JPS649787B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image reading method and apparatus for photoelectrically reading a color image of a document, which is used in a facsimile machine or the like.

[Prior art]

A method that has attracted attention in recent years as a method for photoelectrically reading color images of originals is a method that uses multiple light sources with different spectral characteristics to flash each light source in sequence in synchronization with the original reading scan cycle of an image sensor. By sequentially focusing light on an image sensor, multiple types of photoelectric conversion signals corresponding to the number of light sources are obtained for the same scanning line of the document, and then the reading scanning is performed based on the levels of these photoelectric conversion signals. There is a method of determining the image color in the relevant scanning line of the document. less than,
This color image reading method will be specifically explained with reference to FIGS. 1 to 3.

Here, as an example, two fluorescent lamps, a blue fluorescent lamp and a red fluorescent lamp, are used as the light source to produce "blue",
A method and apparatus for reading three types of color images: "red" and "black" are shown.

That is, in FIG. 1, 1 is a blue fluorescent lamp, 2 is a blue fluorescent lamp,
are red fluorescent lamps, and when these fluorescent lamps are turned on by a lighting circuit (not shown), a blue light signal BC is emitted from the blue fluorescent lamp 1, and a red light signal RC is emitted from the red fluorescent lamp 2. Each light is emitted so as to irradiate the same part (line) of the original MS. Further, the reflected light from the original MS is transmitted through the lens 3, for example.
An image is formed on an image sensor 4 made of a CCD (charge coupled device) line sensor, and converted by the image sensor 4 into an electrical signal (photoelectric conversion signal CE) having an electrical level corresponding to the amount of light. Note that, as the phosphor of the blue fluorescent lamp 1, for example, calcium tungstate is used, and as the phosphor of the red fluorescent lamp 2, for example, magnesium germanate is used. The spectral characteristics of the blue fluorescent lamp 1 and the red fluorescent lamp 2 are shown in FIG.

Now, in this color image reading method, the original MS
When reading the color image described above, the blue fluorescent lamp 1 and the red fluorescent lamp 2 are connected to the image sensor 4.
The light is sequentially blinked in synchronization with the reading scanning period and the feeding of the original MS, and the reading scanning is performed twice on the same line of the original MS, once when the blue light signal BC is irradiated and when the red light signal RC is irradiated. . FIG. 3 is a timing chart showing this driving mode, and FIG. 3a shows the reading and scanning mode of the document MS by the image sensor 4 described above, and FIG. 3b shows the generation mode of the blue light signal BC, that is, the blue fluorescent lamp. 1, FIG. 3c shows the generation mode of the red light signal RC, that is, the blinking mode of the red fluorescent lamp 2, and FIG. 3d shows the photoelectric conversion output from the image sensor 4 in response to the same reading scan. In the mode of the signal CE, in particular, as an example, the first line of the original MS read and scanned by the image sensor 4 is a blue image (line), and the second line is a red image (line). The changes in each case are shown.

That is, suppose that the first line is entirely blue and the second line is entirely red, during the first scan of the first line of the document MS (from time t ₁ to time t ₂ ), the third
Assuming that the blue light signal BC is irradiated as shown in Figure b, the reflected light at this time at the same scanning time (the maximum reflected light is obtained under the same conditions, and this is conveniently referred to as 100% reflected light) ) is accumulated in the image sensor (CCD line sensor) 4, and in the next scanning period (time _t2 to time _t3 ), this accumulated charge is converted into a photoelectric conversion signal CE.
is output from the image sensor 4 as (third
(see figure d). Furthermore, during the scanning period from time _t2 to time _t3 , that is, the second scanning period for the first line of the original MS, the blue light signal BC disappears as shown in FIGS. 3b and 3c. Instead, a red light signal RC is emitted, but the red light signal RC at this time is almost absorbed by the blue image of the first line of the original (see FIG. 2). Therefore, the reflected light at this time is small, and the photoelectric conversion signal CE output from the image sensor 4 in the next scanning period (time _t3 to time _t4 ) is also small as shown in FIG. 3d. Become. Furthermore, in the scanning period for the second line of the original MS (from time _t4 to time _t5 and from time _t5 to time _t6 ), since this second line is completely red, the photovoltaic signal under the same irradiation conditions as above is The output mode of the converted signal CE is also exactly the opposite due to the above-mentioned reason. (See Figure 3d). In addition, the third
Although not shown in the figure, when the image sensor 4 scans the entire white line of the document MS, the reading is approximately 100% over the two scans even under the above irradiation conditions. Since reflected light is obtained, the photoelectric conversion signal CE also becomes a high-level signal corresponding to 100% reflected light over two scanning times.
When the image is applied to an all-black line, both the blue light signal BC and the red light signal RC are absorbed by this black image. The photoelectric conversion signal CE remains at a slight level over two scanning times.

