JP2572601B2 - Exposure control device for copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine for copying an image recorded on a microfilm, and more particularly, to an exposure adjusting device for controlling an exposure lamp so that an image recorded on a microfilm can be copied with an optimum image exposure light amount. About.

[Prior art]

2. Description of the Related Art Electrophotographic microcopiers are known in which an image portion of a microfilm is exposed and an optical image thereof is formed on an electrophotographic photosensitive member such as a photosensitive drum to form a copier. In such a copying machine, adjustment of the exposure amount to the microfilm is one of the most important factors in order to form an optimum copy image on the photoconductor. Therefore, conventionally, an apparatus for automatically determining the exposure amount in consideration of the fog density of the microfilm and the copy magnification has been used. That is, it has a configuration as shown in FIG. In the figure, a light beam emitted from a light source lamp 100 condensed by a condenser lens 101 is irradiated onto a microfilm 102, and an image of the microfilm 102 is passed through a magnifying lens 103 and a slit plate 104 to form a photoconductor 10
5. Slit exposure on top. The slit plate 104 is provided with a plurality of sensors 106 for receiving a part of the optical image. The sensors 106 irradiate the microfilm 102 with a specified illuminance in accordance with the setting of the copy magnification. To control. This exposure control device is configured as shown in FIG. That is, the image on the microfilm 102 is pre-scanned prior to the copying operation, and the outputs of the light beams incident on the sensors 106A to 106C during this pre-scan are amplified by the amplifiers 107A to 107A.
The signal is amplified by 107C, input to the minimum value detection circuit 109 via the detection lines 108A to 108C, and supplies the detection signal having the lowest level to the comparator 111 as the minimum value signal 110. Reference circuit
The reference value signal 113 output from the comparator 112 is compared with the reference signal 113, and the result is supplied as a comparison signal 114 to the exposure adjusting circuit 115 to control the voltage applied to the aperture of the magnifying lens 103 or the light source lamp 100. Copying is performed with the exposure light amount set by the preliminary scanning.

[Problems to be solved by the invention]

However, in such a conventional exposure control apparatus, in a microfilm on which a pattern on a printed circuit board or a normal photograph is recorded, the white portion reaches 10% or more than 50%, and any sensor 106 has a background of image quality. In many cases, the light beam of a portion is not received, and in such a case, the exposure adjustment circuit 115 mistakenly sets the exposure amount with the white portion of the image quality as the background portion, resulting in completely inappropriate exposure. However, there is a problem that useless copying is performed. Furthermore, since a preliminary scan for film density detection is required separately from the copying operation, there is a problem that the time required for one copy is long. An object of the present invention is to use a light exposure of an exposure lamp to reflect or transmit a document surface and project it on a photosensitive member to form a copy image. Is to control an exposure lamp so that a copied image can be projected with an optimum amount of light.

[Means for solving the problems]

An exposure control apparatus for a copying machine according to the present invention is a triac for adjusting a voltage applied to an exposure lamp in a copying machine for forming a copy image by projecting a light image of a document onto a moving photosensitive member by irradiation of an exposure lamp. Is connected to the exposure lamp, an exposure lamp irradiation light amount sensor for detecting the amount of light emitted from the exposure lamp is provided in the vicinity of the exposure lamp, and a reference for setting a light density for projecting a light image of a document onto a photosensitive member. A voltage setting circuit for detecting light obtained from the original when a copy image is formed by irradiating the original with the light of the exposure lamp and outputting a value which changes linearly in accordance with a change in the amount of light; An image light amount sensor is provided on the optical path, and a switch for interrupting the output from the optical image light amount sensor is connected to the optical image light amount sensor. The difference voltage between the voltage value indicating the light amount corresponding to the sensor detection value and the optimum document density value corresponding to the document density detection value output from the optical image light amount sensor as a current value via the switch is output. A comparison circuit for comparing an output value from the calculation circuit with an output value from the reference voltage setting circuit and outputting a value corresponding to a difference voltage to the exposure lamp voltage control circuit; And an exposure lamp voltage control circuit for outputting a siriger signal for controlling the triac so that the output value of the optical image light amount sensor becomes an appropriate value based on the output value from the optical image light amount sensor. Thus, the output of the exposure lamp is controlled to an appropriate exposure amount in real time.

[Action]

A sensor detects the amount of light from an exposure lamp that irradiates a photosensitive member through a document surface such as a microfilm during a copying operation, and feeds back the light amount of the exposure lamp in real time. This may be an enlarged copy,
The optimum amount of light can always be maintained, although there may be some white areas.

