JPH0453356A - Picture reader - Google Patents

Abstract

PURPOSE:To attain always accurate shading correction processing independently of a kind of a light source by selecting a correction coefficient based on the operating time of the light source, generating a shading correction data and executing the shading correction based on the data. CONSTITUTION:A temperature sensor 106 detects a tube wall temperature (ambient temperature) of a light source 105 after the light source 105 is lighted, the temperature data is outputted to a control section 109, a timer 108 counts an ON time of the light source 105 to output the time data to a control section 109 similarly. As a result, the control section 109 fetches the temperature data and the time data. Plural correction coefficients are calculated from the result of measurement and they are stored, and a correction coefficient based on the operating time of the light source 105 is selected to generate a shading correction data, and the shading correction is executed based on the data. Thus, the always accurate shading correction processing is executed independently of the kind of the light source.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image reading device applied to digital copying machines, facsimile machines, electronic files, etc. ,
The present invention relates to shading correction processing that removes shading components caused by the emission distribution of a light source, etc.

[Conventional technology]

Shading correction in image reading processing refers to the color signal read by the image reading unit being converted into a digital signal, and then correcting the digital signal by correcting variations in the sensitivity of the light receiving element, uneven illuminance of the light source, offset of analog system, color This is a process of correcting the white transmittance of the separation filter.

For this shading correction process, for example,
There is one disclosed in Japanese Patent No.-212257.

The shading correction processing disclosed herein A/D converts the image signal of a reference white level original placed in advance for each screen or multiple screens, and creates a correction coefficient table corresponding to the image signal level of each pixel. In this method, a digital multiplier circuit multiplies the correction coefficient read out from the line memory and stored in the line memory by a digital value image signal obtained by A/D converting the image signal, thereby correcting variations in sensitivity and the like.

As a result of employing the configuration as described above, the circuit configuration is simple and highly accurate sensitivity variation correction matching sensitivity variation characteristics can be realized.

In addition, shading is achieved by storing the amount of correction obtained by reading the black reference board and white reference board respectively immediately before inputting the image, and calculating the amount of correction stored at the time of inputting the image for the corresponding color signal. A correction method has also been put into practical use (Japanese Unexamined Patent Publication No. 154357/1983).

[Problem to be solved by the invention]

However, for example, in the case of a light source that rises slowly, such as a fluorescent lamp, the light amount distribution in the main scanning direction changes depending on the ON time t of the light source, as shown in FIG. 4, and the shape thereof is not similar.

As a result, in the conventional shading correction processing described above, the correction data is uniformly calculated based on the correction data obtained from the image signal of the reference white level document placed in advance, or the correction data obtained by reading the black reference board and the white reference board respectively. Since the correction is performed, there is a problem in that shading defects occur due to variations in the level and shape of the light amount distribution during one scan.

The present invention has been made in view of the above, and an object of the present invention is to eliminate shading defects caused by variations in the level and shape of the light intensity distribution during one scan, and to always realize accurate shading correction processing regardless of the type of light source. shall be.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention solves the problem of the tube wall temperature of the light source (
a measuring means for measuring the operating time of the light source (ambient temperature); a control means for calculating a correction coefficient using the measured value from the measuring means as a parameter; and a storage means for storing the plurality of correction coefficients calculated by the control means. a calculation means for calculating shading correction data based on a correction coefficient selected from the storage means based on the operating time of the light source; and a shading device for performing shading correction based on the shading correction data calculated by the calculation means. The present invention provides an image reading device including a correction means.

Further, a measuring means for measuring the tube wall temperature (ambient temperature) of the light source, an operating time of the light source, and a usage time of the light source, a control means for calculating a correction coefficient using the measured value from the measuring means as a parameter, and the control means a storage means for storing a plurality of correction coefficients calculated by the calculation means; a calculation means for calculating shading correction data based on the correction coefficients selected from the storage means based on the operation time of the light source; The present invention provides an image reading apparatus including a shading correction means that performs shading correction based on shading correction data obtained by applying the shading correction data.

[For production]

The image reading device according to the present invention measures the tube wall temperature (ambient temperature) of the light source and the operating time of the light source (and the usage time of the light source), calculates and stores a plurality of correction coefficients from the measurement results, After selecting a correction coefficient based on the operating time of the light source and generating shading correction data, shading correction is executed based on the data.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a block diagram showing the configuration of an image reading device according to the present invention, in which a CCD reads image data from a document.
(charge-coupled device) 101 and an analog processing unit 1 that performs predetermined correction processing such as sample hold and amplification on the analog image data read by the CCD 101.
02, an A/D converter 103 that converts the analog image data after correction processing output from the analog processing unit 102 into digital image data, and an A/D converter 103 that converts the analog image data after correction processing output from the analog processing unit 102 into digital image data, and A memory 104 for writing digital image data, a light source 105 composed of a fluorescent lamp that irradiates light onto the original, and a temperature sensor 106 that detects the tube wall temperature (surrounding temperature) T of the light source 105.
A lighting circuit 107 that controls lighting/extinguishing of the light source 105
and a timer 108 that measures the lighting time of the light source 105 controlled by the lighting circuit 107, and inputs the temperature data from the temperature sensor 106 and the time measurement data from the timer 108 and executes a predetermined calculation process, lighting circuit 10
A control unit (
cpU) 109, a memory 110 that stores the coefficient data output from the control unit 109, white reference data from the memory 104 and coefficient data from the memory 110, and performs shading by multiplying the two data. An arithmetic circuit 111 that outputs correction data, and inputs the shading correction data output from the arithmetic circuit 111, and performs various shading corrections on the image data input from the A/D converter 103 based on the data. a shading correction circuit 112 that performs the shading correction circuit 112, and a T conversion circuit 113 that performs γ conversion processing on image data subjected to shading correction processing by the shading correction circuit 112.
and an I/F unit 114 that outputs the image data output from the γ conversion circuit 113 to the outside.

