JPS6051691B2 - Light amount adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a light amount adjustment device for a slit illumination device in a copying machine.

FIG. 1 is a diagram showing the main parts of a conventional light amount adjusting device using an aperture type fluorescent lamp.

This conventional device is designed to adjust the light by rotating the fluorescent lamp 1 to shift the light condensing position F, so it has drawbacks such as a complicated device configuration and a tendency to cause poor contact at the socket. . FIG. 2 shows another conventional light amount device, in which the amount of light is adjusted according to changes in the amount of light by moving a shield plate 2.

For example, A when there is too much light. , Bo, and moves to positions Al, B when the amount of light decreases. However, in this case, in order to adjust the amount of light, the shielding plate 2 must be placed in advance at a position where it shields a portion of the light, resulting in poor utilization of illumination light. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a light amount adjustment device that can reliably follow changes in light amount and obtain constant illumination light without reducing the utilization rate of light from a light source with a relatively simple configuration. do. The present invention will be described below based on illustrative embodiments.

In FIG. 3, 3 is a glass plate of a manuscript table, 4 is a fluorescent lamp light source, and the light amount adjustment device according to the present invention has a white diffuse reflection plate attached to the upper surface of the glass plate 3 near the effective reading line o from its lower surface. A light amount detector 5 comprising a photoelectric conversion element arranged to detect reflected light from the area O' is provided.
, a control circuit 6 and a drive circuit 8 receive the detection signal, compare it with a preset reference level, and change the position of the reflector 7 according to the deviation output.

The reflector plate 7 is arranged to face the light source 4 and is arranged to illuminate part of the light from the light source 4 onto the illumination position F of the light source 4. Next, the operation will be explained with reference to FIG. 4, which shows the above light amount adjusting device as an electric circuit. Now, if the amount of light from the light source 4 decreases for some reason, the output of the detector '5 decreases, and its value falls below the reference level, the comparator 601
The deviation output of is ``positive''. Then, the ``positive'' output of the comparator 601 is input to the reversible motor 9 via the drive circuit 8, and the reflector 7 moves in the positive direction so that the output of the detector 5 matches the reference level. Corrected automatically.
When the output of the detector 5 increases, the reverse control described above is performed. The gate 602 provided between the comparator 601 and the drive circuit 8 has a 0N delay for a certain period of time in consideration of the transient phenomenon of the light source 4 (fluorescent lamp) (the period of low light intensity at the rise time Tr in FIG. 6). This prevents false detection.

The timer circuit 603 and the latch circuit 604 are connected to the gate 602
This is to delay the opening of the valve for a certain period of time. The above circuit operation timing is shown in the time chart of FIG. Now, in Figure 3 again, the direct illumination light is Φ.

The reflected light by the reflecting plate 7 is Φ1 and Φ2. The effective illumination for illumination position F is Φ. +Φ1 or Φ
. +Φ2. In other words, due to the presence of the reflector 7, an imaginary light source 15 or 16 is generated behind the reflector 7. The reflected lights Φ1 and Φ2 can be regarded as direct illumination light from the imaginary light sources 15 and 16. Therefore, the total illumination light Φ.

By adjusting the +Φ1 position with respect to changes in the light amount of the light source 4, constant illumination light can be obtained. This is achieved with the previously mentioned regulating device. FIG. 7 is a control characteristic diagram of the apparatus of the present invention, where Lr is the reference level, Lc is the controlled illumination value, and Tr is the rise time.

In addition, in FIG. 3, the light amount detector 5 is a white diffuse reflection plate 0.
However, the present invention is not limited to this, and any location where illumination light can be detected can be used.

As shown in FIG. 8, the light amount detector 5 can be arranged near the light source 4 so as to directly detect the light from the light source 4. In FIG. 8, the light amount detector 5 detects the output of the light source 4. is detected and the output level of the light source 4 is transmitted to the control circuit 6.

On the other hand, the amount of parallel movement of the reflecting mirror is controlled by a drive circuit 8, and the drive circuit 8, which includes, for example, a servo motor, transmits and amplifies the output of the control circuit 6. The output level of the control circuit 6 refers to the output of the detector 5 to control the amount of parallel movement of the mirror to an appropriate value. In addition, in the above explanation, the reflection plate 7 is moved in parallel while maintaining a constant angle during adjustment, but as shown in FIG. It is clear that it is also possible to adjust the amount of light.

With the above configuration of the present invention, there is nothing that suppresses the illumination light from the light source when adjusting the light amount, so that the light utilization rate can be improved and changes in the light amount can be reliably compensated for.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing the main parts of a conventional light amount adjustment mechanism, FIG. 3 is a schematic diagram showing an embodiment of the present invention, FIG. 4 is an electric circuit diagram of the device of the present invention, and FIG. The figure is a time chart showing its operation timing, and Figure 6 is a transient characteristic diagram of the fluorescent lamp.
FIG. 7 is a control characteristic diagram of the apparatus of the present invention, FIG. 8 is a schematic diagram showing another embodiment in which the detector position is different, and FIG. 9 is a diagram showing another driving method of the reflecting plate. DESCRIPTION OF SYMBOLS 1...Fluorescent lamp, 2...Change plate, 3...Glass plate, 4...Light source, 5...Light level detector, 6...Control circuit, 7...Reflector plate , 8... Drive circuit, 9... Reversible motor, 601... Comparator, 602... Gate, 6
03... Timer circuit, 604... Latch circuit, 1
5,16...imaginary light source.

Claims (1)

[Claims] 1. In a slit illumination device using a fluorescent lamp as an illumination light source, a reflector plate disposed opposite to the light source so as to have the same light condensing position as that of the light source, and a light quantity detector that detects changes in the light quantity of the light source. and a controller that adjusts the reflection position of the reflector in response to a comparison value between the detection output of the light intensity detector and a reference level, and adjusts the actual illumination light intensity by changing the imaginary light source position generated by the reflector. A light amount adjustment device that maintains a constant amount of light.