JPS61113055A - Flash exposing device of copying machine - Google Patents

Abstract

PURPOSE:To increase energy efficiency and obtain a high reliability exposure adjusting function by using a xenon flash lamp as a light source, and controlling the discharging voltage of this xenon flash lamp and adjusting the quantity of light emission. CONSTITUTION:When the 2nd thyristor SCR2 of a starting circuit 106 turns on by receiving an exposure start signal, charges accumulated in a capacitor 102 for charging flow to xenon lamps 3 and 4 through an inductance 103 for discharge adjustment to emit light. A light quantity decision circuit 12 integrates the detected illuminance with time and outputs a discharge stop signal Cu to the lighting stop circuit 105 of a lighting device 14 when the exposure attains to a specific value. The 1st thyristor SCR1 turns on and the xenon flash lamps 3 and 4 stop emitting light. The charging voltage of the capacitor for charging is adjusted according to copy magnification and the energy discharged through the 1st thyristor is reduced to obtain high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flash exposure device for a copying machine, and particularly to a flash exposure device 6 having an exposure amount adjustment function.

[Prior art]

An exposure device that projects an original to be copied onto a photoreceptor surface using optical means to form an electrostatic latent image generally includes an illumination device that illuminates the original to be copied and a projection device that projects two-dimensional information on the original to be copied. It consists of projection means for

Illumination means can be roughly divided into full-scale illumination, which uses a flash lamp or the like to illuminate the entire area of the copy once, and slit light, which scans the entire surface of the copy with narrow light guided through a slit. Two examples are slit lighting.

Of these, full-surface illumination using flash lamps has the potential to increase speed, and can provide high-intensity illumination with a color temperature of 500 to 7000° with a very short light emission time (1/1000 seconds or less). , is an effective method, but since the method usually involves exposing a stationary document to a photoreceptor that is moving at a constant speed, it is necessary to make the light emission time of the flash lamp extremely short and to perform instantaneous exposure.

In this case, in order to obtain the required exposure amount for the photoreceptor in a short period of time, it is necessary to flow a large current through the flash lamp, and the current may be as high as 8,008 or more.

On the other hand, when changing the copying magnification, the illuminance on the photoreceptor surface also changes, so a method is used to adjust the exposure amount by controlling the flash exposure time to compensate for this change in illuminance. There is. This method connects a thyristor or a bypass discharge tube in parallel with the flash lamp, and when a predetermined amount of exposure is reached, the thyristor or bypass discharge tube releases the charging energy of the flash lamp capacitor. This stops the flash lamp from emitting light.

[Problems to be solved by the invention]

However, in this conventional method, a large amount of wasted energy is emitted, and a large current flows instantaneously through the thyristor and bypass discharge tube, so the reliability of the parts through which this large current flows is low, and it is difficult to withstand large currents. When parts were used, there were problems such as a significant increase in cost.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a flash exposure apparatus that reduces emitted energy, increases energy efficiency, and has a highly reliable exposure adjustment function.

[Means for solving problems]

Therefore, in the present invention, a xenon flash lamp is used as a light source, and the amount of exposure is adjusted by controlling the discharge voltage of this xenon flash lamp.

[Effect]

In other words, a xenon flash lamp emits light by instantly discharging the charge stored in a capacitor.
The voltage used to charge this capacitor is controlled to adjust the amount of light emitted.

Incidentally, the illuminance on the surface of the photoreceptor changes depending on the copying magnification. For example, the illuminance F on the photoreceptor surface when exposing a document at the same magnification. When the copying magnification is N, the illuminance F on the photoreceptor surface is expressed by the following formula (1)%. Therefore, it is necessary to increase the amount of light emitted as the copying magnification increases. In addition, the illuminance F also decreases due to dirt in the housing of the exposure device, deterioration of the lamp, etc., and therefore, as the number of exposures increases, adjustment is required to compensate for the change.

