JP4891208B2 - Image reading apparatus and method for controlling image reading apparatus - Google Patents

Description

The present invention relates to a reading apparatus using a white LED as a light source.

  In recent years, white LEDs have been used for various purposes, and are also used as light sources for scanners (see, for example, Patent Document 1).

  Compared with CCFLs (cold cathode tubes), xenon tubes, halogen lamps, and the like that are conventionally used, white LEDs have a small amount of light, and thus a light source is configured by an array of dozens of white LEDs.

  By the way, recent high-intensity white LEDs can pass a current of several hundreds mA, and a number of white LEDs can constitute a light source of a scanner.

  Although it is not white, a light source for reading is described in which LEDs are mounted on both ends of the light guide (see, for example, Patent Document 2 and Patent Document 3).

In this configuration, it is conceivable to use a high-intensity white LED, whereby a white light source for a scanner can be configured.
JP 2003-8911 A JP-A-6-148435 Japanese Patent Laid-Open No. 7-14414

  As described in Patent Document 1, the white LED has a large variation in chromaticity as compared with a conventional light source. This reason is related to the structure of the white LED.

  The white LED obtains white light having a wavelength of 400 to 700 nm by converting a part of light emitted from the blue light emitting diode into yellow with a yellow phosphor. Due to variations in semiconductor manufacturing, the wavelength of blue varies, and further, the amount of yellow light emitted varies depending on the light emission efficiency of the yellow light body that depends on the blue wavelength and the amount of application of the yellow light body. Due to these variation factors, yellowish white and blueish white LEDs are manufactured.

  FIG. 12 is a diagram showing the chromaticity variation of the white LED on the xy chromaticity diagram.

  Variation in the wavelength of the blue LED causes variation in chromaticity in the A direction, and variation in chromaticity in the B direction occurs due to variation in light emission amount of the yellow light body.

  Therefore, a white LED array with uniform chromaticity rank is used (paragraph 0106 of Patent Document 1), and the parameters for color correction can be changed in order to use an array of a plurality of chromaticity ranks ( Patent Document 1 paragraph 0110).

  When white LEDs with uniform chromaticity rank are used, it is necessary to discriminate, manage and distribute the chromaticity rank in the manufacturing process (inspection process), which increases the cost of the white LED.

  A scanner using a white LED can be provided with a reasonable price if an LED having no chromaticity rank can be used. From this point of view, a method of using a mixture of white LEDs having different chromaticities is described in paragraphs 0122 and after of Patent Document 1.

  Here, a problem in the case of using a mixture of white LEDs having different chromaticities will be described. A system using white LEDs at both ends of the light guide described in Patent Documents 2 and 3 will be described.

  FIG. 13 is a diagram illustrating the influence of the left and right LEDs.

  FIG. 13B is a diagram illustrating the illuminance at the reading position when only the right LED is turned on. FIG. 13 (3) is a diagram illustrating the illuminance at the reading position when only the left LED is lit.

  As shown in FIGS. 13 (2) and 13 (3), in a general light guide whose amount of light attenuates as the distance from the LED increases, as shown in FIG. Depending on the scanning position, which of the left and right LEDs is strongly illuminated differs. That is, the position where the illumination light of the left LED is strong in the position depicted in FIG. 13A (1) is strong, and the position where the illumination light of the right LED is strong in the position depicted thinly.

  In such a light source, when the chromaticity of the left and right LEDs is different, the influence degree of the left and right LEDs is different depending on the position of the main scanning.

  That is, even if a document with a uniform color is read, the illumination light differs depending on the position of main scanning, so that there is a problem that the color of the reading result varies depending on the position of main scanning.

  Depending on the position of main scanning, color conversion is performed while changing the masking coefficient, thereby absorbing variations in chromaticity of white LEDs (paragraph 0127 of Patent Document 1).

