JPH0210932B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in an exposure control device for a copying machine or the like. In copying machines, halogen lamps, fluorescent lamps, mercury lamps, xenon tubes, and the like are used as light sources for exposure. Fluorescent lamps and halogen lamps are most commonly used in electronic copying machines. Since the illuminance of a light source changes in proportion to the voltage, it is necessary to stabilize the voltage in order to keep the illuminance constant. In order to stabilize the voltage, a feedback type using a phase control method using a bidirectional control element such as a triac, and a voltage stabilizing transformer (CVT) using fero-resonance are generally used.

In addition, in a copying machine, it is necessary to adjust the amount of light irradiated onto a photoreceptor made of Se, Cds, etc. to an appropriate value depending on the condition and type of the original to be copied. Methods to adjust the exposure amount include: a. Mechanically changing the aperture blades.

b Electrically change the brightness of the light source itself.

There is a method.

In method a, there is no need to change the amount of light from the light source itself, so it has been used more often than in the past. The disadvantages are that it is mechanical, so it requires a lot of space, and the mechanical structure is very complicated.
It was difficult to make adjustments. Furthermore, the lamp always outputs the maximum amount of light, requiring maximum power even when the amount of exposure is small. Therefore, there was a drawback that there was a lot of power loss and the life of the light source was short.
In b, it is necessary to change the applied voltage in order to change the power applied to the light source and change the brightness of the light source itself. There are various ways to change this voltage, such as energization phase adjustment and variable voltage autotransformer open adjustment, but recent remarkable advances in semiconductor technology have made semiconductor control elements (triacs) highly efficient and highly stable. By using this, it has become possible to obtain something that is small, simple, and has a long life.

However, even if you think that you have adjusted the light intensity to a predetermined level, the actual light intensity may vary due to differences in the return elements, or when you want to finely adjust the predetermined light intensity, it is very difficult and requires a lot of trouble and technique for the operator. It was hot.

The present invention has been made in view of the above points, and includes an exposure lamp for exposing an original that is turned on by application of an alternating current voltage, and an adjustment means for arbitrarily adjusting the light amount of the exposure lamp within a predetermined light amount adjustment range. , an output means for outputting a control signal of a level corresponding to the light amount adjustment by the adjustment means, a bidirectional control element for controlling the firing angle of the AC voltage to be applied to the exposure lamp, and the control element are electrically connected. supply means for supplying an alternating current voltage with a controlled firing angle to the exposure lamp; and a detection means for detecting a terminal voltage of the exposure lamp; and a control means for increasing or decreasing the amount of current supplied to the capacitor in accordance with a comparison between the level of the control signal from the output means and the terminal voltage of the exposure lamp detected by the detection means, and the adjustment means. a setting means for setting the light amount adjustment width in which the light amount can be adjusted; and a setting means for setting the light amount adjustment width by the setting means, which sets a range of change in the level of the control signal output from the output means in accordance with the light amount adjustment by the adjustment means. The present invention provides an exposure control device having an increasing/decreasing means for increasing/decreasing the exposure according to the following.

This makes it easy to adjust the amount of light, and the adjustment range is not impaired by fine adjustment.

Examples will be described below with reference to the drawings.

In the following description of the embodiments, the lamp L is the exposure lamp of the present invention, the variable resistor VR2 is the adjusting means of the present invention, the operational amplifier Q3 is the output means of the present invention, and the thyristor PUT is the control element of the present invention. ,
The capacitor 16 is the capacitor of the present invention, the phase control circuit A is the supply means of the present invention, the transformer 21,
The diode bridge 22, the capacitor 25 and the resistors 23 and 24 serve as the detection means of the present invention, the differential amplifier B consisting of transistors 30 and 31, the transistor 13 and the resistor 15 serve as the control means of the present invention, and the variable resistor VR1 serves as the present invention. The operational amplifiers Q1 and Q2 respectively correspond to the setting means of the present invention and the increasing/decreasing means of the present invention.

FIG. 1 is a schematic sectional view of a copying machine to which the present invention can be applied, and FIG. 2 is a plan view of the operating section of FIG. 1.