Therefore, in the present invention, the amount of light emission (exposure amount) is adjusted by controlling the charging voltage of a capacitor that supplies charge for discharging the xenon flash lamp. Light emitted from the xenon flash lamp illuminates the document on the platen surface, and the reflected light is projected onto the surface of the photoreceptor through an optical system such as a lens. The illuminance of the xenon flash lamp on the photoreceptor surface varies depending on the lamp current, and the amount of exposure corresponds to the time-integrated amount of illuminance. Therefore, when this time-integrated amount reaches the exposure amount required by the photoreceptor, a cut signal causes the charged charge to be released by, for example, a thyristor connected in parallel with the xenon flash lamp, causing the xenon flash lamp to emit light. stops.

Note that control of the charging voltage as the copying magnification changes is performed as follows.

When the capacitance of the capacitor is C0 and the charging voltage is V, the energy Q stored in this capacitor is expressed by the following equation (2
).

Q: Cov2 Scream・・・・・・・・・・(2
) Therefore, since Q<F, the above formulas (1) and (2
) From the formula, ■=VoX Confucianism .....scream....(3)■.

...Charging voltage of the capacitor at the same magnification ■...Charging voltage of the capacitor when the copying magnification is N. If the discharging time of the xenon flash lamp does not change in this way, the current is proportional to the voltage, so the lower the charging voltage, the less current flows through the xenon flash lamp or thyristor, so the capacitor charging voltage can be controlled. By doing so, the lifespan of these parts is extended, reliability is significantly improved, and the amount of reactive energy discharged through the thyristor is reduced, resulting in a more efficient exposure apparatus.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

This flash exposure device uses a xenon flash lamp as a light source, and is characterized in that the lighting device for the xenon flash lamp has a function of controlling the charging voltage of a capacitor. As shown in the figure, there is a high-reflection cavity 2 with a platen glass 1 disposed on its upper surface, and two xenon flash lamps 3 disposed within the high-reflection cavity 2.
and 4, shielding members 5 and 6 provided above the xenon flash lamps to prevent specular reflection images of these xenon flash lamps from being generated by the platen glass, and a document placed on the platen glass 1. In order to guide the reflected light from the high-reflection cavity 2 onto the photoconductor 8 disposed below the high-reflection cavity 2, a projection lens 9 is provided at the bottom of the high-reflection cavity 2; The amount of light detected by the copying magnification detection means 10 disposed on the side, the optical sensor 11 disposed near the exposure area on the photoreceptor 8, and the optical sensor 1] is added to determine the amount of exposure. A light amount judgment circuit 12 configured to detect and issue a discharge stop signal when the amount of exposure reaches a predetermined amount.
, an arithmetic device 13 that calculates the charging voltage of the xenon flash lamp from the copying magnification detected by the copying magnification detection means 10; The lighting device 14 is configured to control the lighting conditions of the two xenon flash lamps based on a discharge stop signal.

This lighting device 14, as shown in the circuit diagram in FIG.
The signal value (voltage) I of the remote signal hole emitted from the charging capacitor 102 of the xenon flash lamp, the inductance 103 for discharging adjustment, and the arithmetic unit [13] accordingly changes the terminal voltage of the DC power supply DC, and the xenon flash lamp The voltage control circuit 104 that controls the voltage applied to both ends of the charging capacitors 102 and the discharge stop signal Cu issued from the light amount judgment circuit 12 cause the xenon flash to release the residual charge in the charging capacitor 102. A lighting stop circuit 105 consisting of a first thyristor 8CR connected in parallel to the lamp 3.4, and a second thyristor S which is turned ON upon receiving the exposure start signal Tr.
G1%, and a starting circuit 106 consisting of a capacitor CO and a trigger transformer To. and,
The voltage control circuit 104 includes a resistor R0, a first transistor TR, and a second transistor TR, and changes the output voltage based on the signal value of the remote signal hole. An inverter circuit 107 including a fourth transistor TR and a transformer T converts and transforms a DC signal into an AC signal, and a full-wave rectifier 108 rectifies the AC signal and applies it to the charging capacitor 102. It is configured as follows.

Next, the operation of this flash exposure device will be explained.

First, when a document is placed on the platen 1 and set by a copy magnification setting means (not shown), a value multiplied by the square root of the copy magnification is calculated, and this signal value is applied to the remote signal terminal of the lighting device 14. It is input to T1.

