JPS60263575A - Picture signal correcting system - Google Patents

Abstract

PURPOSE:To improve dissidence of gradation by setting a correction coefficient corresponding to quantity of light to output characteristic of an image sensor and correcting read signals according to the quantity of light. CONSTITUTION:Quantity of light to output characteristic of a CD-S image sensor 3 is measured before scanning an original and a correction coefficient corresponding to the quantity of light to output characteristic is set and stored in a memory 8. When reading the original, correction coefficient of the memory 8 is selected to become linear characteristic basing on the quantity of light to output characteristic of the Cd-S image sensor 3. By decoding quantized data, linear data can be obtained as luminous intensity of light receiving face of the Cd-S image sensor 5, and the recorded gradation can be conformed with the gradation of actual original.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image signal correction method for obtaining an image signal faithful to the gradation of an actual original in a facsimile machine or the like.

Configuration of conventional example and its problems As shown in FIG. 1, the reading section of a conventional facsimile machine includes a lens 1, a light source 2 for illuminating the document, an image sensor 3,
It is composed of an amplifier 4, an analog-digital converter 5, etc., and illuminates the original 6 with the original illumination light source 2.
The reflected light is imaged by a lens 1, photoelectrically converted by a CD-S image sensor 3, and the converted analog output signal is amplified by an amplifier 4 and digitized by an analog-digital converter 5. By doing so, quantization was performed and an image signal was output.

Experiments have shown that the light intensity vs. output characteristic of the Cd-5 image sensor does not change linearly according to the reading system of 9 parts, but this makes it clear that the reading system of the conventional 77 mm device described above does not change linearly. In some cases, the image signal level does not change linearly in response to changes in the illuminance of the light-receiving surface of the Cd-5 image sensor, and when recording in halftones, the recorded gradation differs from the actual gradation of the original. This is an inconvenience.

Furthermore, although image sensors in 77 and 7mm devices are regularly replaced with new ones, the light intensity vs. output characteristics of CD-S image sensors are different for each CD-5 image sensor, and are recorded each time they are replaced. A problem arises in that the gradation differs from the gradation of the actual document.

Purpose of the Invention The present invention has been made in view of the above circumstances, and by correcting the quantized data, the image signal level is linearly changed in response to changes in the light-receiving surface illuminance of the Cd-5 image sensor, and the recorded level is It is possible to match the gradation of the actual original with the gradation of the original.

It is an object of the present invention to provide an image signal correction method that can improve the mismatch between the recorded gradation and the actual gradation of an original document, which occurs due to differences in the light quantity versus output characteristics of each image sensor.

Structure of the Invention The present invention measures the light intensity versus output characteristic of an image sensor before scanning an original, stores and sets a correction coefficient corresponding to the light intensity versus output characteristic in advance, and corrects the read signal according to the light intensity. By applying this method, the above objective is achieved.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 to 5. 1 and 4 or corresponding parts are given the same reference numerals.

FIG. 2 is a diagram showing a schematic configuration of a reading section of a facsimile machine according to an embodiment of the present invention, in which 1 is a lens, and 2 is a light source for illuminating the original 6 (hereinafter abbreviated as a light source).
, 3 is a Cd-3 image sensor, 4 is an amplifier, 5 is an analog-digital converter, 7 is a power supply, 8 is a correction ROM
, 9 is a controller, 1o is a data ROM, and 11 is a white reference plate.

Next, the operation of this embodiment will be explained. The current normally supplied to the light source 2 to read the original 6 is the reference current f1°. This reference current If1°.

Cd- when supplied to the light source 2 and irradiated the white reference plate 11.
8 The light receiving surface illuminance of the image sensor 3 is Wlo.

shall be. By operating the power supply 7 using the controller o-29, the current supplied to the light source 2 is 'J1oo
z'' and 'f75, 'f50, 1f2, which will be described later.
5 can be selected, but by changing the current supplied to the light source 2, the illuminance on the document surface can be changed, and in turn, the illuminance on the light receiving surface of the Cd-5 image sensor 3 can be changed. .

Here, the above-mentioned "f7rs" is a current value supplied to the light source 2 which is set in advance so that the illuminance of the light-receiving surface of the image sensor becomes the above-mentioned W1oo075%, and similarly, the above-mentioned process f5° is 50% of the above-mentioned W1°. %, the above-mentioned F2. is the current value supplied to the light source 2 which is set in advance to be 26% of the above-mentioned W1°.

