control error occurs.

In addition, since the copying machine according to the present invention uses diffused light to illuminate the document surface, unlike conventional copying machines that focus direct light with mirror-surfaced seven rectors and illuminate the document surface, the copying machine uses diffused light to illuminate the document surface. Even if a quick shooting operation is performed with the shutter open, there is no fear that the illumination light will impair the safety of the user's eyes even if it passes through the platen glass and enters the user's eyes.

[Brief explanation of the drawing]

The accompanying drawings are explanatory diagrams showing one embodiment of the present invention. Code explanation 1... Lamp (light source), 2... Diffusion surface reflector-12a... Same opening, 3... Mirror surface auxiliary reflector-14... Light amount detection hole, 4a... Same opening Part 5...
- Optical sensor, 6... platen glass, 7... original, 8... first mirror, 9... carriage, lO...
・Control circuit, 14...Sliding transformer (light i1 creation 1,
15...Bus line. 1. Indication of the case Patent Application No. 108975 of 1982 2. Name of the invention Exposure control device for copying machine 3. Person making the amendment Relationship to the IJ case Patent applicant name Name Fuji Xerox Co., Ltd. 4. Agent telephone number ( 0) 263 7676 (Representative) 7. Contents of amendment (1) Correct "optical transistor" to "photodiode" on page 4, line 5 of the specification. (2) "Drive the sliding transformer 14" on the 3rd line of page 6 of the specification is corrected to "change the ignition point of the phase-controlled power source 14." (3) Correct the JK on page 7 of the specification Correct "sliding transformer" on line 14 to "phase-controlled power supply". 8. List of attached documents

Claims (1)

[Scope of Claims] An exposure amount control device for a copying machine that compares a detection signal corresponding to the light amount of a light source for document illumination with a predetermined optimal value and controls the light amount according to the difference, comprising: A copying machine characterized in that an amount of diffused light in a space surrounded by a reflective surface of a light source for document illumination is detected by a detection means provided at a position where direct light from the light source does not enter and output as the detection signal. exposure control device.