However, the masking coefficient is, for example, a coefficient of 9 × 2 bytes = 18 bytes. When all the pixels are prepared, the capacity of the masking coefficient storage unit described in FIG. 17 of Patent Document 1 is about 90,000 bytes. (A4, 600 dpi = 600 dots / 25.4 mm ). Furthermore, a recent 4800 dpi = 4800 dots / 25.4 mm scanner requires a capacity of about 720,000 bytes, which increases the cost of memory and image processing ASIC. That is, the cost increases more than the merit of cost reduction by mixing LEDs of different ranks.

  In order to avoid this, only the masking coefficient of the representative point is stored in the masking coefficient storage unit, and the masking coefficient is generated by interpolating between the representative point and the representative point (paragraph 0128 of Patent Document 1).

  However, this method has the following problems. In recent color conversion, a three-dimensional lookup table (3DLUT) is mainly used for “more faithful color reproduction”, “preferred color reproduction”, “color reproduction based on memory color”, etc. (patent) Reference 1, paragraph 0118).

  When 3DLUT is used, the coefficient of 3DLUT cannot be calculated by interpolation between the representative points. That is, since the 3DLUT is used to convert the color space nonlinearly, for example, the 3DLUT coefficient at a position exactly between the representative point and the representative point is obtained by linearly interpolating the coefficients of the two representative points. It will not be.

  Since linear interpolation is not possible, 3DLUT coefficients must be prepared for all pixels. However, the 3DLUT coefficient of 16 * 16 * 16 lattice points is 12288 bytes, and the total number of pixels in one line is several tens of megabytes, which is not practical in constructing the apparatus.

  Further, as color correction means, image data before correction can be imported from a scanner to a PC and corrected. However, in order to apply to a copying machine, it is necessary to perform color correction in real time during copying. There is a problem that this method cannot be adopted.

The present invention provides an image reading apparatus capable of inexpensively and surely correcting a color when using a white LED having no chromaticity rank in a light source for a scanner using white LEDs at both ends of a light guide. For the purpose.

It is another object of the present invention to provide an image reading apparatus that can use a scanner of a white LED light source that does not have a uniform chromaticity rank as a reading unit of a color copying machine.

An image reading apparatus according to the present invention includes a plurality of white light sources associated with each chromaticity information, a color line sensor that reads a document illuminated by the plurality of white light sources, and an output from the color line sensor. Signal color space is converted into a standard color space according to the chromaticity of each of the white light sources, the same number of color conversion units as the plurality of white light sources, and outputs from the plurality of color conversion units, Each pixel of the line sensor includes a weighted average unit that performs weighted averaging according to a light amount ratio from the plurality of white light sources.

  According to the present invention, since white LEDs having no chromaticity rank can be used, it is not necessary to select the chromaticity rank in the white LED manufacturing process, and an inexpensive scanner can be provided by reducing the number of steps. There is an effect.

  Further, according to the present invention, since the two outputs of the color conversion means are weighted and averaged, color correction can be performed in real time even during copying in a color copying machine. Even in a color copying machine, two chromaticity ranks can be obtained. It is possible to use white LED light sources that are not uniform.

According to the present invention, the read image can be simultaneously subjected to color conversion corresponding to the chromaticity of each LED, and the result of each color conversion is weighted and averaged for each pixel with a weight corresponding to the degree of influence of each LED. Therefore, there is an effect that appropriate color conversion can be performed at any position in the main scanning.

  The best mode for carrying out the invention is the following embodiment.

  FIG. 1 is a block diagram illustrating an inkjet multifunction peripheral 100 that is Embodiment 1 of the present invention.

  The inkjet multifunction peripheral 100 has a color copying function and is an example of an image reading apparatus.

  The inkjet multifunction peripheral 100 includes a CPU 1, a ROM 2, a RAM 3, an operation unit 6, a recording unit 7, a color reading unit 8, a system bus 10, a card slot 11, and a USB interface 12.