Place the original 1 on the optical system platen 2, adjust the exposure dial VR2 (Fig. 2) to set the lamp exposure to the desired value, and then press the copy button CPB to turn on the switch (Fig. 3) and turn on the lamp L. Light. The light reflected from the original 1 by the L passes through a filter 3 that cuts out infrared rays (cuts out light other than visible light), passes through a lens 4 and a mirror 5, and then reaches a photoreceptor 6.
exposed to light. Exposure is performed by slit scanning by reciprocating movement of the platen 2. Since the surface of the photoreceptor 6 has already been uniformly charged by the corona charger 7, an electrostatic latent image is created by the exposure. This image is visualized by a developing device 8, transferred to paper 9, fixed by a fixing device 11, and then discharged outside the machine to obtain a desired copy.
The variable resistor VR2 is arranged as an exposure dial on the operation panel of the copying machine. Then, the variable resistor VR3 is adjusted so that the center value (that is, the center value of the exposure dial) becomes an appropriate value. With this variable resistor VR2, it is possible to correct variations in the lamp L, including variations in C, Q2, and Q1, and to compensate for the sensitivity of the photoreceptor. Dial values vary.

Note that the lamp L is a halogen lamp, and is controlled to maintain a constant light amount even if the lamp light amount changes due to fluctuations in the voltage applied to the lamp. Filter 3
is provided to correct the color temperature of the lamp which changes when exposure is adjusted.

Figures 3 and 4 are circuit examples of the lamp illuminance control device according to the present invention, where A in the frame controls the firing angle of the bidirectional control element 12 using an N-gate thyristor (PUT) and applies it to the lamp L. This is a phase control circuit that maintains the effective value of AC voltage at a predetermined value. Here, the firing angle is determined by comparing the terminal voltage of the lamp L with a constant value and detecting an error through the output of the differential amplifier B and the resistor 14.
determined by the line voltage applied to the anode terminal of PUT.

To explain this differential amplifier B, the emitters of transistors 30 and 31 are connected in common, and this contact is grounded through a resistor 32. Also, the collector of the transistor 30 is a resistor 29
The collector of transistor 31 is directly connected to power supply B through the power supply. Furthermore, transistor 3
1 base is the 3rd base connected to T1, T2, T3
It is connected to a constant potential point T3 created by the adjustment circuit shown in the figure. The lamp L changes due to the change in the applied voltage of T3.
The voltage applied to can be changed. On the other hand, an error detection transformer 2 connected to the lamp L is connected to the base of the transistor 30 in order to detect the terminal voltage of the load 3.
1 is rectified by a diode bridge 22, voltage-divided by resistors 23 and 24, and an error signal from which ripples are removed to some extent by a capacitor 25 is applied through a resistor 26. Furthermore, a capacitor 27 is connected between the base and collector of the transistor 30.
A feedback path is provided in which a resistor 28 and a resistor 28 are connected in series.

The firing phase angle of the bidirectional control element 12 is determined by the pulse obtained from PUT, but the phase relationship between this pulse and the power frequency of the AC power supply AC is changed by β times by the current charging the capacitor 16, that is, by the transistor 13. The current and resistance increased by 14
It changes depending on the sum of the current flowing through the

Now, if we consider the case where the voltage across the lamp L becomes lower than the reference voltage for some reason, the voltage at the output end of the diode bridge 22 decreases, the base current of the transistor 30 decreases, and this transistor 30 lowers the base potential. Since a differential amplifier is formed together with the transistor 31 which is kept constant, the collector current decreases, and therefore the collector potential increases and approaches the DC power supply voltage. This increases the current flowing through resistor 15 and the emitter current of transistor 13, and reduces the time per AC half cycle during which capacitor 16 is charged to the potential required to turn on PUT. That is, the firing pulse will advance in phase, causing the bidirectional control element 12 to conduct every half period earlier than it originally did, thus causing the load 3 to
The terminal voltage of increases and approaches the reference voltage. When the lamp voltage increases, the opposite operation occurs.