【Example】

Hereinafter, examples of the present invention will be described. FIG. 1 shows an embodiment of the present invention. In the figure, a condenser lens 2 is arranged on the optical path of an exposure lamp 1, and a document 3 such as a microfilm is set in front of the condenser lens 2. A magnifying lens 4 is provided in front of the original 3 such as a microfilm.
Are arranged, and a slit plate 5 is provided in front of the magnifying lens.
Is provided. A photosensitive member 6 is provided in front of the slit plate 5.
Is provided. The slit plate 5 is provided with an optical image light amount sensor 7 for detecting light projected through the original 3 and through the magnifying lens 4. As shown in FIG. 2, the output of the optical image light quantity sensor 7 changes linearly in accordance with the quantity of light quantity of the light beam irradiated through the magnifying lens 4. An exposure lamp voltage control circuit 8 for adjusting the voltage applied to the exposure lamp 1 is connected to the optical image light quantity sensor 7. The output signal of the exposure lamp voltage control circuit 8 is supplied to a triac 9, which controls the voltage applied to the exposure lamp 1 according to the output from the optical image light quantity sensor 7 as shown in FIG. In addition, an exposure lamp irradiation light amount sensor 10 for detecting light emitted from the exposure lamp 1 is provided near the exposure lamp 1. The exposure lamp irradiation light amount sensor 10 includes:
The overvoltage detection circuit 11 and the arithmetic circuit 12 are connected. The arithmetic circuit 12 is configured so that the output from the optical image light quantity sensor 7 can be input via the switch 13. The arithmetic circuit 12 has a configuration as shown in FIG. That is, the arithmetic circuit 12 receives a sensor detection value output as a current value from the exposure lamp irradiation light amount sensor 10, and outputs a voltage value indicating a light amount corresponding to the sensor detection value, and a sensor-light amount conversion circuit 121, A detection value corresponding to the amount of light passing through the document 3 output as a current value from the optical image light quantity sensor 7 is input, and the density of the document passing through the document 3 corresponding to the detected value is optimized when the document 3 passes. A sensor-film density conversion circuit 122 that outputs an increase / decrease (±) value as a voltage value depending on whether the original density value is too large or too small, and an addition circuit 123 that adds and outputs the output values from the two conversion circuits. It is configured. A comparison circuit 15 is connected to the arithmetic circuit 12, and a reference voltage (Vref) setting circuit 16 is connected to the comparison circuit 15. The passing voltage detection circuit 11 uses an effective value voltage applied to the exposure lamp 1 based on the amount of light emitted from the exposure lamp 1 (the voltage applied to the exposure lamp 1 is obtained by phase-controlling an alternating current). This is for detecting whether or not the exposure lamp 1 is larger than a predetermined value (limit value). That is, it functions as a high-frequency limiter for the voltage applied to the exposure lamp 1. The switch 13 is set to automatic adjustment (auto) when turned on and to manual adjustment (manual) when turned off. That is, when the switch 13 is OFF (manual), the arithmetic circuit 12 outputs
The value converted by the output from is output to the comparison circuit 15. In the automatic mode (when the switch 13 is ON), the value converted by the output from the exposure lamp irradiation light amount sensor 10 and the value converted by the light image light amount sensor 7 are output. Then, a value obtained by adding the value converted by the output of (i) is output to the comparison circuit 15. The comparison circuit 15 has a configuration as shown in FIG. That is, the comparison circuit 15 includes a set value-reference voltage conversion circuit 151 for converting a voltage corresponding to the value set by the reference voltage setting circuit 16 for setting the light density for projecting the light image of the document onto the photoconductor, The output from the addition circuit 123 of the arithmetic circuit 12 is compared with the output from the set value-reference voltage conversion circuit 151 to obtain a difference voltage (the value obtained by subtracting the value output from the addition circuit 123 of the arithmetic circuit 12 from the reference value). The reference voltage setting circuit 16 is composed of, for example, a volume and the like, and can be freely set from the outside. The exposure lamp voltage control circuit 8 outputs a trigger signal for controlling the phase of the triac 9 by a signal from the comparison circuit 15. With this configuration, the output from the optical image light quantity sensor 7 is 0 (zero) because the switch 13 is OFF at the time of manual operation. Therefore, the arithmetic circuit 12
Is only a value based on the detection value of the exposure lamp irradiation light amount sensor 10. This value corresponds to the reference voltage setting circuit 16
The output value is compared with the set value input from the control circuit 152, and the light amount of the exposure lamp 1 is controlled by the reference value (set value). Therefore, at the time of manual operation, the light amount of the exposure lamp 1 is set by the reference voltage setting circuit 16. That is, the addition circuit 12 of the arithmetic circuit 12 is more than the reference voltage.
If the signal from 3 is low (in the case of a positive value), the exposure lamp voltage control circuit 8 increases the light amount of the exposure lamp 1.
Performs control. If the signal from the adding circuit 123 of the arithmetic circuit 12 is higher than the reference voltage (in the case of a negative value), the exposure lamp voltage control circuit 8 controls the light amount of the exposure lamp 1 to decrease. At the time of the auto mode, the switch 13 is turned on. For this reason, the output value from the arithmetic circuit 12 is
And the value based on the detected light amount of the exposure lamp 1 and the value based on the detected light amount of the photoreceptor projected light detected by the optical image light amount sensor 7. This value is compared with the set value input from the reference voltage setting circuit 16 in the difference voltage output circuit 152,
The light amount of the exposure lamp 1 is controlled by this comparison value.
The set value of the reference voltage setting circuit 16 is set in advance to a set value set at the time of the automatic operation at the time of the automatic operation. The setting of the reference voltage setting circuit 16 can be changed in either the manual mode or the automatic mode, and can be changed freely even during exposure. However, here, the set value of the reference voltage setting circuit 16 is
Description will be made assuming that a standard value is set as a value to be set in advance in the automatic mode. Now, when the film density is lower than the standard density, the amount of light transmitted through the film becomes larger than the reference value, so that the output from the optical image light quantity sensor 7 is (+), and the output from the addition circuit 123 of the arithmetic circuit 12 is the standard density. Of the film. For this reason,
Since the output from the comparing circuit 15 is larger than the value set at the time of auto by the reference voltage setting circuit 16, the output from the adding circuit 123 becomes (−) and is output to the exposure lamp voltage control circuit 8. , The light quantity of the exposure lamp 1 is controlled to decrease. When the film density is higher than the standard density, the amount of light transmitted through the film becomes smaller than the reference value, so that the output from the optical image light quantity sensor 7 is (-), and the output from the addition circuit 123 of the arithmetic circuit 12 is the standard. The density is lower than that of the film. For this reason, the output from the comparing circuit 15 is smaller than the value set at the time of the automatic operation by the reference voltage setting circuit 16 from the adding circuit 123. And the amount of light of the exposure lamp 1 is controlled to increase. Even in the automatic mode, the setting value of the reference voltage setting circuit 16 can be changed according to the preference of the person who is exposed. This is to enable automatic adjustment.