The CPU 1 is a central processing unit that controls the entire inkjet multifunction peripheral 100. The ROM 2 stores programs and data. The RAM 3 is a DRAM and stores CPU work data, display data, image data, and the like. The DMA controller 4 performs data transfer between each block at high speed.

  The operation unit 6 includes an LCD, a cursor key, a start key, and the like that perform status display of the inkjet multifunction peripheral 100 and operation guidance display. The recording unit 7 is a printer or the like. The color reading unit 8 includes a color contact image sensor or the like. The system bus 10 connects the above processing units. The card slot 11 can read a memory card such as a digital camera.

  The USB interface 12 is for connecting to the PC when the inkjet multifunction peripheral 100 is used as a scanner, a printer, or a memory card reader. The nonvolatile memory 13 stores the chromaticity rank of the LED. The color correction unit 14 performs color correction.

  FIG. 2 is a configuration diagram illustrating an appearance of the operation unit 6 of the inkjet multifunction peripheral 100.

The operation unit 6 includes an LCD 21, a mode key 27 for designating an operation mode of the MFP, a menu key 22 for entering various setting modes, a cursor key 26 used for moving setting items and changing values, And a determination key 25 which is a setting input key. The operation unit 6 also includes a start key 23 for starting various jobs such as copying and scanning, and a cancel key 24 used for canceling jobs and resetting settings.

  FIG. 3 is a diagram illustrating the configuration of the scanner of the inkjet multifunction peripheral 100.

The scanner includes an original table glass 31, a scanner housing 44, a carriage unit 32 in which a reading unit is unitized, a light guide 35 that guides LED light to a reading surface, and power white LEDs 33 and 34. Further, the scanner includes mirror groups 36 to 38 for folding a reading optical path, a lens 39, a color CCD 40 as a reading device, a printed circuit board 41 on which a CCD is mounted, and a white reference plate 43 used for shading. .

  In FIG. 3, a thick arrow AR1 indicates illumination light on the reading surface radiated from the light guide. A broken line indicates a reading optical path.

  Next, means for determining the chromaticity rank of the LED will be described.

  As described above, the chromaticity variation in the A direction in FIG. 12 occurs due to the wavelength variation of the blue LED, and the chromaticity variation in the B direction occurs due to the light emission amount variation of the yellow light body. Therefore, if these two variations can be measured, the chromaticity can be determined.

In order to detect the emission wavelength of the blue LED, it is only necessary to read a purple chart having a reflectance spectrum peak on the shorter wavelength side than the wavelength of the blue LED. Reading this purple chart, if the B channel output of the scanner is small, the emission wavelength varies on the long wavelength side, and if the B channel output of the scanner is large, the emission wavelength varies on the short wavelength side.

  The power white LEDs 33 and 34 are examples of a scanner light source including a plurality of light sources having different chromaticities. The CPU 1 is an example of a unit that determines chromaticity ranks of the plurality of light sources, and is an example of a plurality of color correction units. The number of color correction means is the same as the number of light sources.

  The operation unit 6 is an example of a unit that sets a color conversion parameter corresponding to the chromaticity rank in the plurality of color correction units. The CPU 1 is an example of means for weighted average of output signals of a plurality of color correction means, an example of means for outputting the weighted average weight, and during color conversion of one main scanning line, It is an example of a means to change the weight of the said weighted average.

  Further, the CPU 1 is an example of means for individually lighting a plurality of LEDs, and is an example of means for calculating a weighted average weight based on the luminance of the paper surface illuminated by the individual LEDs.

  Next, the purple chart is read, and if the scanner's B channel output is small, the emission wavelength varies on the long wavelength side, and if the scanner's B channel output is large, the reason why it is scattered on the short wavelength side is explained. To do.

  FIG. 4 is a diagram illustrating the relationship between the purple chart and the wavelength of the blue LED.

