JP2000358133A - Image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize dispersion in luminance of a light source section in an image input device without relying on manual operations. SOLUTION: A light source section 5 consisting of a plurality of light elements is divided into N-sets of blocks, a D/A converter section 2 is connected to each block. A setting value of a current supplied to each block is varied by the number of combinations between a gradation width of setting values set to each D/A converter section 2 and patterns corresponding to the number of the blocks N, the standard deviation of image data by one line each is calculated, the setting value of each D/A converter section 2 of each block with the least calculated standard deviation is stored, this setting value is set to each D/A converter section 2 when the light source section 5 is turned on so as to uniformize the light source in the main scanning direction of the image in this image input device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device, and more particularly, to a technique useful for equalizing a light source output.

[0002]

2. Description of the Related Art Generally, a light source of an image input device is required to have uniform luminance in the main scanning direction of an image. However, since the photoelectric elements inherently have a variation in luminance, when a light source is manufactured by simply arranging a plurality of photoelectric elements in the main scanning direction, the luminance variation in the main scanning direction becomes too large, and the image input device has Sometimes it cannot be used as a light source.

For this reason, in a conventional image input apparatus, a light source is divided into a plurality of blocks, and an operator monitors a luminance distribution in a main scanning direction with an oscilloscope or the like and observes a current flowing in each block. It was necessary to obtain a light source having a uniform luminance distribution in the main scanning direction by manually changing the limiting resistance values (R1 to Rn) for determining the values.

[0004]

However, in the above-mentioned conventional image input apparatus, when a light source having a uniform luminance in the main scanning direction is to be produced, a dedicated operator is required, and it is necessary to find an optimum limiting resistance value. It takes a lot of time to replace the limiting resistor, and as a result, there is a problem that it takes a lot of cost and time to make one light source.

[0005]

Therefore, according to the present invention, a light source made of a plurality of optical elements is divided into a plurality of blocks, and a digital / analog conversion unit is connected for each block. The standard value of the image data for each line is calculated by varying the set value of the current flowing through each block by the combination of the gradation width of the set value set in the digital-analog conversion unit and the pattern corresponding to the number of blocks. ,
The set value of the digital-to-analog converter of each block when the calculated standard deviation is the smallest is stored. When the light source is turned on, the set value is set in the digital-to-analog converter and the light source for the main scanning direction of the image is set. Provided is an image input device characterized in that the configuration is made uniform.

According to a second aspect of the present invention, in the first aspect, the combination of the gradation width of the set value set in the digital-to-analog conversion unit and the pattern corresponding to the number of blocks is obtained by subtracting 1 from the number of blocks. There is provided an image input apparatus characterized in that a combination of a factorial pattern of a value obtained by adding one to a key is configured. According to a third aspect of the present invention, a light source made of a plurality of optical elements is divided into a plurality of blocks, a digital-to-analog converter is connected to each block, and only one block is used for each block. Turn on the light, calculate the average value of the image data for one line, and change the current flowing through the one block by the number of gradations of the gradation width of the set value set in the digital-to-analog converter. The average value of the image data for one line is obtained, and the image of the optical system adjustment medium is acquired when the image of the optical system adjustment medium is acquired with the light source having the uniform luminance distribution in the main scanning direction in which the optical element having the average luminance is mounted. When the average value of the image data is set as the adjustment medium average value, the state in which the average value obtained by dividing the adjustment medium average value by the number of blocks is the closest among the obtained average values is determined. Memorize the set value of Provided is an image input apparatus characterized in that when the light source is turned on, the set value obtained for each block is set in a digital-to-analog conversion unit so as to make the light source uniform in the main scanning direction of the image. I do.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited by this. First Embodiment FIG. 1 is a block diagram of an image input device according to an embodiment. In the figure, reference numeral 1 denotes a control circuit unit for controlling a light source. In this embodiment, the control circuit unit has a brightness distribution uniforming function for making the brightness distribution uniform in the main scanning direction. 2-1
N is a DA converter which converts a digital signal from the control circuit unit 1 into an analog signal and outputs it as a light source bias voltage. Reference numerals 3-1 to N denote light source driving circuits, which are divided into N blocks, and are driven by light source bias voltages from the DA converters 2-1 to N. Reference numeral 4 denotes a memory for recording values set in the DA converters 2-1 to N. Reference numeral 5 denotes a light source unit, which is a substrate on which LEDs, semiconductor lasers, and the like are mounted;
Each block is driven by the light source drive circuits 3-1 to 3-1N. Note that M optical elements exist in one block (M = 1, 2, 3,...).

