JP2003060845A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satisfactory image of no non-uniformity in the density. SOLUTION: This image processor has a plurality of sensor chips each containing a plurality of pixels and a correction means for correcting signals from the sensor chips, and the correction means has at least two or more correction values and performs the correction by selectively using the correction value corresponding to the sensor chip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus using a plurality of sensor chips each having a plurality of pixels.

[0002]

2. Description of the Related Art In recent years, a contact type image sensor has been developed and put into practical use in a scanner device for inputting an image into a personal computer and a document reading device in a facsimile device, along with the trend toward miniaturization and weight reduction. The close contact type is a type composed of a light source, a rod lens that realizes an equal-magnification erecting optical system, and a one-dimensional light receiving sensor having an effective width that is the same as the main scanning width of the read document, and is called a reduction optical system. Use to scan the main scanning width of the read original to a fraction
Since the optical path length of the optical system can be configured to be shorter than that of an optical system that reads with a one-dimensional CCD sensor or the like after being reduced to 1, there is an advantage that the document reading device can be downsized and lightweight.

[0003]

Further, in these contact type image sensors, the length of the sensor chip equal to the width of the original image is required when reading the image, and the sensor of this length is composed of one sensor chip. This has little advantage in terms of technology and cost, and a plurality of sensor chips are arranged in a line to secure the reading length of the document image width.

[0004]

In order to solve the above-mentioned problems, a plurality of sensor chips each including a plurality of pixels and a correction means for correcting signals from the plurality of sensor chips are provided, and the correction is performed. The means provides an image processing apparatus characterized by having at least two or more correction values, and performing the correction by selectively using the correction values according to the sensor chip.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading unit of an image processing apparatus according to this embodiment will be described with reference to FIG.

Reference numeral 1 is a platen glass on which a document is placed, 2 is a pressure plate that presses the platen and can be opened and closed, 3 is a document placed on the platen, and 4 is for reading an image of the document 3. Contact image sensor (hereinafter referred to as CIS) which is a scanning optical system of 5 is a carriage that holds the CIS, 9 is a shaft that serves as a guide function when moving the carriage in the sub-scanning direction when reading an original, and 8 is A timing belt fixed to the carriage 2-5, pulleys 6 and 7 arranged at both ends of the timing belt so that the timing belt 8 can move smoothly, and a stepping 10 in which drive is connected to one of the pulleys. Motor, 11 is C
A home position sensor for detecting the position of the carriage 2-5 holding IS4 in the sub-scanning direction, 13 is the home position 11 side on the platen glass 1, and the light amount adjustment control and shading correction operation are performed at the end. A density reference plate serving as a reference for performing the operation, 12 is an operation unit, which includes a switch for operating the image processing device and a display unit for displaying the state of the reading device. Based on the above, it is possible to set the above-mentioned operating condition and select the operation.

The configuration of the CIS 4 will be described in detail with reference to FIG.

Reference numeral 4a is a linear light source unit for guiding the light from the LED light source unit 4b arranged at the end of the light source unit and for uniformly diffusing the light in the main scanning direction.
It consists of c.

The irradiation light emitted from the light guide 4c is reflected by the original 3 on the original platen glass 1, and the reflected light is main-scanned through a plurality of sensor chips fixed on the substrate 4f through the SELFOC lens array 4d. An image is formed on the multi-chip sensor 4e arranged in the direction.

The imaged light is photoelectrically converted by the multi-chip sensor 4e and sequentially output as an image signal.

The light amount of the LED light source is driven by a constant current circuit (details will be described later) that can be controlled by a constant current, and the lighting time is PW within the time for one line of the multi-chip sensor.
M control is performed to control the light amount accumulation time for the multi-chip sensor 4e.

The above multi-chip sensor will be described in detail with reference to FIG.

In the multi-chip sensor 4e used in the present embodiment, about 650 pixels per sensor chip are arranged in the main scanning direction, and these sensor chips are arranged in 8 rows.
They are arranged in a line in the main scanning direction.

With such a configuration, one line (a document having an A4 width of 210 mm) can be read at a resolution of 600 dpi.

For driving the multi-chip sensor 4e, a driving circuit outputs a driving clock pulse capable of reading the total number of pixels constituting one line and a charge of the pixel within a time corresponding to one line of the reading time. At this time, a reset pulse for resetting the output value for each pixel is supplied with a horizontal synchronizing signal which serves as a trigger for starting reading of one line.

Then, in synchronization with the timing of these pulses, an image signal is output for each pixel, and the AGC circuit and A
The signals are sequentially output through an output circuit including a / D conversion circuit and the like.

The image processing unit of the image processing apparatus for performing various image processes on the image signal output from the CIS 4 will be described with reference to FIG.