When the purple chart shown in FIG. 4 is read, the output of the B channel is obtained by multiplying the emission spectrum of the LED, the reflectance spectrum of the purple chart, and the sensitivity spectrum of the B channel, and integrating them in the wavelength range of visible light. Is.

In FIG. 4, the spectrum of the LED having the characteristic be3 has more overlap with the reflectance spectrum of the chart than the characteristic be1, so that the B channel output when the LED having the characteristic be3 is used uses the characteristic be1. Bigger than time. That is, the variation in the emission wavelength of the blue LED can be estimated from the output of the B channel.

To know the light emission intensity of the yellow phosphor may upon reading the spectral reflectance of the yellow chart having a steep slope on the green near 480～580Nm. If the reflectance spectrum of this yellow chart is read and the blue channel (hereinafter also referred to as “B channel”) output of the scanner is small, the amount of light emitted by the yellow light body varies to the small side, and the blue channel output of the scanner is If it is larger, the amount of light emitted from the yellow light body varies on the larger side. The reason for this will be described.

  FIG. 5 is a diagram showing the relationship between the yellow chart and the wavelength of the blue LED.

In FIG. 5, the output of the B channel when the yellow chart is read is obtained by multiplying the emission spectrum of the LED, the reflectance spectrum of the yellow chart, and the sensitivity spectrum of the B channel, and integrating them in the visible light wavelength range. Is.

In FIG. 5, the spectrum of the emission intensity of the LED indicated by the characteristic bf2 has more overlap with the reflectance spectrum of the chart than the characteristic a52, and therefore the B channel output when the LED having the characteristic bf2 is used. The characteristic a52 is larger than when it is used. That is, it is possible to estimate the variation in the light emission amount of the yellow phosphor by the output of the B channel.

  FIG. 6 is a diagram illustrating a reading unit and a chart.

  Specifically, before shipping from the factory, as shown in FIG. 6A, a chromaticity determination chart 42 can be placed and read, and determination can be made based on the B channel output. As shown in FIG. 6B, the chart 42 is composed of purple and yellow. The determination result is stored in the nonvolatile memory 13.

  Next, this operation will be described.

  FIG. 7 is a flowchart showing the operation in the factory mode in the inkjet multifunction peripheral 100 of the present embodiment.

  When a specific key operation not disclosed to the user is performed from the operation panel shown in FIG. 2, the operation in the factory mode shown in FIG. 7 is started.

  In S1, a key input is waited. If there is an input, it is determined which process is performed in S2, S4, and S6 according to the input key. If it is LED chromaticity determination, the process proceeds to S3 to perform chromaticity rank determination operation. If another process is performed in S4, the process proceeds to S5, and another corresponding process operation is executed. If it is determined in S6 that the input is an instruction to end the factory mode, the process proceeds to the end of the factory mode.

  Next, the LED chromaticity determination operation will be described.

  FIG. 8 is a diagram illustrating a chromaticity rank determination operation.

  When the control proceeds to S3, the process waits for a start key in S11 shown in FIG. At this time, the operator of the factory places the chromaticity determination chart 42 against the housing as shown in FIG. 6 and presses the start key. Thereby, it progresses to S12 and turns on the left power white LED33.

  In S13, the carriage unit 32 is moved so as to read a position at a predetermined distance from the abutting position of the housing, and is read. Since the chart is placed at the reading position, the purple color of the chart 42 is read. Further, the carriage unit 32 is moved by a predetermined amount and read, and the yellow portion of the chart 42 is read.

  Next, in S14, the chromaticity rank of the power white LED 33 is determined. In S <b> 14, the read luminance data of the B channel in the vicinity of position A in FIG. 6 among the read data is averaged, and the chromaticity is determined from the read luminance data and stored in the nonvolatile memory 13.

  When this determination is made, as described above, the B channel output read from the purple and yellow charts is compared with a predetermined value. For example, if the result of reading the purple chart is determined in three stages and the result of reading the yellow chart is determined in four stages, the chromaticity can be determined in a total of 12 ranks.