The incoming signal value enters the base terminal of the second transistor TR7 and controls the collector current. This current enters the base of the first transistor TR1, and the terminal voltage of the DC power supply DC changes depending on the amount of voltage drop caused by the current flowing through the resistance ratio 0 connected between the base and collector of this first transistor. It will be done. Further, it enters the inverter circuit 107 and is changed into alternating current by the third transistor Tll, 3 and fourth transistor TR, l, and is transformed by the transformer T. Further, the signal is rectified by a full-wave rectifier 108 and applied to the charging capacitor 102.

Then, an exposure start signal is obtained from an exposure start switch (not shown), etc., and the second thyristor 5CR2 of the starting circuit 106 is activated.
turns on, and the capacitor co and the trigger transformer To connect the trigger wires Wi on the lamp wall to 8 to 12.
When a high voltage of KV is generated, the charges charged in the charging capacitor 102 flow through the xenon flash lamps 3 and 4 through the discharge adjustment inductance 103, and discharge and emit light.

In this way, the light irradiates the document surface, and the reflected light passes through the projection lens 9 and irradiates the photoreceptor 8.

On the other hand, when the optical sensor 11 detects the illuminance E on the photoreceptor 8 (Fig. 3), the light amount judgment circuit 12 integrates the detected illuminance over time and determines that the amount of exposure has reached a predetermined amount. The discharge stop signal Cu is sent to the lighting stop circuit 1 of the lighting device 14.
Output to 05. Upon receiving this signal, the first thyristor 5C11, is turned on, and the charging capacitor 10
2 flows through the first thyristor SCR, and the xenon flash lamps 3 and 4 stop emitting light.

In this way, exposure of the photoreceptor is stopped and the amount of exposure is adjusted. In this device, the charging voltage of the charging capacitor is adjusted according to the copying magnification.
Less energy is discharged through the thyristor, resulting in higher efficiency, and the frequency with which large currents flow through the lamp and surrounding lighting circuits is reduced, resulting in longer life and improved reliability.

In the embodiment, we have described the case where the charging voltage of the charging capacitor is adjusted according to the copying magnification, but in addition to this, the charging voltage can be gradually increased depending on the cumulative number of copies, to prevent dirt on the optical system or the lamp. The reduction in the amount of light emitted due to the deterioration of the light may be corrected. In this case as well, the cumulative number of copies is detected and the remote signal terminal T of the lighting device 14 is detected.
, just adjust the signal value input to .

〔Effect of the invention〕

As described above, according to the present invention, in an exposure apparatus using a xenon flash lamp as an exposure light source, the amount of light emitted is adjusted by adjusting the discharge voltage. Less reactive energy,
It becomes possible to provide a highly efficient and reliable exposure apparatus.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a flash exposure device according to an embodiment of the present invention, FIG. 2 is a diagram showing a lighting circuit of the same device, and FIG. 3 is a diagram showing the illuminance and time on the photoreceptor surface detected by the optical sensor. FIG. ■...Platen glass, 2...High reflection cavity,
3.4...Xenon flash lamp, 5,6...
Shielding member, 7... Original, 8... Photoreceptor, 9... Projection lens, 10... Copying magnification detection means, 11... Optical sensor, 12... Light amount judgment circuit, 13... - Arithmetic device, 14... Lighting device, 102... Charging capacitor,
103...Inductance, 104...Voltage control circuit, 105...Lighting stop circuit, 106...Starting circuit, 107...Inverter circuit, 108...Full wave rectifier, SCR,...th Thyristor 1, 5Ca2...
Second thyristor, co... capacitor, l1lo...
...Trigger transformer, Ro...resistance, TR,...
First transistor, 1%, . . . second transistor, TR3 . . . third transistor, TR, . . . fourth transistor, T . . . transformer, DC . OCJ)” @ (4 criminals also -1

Claims (3)

[Claims] (1) A flash exposure device for a copying machine, characterized in that the exposure device uses a xenon flash lamp as a light source for exposure, and the amount of light emitted is adjusted by controlling the discharge voltage of the xenon flash lamp. . (2) Copying machine flash exposure according to claim (1), characterized in that the discharge voltage of the xenon lamp is controlled according to a copying magnification detected by a copying magnification detection means. Device. (3) The discharge voltage of the xenon lamp is controlled according to the count value of a counter that counts the number of flashes. flash exposure device for copying machines.