The operation of the above configuration will be explained in detail using the flowchart shown in FIG.

The analog image data signal read by the CCD 101 is first input to the analog processing circuit 102, where it undergoes predetermined correction processing such as sample hold and amplification.
The signal is input to the A/D converter 103 and converted into a digital signal.

In addition, when reading the white reference plate before reading the original, the above
Digital data after A/D conversion by the /D converter 103 is written and stored in the memory 104. This digital data is generated by the light source 105 at the timing of reading the white reference plate.
This is one line output data of the above CCD 1.01 in the light amount distribution.

Next, at the start of the scan, the control unit 109 outputs a control signal to the lighting circuit 107, and the lighting circuit 107
Turn on 5. As the light source 105 turns on, the temperature sensor 106 detects the tube wall temperature (ambient temperature) T of the light source 105 and outputs the temperature data to the control unit 109, and the timer 10 sets the ON time of the light source 105. , and similarly outputs the time data to the control unit 109. As a result, the control unit 109 takes in the temperature data and time data (step 301).

The control unit 109 controls the light source light amount distribution that changes depending on the light source ON time t at the temperature T (how it changes is as follows).
A correction coefficient to be multiplied by each pixel position of the CCD 101 according to the pre-programmed data is written and stored in the memory 110 for each block within a predetermined range (step 302).

FIG. 2 shows the memory space after coefficient data has been written.

As described above, when the document reading process by the CCD 101 starts after various data have been collected in the memories 104 and 110, the read image data is transferred to the analog processing circuit 10.
2. Input to the shading correction circuit 112 via the A/D converter 103.

At the same time, white reference data corresponding to the main scanning position of the image data is read out from the memory 104, and coefficient data corresponding to the main scanning position and light source ON time t is read out from the memory 110 (correction coefficient data from the memory 110 Data reading is executed by measuring the time t during which the control unit 109 outputs the ON signal to the lighting circuit 107 using the timer 108 and controlling the memory address), the arithmetic circuit 1
11. The above two data are stored in the arithmetic circuit 111
, and shading correction data is created (step 303). The shading correction data created by the arithmetic circuit 111 is sent to the shading correction circuit 11.
2, and shading correction processing is executed (
Step 304).

Several methods are known for the detailed content of the shading correction circuit 112, and for example, a method may be considered in which correction is performed by multiplying the original image data by the reciprocal of the shading correction data.

The image data after the shading correction process in the shading correction circuit 112 is converted to T in the T conversion circuit 113.
After the conversion, the I/F unit 114 outputs the data to the outside.

In the above embodiment, the correction coefficient using the tube wall temperature (ambient temperature) T and the ON/OFF time of the light source as parameters is calculated in the control unit 109, but the correction coefficient is The data for the fluctuation range of tube wall temperature (ambient temperature) T and light source ON time are created as a table R.
You can also have OM have it.

Further, when a fluorescent lamp is used as a light source, the characteristics due to the tube wall temperature T and the light source ON time t change depending on the usage time of the fluorescent lamp (change over time).

Therefore, there is a method of measuring the usage time of the light source and calculating a correction coefficient based on the measurement result, and also based on the measurement result, the tube wall temperature (ambient temperature) T and the light source O
A method may also be considered in which the data table is changed over a variation range of N hours.

In the above embodiment, in order to measure the usage time of the light source, a non-volatile memory or a backup battery is required in order to store the usage time of the light source in a series of time flows.

〔Effect of the invention〕

As explained above, according to the image reading device of the present invention, the tube wall temperature (ambient temperature) of the light source and the operating time of the light source (and the usage time of the light source) are measured, and a plurality of correction coefficients are calculated from the measurement results. Then, after storing and selecting a correction coefficient based on the operation time of the light source to generate shading correction data, shading correction is executed based on the data, so that the level and shape fluctuations of the light amount distribution during one scan are It is possible to eliminate shading defects due to shading and to always achieve accurate shading correction processing regardless of the type of light source.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an image reading device according to the present invention, and FIG. 2 is a memory 1 after coefficient data has been written.
3 is a flowchart showing the operation of the image reading device shown in FIG. 1, and FIG. 4 shows that the light amount distribution in the main scanning direction changes depending on the ON time of the light source. This is a graph showing. Explanation of symbols 101-CCD 102-Analog processing circuit 103-
A/D converter 104.110-Memory 105-Light source 106-・Temperature sensor 107-Lighting circuit 10B-Timer 109-Control unit 111-Arithmetic circuit 112-Shading correction circuit

Claims (2)

[Claims] (1) a measuring means for measuring the tube wall temperature (ambient temperature) of the light source and the operating time of the light source; a control means for calculating a correction coefficient using the measured value from the measuring means as a parameter; storage means for storing a plurality of correction coefficients; calculation means for calculating shading correction data based on the correction coefficients selected from the storage means based on the operating time of the light source; and shading correction data calculated by the calculation means. An image reading device comprising: shading correction means for performing shading correction based on. (2) a measuring means for measuring the tube wall temperature (ambient temperature) of the light source, the operating time of the light source, and the usage time of the light source; a control means for calculating a correction coefficient using the measured value from the measuring means as a parameter; and the control storage means for storing a plurality of correction coefficients calculated by the means; calculation means for calculating shading correction data based on the correction coefficients selected from the storage means based on the operation time of the light source; and shading correction means for performing shading correction based on the calculated shading correction data.