In the color discrimination circuit 5 shown in FIG.
In effect, the above-described level determination of the photoelectric conversion signal CE is carried out, for example, by sequentially determining the image color of the read and scanned document MS based on a combination of its change modes.

[Problems with conventional technology]

As mentioned above, if a color image reading method is adopted in which multiple light sources with different spectral characteristics are sequentially blinked, the configuration of the optical system in the device will certainly be simplified and the reading accuracy will be improved, but on the other hand, the light source Inconveniences also arise, such as the reading speed being limited by its own blinking response characteristics.

For example, in the above example, the red-emitting phosphor (e.g., magnesium germanate) used in the red fluorescent lamp 2 is different from the blue-emitting phosphor (e.g., calcium tungstate) used in the blue fluorescent lamp 1. In comparison, the blinking response characteristics are generally poor and the afterglow time is long (about 2 msec). Therefore, when the red fluorescent lamp 2 is blinked, the red light signal RC becomes a light signal with a slow response as shown in _FIG .
The above-described reading scan cannot be performed during the afterglow time period (shaded area in the figure) at time t ₄ and from time t ₆ to time t ₇ . For this reason, various countermeasures have been taken in the past, such as using the above-mentioned afterglow time period as the period for feeding the document MS, but this still effectively limits the document reading speed, and in the end, Application to aircraft was in doubt.

[Purpose of the invention]

An object of the present invention is to provide a color image reading device that can read documents at high speed by eliminating the drawbacks of the above-described method of reading color images based on blinking of a plurality of light sources with different spectral characteristics. purpose.

[Structure of the invention]

In the present invention, when reading and scanning a document having a color image, an optical color filter is disposed between at least one of a plurality of light sources and the document, so that light irradiated from the light source to the document is provided. The illumination of the original is made to have a predetermined spectral characteristic different from that of the light irradiated from other light sources, and is made to blink at a predetermined period corresponding to the reading scanning period by at least one image sensor of the plurality of light sources. The same scanned portion is irradiated with light at least twice, and the image color of the scanned document is determined based on the level of the photoelectric conversion signal output from the image sensor.

In this way, by using an optical color filter to set the spectral characteristics of the light source, it is possible to improve the blinking response characteristics caused by using a special phosphor such as magnesium germanate (red-emitting phosphor) in the light source. The deterioration is effectively eliminated, and the document reading speed of the image sensor is no longer limited by the blinking response characteristics of the light source. Further, there is no need to use special fluorescent lamps each having different spectral characteristics as the plurality of light sources.

〔Example〕

FIG. 4 shows an embodiment of a color image reading device according to the present invention.

In this embodiment, two natural white fluorescent lamps are used as the light source, and one of them is provided with a red-transmissive optical color filter (colored glass filter) to display "red", "black", and "white" lights. It is assumed that three types of color images are to be read.

That is, in FIG. 4, 10 and 20 are white fluorescent lamps (hereinafter simply referred to as fluorescent lamps), and 6 is the red transmission type color filter, and the fluorescent lamp 10 is turned on by driving the lighting circuit 12. Then, the original MS is irradiated with a natural white light signal WC, and when the fluorescent lamp 20 is turned on by driving the lighting circuit 22, the original MS is irradiated with a red light signal RC. It should be noted that these optical signals WC and RC are emitted so as to respectively irradiate the same part (line) of the original MS, and that the reflected light from the original MS is transmitted through the lens 3 to an image sensor 4 consisting of, for example, a CCD line sensor. As in the case of the device shown in FIG. 1, the image is formed into an image and converted by the image sensor 4 into an electrical signal (photoelectric conversion signal CE) having an electrical level corresponding to the amount of light. .

