JPS5818655A - Exposing device of copying machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to an exposure device for a copying machine.

Many copiers scan documents by moving the illumination device and optical system or by moving the document table, or by using an automatic document feeder. 1 as shown in Figure 1, which can illuminate
Consists of book lamps.

However, since such illumination devices illuminate the original with a single lamp, they always require power for the maximum original size regardless of the size of each original, and always generate heat equivalent to the maximum original size, causing other problems. It also affects parts of In addition, in order to obtain the required light distribution of the lamp, the filaments (Fl to F6) have two lengths, two turns, and two positions, etc., as shown in FIG. 1, which makes manufacturing complicated. Furthermore, since the lamp is long, in a method in which the lamp and optical system are moved, the lamp itself vibrates, which adversely affects the copied image. Furthermore, even if one point of the lamp is damaged, the entire lamp will no longer function, which increases the cost of replacing the lamp. Furthermore, if uneven illuminance of the lamp occurs on the copied image, adjustment is not easy because the entire lamp must be moved, not just the affected area. In addition, since the position of a reflector or the like is adjusted to improve illuminance unevenness, it is not possible to obtain an appropriate light distribution that matches the document size and document density.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus for a copying machine that uses a plurality of light sources and controls them individually to improve the above-mentioned drawbacks.

The present invention will be described below by way of examples with reference to the drawings.

In an embodiment of the present invention, an exposure apparatus of a well-known copying machine in which a document is scanned by moving an illumination device and an optical system (or by moving a document table) (or a document is scanned by an automatic document feeder) is shown in FIG. A lighting device such as the following is used. In this lighting device, a plurality of lamps LAI to LA6 are mounted in a line in a socket S, and the lamps LAI to LA6 are arranged in a direction perpendicular to the document scanning direction in a copying machine. In the exposure device of a copying machine, the light distribution power as shown in Figure 3A is generally required due to lens aberrations, reflector tolerances, etc.; for example, for an A4 document size and a large contrast document, the light distribution power is as shown in Figure 3B. Light distribution power; required.

FIG. 4 shows a lamp lighting control circuit, in which lamp voltage control circuits 10A to IOF each have a sino-1 nostar 1 degree bidirectional switching element 2. Resistance 3-5. A photocoupler 7 consisting of a converter 6, a light emitting diode 7a and a phototransistor 7b. A 4-bit digital/analog converter 8.
．． A well-known thyristor phase control circuit constituted by diodes DEG9 controls each of the lamps LAI-LA6. The control circuit 20 of the copying machine is composed of a microcomputer or the like, and a detection signal is input to the input line 20G from a document size detection circuit that detects that the size of the document to be copied on the document table is A4. A detection signal is input to the input line /20H from a document density detection circuit that detects that the density of the document to be copied on the document table is high.

When copying an A4 size original with a high density, the control circuit 2 is used from both the original size detection circuit and the original density detection circuit.
0, and the control circuit 20 sends a 4-bit signal (set in advance by experiment) to the lamp voltage control circuits 10A to IOD from the output lines 20A to 20D at the exposure timing to obtain the light distribution shown in FIG. 3B. The lamp voltage control circuit 10E is output from 20F to the output line 20.

Lamp LA5 on 10F. Outputs a 4-bit signal (oooo) that turns LA6 off. For example, a 4-bit signal (
1000) is outputted from the output line 20A) and converted into an analog voltage by the digital/analog converter 8, and the light emitting diode 7a of the photocoupler 7 lights up with a light intensity set in advance in an experiment. The phototransistor 7b exhibits a resistance value depending on the amount of light.
b. The thyristor 1 is gated by the bidirectional switching element 2 using the time constant of the resistor 5 and the capacitor 6 to control its flow angle, and the phase of the voltage applied from the AC power source to the lamp LAI via the thyristor 1 is controlled. Te lamp LA
1 is lit with a light intensity matching the light distribution shown in FIG. 3B.

Similarly, the other lamps LA2 to LA4 are lit with a light intensity matching the light distribution shown in FIG. 3B, and the lamp LA5°Li2 is not lit.

When copying an original other than an A4 size original with high density, the control circuit 20 uses the lamp voltage control circuit from the output lines 20A to 20F at the exposure timing since detection signals are not input to both input lines 20G and 20H. Output a 4-bit signal (signal set in the preliminary experiment) to obtain the light distribution shown in Figure 3A to 10A to IOF, and set the lamps LAI to LA6 with the light distribution shown in Figure 3A. Turn it on.

Note that the control circuit 20 changes the output signal depending on whether or not the detection signal is input from both the original size detection circuit and the original density detection circuit, but the control circuit 20 changes the output signal depending on whether or not the detection signal is input from both the original size detection circuit and the original density detection circuit. The output signal may be changed.

As described above, according to the present invention, a plurality of light sources are arranged in a direction perpendicular to the document scanning direction and these light sources are individually controlled according to the document size and/or document density. A suitable copy can be obtained by obtaining a suitable light distribution.

Further, variations in each light source can be easily corrected, and manufacturing is easy and inexpensive. Further, depending on the size of the document, unnecessary light sources can be turned off to save power, and the cost of replacing the light source is also low, and the vibration of the light source is also reduced.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a conventional document illumination lamp, FIG. 2 is a front view showing a document illumination light source in an embodiment of the present invention, and FIG. 3 is a light distribution for explaining the same embodiment. 4 are block diagrams showing the lamp lighting control circuit of the same embodiment. LAI to LA6... lamp, 1oA to IOF... lamp voltage control circuit, 2o... control circuit. −Toto −

Claims (1)

[Claims] An exposure device of a copying machine that scans an original, including a plurality of light sources arranged in a direction perpendicular to the original scanning direction,
An exposure device for a copying machine, characterized in that the light distribution is controlled by controlling the plurality of light sources according to the document size and/or document density to illuminate the document.