JPS63136274A - Picture input device - Google Patents

Abstract

PURPOSE:To obtain an output which is not affected by the change of light quantity of an illumination means by inputting lightness of a fluorescent lamp with fixed timing and varying a gain by said lightness against the output signal of a camera. CONSTITUTION:The signals equivalent to the light quantity of a fluorescent lamp 2 are quantized and inputted to a correction data generating part 6. The output of an A/D converter 5 obtained with input of a correction data storing signal S1 is stored in a register 61. The correction data is previously stored in a look-up table 62. The lightness of a new lamp 2 is set at 1; while the lightness of an old lamp 2 is set at 0.8 respectively. Then 1/0.8=1.25 is applied to the correction data. In other words, the output of a sensor 3 is set at V0 with the new lamp 2 and at V1 with a slightly dark lamp 2. Thus the value DAT stored in the address of an output V1 of the table 62 is calculated from V0/V1 and inputted to a gain variable amplifier 8 in the form of a gain control signal undergone D/A conversion. This control signal amplified in response to the lightness of the lamp 2 and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image input device, and particularly to an image input device that reads images using photoelectric conversion means.

BACKGROUND OF THE INVENTION Conventionally, in this type of apparatus, the following measures have been taken against changes in the amount of light from the illumination means over time.

Each time the device was turned on, or about once a week, the margin of the form was read, and the output signal was stored in memory or an FD (floppy disk) as a white level and used for correction. Correction is performed by inputting the reciprocal of the ratio between the output signal of a memory that stores all-white data obtained by reading all-white forms and the reference value in the brightest case to a variable gain amplifier that amplifies the photoelectric conversion output signal. It was carried out by In the case of an FD, at startup, all-white data in the FD, which had been stored by reading all-white forms, was downloaded to the memory in the same manner as described above.

Problems to be Solved by the Invention If the conventional device described above has only a memory, it is necessary to read a standard all-white form and write white data into the memory every time the power is turned on.

Furthermore, when registering on an FD, it is necessary to download it every time the power is turned on, as in the case of memory, and furthermore, it is necessary to re-register before the lighting means deteriorates significantly over time. Therefore, conventional devices require special operations to compensate for changes in the amount of light from the illumination means, need to always prepare a form with margins to be used as a reference, and use a completely white sheet to be read as a reference. Status of the form (
There were problems such as the correction being affected by the degree of whiteness.

The present invention has been made in view of the above-mentioned conventional situation,
Accordingly, an object of the present invention is to provide a novel image input device that makes it possible to solve the above-mentioned problems inherent in the conventional technology.

Means for Solving the Problems In order to achieve the above objects, an image input device according to the present invention reads an image using photoelectric conversion means, and includes a lighting means for illuminating an input object. , a photoelectric conversion means for converting an input object into an electrical signal by photoelectric conversion;
a light amount detection means installed near a light emitting portion of the illumination means so that external light other than the illumination means does not enter; a first A/D conversion means for digitizing an output signal of the light amount detection means; a correction data generation means for outputting correction data according to the output of the A/D conversion means 1; a D/A conversion means for D/A converting the output data of the correction data generation means and outputting it as a gain adjustment signal; a signal amplification means for changing the amplification factor of the output electric signal of the photoelectric conversion means according to the level of the gain FA''Jli signal output from the D/A conversion means; and a second signal amplification means for digitizing the output signal of the signal amplification means. A/D conversion means,
It is characterized by being able to obtain an output that is not affected by changes in the amount of light from the illumination means.

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, reference number 1 indicates a camera with a built-in one-dimensional CCD line sensor (hereinafter abbreviated as sensor) and an optical lens, 2 indicates a fluorescent light for illuminating the form 4, and 3 indicates a camera. It is a photosensor for detecting the light J1 of the fluorescent light 2, and 4 is a form to be manually operated. A photosensor 3 is provided to constantly monitor the amount of light from the fluorescent lamp 2.

Therefore, in its arrangement, care must be taken to prevent outside light other than the light from the fluorescent lamp 2 from entering. For example, a lens system may be used to form an image of a portion of the fluorescent lamp 2 on the photosensor 3.

The output signal of the photosensor 3, ie, the signal corresponding to the amount of fluorescence m, 2, is input to the first A/D converter 5 and quantized. The output of this first A/D converter 5 is input to a correction data generating section 6. moreover.

The output of this correction data generating section 6 is input to a D/A converter 7, converted into an analog signal, and input to a variable gain amplifier 8 as a gain control signal.

The sensor output signal from camera 1 is sent to variable gain amplifier 8
The signal is input to the gain control signal, and is amplified with an amplification degree corresponding to the brightness of the fluorescent lamp 2 at that time, and is output. The output is input to the second A/D converter 9, quantized, and output as digital data.

FIG. 2 shows a detailed block configuration of the correction data generating section 6. In FIG. 2, 61 is a register in which the output of the A/D converter 5 when the correction data accumulation signal S1 is input is accumulated. That is, the brightness of the fluorescent lamp 2 when the correction data accumulation signal St is input is accumulated. The input timing of the correction data accumulation signal Sl is usually the timing at which the sensor 3 starts horizontal scanning.

Selected when reading the form starts. Reference numeral 62 denotes a look-up table, which uses the output data from the register 61 as an address and outputs the correction data stored at that address.

As the correction data stored in advance in the lookup table 62, for example, if the relative value of the brightness of the fluorescent light 2 is 1 when it is new, then the relative value of the brightness is 0 when the fluorescent light 2 is old.
．． If the number becomes 8, then the reciprocal of 1 and 25 are used. In other words, if the output of the photosensor 3 when the fluorescent light 2 is new and bright is vO1, and the output of the photosensor 3 when it gets a little dark after an hour has passed is ■1, then the output of the lookup table 62 is stored at the address ■1. The value DA is calculated using the following formula.

D A T = V O / V 1 , , , , , ,
,, (1) Suppose that the conversion resolution of the first A/D converter 5 is 8
If it is a bit, the lookup table 62 needs to store 256 types of correction data.

As described in detail, according to the present invention, the brightness of the fluorescent light at that time is input at a certain timing, and the gain for the output signal from the camera is varied (controlled) according to the brightness. This makes it possible to input data while always taking into account changes in the brightness of the fluorescent lights. Therefore, there is no need for special operations every time the power is turned on, there is no need to increase the value of the standard margin form, and furthermore, the correction is not affected by the state of the all-white form that serves as the standard. The effect is that there is no such thing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a detailed block diagram of the correction data generating section 6. As shown in FIG. 110. Camera, 200. Fluorescent light, 301. Photo sensor, 401. Form, 5. ,, first A/D converter, 60
9. correction data generation section, 7. ,. D/A converter, 810. Variable gain amplifier, 91. . 2nd A/l) converter

Claims (1)

[Claims] A lighting means for illuminating an input object, a photoelectric conversion means for converting the input object into an electrical signal by photoelectric conversion, and a light amount installed so that no outside light other than the illumination means enters near the light emitting part of the illumination means. a detection means, a first A/D conversion means for digitizing the output signal of the light amount detection means, and a correction data generation means for outputting correction data according to the output of the first A/D conversion means; D/A conversion means converts the output data of the correction data generation means into D/A and outputs it as a gain adjustment signal; a signal amplification means that changes the amplification factor according to the level;
An image input device comprising: second A/D conversion means for digitizing the output signal of the signal amplification means.