However, the driving of the lighting circuit 12 is controlled by the lighting control section 11, and the driving of the lighting circuit 22 is controlled by the lighting control section 21. Of these, the lighting control section 11 controls the lighting control section 11 based on the scan start signal SS output from the image sensor drive circuit 40 when the image sensor drive circuit 40 instructs the image sensor 4 to start reading scan for each line. The driving mode of the lighting circuit 12 is controlled so that the fluorescent lamp 10 repeats blinking in synchronization with the document reading scan period by the image sensor 4, and the other lighting control section 21 controls, for example, when starting document reading (not shown) The original is printed after the button is operated.
Based on the drive signal DS, which remains at the active level until the entire reading of the original MS is completed, the fluorescent light 20 is turned on and off from the original document based on the drive signal DS, which can indicate that at least the start button has been operated and that all reading of the original MS has been completed. The driving mode of the lighting circuit 22 is controlled so that the lighting is maintained during the entire reading scanning period of the MS. Note that the image sensor drive circuit 40 generates the above-mentioned scan start signal based on the drive signal DS.
This is a well-known circuit that supplies SS and an image signal clock CLK corresponding to the image signal bits in one scanning line to the image sensor 4, and essentially controls the document reading and scanning operation by the image sensor 4.

By using such a device, the original MS
When reading the image, the image surface of this document MS is irradiated with light using only the red light signal RC, and
The light irradiation by the mixed light of the red light signal RC and the natural white light signal WC is alternately repeated in synchronization with the reading scanning period of the image sensor 4. For reference, the spectral distribution of each of these irradiated lights is shown in FIG.

That is, FIG. 5a is a spectral distribution diagram of a natural white fluorescent lamp, and this light, that is, a natural white light signal WC.
contains about 30% of the total components, which are red components with wavelengths of 600 nm or more. FIG. 5b is a spectral distribution diagram when the same natural white fluorescent lamp is applied with a red transmission type color filter 6, and this light, that is, the red light signal RC has almost a red component. FIG. 5c is a spectral distribution diagram when the natural white light signal WC and the red light signal RC are combined, and the above-mentioned red component of this mixed light is about 50% of the total components.

In the image sensor 4, two reading scans are performed for each line to be read of the original MS based on two types of light irradiation: only the red light signal RC and the mixed light.

FIG. 6 is a timing chart showing this driving mode, and the color image reading operation in this embodiment will be explained below with reference to this timing chart. However, in FIG. 6, FIG. 6a shows how the image sensor 4 reads and scans the original MS, FIG. 6b shows how the natural white light signal WC is generated, and FIG. 6c shows the red light signal RC. The mode of occurrence of
FIG. 6d shows the form of the photoelectric conversion signal CE output from the image sensor 4 in response to the reading scan, and in particular, as an example, the first line of the document MS read and scanned by the image sensor 4 is The second line is an all-white image (line), the third line is an all-cyan image (line), and the fourth line is an all-red image (line). The changes in the case of heat are shown respectively.

