JPH0210968A - Automatic level adjusting device - Google Patents

Abstract

PURPOSE:To constitute a stable feedback loop by scanning a CCD reference white plate even in the standby and applying the automatic level adjustment in a signal system reading an actual original. CONSTITUTION:As a pre-operation to read an original, a CCD image sensor 3 reads a reference white plate 2. This signal is compared with a voltage of a reference voltage generating circuit 21 by a comparator circuit 22. The output of the circuit 22 is connected to a lighting circuit 24 via a relay 25 and the output of the circuit 24 is connected to a fluorescent light 1. The circuit 22 is operated to increase the luminous quantity of the fluorescent light 1 when the output voltage of the sensor 3 is lower than the reference voltage and to decrease the luminous quantity of the fluorescent light 1 when the output voltage is higher than the reference voltage conversely. In the case of reading an actual original, the relay 25 is thrown to the position of (b) and the input voltage of the circuit 24 is fixed to the voltage just before by the voltage holding circuit 23 to keep the luminous quantity of the fluorescent light 1 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic level adjustment device in a facsimile machine, and in particular, in a plane scanning type reader of image information including halftones, it is used to adjust the amount of light emitted from a fluorescent lamp as a light source. The present invention relates to an automatic level rA adjustment device that prevents fluctuations in output level caused by fluctuations in output level.

Conventional technology Image reading devices that include halftones need to detect absolute levels, so the amount of light emitted by the fluorescent lamp that is the light source must be kept constant, or changes in the amount of emitted light do not result in fluctuations in the output level. Therefore, it is necessary to control the output level.

2. Description of the Related Art Conventionally, as an automatic level adjusting device of this type that maintains the amount of light emitted from a fluorescent lamp constant, the one shown in FIG. 3 is known. That is, a light receiving diode 32 installed near the fluorescent lamp detects the amount of light emitted from the fluorescent lamp 31, and a comparator circuit 33 compares the output voltage from the light receiving diode 32 with a predetermined reference voltage from a reference voltage generating circuit 34. By controlling the input current of the fluorescent lamp by the lighting circuit 35 according to the comparison result, the amount of light emitted from the fluorescent lamp is made constant.

Furthermore, as a device that controls the output level so that changes in the amount of emitted light do not result in fluctuations in the output level, the one shown in FIG. 4 is known. That is, a reference white plate or the like is read as a pre-scan before reading the original, and the image information is stored in the memory 42.

The ROM 43 has addresses and data that are inverse numbers, and the output of the memory 42 is connected to the address of the ROM 43. When reading an actual document, the relay 41 is connected to the b side, and the level is corrected by multiplying the output image signal and the output of the ROM 43 by the multiplier 44.

Problems to be Solved by the Invention The above-mentioned conventional device that uses a light-receiving diode to keep the amount of light emitted from a fluorescent lamp constant has a signal detection system that is separate from the COD that actually reads the document, so it is difficult to detect both signals. There are problems with gain adjustment, etc.

In addition, devices that control the output level so that changes in the amount of light emitted per flash do not cause fluctuations in the output level have a high S/N ratio (I However, in image reading apparatuses that particularly require high halftone reproduction accuracy, the image quality deteriorates.

The present invention has been made in view of the conventional situation of L.
Therefore, the object of the present invention is to create a new automatic level that makes it possible to overcome the above-mentioned drawbacks inherent in the prior art! I!
The purpose of the present invention is to provide an I adjustment device.

Means for Solving the Problems In order to achieve the above object, an automatic level U according to the present invention:
The J adjustment device has a fluorescent lamp for illuminating the i draft, a CCD image sensor as a photoelectric conversion element, and a reference white plate 1 for detecting a white signal, and has a function of making the output signal of the white plate constant. In the automatic level adjustment device, the CCD image sensor is configured to be able to scan the reference white plate even during standby, so that automatic level adjustment functions.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

Referring to FIG. 1, an original 6 such as a photograph is placed flat on an original table 7 and is held down by a glass 5. As shown in FIG. A reference white plate 2 is installed in front of the original 6. The reference white plate 2 protrudes from the front of the glass 5 so that the CCD can be operated even when the apparatus is on standby. The glass 5 is designed so that it does not come into contact with the optical system cover 8 when the apparatus is opened or closed when the apparatus is on standby. Fluorescent light 1
The light uniformly illuminates the reference white plate 2, and the reflected light passes through the objective lens 4 and is received by the CCD image sensor 3.

FIG. 2 shows a block configuration of the embodiment shown in FIG. 1.

Referring to FIGS. 1 and 2, the CCD image sensor 3 reads the reference white plate 2 as an operation before reading a document. This signal is compared with the voltage of the reference voltage generation circuit 21 in the comparison circuit 22. The output of the comparator circuit 22 is connected to the relay 25
The output of the 0 lighting circuit 24, which is connected to the lighting circuit 24 via the 0 lighting circuit 24, is connected to the fluorescent lamp 1. The comparison circuit 22 is
(1: When the output voltage of the cD is lower than the reference voltage, the light intensity of the fluorescent lamp 1 is increased, and when it is higher than the reference voltage, the light intensity of the fluorescent lamp 1 is decreased. When actually reading a document , the relay 25 switches to the b side, and the input voltage of the lighting circuit 24 is fixed by the voltage holding circuit 23 to the voltage immediately before the relay 25 operates, and the amount of light from the fluorescent lamp is kept constant6.Details of the Invention As described above, according to the present invention, the reference white plate can be operated by the CCr even during standby.

A stable feedback loop can be constructed by automatically adjusting the level in the signal system used to read the actual original. Also, in halftone reading.

In particular, it is possible to obtain the effect that the required S/N ratio can be made constant regardless of variations in the amount of light emitted by individual fluorescent lamps or deterioration in the amount of light of the fluorescent lamp.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing an embodiment of the present invention, and FIGS. 3 and 4 are block diagrams of a conventional automatic level adjustment device. 106. Fluorescent lights, 2. ,,Reference white plate, 3. ,,
CCD image sensor, 419. Objective lens 5,
,, glass, 600. Manuscript, 7. ,,manuscript table,
811. Cover, 21°0. Reference voltage generation circuit, 22.
,,comparison circuit, 23. ,,voltage holding circuit, 24. ,. Lighting circuit, 25. relay

Claims (1)

[Claims] Fluorescent lamp that illuminates the original and CCD as a photoelectric conversion element
In an automatic level adjustment device that includes an image sensor and a reference white plate for white signal detection, and has a function of keeping the output signal of the white plate constant, the CCD image sensor detects the reference white plate even during standby. An automatic level adjustment device that is capable of scanning and has an automatic level adjustment function.