JPS6010310B2 - Color electrophotographic exposure method - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exposure method for a color electrophotographic camera.

Generally, in the exposure method of a color electrophotographic machine, a document is illuminated by a light source, and the original image on the document is sequentially separated into each color component by a filter, and then exposed onto a photoreceptor.

However, the output of the light source is not uniform in size for each wavelength component, and the transmittance of each filter is different. The electric potentials of the Denko images are significantly different from each other under standard conditions, and the colors are completely unbalanced. For this reason, the exposure amount must be adjusted so that the potential of each electrostatic latent image is at the same level and the color balance is achieved, but this adjustment must be made extensively, so it is difficult for general users of color electrophotographic machines to do so. It is difficult to do. Furthermore, if the width of the adjustment for color balance and the adjustment of the total exposure amount is set too small, the adjustment cannot be performed sufficiently, and conversely, if it is set too large, the adjustment operation becomes difficult. SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure method for a color electrophotographic camera that eliminates the above-mentioned drawbacks and allows sufficient and easy adjustment.

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, in a color electrophotographic machine, an original 11 is illuminated by lamps 12 and 13 serving as light sources, and the reflected light is reflected by a mirror 14, a color separation filter 15,
The light is guided to a photoreceptor 18 via a lens 16 and a mirror 17.

The filter 15 is a blue filter, a green filter, and a red filter that are used to separate the original image of the original 11 into predetermined color components, that is, a blue component, a green component, and a red component, respectively. Each color component is sequentially exposed, and if necessary, a white filter is used to further extract black portions of the original image. The photoreceptor 18 is uniformly charged before each color component of the original image is exposed, and a static exposure latent image is formed by sequentially exposing each color component of the original image. lamps 12, 13
is controlled on and off by a circuit shown in FIG. 2, in which resistors R, R2t, variable resistor VR, and resistor R3 are connected in series between a positive DC power source and a ground point.

The non-inverting input terminal of the operational amplifier A is connected to the connection point of the resistors R and R2, and the total shift variable resistor VR2, the resistor R4, and the capacitor C are connected between the slider of the variable resistor VR and the ground point. , are connected in series, and the connection point between resistor R4 and capacitor C is connected to the inverting input terminal of operational amplifier A. Furthermore, in the operational amplifier A, diodes D, D2 for preventing excessive input are connected in antiparallel between the inverting input terminal and the non-inverting input terminal, and a capacitor C2 is connected between the output terminal and the inverting input terminal. . Exposure start switch SW,
opens at the start of exposure and closes at the end of exposure,
It is connected in parallel with capacitor C2 via resistor R5.
The output terminal of the operational amplifier A is connected to the inverting input terminal of the operational amplifier A2, and a resistor R6 is connected between the movable tip of the switch SW2 and the ground point. The operational amplifier A2 has over-input prevention diodes D3 and D4 connected in antiparallel between the inverting input terminal and the non-inverting input terminal, and a capacitor C3. Connected to a connection point. Resistors R7 to R,o are connected between each fixed terminal of switch SW2 and the DC power supply.
, semi-fixed resistances VR3 to VR6, variable resistances for color balance VR7 to VR,. are connected in series, lamps 12,1
3 is controlled by the output signal of operational amplifier A2. Thus, operational amplifier A, together with capacitor C2, etc., constitutes a Miller integration circuit, and the connection point of resistors R, , R2 and variable resistor V
A constant voltage is input between the slider of R and the switch SW, but when the switch SW is closed, the capacitor C is connected to the switch SW,
This short-circuits through the resistor R5, and the output voltage becomes zero.

When exposing each color component of the original image, the switch SW is opened at the same time as the lamps 12 and 13 are turned on at the start of each exposure.
Operational amplifier A amplifies a constant input voltage, and its output is fed back via capacitor C2 to perform Miller integration, so that the output voltage increases linearly. Operational amplifier A
2 functions as a comparator, and compares the output voltage of the operational amplifier A2 with a reference voltage. When the output voltage exceeds the reference voltage, an output voltage is generated to turn off the lamps 12 and 13. Therefore, the lighting time of the lamps 12 and 13, that is, the exposure time, is determined by the integral constant of the Miller integration circuit and the reference voltage, but it is possible to shift the total exposure time by adjusting the integral constant with the variable resistor VR2. The exposure time can be adjusted while maintaining color balance without changing the exposure time ratio of each color component of the image. Also, the reference voltage is 6~R. , semi-fixed resistances VR3 to VR6, variable resistances VR7 to VR,. and switch SW2, which is switched each time the original image is exposed for each color component, and resistors R7 to R, o,
Semi-fixed resistances VR3 to VR6 and variable resistances VR7 to VR,
Switch each series circuit of o. Therefore, the reference voltage is set for each exposure of each color component of the original image, and the exposure time of each color component of the original image is set by the variable resistors VR7 to VR, respectively. You can adjust the color balance using the . Incidentally, in this example, halogen lamps having the light emission characteristics shown in FIG. 3 are used as the lamps 12 and 13, and gelatin filters having the characteristics shown in FIG. 4 are used as the blue filter, the green filter, and the red filter. , an organic photoconductive photoreceptor having characteristics as shown in FIG. 5 is used as the photoreceptor 18, and the potential of each electrostatic latent image formed on the photoreceptor 18 by each color component of the original image is It exhibited the characteristics shown in the figure.