【The invention's effect】

As described above, according to the present invention, it is possible to copy an image recorded on a document such as a microfilm with an optimum amount of light.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an exposure control device of a copying machine according to the present invention, FIG. 2 is a characteristic diagram showing a relationship between a light amount and a sensor output,
FIG. 3 is a characteristic diagram showing a relationship between a sensor output value and an exposure lamp applied voltage, FIG. 4 is a detailed diagram of an arithmetic circuit and a comparison circuit shown in FIG. 1, and FIG. Figure,
FIG. 6 is a block diagram of the apparatus shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Exposure lamp 2 ... Condenser lens 3 ... Document 4 ... Magnifying lens 5 ... Slit plate 6 ... Photoconductor 7 ... Sensor 8 ... Exposure lamp voltage control circuit 9 ... Triac 10 ... Exposure lamp Irradiation light amount sensor 11: Overvoltage detection open circuit 12: Operation circuit 13: Switch 15: Comparison circuit 16: Reference voltage setting circuit

Claims (1)

(57) [Claims] 1. A copying machine for forming a copy image by projecting a light image of a document onto a moving photosensitive member by irradiating light from an exposure lamp, wherein a triac for adjusting a voltage applied to the exposure lamp is connected to the exposure lamp. An exposure lamp irradiation light amount sensor for detecting an amount of light emitted from the exposure lamp in the vicinity of the exposure lamp, and a reference voltage setting circuit for setting a light density for projecting a light image of a document onto a photoreceptor; A light image light amount sensor that detects light obtained from the original when a copy image is formed by irradiating the light of the exposure lamp onto the original and outputs a value that changes linearly in accordance with a change in the light amount of the light is provided on the optical path. A switch for connecting and disconnecting the output from the light image light amount sensor to the light image light amount sensor, and corresponding to a sensor detection value output as a current value from the exposure lamp irradiation light amount sensor. An arithmetic circuit for adding and subtracting a difference voltage between a voltage value indicating the light amount and an optimum document density value corresponding to a document density detection value output as a current value from the optical image light amount sensor via the switch; A comparison circuit that compares an output value from the arithmetic circuit with an output value from the reference voltage setting circuit and outputs a value corresponding to a difference voltage to the exposure lamp voltage control circuit; An exposure lamp voltage control circuit that outputs a trigger signal for controlling the triac so that the output value of the light image light amount sensor becomes an appropriate value based on the output value of the light image light amount sensor; An exposure control device for a copying machine, wherein an output is controlled to an appropriate exposure amount in real time.