Reference numeral 41 denotes an AGC circuit 41a for adjusting the gain of an image signal output from the CIS and an A / D conversion circuit 41b for converting an analog signal into a digital signal.
Is an output circuit having.

Reference numeral 42 denotes an LED control circuit (details will be described later) for controlling the light quantity of an LED light source which is a light source in the CIS 4.
A part that controls so that a constant amount of light is obtained when the LED light source is turned on and an image signal is output, and that a plurality of colors of light sources are turned on at a constant light amount ratio. And a part for controlling the timing of turning on the LED (a PWM (pulse width modulation) control part for turning on the LED for a certain period of time with reference to a predetermined timing).

Reference numeral 43 denotes image processing for the image signal output from the output circuit 41, and LED control circuit 42.
Is a control circuit for controlling the.

In the control circuit 43, an image processing circuit 43a which is a correction means for performing correction such as shading correction and brightness correction on an image signal, an image processing memory 43b, a CPU 43c which controls the entire image processing apparatus, It includes a control memory 43b, an interface circuit 43d, and a motor drive circuit 43e.

Then, the CPU 43c sets the offset value, the gain value, etc. of the output circuit 41, the PWM control value setting of the LED of the LED control circuit 42, and the image processing circuit 4 described above.
Setting of each parameter for image processing to 3a,
It sets various operating conditions of the image processing apparatus such as the setting of interface conditions of the interface circuit 43d, controls the start and stop of the operation, and controls the interface with external devices.

Further, the image data of the image memory 43b in which the image data processed by the image processing circuit 43a is accumulated can be read out via the image processing circuit 43a by the data bus of the CPU 43c.

Further, the CPU 43c controls the home position sensor 11 described above as a control for reading an image.
, The reference position of CIS4 is detected, and C is read when the image is read.
A predetermined excitation pattern is output to the stepping motor 10 so that the IS4 can be moved at a constant speed, and the stepping motor 10 is driven via the motor drive circuit 43e to drive the motor so that a desired image can be read. .

Next, the control and operation relating to image reading and image processing of the image processing apparatus will be described with reference to FIGS.

When reading a document, an instruction to start a reading operation is first issued from the operation unit 12, and it is confirmed whether the carriage 5 is located at the home position sensor 11. If not, the stepping motor 1
0 is driven, the carriage 5 detects the home position sensor, and the motor is stopped at a position where a predetermined pulse has been driven to bring the carriage to the home position.

The carriage 5 is the home position sensor 1
When 1 is detected from the beginning, the stepping motor is driven in the sub-scanning direction, the carriage 5 once passes through the home position sensor, and then the stepping motor is reversed to detect the home position sensor again, and the predetermined pulse is output. Stop the motor at the driven position and move it to the home position.

Before the image reading is started, P of each color of the LED light source is used at this position by using the density reference plate 13 described above.
Set the WM value.

The PWM value is set by detecting the image signal value of the CIS4 described above. First, the offset value and the gain value of the analog signal processing circuit 4-1 are set to predetermined reference values, and the light amount of each color of the LED is set. After setting the ratio, the PWM value for each color is set.

Next, the density reference plate 13 is set with the set light quantity.
Turn on, and set the correction value for shading correction.

When the above-mentioned operation is completed, the stepping motor 10 is driven in the operation direction to start reading the original image.

When the reading is started, the read image of the original is photoelectrically converted by CIS4, and the image signal of the original image is image-processed.

First, the output circuit 41 samples and
After the offset level of the signal is corrected and the signal is amplified, the analog signal processing is completed.
It is converted into a digital signal by b and output.

The digitized image data is stored in the image memory 43b after being subjected to shading correction, spatial filter processing, magnification correction, luminance signal conversion, binarization processing, etc. by the image processing circuit 43a in the control circuit 43. . The above-mentioned image processing conditions and operation parameters can be set by the CPU 43c in the control circuit.

The image data stored in the image memory 43b is output via the interface circuit 43d while being synchronized with the external device at the control timing.

Here, the LED control system of the LED light source 4b will be described with reference to FIG.

In FIG. 7, reference numeral 43 is a control circuit, which is a CPU.
43c and a control memory 43d, the overall image reading apparatus is controlled as described above.

The LED control circuit 42 includes a Red (red) LED, a Green (green) LED, and a B of the LED light source 4b.
LED of each color having a constant current circuit and switching circuits 42a, B, C corresponding to each LED of blue (blue)
4b (red, green, blue) are independently connected.

A common potential is supplied to all LEDs,
The constant current value and the switch-on time (lighting time) in the constant current circuit are controlled by the control signal based on the image signal from the multi-chip sensor input to the control circuit 43.
It can be changed.

An operation unit 12 is a setting means, which can set each initial value and LED lighting ratio in the processing block.