In other words, if the first line is completely white and the second line is completely white,
During the first scan (from time t ₁ to time t ₂ ) of the first line of the original MS, where the lines are all black, the third line is all cyan, and the fourth line is all red, the lines shown in FIGS. 6b and c Natural white light signal WC as shown in
If mixed light of RC and red light signal RC is irradiated, the charge for the reflected light at this time (100% reflected light) is accumulated in the image sensor 4 during the same scanning time, and the charge is accumulated in the image sensor 4 in the next scanning period (time t ₂ ~ time
At t ₃ ), this accumulated charge is output from the image sensor 4 as a photoelectric conversion signal CE (see FIG. 6d). Furthermore, during the scanning period from time _t2 to time _t3 , that is, the second scanning period for the first line of the same document MS, the natural white light signal WC disappears as shown in FIGS. 6b and 6c. Only the red light signal RC is irradiated, but since the line is completely white, it is 100% irradiated even during this scanning time.
Charges corresponding to the reflected light are accumulated in the image sensor 4, and in the next scanning period (time _t3 to time _t4 ), the accumulated charges are outputted from the image sensor 4 as a photoelectric conversion signal CE (sixth (see figure d).
That is, when the scanning line is completely white, the photoelectric conversion signal CE also becomes a high level signal corresponding to 100% reflected light over two scanning times. In addition, in the scanning period for the second line of the same document MS (time t ₃ to time t ₄ and time t ₄ to time t ₅ ), since this second line is completely black, the irradiation light to this image is Even if it is the above-mentioned mixed light or the red light signal RC, it is absorbed both, and in the end, the photoelectric conversion signal CE at this time is transmitted over two scanning times, contrary to the time of reading the first line. The signal is at a very low level. Next, in the first scan (time t ₅ to time t ₆ ) of the third line of the original document MS, which is assumed to be all cyan, the above-mentioned mixed light is irradiated. In this case, approximately 50% reflected light (hereinafter referred to as 50% reflected light for convenience) is obtained from the cyan image, which is approximately half of the 100% reflected light mentioned above, and a charge corresponding to this amount of light is obtained. is accumulated in the image sensor 4. This accumulated charge is outputted from the image sensor 4 as a photoelectric conversion signal CE having an intermediate level in the next scanning period (time _t6 to time _t7 ) (see FIG. 6d). Also,
During the scanning period from time _t6 to time _t7 , that is, the second scanning period for the third line of the original MS, only the red light signal RC is irradiated, but since the line is entirely cyan, Most of this irradiated light is absorbed, and eventually the photoelectric conversion signal at this time
CE will be at a slight level. That is, if the scan line is all cyan, it is a "natural white light signal".
When light irradiation is performed in the order of "mixed light of WC and red light signal RC" → "red light signal RC only", the photoelectric conversion signal CE is 1 as shown in Figure 6d.
The period corresponding to the second scanning cycle is an intermediate level corresponding to 50% reflected light, and the period corresponding to the second scanning cycle is a slight level. And then,
When the above-mentioned mixed light is irradiated during the first scan (time t ₇ - time t ₈ ) on the 4th line of the same document MS, which is assumed to be completely red, the 100% reflected light from the red image is reflected. 50% reflected light, which is about half of that, is obtained (see FIG. 5c), and a charge corresponding to this amount of light is accumulated in the image sensor 4. This accumulated charge is also transferred to the next scanning period (time t ₈ to time t ₉ ).
is output from the image sensor 4 as a photoelectric conversion signal CE having an intermediate level. Also, this time
The scanning period from t ₈ to time t ₉ , that is, the same original
In the second scanning period for the fourth line of MS, only the red light signal RC is irradiated. In this case, of course, 100% reflected light is obtained, so in the next scanning cycle (time _t9 to time _t10 ), a photoelectric conversion signal CE of a high level corresponding to this 100% reflected light is output from the image sensor 4. be done. That is, if the scanning line is entirely red and the "natural white light signal WC
"Mixed light with red light signal RC" → "Red light signal RC
When light irradiation is performed in the order of ``only'', the photoelectric conversion signal CE is at an intermediate level corresponding to 50% reflected light during the period corresponding to the first scanning cycle, as shown in Fig. 6d; The period corresponding to the second scanning cycle becomes a large level corresponding to 100% reflected light.

In this way, the photoelectric conversion signal CE obtained by the same embodiment takes on the above-described specific characteristic form, depending on the image color of the read image.

When the correspondence relationship between the form of this photoelectric conversion signal CE and the image color of the read image is graphed, a color distribution diagram as shown in FIG. 7 is obtained.