FIG. 4 shows the adjustment section in the exposure control circuit according to the invention. In the figure, T1 to T3 are T1 to T3 in each figure 3.
Connected to T3. Q1 to Q3 are operational amplifiers whose input voltage and output voltage match and have a high input impedance and a low output impedance, which are commonly called voltage followers, and Q4 is a comparison circuit. VR2 is a variable resistor for setting the exposure amount and is connected to the output side of the operational amplifiers Q1 and Q2. VR3 is a variable resistor for finely adjusting the exposure amount set by VR2, and VR1 is a variable resistor for determining the adjustment range by VR2.
3 is connected to the base of transistor Q6.

C1, R8 to R10, and VR4 are a capacitor, a resistor, and a variable resistor that constitute a delay circuit, and Q7 is a transistor for discharging the charge of the capacitor C1.

To explain the operation, when the power is turned on by turning on the switch SW, a voltage is applied to T1 and T2, and a potential determined by variable resistors VR1, VR2, and VR3 is applied to the input of operational amplifier Q3, and that potential is instantaneously output from T3. . However, when the power is turned on, the comparator Q
Since the potential determined by the resistors R9 and R10 is applied to the negative input terminal of T4, and the potential of the capacitor C1 is applied to the positive input terminal, the potential of T3 is as follows. In other words, after the power is turned on, capacitor C1
It is charged with the time constant of VR4, R8, and C1, and the potential of C1 gradually increases. Comparator Q4 outputs 0 while the potential of its + input is lower than that of its - input. Therefore, during the delay period, transistor Q5 is turned on, so that the potential applied to T1 is applied to amplifier Q3.
VR1,
A potential T1 higher than the potential determined by VR2 and VR3 will be output. After the delay time, the comparator Q4 outputs 1 when its +input potential becomes higher than the -input potential due to charging. Therefore, transistor Q
5 is turned off, and from the output T3 of the operational amplifier Q3,
It will output the potential determined by VR1, VR2, and VR3.

Therefore, during the time constant time determined by R8, VR4, and C1 when lighting the lamp, a high potential for lighting the lamp at its rated value is output from T3, and after that, the potential set by VR2 is output, so that the lamp starts up quickly, and After a certain period of time, the lamp shifts to a lighting operation of a predetermined amount of light. Further, by adjusting VR4, the timing of switching the output from T3 can be adjusted. VR
If you try to turn it on with a voltage lower than the rated voltage adjusted by 2, the rise to the rated light intensity will be longer than the rated light intensity when the rated light intensity is turned on, but since the rated voltage is initially applied when adjusting by VR2, the light intensity will be adjusted in the opposite direction. The rise time will be shorter than that at the rated value. Therefore VR
By adjusting step 4, the rise correction time can be minimized.

Here, when the potential of T3 is equal to the potential of T1, the rated voltage (100V) is applied to the lamp, and when the potential of T2 is equal, 30% of the rated voltage is applied.

Next, light amount adjustment will be explained. Adjusted VR
2, when the variable resistor VR1 is adjusted after the power is turned on and the light is on in a predetermined state, the operational amplifier Q2
By changing the voltage to the + input of the operational amplifier Q1, Q
The potential difference between the two outputs can be changed. As a result, the potential range that can be determined by the variable resistor VR2 is changed, and the exposure adjustment range is limited. adjusted
Changing VR3 under VR1 and VR2 changes the current flowing through transistor Q6, thereby changing the potential drop across resistor R2. If the resistance value of this resistor R2 is made sufficiently larger than that of the variable resistor VR2, the potential drop due to the variable resistor VR2 can be ignored. Therefore, only the change in potential drop due to resistor R2 will affect the output of T3,
Therefore, without changing the adjustment range set in VR1, this range can be level-shifted by adjusting VR3.