Reference numeral 6 denotes a light receiving sensor unit, which comprises a light receiving element such as a CCD linear image sensor, a photodiode, a photodiode array, a phototransistor, and a driving circuit thereof, receives light from the light source unit 5, photoelectrically converts the light, and converts the analog signal into an analog signal. Is output. Reference numeral 7 denotes an amplifying unit that amplifies an analog signal from the light receiving sensor unit 6. Reference numeral 8 denotes an AD converter, which converts the analog signal amplified by the amplifier 7 into a digital signal and sends it to the control circuit 1. Reference numeral 9 denotes an optical system adjustment medium, which is used when checking the luminance distribution of the light source in the main scanning direction. Reference numeral 10 denotes an optical system unit comprising the light source unit 5 and the light receiving sensor unit 6. The present optical system has a function applicable to all optical systems such as a reduction optical type, a contact type, a reflection type, and a transmission type. Is checked, the optical system adjusting medium 9 is set.

Next, a method for acquiring an image will be described. First,
It is assumed that the optical system adjusting medium 9 is set between the light source unit 5 and the light receiving sensor unit 6 of the optical system unit 10, and a luminance distribution adjustment command is input to the image input device by an operator. Then, the control circuit unit 1 sets data for each block in each DA conversion unit 2 in order to set a current value to be passed to each block of the light source unit 5 and then sets a DA output by a control signal. The light source driving bias voltage corresponding to the data is input to each block of the light source driving circuit 3.

Here, the value of the current flowing through the light source unit 5 is proportional to the magnitude of the light source driving bias voltage. In this state, the light source lighting signal is turned on and the light source unit 5 is turned on. The emitted light irradiates the optical system adjusting medium 9, and the reflected light (diffused light) or transmitted light from the medium enters the light receiving sensor unit 6, the sensor output is amplified by the amplifier 7, and the AD converter 8 AD
By performing the conversion, image data for one line in the main scanning direction of the image is obtained.

Next, a procedure for determining an optimum value to be set in each block of the DA converter 2 in order to obtain a more uniform luminance distribution in the main scanning direction of an image will be described. FIG. 2 is a flowchart of the light source output equalizing process according to the first embodiment. Here, the gradation width of the data set in the DA converter 2 is K gradation, the number of pixels for one line in the main scanning direction of the image is S pixels, and the gradation width of the image data is F.
Further, as an image input device, when an image on the same medium is acquired by a plurality of devices, an image having the same brightness needs to be acquired. For this reason, as an initial condition, it is necessary to adjust the brightness obtained when the optical system adjustment medium 9 is acquired to a certain level, and when the average value of the acquired S image data is H, this average It will be adjusted to the value H.

First, a T-th block in the N blocks of the DA converter 2 is selected. All 0s are set in the DA conversion units 2 of the N-1 blocks other than the T-th block (Sa1 to S1).
a3). Here, the case where the set value is 0 means that the light source drive bias voltage is not output to the light source drive circuit 3, and the current is not supplied to the target block, so that the light source unit 5 emits light even when the light source unit 5 is turned on. No setting.

In this state, the value i set in the T-th DA converter 2 is sequentially changed from 1 to F, and every time the value is changed, the average value U (i) of the image data for S pixels in the main scanning direction is obtained. (Sa2 to Sa6). At this time, one of U (1) to U (F) closest to H / N is found. Where H / N
Represents an average value per block. The set value for the DA converter 2 at this time is Y. Thereby, the set value Y of the DA converter 2 of the T block is determined (Sa
7).

Next, in order to make the light source uniform in luminance in the main scanning direction of the image, D-1 of N-1 blocks other than T blocks
The values from 0 to K are set in the A conversion unit 2 for all combinations, and the light source lighting signal is turned on every time one combination is set in the DA conversion units 2 for N blocks, and an image is captured. . The total number of images to be captured is (N-1) ^{(K + 1)} times (Sa8 to Sa13).