Further, in order to clarify the contents, description will be made based on the following premise. However, the preconditions do not limit the present invention.

The LED light source 4b is an LED light source having an RGB (red, green, blue) wavelength (array type, light guide type).

Therefore, the amount of light received by the multi-chip sensor pix_
R, pix_G, pix_B are proportional to the LED light intensity l_R, l_G, l_B, and are pix_R ∝ l_R = i_R × t_R pix_G ∝ l_G = i_G × t_G pix_B ∝ l_B = i_B × t_B, and the constant current value of each LED and lighting time. Can be stored independently, and can be independently driven by the value. The LED light source is turned on so that a constant amount of light can be obtained when the image signal is output, and when the light sources of a plurality of colors are turned on, the LED can be turned on at a constant light amount ratio.

It is composed of a control part and a part for controlling the timing of turning on the LED (a PWM (pulse width modulation) control part for turning on the LED for a predetermined time with reference to a predetermined timing).

As the image output signal value, the output value of the white reference plate (commonly called a shading plate, hereinafter referred to as a shading plate) is 255, and the output value of the black reference plate (or when the light source is off) is 0.
, And 8-bit 256 gradation output.

The main control unit is a software control mainly including a microcomputer (CPU). However, the present invention includes a case where the gate array is mainly used for hardware control.

Next, the image processing circuit 43a described above.
The detailed configuration and operation of the above will be described.

First, the structure will be described.

The configuration of the image processing circuit 43a described above has a shading processing block 61 as shown in FIG.
a, filter block 62a, magnification correction block 63
a, a luminance signal conversion block 64a, a binarization processing block 65a, and memories 61b, 62b, 63 for storing image data and coefficients corresponding to the respective blocks.
b, 64b, 65b.

Further, the shading block memory 61b, the scaling correction memory 62b, and the luminance signal processing block correction table memory 63b described above write image data, and read from the CPU 43c in the control circuit 43 to write data. Is a memory that is configured to enable.

FIG. 7 is a detailed diagram of the luminance signal conversion processing block of FIG. 6, which is a circuit block for converting the input image luminance data for each pixel into density data.

The luminance signal conversion processing block includes three types of correction table memories 7 that differ depending on the characteristics of the sensor chip.
4a, 74b, 74c, an address counter 71 for counting pixel addresses, and a correction table selector circuit 73 for switching control of the memory table according to the value of the address counter. Again 72
Is a setting register for holding a comparison value for comparison with the output value of the address counter 71 and a selection setting for the selector 73.

Next, the operation will be described.

The structure of the density reference plate 13 described above is shown in FIG. The density reference plate 13 is composed of two types of reference density areas, a white reference area 13a used for shading correction when reading an image and a halftone gray reference area 13b used for determining the characteristics of the sensor chip. There is.

When setting the correction table corresponding to the sensor chip, first, as described above, the white reference plate area 1
3a is read by a multi-chip sensor, data for shading correction is obtained, and shading correction is performed by the data.

After that, the intermediate gray reference area 13b
Is read by the multi-chip sensor, and the read image data is stored in the memory 63b of the magnification correction block.

The stored image data is the CP in the control circuit.
The data is read out by the U43c, and the average value of the pixel data of the halftone density is calculated for each sensor chip. The calculated average value data is stored in the memory 43d. The conversion data of the correction table memories 74a, 74b, 74c are set for each memory chip by comparing the reference value of the gray-scale image stored in advance in the memory 43d with the average value of each sensor chip described above.

The sensor chip used in this embodiment is composed of eight sensor chips as described with reference to FIG. 3, and the correction tables corresponding to the eight sensor chips are of the three types described above. Which correction table in the correction table memory is used is set in the setting register 72.

The correction characteristics of the correction table are shown in FIG. Reference numeral 91 in FIG. 9 is a table in which the correction characteristics are almost ideal, 92 is a characteristic table used when halftone image data is less than the reference value, and 93 is when the halftone image data is more than the reference value. It is a characteristic table used.

Specifically, for example, if the average value of the first halftone of the sensor chip is approximately equal to the reference value in the memory described above, the correction table 1 is set. Next, the sensor chip 2
If the average value of the th halftone is larger than the reference value in the memory described above, the correction table 3 is set. If the average value of the third halftone of the sensor chip is smaller than the reference value in the memory described above, the correction table 2 is set. In this way, which table of the three correction table memories is used for the correction table data corresponding to the eight sensor chips is set. This setting information is stored in the setting register of FIG.

If the characteristics of the sensor chip are known in advance, a correction table may be selected and set for each sensor chip using the operation unit 12 described above.

In the present embodiment, as described above, one correction table is not provided for each sensor chip, but a plurality of correction tables smaller than the number of sensor chips are provided, and a plurality of correction tables are provided. By using the correction table in common for the sensor chips, it is possible to prevent a large increase in the image processing circuit 43a even if the number of sensor chips is large.