  In S15, the left power white LED 33 is turned off, and the right power white LED 34 is turned on. In S16, as in S13, the purple portion and the yellow portion of the chart 42 are sequentially read. In S17, the chromaticity rank of the power white LED 34 is determined. In S17, the read luminance data of the B channel near the B position shown in FIG. 6 among the read data is averaged, and the chromaticity is determined from the read luminance data and stored in the nonvolatile memory 13.

  As described above, the chromaticity rank of each of the two LEDs can be determined in the nonvolatile memory 13 at the time of factory shipment, and the determination result can be stored in the nonvolatile memory 13.

  Next, the reading operation of the inkjet multifunction peripheral 100 will be described.

  FIG. 9 is a diagram illustrating the color correction unit 14.

  The color correction unit 14 converts device RGB (device-dependent RGB color space) into standard RGB. Specifically, the device RGB on the RAM 3 is converted into standard RGB and written back on the RAM 3. . That is, the device RGB is specifically an output signal from each of the RGB sensors of the scanner. If the illumination, filter density, sensor sensitivity, and the like are examined in detail for each model, there is variation for each device, that is, for each device. This variation is directly expressed. For this reason, even RGB signals obtained by reading the same document vary from one device to another. If this individuality is removed and the same original is read, the standard RGB is corrected so that the same RGB signal is obtained.

The device RGB image data read by the scanner is read from the RAM 3 and transferred to the input buffer 52 via the system bus 10 and the internal bus 51 shown in FIG. The input buffer 52 is configured by a FIFO or the like. This transfer is performed as the DMA controller 4 operates in response to the trigger of the timing control unit 54. The device RGB data transferred to the input buffer 52 is sent simultaneously to the color converters 53R and 53L. Outputs of the color conversion units 53R and 53L are sent to weighted average units 57R, 57G, and 57B provided for each RGB color, and outputs of 53R and 53L are weighted averaged here and transferred to the output buffer 58. Is done. The output buffer 58 is configured by a FIFO or the like. The output of the output buffer 58 is transferred to the RAM 3 under the control of the DMA controller 4 like the input.

  In the weighted average process, the weight generation unit 55 generates a ratio between the color conversion units 53R and 53L. That is, for example, in FIG. 13, if it is 13- (2) and 13- (3), the leftmost illumination light is weighted 60% for LED-L and 40% for LED-R. . In the rightmost illumination light, LED-L is 20% weighted and LED-R is 80% weighted. At this rate, it is considered that the color gradually changes from the left end to the right end. This ratio is expressed as a weight.

  Specifically, the weight information of all the pixels is stored in advance in the local memory 56 connected to the weight generation unit 55. The weight generation unit 55 reads the weight from the local memory 56 and supplies it to the weighted average units 57R, 57G, and 57B.

  In this way, the color correction unit 14 performs two types of color conversion on the device RGB on the RAM 3, and writes back the result of weighted averaging on the RAM 3 as standard RGB.

  The color converters 53R and 53L and the local memory 56 can be accessed from the CPU 1 via the system bus 10 and the internal bus 51. Therefore, the CPU 1 can set the color conversion parameters in the color conversion units 53R and 53L. Furthermore, weights corresponding to all pixels can be written in the local memory 56.

  The above description is the description of the configuration of the color correction unit 14.

  Next, the operation of the color correction unit 14 in the copy operation will be described.

  FIG. 10 is a flowchart showing the copy operation.

When the user performs a copy start operation via the operation unit 6, the control shifts to S21. In S21, a shading operation is performed. The “shading operation” is an operation of moving the carriage to a position for reading the white reference plate 43 and reading it. Read data including non-uniform characteristics of CCD and light source is acquired and stored as reference data. At the time of reading, the calculation of “read CCD output / CCD output at white reference reading” is performed for each pixel, and the calculation result is the luminance of the original surface from which the non-uniform characteristics are removed.