Image data obtained for the i-th time (for S pixels)
The output values of 1 pixel to S pixel of Xi (1), Xi (2),.
Xi (S). In addition, the average value of these is defined as X bar.
Here, the standard deviation σi of the image data is obtained by the following formula.

[0016]

(Equation 1)

This arithmetic processing is performed in the control circuit unit 1 by a microprocessor or the like. By finding the combination having the smallest value among the standard deviations σi thus obtained, the DA of N-1 blocks other than the T block is found.
The value to be set in the conversion unit 2 is determined (Sa14). In addition,
In order to reduce the time required for the determination, an allowable range of the standard deviation is determined in advance, and when the standard deviation σi falls within the allowable range, the processing is terminated, and the DA conversion unit 2 of N-1 blocks other than the T block is used. May be determined.

The set values of the DA converter 2 for the N blocks thus obtained are recorded in the memory 4 (Sa15). Lastly, an operation when the light source is controlled to be turned on using the set values recorded in the memory 4 will be described. N recorded in the memory 4
The set values for the blocks are set in the DA converter 2, and the light source bias voltage is input to the light source drive circuit 3. Next, the light source lighting signal is turned on, and block 1 is turned on.
To N light sources. As described above, the light source output can be made uniform.

According to the first embodiment, a light source made of a plurality of optical elements is divided into N blocks,
Using the A conversion unit 2 (one per block), the current value flowing through each block is changed for each combination of (N-1) ^{(K + 1)} patterns, and the standard of image data for one line is successively changed. Find the deviation σi. Out of these, by using the value set in the DA converter 2 of each block when it is the smallest, it is possible to obtain an excellent light source unit 5 with less variation in luminance in the main scanning direction of the image. .

Second Embodiment A description will be given of a process of equalizing the light source output according to a second embodiment.
Since the block configuration of the image input apparatus is the same as that of the first embodiment, the description of each element is omitted, and FIG.
Will be described with reference to the above. Next, a method for acquiring an image will be described. First, it is assumed that the optical system adjusting medium 9 is set between the light source unit 5 and the light receiving sensor unit 6 of the optical system unit 10, and a luminance distribution adjustment command is input to the image input device by an operator. Then, the control circuit unit 1 sets data for each block in each DA conversion unit 2 in order to set a current value to be passed to each block of the light source unit 5 and then sets a DA output by a control signal. The light source driving bias voltage corresponding to the data is input to each block of the light source driving circuit 3.

Here, the value of the current flowing through the light source unit 5 is proportional to the magnitude of the light source driving bias voltage. In this state, the light source lighting signal is turned on and the light source unit 5 is turned on. The emitted light irradiates the optical system adjusting medium 9, and the reflected light (diffused light) or transmitted light from the medium enters the light receiving sensor unit 6, the sensor output is amplified by the amplifier 7, and the AD converter 8 AD
By performing the conversion, image data for one line in the main scanning direction of the image is obtained.

FIG. 3 shows a flowchart of the light source output equalizing process according to the second embodiment. Here, the gradation width of the data set in the DA converter 2 is K gradation, the number of pixels for one line in the main scanning direction of the image is S pixels, and the gradation width of the image data is F. Also, as an image input device,
When an image of the same medium is acquired by a plurality of devices, an image having the same brightness needs to be acquired. Therefore, as an initial condition, it is necessary to adjust the brightness obtained when the optical system adjustment medium 9 is obtained to a certain level,
Assuming that the average value of the acquired S image data is H, the image data is adjusted to the average value H.

First, the X-th block in the N blocks of the DA converter 2 is selected. All 0s are set in the DA conversion units 2 of the N-1 blocks other than the X-th block (Sb1 to Sb1).
b4). Here, the case where the set value is 0 means that the light source drive bias voltage is not output to the light source drive circuit 3, and the current is not supplied to the target block, so that the light source unit 5 emits light even when the light source unit 5 is turned on. No setting.