However, the present embodiment is not limited to the above-mentioned configuration, and one correction table may be provided for each sensor chip.

Further, when the power consumption of the image processing apparatus is reduced, the image quality deterioration is conspicuous in the image of the halftone density only by the shading correction, and the configuration of the present embodiment is particularly effective.

Next, the flow of the actual operation of the image processing circuit will be described.

As described above, the digitally converted image signal from the multi-chip sensor is input to the image processing circuit 43a, is subjected to shading correction in the shading block 61a, and then in the filter block 62a.
Edge enhancement processing or smoothing processing is performed.
After that, the image magnification correction block 63a performs reduction and enlargement processing, and the result is input to the luminance signal conversion block 64a.

The image data is 8 bits in this embodiment.
The image data for one line is sequentially processed on the basis of the horizontal synchronizing signal.

The image data for one line is sequentially input to the luminance signal conversion block from one of the eight sensor chips described above in a form corresponding to each pixel. At this time, the number of pixels is counted by the address counter 71, and the pixel address value at the head of each sensor chip is set in the setting register 72.
The number of the correction table memory to be selected when it matches with the set value set in (1) is written in the setting register 72.

For example, if the first chip of the multi-chip sensor is set in the correction table memory 1, all the image signals of the first chip are subjected to characteristic correction according to the correction table of the correction table memory 1 and output. It
Next, if the value counted by the address counter 71 at the time of the first pixel on the second chip matches the start address of the second chip, and if this match signal is set for selection of the correction table 2, then 2 The characteristics of all the image signals of the chips are corrected according to the correction table of the correction table memory 2.

In this way, the image signal from the 8-chip sensor is corrected based on the characteristics that match the characteristics of the respective chips, so that even in the halftone portion of the image, density unevenness due to the difference in characteristics between the chips is caused. It is possible to correct without correction.

[0071]

As described above, a good image without density unevenness can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an image reading unit of an image processing apparatus.

FIG. 2 is a diagram showing a contact-type image sensor.

FIG. 3 is a diagram showing a multi-chip sensor.

FIG. 4 is a diagram illustrating an image processing unit of the image processing apparatus.

FIG. 5 is a diagram illustrating a part of an image processing apparatus.

FIG. 6 is a diagram illustrating an image processing circuit.

FIG. 7 is a diagram illustrating a luminance conversion block.

FIG. 8 is a diagram showing a density reference plate.

FIG. 9 is a diagram showing a characteristic diagram of a correction table.

[Explanation of symbols]

71 address counter 72 setting register 73 selector 74a Correction table memory 1 74b Correction table memory 2 74c Correction table memory 3

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B047 AA01 AB02 BA02 BB02 DA04                       DB01 DC01                 5C051 AA01 BA04 DA03 DB01 DB07                       DB22 DB29 DC03 DE17 DE18                 5C072 AA01 BA08 CA05 CA14 DA25                       EA07 FB12 RA16 UA02 UA06                       UA11                 5C077 LL02 LL19 MM05 NP01 PP06                       PP11 PP12 PP15 PP44 PP45                       PP72 PQ12 PQ23 RR01 SS01

Claims (7)

[Claims] 1. A plurality of sensor chips each including a plurality of pixels, and a correction unit that corrects signals from the plurality of sensor chips, wherein the correction unit has at least two or more correction values. ,
An image processing apparatus, which performs correction by selectively using the correction value according to the sensor chip. 2. The sensor chip has at least one density reference plate for detecting characteristics of the sensor chip, and the correction means sets the sensor chip based on a signal read by the plurality of sensor chips from the density reference plate. The image processing apparatus according to claim 1, further comprising setting means for setting a corresponding correction value. 3. The image processing apparatus according to claim 1, wherein the density reference plate has a halftone gray reference area. 4. A plurality of sensor chips each including a plurality of pixels, a correction unit that corrects signals from the plurality of sensor chips, and a density reference plate having a white reference area and a halftone gray reference area. And the correction means has at least two or more correction values,
The first correction that performs shading correction based on a signal obtained by reading the white reference area by the plurality of sensor chips, and the sensor based on a signal obtained by reading the halftone gray reference area by the plurality of sensor chips An image processing apparatus, which performs a second correction for performing a correction by selectively using the correction value according to a chip. 5. The image processing apparatus according to claim 4, wherein the correction unit performs the second correction after the first correction. 6. The correction means has a smaller number of the correction values than the plurality of sensor chips, and uses the common correction value for signals from the plurality of sensor chips. The image processing apparatus according to any one of claims 1 to 5. 7. The image according to claim 1, further comprising a light source that illuminates an object and a lens that forms an image of light from the object on the plurality of sensor chips. Processing equipment.