  In S22, only the left LED is turned on, and in S23, the white reference plate is read and the waveform of one main scanning line is acquired in the same manner as during shading.

  In S24, only the right LED is lit, and in S25, the white reference plate is read and the waveform of one main scanning line is acquired in the same manner as during shading.

  In S26, the weight is calculated. First, a weight is calculated for the R component. For the nth pixel, the following calculation is performed using the luminance when the left is lit (luminance Ln) and the luminance when the right is lit (luminance Rn).

Weight n = luminance Ln / (luminance Ln + luminance Rn)
That is, weight = weight on the left side. That is, what is simply described as “weight n” is the weight of the left LED, and the weight of the right LED at the position n is “1−weight n”.

  This is calculated for all pixels and set in the local memory 56 of the color correction unit 14. Similarly, the weights for the G component and the B component are calculated and set in the local memory 56 of the color correction unit 14. Thus, the influence degree of the left LED for each pixel is set as a weight. When a light guide that does not have a difference in color is used as the weight of each color of R, G, and B, for example, the weight of only the G component is calculated and adopted as all the weights of R, G, and B You may do it.

  FIG. 11 is a diagram illustrating weights.

  As shown in FIG. 11, the left weight is larger on the left side and the left weight is gradually smaller toward the right if the light guide is a general light guide that attenuates illumination light as it moves away from the LED.

  In S27, color conversion parameters are set in the color conversion unit 53R and the color conversion unit 53L. A color parameter corresponding to the chromaticity of the right LED is read from the ROM 2 and set in the color converter 53R. A color parameter corresponding to the chromaticity of the left LED is read from the ROM 2 and set in the color conversion unit 53L. Color parameters corresponding to all chromaticity ranks of the white LEDs are stored in the ROM 2 in advance. In the above example, 12 chromaticity ranks are determined. In this case, color parameters corresponding to all 12 ranks are stored in the ROM 2 in advance.

  Next, in S28, a copy operation is performed.

  During the copying operation, the color correction unit 14 operates. At this time, the device RGB is input to both the color conversion units 53L and 53R. If the pixel being processed is strongly illuminated by the left LED, the weight increases, so the weight to the output of the color converter 53L increases, and the weighted average is obtained. On the other hand, if the pixel being processed is strongly illuminated by the right LED, the weight becomes small, so the weight to the output of the color converter 53L becomes small, the weight of the color converter 53R becomes large, and the weight Averaged. If the pixel being processed is equally illuminated by the left and right LEDs, the weight is 0.5, and the outputs of the color converter 53R and the color converter 53L are simply averaged and output.

In this way, color conversion corresponding to the chromaticity of both the left and right LEDs is performed simultaneously, and the results of the two color conversions in the conversion units 53L and 53R are appropriately weighted and averaged for all pixels. On the other hand, appropriate color conversion can be performed. Even if the left and right LEDs have different chromaticities, that is, the illumination light is not uniform within the main scan, proper conversion from the device RGB to the standard RGB can be performed.

In this embodiment, the reading system has two white LEDs. However, the number of white LEDs is not necessarily two. When there are m white LEDs, the LEDs are turned on one by one, the chromaticity is determined for each, and m color conversion units shown in FIG. 9 are provided, and all the m color conversion unit outputs are weighted. Thus, a weighted average may be used. For the weight, m LEDs are sequentially turned on for each pixel, and the brightness of each LED is used. The weight of the kth (k ≦ m) LED in the nth pixel is weight kn = luminance kn / (luminance 1n + luminance 2n +... + Luminance mn)
And However, the luminance on the white reference plate at the nth pixel position when only the kth LED is turned on is defined as luminance kn. Thus, the present invention can also be applied to a scanner using m white LEDs.