That is, in FIG. 7, the abscissa is the ratio level of the photoelectric conversion signal CE when irradiated with "mixed light of the natural white light signal WC and the red light signal RC",
The ordinate is the ratio level of the photoelectric conversion signal CE when irradiated with "red light signal RC only",
The area where these two ratio levels intersect represents the image color of the read image. For example, if the ratio level (abscissa) of the photoelectric conversion signal CE when irradiated with the above-mentioned "mixed light" is 50%, the photoelectric conversion when irradiated with the above-mentioned "red light signal RC only" is 50%. Ratio level of signal CE (ordinate)
When is 100% (corresponding to point A in the figure), this image color cannot be anything other than "red". Of course, this amount of drying coincides with the result from time t ₈ to time t ₁₀ in FIG. 6d. This is the ratio level of the photoelectric conversion signal CE when light is irradiated with the above-mentioned "mixed light" and the ratio of the photoelectric conversion signal CE when light is irradiated with the above-mentioned "red light signal RC only". If it can be determined, the target image color (here "red")
``black'' and ``cyan'') are all clearly distinguished.

An example of this electrical processing method will be explained with reference to FIG. 4 again.

Photoelectric conversion signal output from image sensor 4
CE is A/D (analog/digital) conversion circuit 5
1 is input. The A/D conversion circuit 51 determines the level of the input analog signal in synchronization with the image signal clock CLK output from the image sensor drive circuit 40, and generates a digital signal indicating a value corresponding to the relative analog level of this signal. The photoelectric conversion signal CE is successively converted through this A/D conversion circuit 51 into a digital signal (hereinafter referred to as the encoded photoelectric conversion signal DCE) indicating a value corresponding to the ratio level described above. Ru.

This encoded photoelectric conversion signal DCE is then input to the switch circuit 52. The switch circuit 52 is a circuit that distributes input signals in synchronization with the document reading scan period by the image sensor 4 described above based on the scan start signal SS output from the image sensor drive circuit 40. The encoded signal of the photoelectric conversion signal CE (hereinafter referred to as the first encoded photoelectric conversion signal DCE1) formed corresponding to the first scanning cycle for the same reading level among the encoded photoelectric conversion signals DCE is transmitted to the same switch. It is distributed to the output terminal T1 side of the circuit 52 and added to the line memory 53, and also the above-mentioned 2
The encoded signal of the photoelectric conversion signal CE formed corresponding to the second scanning cycle (hereinafter referred to as the second encoded photoelectric conversion signal DCE2) is transmitted to the same switch circuit 52.
Assume that the data is distributed to the output terminal T2 side of the computer and directly added to the color information memory 54 consisting of a ROM (read only memory). Here, the line memory 53 is a memory having a capacity corresponding to the number of pixels for one scanning line, and the first encoded photoelectric conversion signal DCE1 added to this line memory 53 is transmitted every signal corresponding to each pixel. The color information is sequentially shifted and added to the color information memory 54 after being delayed by exactly one scanning period. That is, the first encoded photoelectric conversion signal regarding the same reading line of the original MS
The DCE1 and the second encoded photoelectric conversion signal DCE2 are simultaneously added to the color information memory 54 for each signal corresponding to the same pixel.

The color information memory 54 stores coded white information WT indicating "white", coded black information BK indicating "black", and coded black information BK indicating "cyan" based on the color distribution shown in FIG. 7, for example. Coded cyan information
CY, and a memory in which coded red information RD indicating "red" are stored in advance, and the two signals added above, the first coded photoelectric conversion signal DCE1 and the second coded photoelectric conversion signal DCE2, are used as address signals. The above encoded color information WT, BK, SY and
It operates to sequentially read out a corresponding one of the RDs. In the example mentioned above, this color information memory 5
4, the address corresponding to point A in FIG. 7, that is, the value indicated by the first encoded photoelectric conversion signal DCE1 is "50", and the second encoded photoelectric conversion signal
Encoded red information RD indicating "red" is stored in advance at an address designated by an address signal whose value indicated by DCE2 is "100", and the coded red information RD indicating "red" is stored in advance. When the applied signal shows the value "50" and the applied signal of the second encoded photoelectric conversion signal DCE2 shows the value "100", this coded red information RD is read out from the memory 54. If the device to which this is applied is, for example, a facsimile device, the read encoded color information is appropriately transmitted to the transmitting device and reproduced by a color printer on the receiver side.