In the figure, D1 is a diode provided for temperature compensation of the transistor Q6, and D2 and D3 are diodes provided for reverse breakdown voltage of the transistor Q5. VR1 and VR3 can also be provided on the circuit board inside the machine so as not to impair the complexity of the operation section. Further, a reset signal R for turning on the transistor Q7 is inputted when the lamp is turned off. Further, the switch SW in FIG. 3 is turned on by the copy button CPB (FIG. 2) before the start of exposure scanning by the platen. After the lamp reaches a predetermined illuminance, exposure scanning by moving the platen starts, and at the end of the movement for exposure, the lamp goes out. If you turn on the copy button once and make copies repeatedly from the same original by moving the platen back and forth, after the second copy, turn the switch SW when the platen moves backwards (referred to as forward exposure) before starting forward movement. This can be achieved by turning it on. That is, as shown in FIG. 5, the switch SW is turned on by turning on the reed switch 50 provided in the platen movement path during the backward movement when the magnet 51 provided on the platen passes, and this on state is further maintained during the forward movement of the platen. The switch SW is turned off by turning on the reed switch 53 provided at the end point when the magnet 51 reaches it. Since this blinking method is not limited by the drum position, it is possible to take advantage of the characteristics of the drum having a seamless photoreceptor. The present invention is applicable not only to copying but also to various devices that perform exposure processing, such as projectors.

As described above, the configuration of this embodiment makes it possible to shift the center level of the adjustment range up and down without changing the range in which the light amount can be adjusted, making it extremely easy to adjust the light amount, especially when changing the light amount of the lamp by adjusting the power. It is extremely effective in automatic control devices that maintain the amount of light at a constant level. Furthermore, the light amount is adjusted to compensate for the slow start-up time when the lamp is turned on at a voltage below the lamp's rated voltage, making it possible to keep the start of work such as copying processing related to exposure constant, and to reduce the processing speed by adjusting the lamp. The decline can be prevented.

As explained above, according to the present invention, a capacitor for forming a firing signal by charging a predetermined potential to conduct a bidirectional control element for controlling a firing angle of an AC voltage to be applied to an exposure lamp. The control means increases or decreases the amount of current supplied to the exposure lamp according to a comparison between the level of the control signal corresponding to the light amount adjustment by the adjusting means and the detected terminal voltage of the exposure lamp. By outputting a control signal at a level corresponding to the light amount adjustment by the adjusting means that arbitrarily adjusts the light amount within the light amount adjustment width, it is possible to stably light the exposure lamp at an arbitrary light amount, and furthermore, a setting means for setting a light amount adjustment range in which the amount of light can be adjusted by the adjustment means; and a setting means for increasing or decreasing the change range of the level of the control signal output in response to the light amount adjustment by the adjustment means in accordance with the setting of the light amount adjustment range by the setting means. For example, even if the light amount adjustment range by the adjustment means does not correspond to the actual light amount change range of the exposure lamp due to aging or differences in the usage environment, the capacitor for forming the ignition signal can be charged. By increasing or decreasing the range of change in the level of the control signal, it is possible to easily match the light amount adjustment range with the actual light amount change range of the exposure lamp without requiring the effort of adjusting a constant.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a copying machine to which the present invention can be applied, FIG. 2 is a plan view of the operation section of the copying machine shown in FIG. 1, and FIGS. Figure 5 is a partial sectional view of the copying machine shown in Figure 1, and in Figures 2, 3, and 4, L is a lamp, SW is a lighting switch, 12 is a triax, B is a differential amplification circuit, and VR2 is an exposure adjustment. The resistor VR3 is an exposure shift resistor.

Claims (1)

[Scope of Claims] 1: an exposure lamp for exposing documents that is turned on by application of an alternating current voltage; an adjusting means for arbitrarily adjusting the light amount of the exposure lamp within a predetermined light amount adjustment range; and a light amount by the adjusting means. output means for outputting a control signal at a level corresponding to the adjustment; a bidirectional control element for controlling the firing angle of the AC voltage to be applied to the exposure lamp; and a firing signal for making the control element conductive. a supply means for supplying an alternating current voltage with a controlled firing angle to the exposure lamp, the supply means comprising a capacitor for forming a capacitor by charging to a predetermined potential; a detection means for detecting a terminal voltage of the exposure lamp; control means for increasing or decreasing the amount of current supplied to the capacitor in accordance with a comparison between the level of the control signal and the terminal voltage of the exposure lamp detected by the detection means; and the light amount adjustment capable of adjusting the amount of light by the adjustment means. a setting means for setting a width; and an increasing/decreasing means for increasing or decreasing the range of change in the level of the control signal output from the output means in accordance with the setting of the light amount adjustment width by the setting means in accordance with the light amount adjustment by the adjusting means. An exposure control device comprising: