JPS61277269A - Color picture reader - Google Patents

Abstract

PURPOSE:To read color pictures of high quality with a CCD by providing a program amplifier and a program offsetter between a head amplifier and an A/D converter and adjusting their values alternately by a control part. CONSTITUTION:An original set to an original platen is separated into colors by a color separation filter 118 and is read by a CCD 101 and is amplified by a head amplifier 106. The clock period of the CCD 101 is switched and selected by a clock switching part 104 to reduce the sensitivity difference due to filter switching. Further, the sensitivity difference is adjusted finely by a head amplifier switching part 105 to equalize the input level to a program amplifier 107. After while point level and black point level values are set by the program amplifier 107 and a program offsetter 108, digital conversion is performed by an A/D converter 109. Thus, good color pictures without shading which are well-color balanced are read.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color image reading device using a CCD 1.

Conventional technology Color image reading devices have long been used in the so-called drum type, in which a document is wound around a drum, the drum is rotated and scanned, and an optical sensor with a three-primary color separation optical system is moved along the drum to read the document. scanner is used. On the other hand, instead of wrapping the original around the drum, COD
A COD scanner has also been developed that uses a one-dimensional line sensor such as the
Currently, it is widely used for reading black and white documents for fax machines. However, COD uses the same sensor to read the three primary colors, so a balance between each color is required, and the sensitivity of blue in particular is low, making good full-color reading insufficient. An example of a conventional color COD scanner will be described below.

In FIG. 3, 301 is a CCD for reading.

311 is a mechanical scanner having a CCD 301 that mechanically performs one-dimensional scanning on a document image formed by a lens 313; 302 is a CC that is perpendicular to the scanning direction of the mechanical scanner;
D301 (i-COD driver that electrically scans and obtains read output; 303 is a video process mainly consisting of an A/D converter for interfacing the signal of the COD driver 302 to the line buffer 304; 3051
j A digital process that compensates for the sensitivity difference between each element of the CCD 301, 306 is a shaping collector that compensates for the two-dimensional sensitivity difference between the illumination system and the lens system, and 307 binarizes the data as necessary. 309 is a color separation filter 31
Filter scanner 310 and CCD 301 that control 2
A motor driver 308 controls both of the mechanical scanners 311 for scanning.

Also, as another conventional example, Sanyo Technical Review (VoL, 16 & I Feb, 1984)
There is also one shown in FIG.

In Figure 4, three CODs for each primary color are used for the purpose of simultaneously obtaining color separation outputs, 401 is an illumination light source, 40
2 is a transparent original table, 413 is a mounted original, an OS' mirror, 404 is glass, 405 is a Fi lens, 406 is a dichroic mirror for color separation, and 407 to 409 are blue and red, respectively.

The peripheral color separation filters 410 to 412 are blue, red, and peripheral COD image sensors, respectively.Problems to be Solved by the InventionHowever, in the configuration as shown in FIG. When reading, the S/N ratio of each color differs depending on the sensitivity difference between each color, and in particular, the S/N ratio of the blue output deteriorates due to a decrease in blue sensitivity. Therefore, even if the white peak value and black dark value of the original are set to desired values, errors due to noise are added to the setting values of each color, making it difficult to obtain images with good color balance. Three CCDs 410 to 412 shown in the figure
In the method using , since each independent COD is used,
Although it is possible to adjust the S/N by adjusting the light intensity or adjusting the driver of each COD,
There was a problem in ensuring mechanical positional accuracy of D410-412.

The present invention solves the above-mentioned problem and converts color separation output into S
/N By reading out in a well-balanced manner, and by adjusting and setting the output level of each of the white peak point and black dark point of the document to the desired output level, ・The purpose is to read high-quality color images using CCDI. .

Means for Solving the Problems The present invention uses a COD clock switching stage to switch the operating clock of the COD depending on the type of color filter, adjust the sensitivity, and further adjust the speed of the head amplifier and A/D converter. The above object is achieved by providing a program amplifier and a program offseter between them, and having the control section alternately adjust this value.

Effect The present invention has the above-mentioned configuration, so that when the filter is switched, the C
By switching the OD operation clock and adjusting the time that the amount of incident light is accumulated in each COD sensor element,
Equalize the COD output level for each filter. In addition, since the noise level does not change due to changes in the clock, the CCD output that is not color-separated as a result is
/N ratio.

The program amplifier outputs C at the position of the white spot on the document.
The control section automatically adjusts the gain so that the maximum value of the CD output becomes a desired value. The program offseter is a program amplifier that adds an offset to the A/D converter input after gain adjustment, and automatically controls the control unit so that the minimum value of the CCD output becomes the desired value at the position of the black dot on the document. If the white peak value is adjusted, the white peak value will change, so the adjustment of the program amplifier is repeated again until the white peak value converges to the desired value. The control section performs the above adjustment work for each color of the filter, and calculates a program amplifier value and a program offset value. When switching filters,
By setting these pre-calculated values, it is possible to quickly set good reading conditions for each color.Embodiment FIG. 1 is a block diagram of a color image reading device according to an embodiment of the present invention. .

In FIG. 1, 101 is a CCD, 102 is a CCD1o
a COD driver that provides the necessary drive pulses to 1; 10;
6 is a head amplifier that amplifies the analog output of the CCD 101; 107 is a program amplifier that can set the output of the head amplifier 106 to an arbitrary value by a program; and 108 is a program amplifier that generates an arbitrary voltage according to a program to offset the output of the program amplifier 107. A program offseter 109 that can be added is an analog/digital converter that converts the output of the CCD 101 into a digital signal. 1
Buffers 10 and 111 each temporarily store one line of output from the CCD 101, and are used selectively as an output buffer for outputting the final output to an external device and as a reading buffer for reading operations. 112 is a multiplier for shading correction, which multiplies the output of the shading correction RAM 113 in which pre-calculated shading correction values are stored;
Compensates for sensitivity differences between GDlol elements ◇114 is a look-up table (LUT), performs brightness/# degree conversion and tone conversion as necessary, and outputs image data to an external device 0118 is a color switchable filter,
103 is a filter switching unit that controls a filter moving motor (M2) and a filter position sensor (81);
104 is a clock switching unit that switches the clock of the COD driver 102; 105H is an amplifier switching unit that switches the amplifier gain of the head amplifier 106; 116 is a motor control unit that controls the document table moving motor (Ml); and 117 is the control unit that controls the illumination light source (Ll). A light source control unit 116 is a CPU that controls the entire system.

The operation of the above configuration will be explained below. First, before starting the reading operation, perform the shading correction RA.
The operation of setting data of M11s and setting black point output value and white point output value of the original will be described.

The data setting of the shading correction RAM value is performed by attaching a uniform white document, setting an appropriate filter 118 in the filter switching section 103, and predetermining the clock switching section 104, amplifier switching section 105i, and filter 118 accordingly. Set the value. Furthermore, a certain value is written in the shading correction RAM 113. Then, the output of the head amplifier 106 is passed through the program amplifier 1σ and added to the output of the program offseter 108, and A
After digital conversion by /D converter 109, the data is written to buffers 110 and 111. The output of the buffer is multiplier 1
12, the constant value is temporarily multiplied by the written shading correction RAM value, and the CPU 116 outputs CGDlo.
The output of l is sent as is to the CPU 116. In this state, when the illumination light source is turned on by the light source control unit 117, the CPU
The values of the program amplifier 1o7 and the program offseter 10B are alternately set so that the maximum value of the read data of 116 becomes the desired value and the minimum value of the read data of the CPU 116 when the illumination light source is turned off becomes zero or the desired value. A when adjusting to and calculating the shading correction value
/D converter 109 input level value is adjusted. Next, a white uniform document is read under the above adjustment conditions, and the CPU 11
6 gets that data. The CPU 116 calculates a correction coefficient so that the read data values are uniform, and writes the value into the shading correction RAM 113. The average value of multiple readings is used as necessary to calculate the correction coefficient. After the correct shading correction value is set, the output from the multiplier 112 is a uniform COD image output without shading.

Next, the operation of setting the black point output value and white point output value of the original according to the read original will be described.

This adjustment consists in setting the values of the glogram amplifier 107 and program offseter 10B for each filter color. Illumination light Y1 illuminates the document table with the original to be read.
p, L1, and set the COD clock switching section 104 and amplifier switching section 10B corresponding to the filter color. Clock switching is especially important for setting the white point and black point level values, and for each filter color switching, the output S/N
It is effective in making the ratio uniform and reducing setting errors. First, move the document table to a position that includes the white point, and while reading the document, set the gain of the program amplifier 107 in sequence, and then pass through the A/D converter 1o9, buffer 110, then 111, and multiplier 112. /2. CPU11
The program amplifier value is set so that the maximum value of the image data read by 6 becomes the desired white point data setting value. Next, move the document table to a position that includes the black dot, read the document data, adjust the program offset value, and similarly set the minimum value of the read image data of the CPU 116 to the desired value (
D Set the program offsetter value to match the black point f-tar setting value. While repeating these two operations, the white point and black point level values are both adjusted until they reach desired values. Set an allowable setting range for the set value as necessary.

The set values are stored in the CPU 116 and written to the program amplifier 107 and program offseter 108 when each filter is selected.

Next, an actual document reading operation will be explained.

Before setting the original, load the shading correction RAM in advance.
It is assumed that the data writing operation to 113 has been completed, and that the setting of the white point level value and black point level value of the attached document has been completed using the method described above.