In order for the potential of the electrostatic latent image of each color component to be the same in the standard state and for color balance to be achieved, it is necessary to expose the blue, green, and red components of the original image for a period of time TB, To, and T.
Experiments have revealed that the ratio of R should be approximately 7:4:1, preferably 20:13:3. Also, if the exposure time Tw of the black part of the original image is taken into account, T8:TG:TR:T
The ratio of w is approximately 7:4:1:2, preferably 20:13:
The ratio was 3:5. Therefore, in the standard state with the variable resistors VR7 to VR,o set to neutral positions, the exposure time T8, TG, TR
, Tw have the above ratio, the values of the resistors R6 to R,o, the semi-fixed resistors VR3 to V&, and the variable resistors VR7 to VR,o were set. In addition, in practice, the exposure time is 20% longer than the standard state when performing color balance and when performing a total shift.
It was possible to obtain a copy color image that matched the original image by adjusting the position, and even for a special original image, it was possible to obtain a copy color image that matched the original image by adjusting the position by about 40% from the standard state.
Therefore, the exposure time adjustment range by variable resistor VR2 is set to 40% from the standard state, and variable resistors VR7 to VR, o
The exposure time adjustment range was also ±40% from the standard state. It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with arbitrary changes, such as application to a slit exposure method, without changing the gist.

As described above, according to the exposure method of the color electrophotographic camera according to the present invention, the ratio of the exposure times for the blue component, green component, and red component of the original image is approximately 7:4:1 in the standard state. In this state, the potentials of the electrostatic images of each color component are approximately at the same level, and the adjustment for achieving color balance is reduced by 4 mm, and can be easily performed even by a general user of a color electrophotographic machine.

In particular, the mirror integration circuit is activated at the same time as the exposure starts, its output is compared with each reference voltage set separately for each color component exposure, and the exposure is terminated based on the output signal, so the integration constant of the mirror integration circuit is adjusted. By doing this, the total exposure time can be shifted while maintaining the color balance. Also, the exposure time adjustment range has been changed from the standard condition to 4
Since it is set to 0%, even when copying a special original image, a copied color image that fully matches the original image can be obtained, and the exposure time adjustment operation can be performed relatively easily.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an exposure apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing an exposure time adjustment circuit of the exposure apparatus, and FIG. 3 is a characteristic diagram of a halogen lamp in the exposure apparatus. FIG. 4 is a characteristic diagram of the filter in the exposure apparatus, and FIGS. 5 and 6 are characteristic diagrams of the photoreceptor. 11...Manuscript, 12,13...Lamp, 1
5...Filter, 18...Photoconductor, H...Operation amplifier, C2...Integration capacitor, SW...Exposure start switch, SW2...
・Color changeover switch, VR2......Variable resistor for total shift, VR7~VR,o...・Variable resistor for 1 color balance. 2nd figure 3rd figure 4th figure mackerel 5th figure 6th figure

Claims (1)

[Claims] 1. Separating the original image into each color component and exposing each to the photoreceptor, activating a mirror integration circuit at the same time as the start of exposure, and setting the output of this mirror integration circuit separately for each color component exposure. This is an exposure method for a color electrophotographic camera in which the exposure is terminated based on the comparison output signal compared with a reference voltage that has been set. An exposure method for a color electrophotographic machine, characterized in that the ratio is approximately 7:4:1, and the total exposure time is shifted while maintaining color balance by adjusting the integration constant of the mirror integration circuit. 2 Separate the original image into each color component, expose each to the photoreceptor, activate the mirror integration circuit at the same time as exposure starts, and compare the output of this mirror integration circuit with a reference voltage set separately for each color component exposure. This is an exposure method for a color electrophotographic camera in which the exposure is terminated based on this comparison output signal, and the ratio of each exposure time for the blue component, green component, and red component of the original image is approximately 7:4:1 in a standard state. By adjusting the integral constant of the mirror integrating circuit, the total exposure time can be shifted while maintaining the color balance, and each adjustment width for the exposure time of each color component of the original image and the total exposure time can be changed from the standard state. An exposure method for a color electrophotographic camera characterized by setting the exposure to ±40%.