In this state, the value i set in the X-th DA converter 2 is sequentially changed from 1 to F, and every time the value is changed, the average value Ux (i) of the image data for S pixels in the main scanning direction is obtained. (Sb3 to Sb7). At this time, Ux (1) to Ux
Find the one closest to H / N in (F). Here, H / N represents an average value per block. The set value for the DA converter 2 at this time is Y. Thus, the set value Y of the DA converter 2 of the T block is determined (Sb8).

At this time, one of Ux (1) to Ux (F) closest to H / N is found. X = 1
To N (Sb9 to Sb11). Thus, the values to be set in the DA converter 2 for N blocks are determined. The set values of the DA converter 2 for the N blocks thus obtained are stored in the memory 4.
(Sb12). Lastly, an operation when the light source is controlled to be turned on using the set values recorded in the memory 4 will be described.

The set values for N blocks recorded in the memory 4 are set in the DA converter 2, and the light source bias voltage is input to the light source drive circuit 3. Next, the light source lighting signal is turned on to light the light sources of the blocks 1 to N. As described above, the light source output can be made uniform. According to the second embodiment, a light source made of a plurality of optical elements is divided into N blocks, only one block is turned on, and
The average value of the image data for the line is determined. DA of K gradation
Using the conversion unit 2 (one per block), the current value flowing through one block is changed into K values, and the average value of the image data for one line is obtained for K values. Here, when an image of the optical system adjustment medium is acquired with a light source having a uniform luminance distribution in the main scanning direction in which an element having an average luminance is mounted, the average value of the image data for one line is set to H. . The state closest to H / N is found out of the obtained K average values, and the value set in the DA converter 2 at that time is recorded. This process is performed for all the N blocks, and the values set in the DA converter 2 are recorded. If the light sources are turned on using the values to be set in the respective DA converters 2 obtained here, it is possible to obtain an excellent light source unit with less variation in the amount of light in the main scanning direction of the image.

[0027]

As described above, according to the image input apparatus of the present invention, even when a light source having a uniform luminance in the main scanning direction is produced, an exclusive worker is not required, and an optimum limiting resistance value is found. Since the time required for the work and the work of changing the limiting resistance is not required, as a result, the effect of reducing the cost and time for manufacturing one light source is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image input device according to a first embodiment;

FIG. 2 is a flowchart of a light source output uniforming process according to the first embodiment;

FIG. 3 is a flowchart of light source output equalization processing according to the second embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control circuit part 2 DA conversion part 3 Light source drive circuit 4 Memory 5 Light source part 6 Light receiving sensor part 7 Amplification part 8 AD conversion part 9 Optical system adjustment medium 10 Optical system part

Claims (3)

[Claims] 1. A light source formed by a plurality of optical elements is divided into a plurality of blocks, and a digital-to-analog converter is connected to each of the blocks. The set value of the current flowing through each block is varied by the combination of the patterns according to the number of blocks, and the standard deviation of the image data for each line is calculated. When the standard deviation of the calculated standard deviation is the smallest, An image characterized by storing a set value of a digital-to-analog converter and setting the set value in the digital-to-analog converter when the light source is turned on so as to make the light source uniform in the main scanning direction of the image. Input device. 2. A combination of a gradation width of a set value set in a digital-to-analog conversion unit and a pattern according to the number of blocks is a value obtained by subtracting one from the number of blocks and adding one to the number of gradations. An image input device comprising a combination of factorial patterns. 3. A light source made of a plurality of optical elements is divided into a plurality of blocks, a digital-to-analog converter is connected to each block, and only one of the blocks is turned on for each block. The average value of the image data for one line is obtained, and the current flowing in one block is changed by the number of gradations of the gradation width of the set value set in the digital-to-analog conversion unit. Find the average value of the image data of
When the average value of the image data for one line when the image of the optical system adjustment medium is acquired with a light source having a uniform brightness distribution in the main scanning direction in which the optical element having the average brightness is mounted is defined as the adjustment medium average value. The state obtained by dividing the average value of the adjustment medium by the number of blocks, the state closest to the obtained average value is determined, and the set value of the digital / analog conversion unit at this time is stored. An image input apparatus characterized in that the set value obtained for each is set in a digital-to-analog conversion unit so as to make the light source uniform in the main scanning direction of the image.