The document mounted on the document table is passed through a color separation filter 11.
8, read by ccDlol, and amplified by head amplifier 106. In the CCD 101, the clock cycle is switched and selected by the clock switching section 104, thereby reducing sensitivity differences due to filter switching. Further, the head amplifier switching section 105 performs fine adjustment of the sensitivity difference and equalizes the input level to the program amplifier 107.

Next, the white point level and black point level values are set by the program amplifier 107 and the program offsetter 108, and then digitally converted by the A/D converter 109. The converted output is alternately sent to two one-line buffers 110 and 111, and alternately sent to the next multiplier 112.

The two buffers 110 and 111 are used to read the CCD 101 and output data to an external device in parallel. The multiplier 112 multiplies the output of the sRAMll 3 into which the aging correction value is stored, thereby compensating for the difference in sensitivity between the COD elements.
The output of the zero multiplier 112, which outputs a correctly leveled, unshaded reading, is further output via a look-up table (LUT) 114, which performs print signal conversion and tone conversion, as required. Appear to the device. After reading one page of one color of the manuscript, the CPU 116
The motor control unit 115 reads the document 9, returns it to the starting point, changes the filter, changes the clock, changes the amplifier,
The program amplifier value and program offset value are reset, and the original data is sequentially read for each filter.

FIG. 2 shows how desired white point and black point data values are set using the program amplifier 107 and program offsetter 108, and the offset is adjusted in the negative direction with a sufficient offset in the positive direction in advance. This shows that by doing this, it is possible to set the black dots on the document to any desired level.

In FIG. 2, vl is a read image output with a sufficient offset in the positive direction of the image by setting a bias in the program offsetter in advance, and v2 is an offset voltage V at the program offsetter. 0' which is the reading salt 9 image output with S subtracted and the amplitude adjusted to v9 by the program amplifier.
The max value and darkness value of V2 are digitally converted, and the white spot image reading level D01a! , and the black point image reading level. Also, as is clear from this figure, if noise is mixed in (2) or v2, the maximum and minimum values are set including that noise level. Therefore, it is desirable that the noise level is sufficiently low, and it is important that the level is equal to the reading of each color in order to maintain the balance of the set value of each color. ) Clock switching section 104
According to this embodiment, the clock of the CCD 1o1 is switched so that the sensitivity is equalized for each filter switching,
In addition, the program amplifier 107 and the program offsetter 108 adjust and set the white point and black point level values of the document, and by using the shading correction function, it is possible to improve color balance and read color image data in good quality. I can do it.

Effects of the Invention As described above, the present invention allows the white point/horse level value settings to be set correctly to arbitrary values when reading a COD image, and reads a good color image without shading due to color paralysis. The effect on the quality of read image data is remarkable.

[Brief explanation of the drawing]

FIG. 1 is a block wiring diagram of a color image reading device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of the electrical parts shown in FIG.
4 are block wiring diagrams of a conventional color image reading device. 101...CCD, 102...COD
Driver, 103...Filter switching unit, 1
04... Clock switching unit, 105...
Amplifier switching section, 106...Head amplifier, 10
7...Program amplifier, 108...
Program offsetter, 109...A/D converter, 110, 111, river, buffer, 112...-
... Multiplier, 113 ... Shading correction RAM, 114 ... LUT 1115 - Motor control section, 116 ... CPU, 11.7.
...Light source control unit, 118... Color separation filter 0 Name of agent: Patent attorney Toshio Nakao and one other person Figure 2, Figure 4, Figure 40f-11 Ode to Shiro 41! ---Ichika'ru Yokusu Chidel@3 ---Mirror 4t4-1-γ With Russ & ---Lens 1 40 Togakuic old f mirror 4#7~409 --- Qi or 9 f fins Lg4fO
N41'2-- CCJ) 3 Suji 7 amp 413-11 ear meicho l hole brown

Claims (1)

[Claims] a document placement table on which a document to be read is placed; a document placement table drive unit for controlling movement of the document placement table; a light source for illuminating the document; and a color separation filter selectable from several types.
filter selection means for selecting an appropriate filter from the color separation filters; reading means for causing a charge-coupled device to read information on the document via the color separation filter and amplifying the read signal by an amplification means; amplification control means for changing the amplification factor of the means; reading time control means for changing the reading time of the charge-coupled device according to the selected filter; and maximum and minimum values of the read signal of the reading means. an adjustment/setting means for adjusting and setting an arbitrary level; an analog/digital conversion means for converting the output of the adjustment/setting means from analog to digital; and a storage means for temporarily holding the output of the analog/digital conversion means; A color image reading device comprising: a multiplication unit that multiplies the output of the storage unit by a preset shading correction value; and a control unit that controls each of the units.