First, before scanning the original 6, the controller 9 performs the scanning f7. Select f7. for light source 2. is supplied and turned on to irradiate the white reference plate 11. Then, the image is formed by the lens 3 and photoelectrically converted by the Cd-5 image sensor 3, and the analog output signal is amplified by the amplifier 4 and then quantized by the analog-digital converter 5. ○Quantized electricity C signal
The light receiving surface illuminance of the d-5 image sensor 3 is Wl. . The end of 5
Stored in the controller as image sensor output data during engagement. Next, operate the power supply 5 with the controller 9, and
so is selected, quantized, and the quantized data is set to 5 when the light receiving surface illumination of the Cd-3 image sensor 3 is Wlooo.
Stored in the controller as image sensor output data at o%.

Next, the controller 9 operates the power supply 6, selects the function f26, performs quantization, and converts the quantized data to the light-receiving surface illuminance of the Cd-5 imager. . It is stored in the controller as image sensor output data at 25% of the time. - The data ROM 10 stores all possible values of image sensor output data when the light-receiving surface illuminance of the Cd-5 image sensor is 75%, 50%, and 25% of Wloo.

As shown in FIG. 3, each Cd is determined by the three image sensor output data stored in the ROM 10.

-s The image sensor determines the variable light quantity versus output characteristics. In addition, in Fig. 3, the curve a is Cci
The curve ab shows an example of the light amount versus output characteristic of a newly used Cd-5 image sensor (not shown).

Based on the determined light quantity versus output characteristic of the Cd-5 image sensor, the correction coefficient of the ROM 8 is selected so as to have a linear characteristic. This correction ROM 8 functions as a decoder, and for example, FIG. 4 shows the correction coefficients of the Cd-5 image sensor 3. If the correction coefficients are selected as shown in FIG. A curve C of quantized data having characteristics such as is decoded to become a straight line d. To give a concrete numerical example, quantized data 86 is 60.65
is decoded as 35, 45 as 2o, and so on. By decoding the quantized data, linear data can be obtained as the light-receiving surface illuminance of the Cd-5 image sensor, and the recorded gradation can match the gradation of the actual document.

When a new CD-S image sensor is used due to replacement, etc., a correction coefficient is selected based on the output data of the newly used image sensor stored in ROM10, and linear correction is performed by ROM5. It is possible to match the recorded gradation with the actual gradation of the original document.

In addition, as a method for obtaining image sensor output data when the light-receiving surface illuminance of the image sensor is 75%, 50%, and 26% of Wloo, the current supplied to the document illumination light source is a reference current factor f1°. . There is a method of reading the gray pattern instead of the white reference plate without changing it. In this method, the illuminance of the light receiving surface of the Cd-5 image sensor is reduced by the difference in reflected light due to the difference in gray pattern shading.
Image sensor output data is obtained at 75%, 50%, and 25%. In addition, in the above embodiment, the number of samples of the light receiving surface illuminance of the image sensor is three, but the RO
M10, ROM8, power supply 6. It can be changed freely by changing the setting values of the controller 9 and the like. Similarly, ROM10. ROM8, power supply 6. control o-2
It is also possible to freely change the percentage value of the light-receiving surface illuminance of the Cd-5 image sensor by changing a setting value such as 9.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, it is possible to measure the light intensity versus output characteristics of a CD-S image sensor and perform corrections that are suitable for the CD-5 image sensor. It has the effect of being able to output an image signal compatible with linear, ensuring good image quality, and
This has the effect of easily improving gradation errors caused by replacing the A-5 image sensor and ensuring good image quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the reading section of a conventional facsimile machine, FIG. 2 is a block diagram of the reading section 9 of a facsimile machine using the image signal correction method according to the present invention, and FIG.
5 Characteristic diagram showing the light amount vs. output characteristics of the image sensor, 4th
FIG. 5 is an explanatory diagram showing an example of a correction coefficient, and FIG. 5 is an explanatory diagram showing the relationship between uncorrected data obtained by quantizing the output of the Cd-5 image sensor and corrected data. 3...Cd-5 image sensor, 4...
Amplifier, 5...Analog-digital converter,
8...Correction ROM, 9...Controller, 10...Data OM Name of agent Patent attorney Toshio Nakao and one other person,
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Claims (1)

[Claims] It has a photoelectric conversion element and a storage means for storing correction data for correcting the output characteristics in accordance with a plurality of light receiving surface illuminance values of the photoelectric conversion element, and the correction data is stored in advance by changing the light amount of the light source. An image signal correction method characterized in that the image signal is corrected so that the image signal changes substantially in proportion to the light-receiving surface illuminance value when reading a document.