  The scanned image converted into standard RGB is converted into CMYK density by the recording unit 7 at the time of copying, for example, and converted into ink dot information, and is configured as an image on the paper surface.

It should be noted that, in the above-described embodiment, when each means and process are replaced, an embodiment of the method is obtained.

1 is a block diagram of an inkjet multifunction peripheral 100 that is Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating an appearance of an operation unit 6 of the inkjet multifunction peripheral 100. FIG. 2 is a diagram illustrating a configuration of a scanner of the inkjet multifunction peripheral 100. FIG. It is a figure which shows the relationship between a purple chart and the wavelength of blue LED. It is a figure which shows the relationship between a yellow chart and the wavelength of blue LED. It is a figure which shows a reading part and a chart. 3 is a flowchart illustrating an operation in a factory mode in the inkjet multifunction peripheral 100 of the present embodiment. It is a figure which shows chromaticity rank determination operation | movement. FIG. 3 is a diagram illustrating a color correction unit 14. It is a figure which shows copy operation | movement. It is a figure which shows a weight. It is a figure which shows the chromaticity dispersion | variation of white LED on an xy chromaticity diagram. It is a figure which shows the influence of LED on either side.

Explanation of symbols

1 ... CPU,
2 ... ROM,
3 ... RAM,
6 ... operation part,
7 ... Recording part,
8: Reading unit,
10 ... System bus,
11 ... card slot,
12 ... USB I / F,
13 ... Non-volatile memory,
14 ... color correction unit,
21 ... LCD,
22 ... Menu key,
23 ... Start key,
24 ... cancel key,
25 ... Enter key,
26 ... Cursor keys,
27 ... Mode key,
31. Document glass,
32 ... Carriage unit,
33, 34 ... Power white LED,
35 ... light guide,
36-38 ... Mirror,
39 ... Lens,
40 ... CCD,
41 ... substrate,
42 ... chart,
43 ... White reference plate ,
44. Scanner housing,
51. Internal bus,
52 ... Input buffer,
53R, 53L ... color conversion unit,
54 ... Timing control unit,
55 ... a weight generation unit,
56 ... Local memory,
57R, 57G, 57B ... weighted average part,
58 ... output buffer,
59 ... Internal bus.

Claims (5)

A plurality of white light sources associated with each chromaticity information;
A color line sensor for reading a document illuminated by the plurality of white light sources;
A color conversion unit that converts the color space of the output signal from the color line sensor into a standard color space according to the chromaticity of each of the white light sources, and the same number of color conversion units as the plurality of white light sources;
A weighted average unit that performs a weighted average of the outputs from the plurality of color conversion units for each pixel of the color line sensor according to a light amount ratio from the plurality of white light sources;
An image reading apparatus comprising:   The plurality of white light sources are composed of a plurality of white LEDs, and the light quantity ratio is acquired based on a luminance signal obtained by individually lighting the plurality of white LEDs and reading a white reference plate with the color line sensor. The image reading apparatus according to claim 1.   The chromaticity of the white light source is divided into a plurality of ranks according to the position on the chromaticity diagram, and information on the chromaticity indicating which rank of the light sources is mounted as the plurality of light sources. The image reading apparatus according to claim 1, further comprising: a first memory that stores the rank of the image. A second memory for storing a conversion parameter of the color conversion unit corresponding to each chromaticity of the plurality of ranks;
The plurality of color conversion units read conversion parameters corresponding to the rank stored in the first memory from the second memory and set them as conversion parameters for the conversion. The image reading apparatus according to 3. A color line sensor reading a document illuminated with a plurality of white light sources associated with each chromaticity information;
Converting the color space of the output signal from the color line sensor into a standard color space according to the respective chromaticities of the white light source using the same number of color conversion units as the white light source ;
A step of weighted averaging the outputs from the plurality of color conversion units for each pixel of the color line sensor according to a light amount ratio from the plurality of white light sources;
An image reading apparatus control method comprising:

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