In the explanation regarding FIG. 6 above, in order to facilitate understanding, the image of the target scanning line of the original MS is illustrated as being "all white,""allblack,""allcyan," or "all red." However, in reality, as described in the above processing method, reading and image processing are performed in pixel units corresponding to the cycle of the image signal clock CLK, and the sixth
The photoelectric conversion signal CE shown in FIG. d also takes a complicated form of change depending on the difference in pixel color when the pixel colors of the target scanning line are various colors.

By the way, in the above-mentioned embodiment, the fluorescent lamp 20 on the side where the red transparent color filter 6 is provided
The fluorescent lamps 10 are kept lit and only the other fluorescent lamps 10 are blinked, but instead of this, the fluorescent lamps 10 are kept lit and the fluorescent lamp 20 on the side where the color filter 6 is provided is blinked. Of course, it is also possible to make these two fluorescent lights 10 and 20 blink alternately. In other words, in this invention, since the spectral characteristics of the light source are set using an optical color filter in principle, the afterglow time of the irradiated light is not required regardless of the spectral characteristics of the irradiated light. Therefore, the selection of the flashing fluorescent lamp does not limit the document reading speed of the image sensor 4. Of course, if the lighting mode of the fluorescent lamps 10 and 20 is changed as described above, the variation mode of the photoelectric conversion signal CE shown in FIG. 6d and the color distribution mode shown in FIG. 7 will also change. However, the photoelectric conversion signal CE still changes in a regular manner for each color to be discriminated, and color discrimination can be effectively performed based on this combination of electrical levels. That is, in the color discrimination circuit 50 shown in FIG. 4, the storage position of each color information in the color information memory 54 is set so as to correspond to the color distribution formed based on the above-mentioned regular variation pattern of the photoelectric conversion signal CE. Just change it.

In addition, in the above embodiment, two natural white fluorescent lamps are used as the light source, and one of them is provided with a red-transmissive color filter to produce three types of colors: "red,""black," and "cyan." We have shown a device for reading images (in practice, "white" is a blank and is not included in the image), but the number of these light sources,
The number of color filters, the selection of target transmission colors of the color filters, and the selection of image colors to be read (discriminated) are not limited at all, and can be arbitrarily determined depending on the actual situation. In particular, when reading the three types of color images mentioned above, it is possible to distinguish between the same color images by installing a cyan transmission type color filter on the other light source of the light source equipped with the red transmission type color filter. will also become more clear. In the first place, the image color to be read is incidentally selected based on the selection of a color filter, and in the color image reading device according to the present invention, color filters having slightly different light wavelength transmission characteristics are appropriately used. If this is done, this separation can be effectively performed even for color images with slightly different colors. Note that colors other than the above that are usually considered to be used as the image colors to be read include "green,""blue,""magenta," and "yellow." Of course, if you use three light sources such as the above-mentioned light source equipped with a red transmission type color filter, a light source equipped with a blue transmission type color filter, and a light source equipped with a green transmission type color filter, the so-called so-called Multi-color reading (discrimination) is also possible. In other words, in this case, the image sensor scans the same part of the document three times, and in synchronization with this scanning cycle, two of the three light sources are scanned each time.
All you have to do is make one or all of them blink.
Note that the lighting order of the light sources is arbitrary as long as the periodicity is not impaired. For example, in the case of the embodiment described above, 1 for the same line of the image sensor 4
At the time of the second reading scan, only the fluorescent lamp 20 is turned on to irradiate light with "red light signal RC only",
During the second reading scan, the fluorescent lamps 10 and 20 or only the fluorescent lamps 10 are turned on and the "red light signal RC" is turned on.
Light irradiation may be performed using a mixture of light and natural white light signal WC or only natural white light signal WC.

Further, in the above embodiment, a CCD line sensor is used as the image sensor 4, but this selection is also arbitrary, and any sensor may be used as long as it is a photoelectric conversion sensor used for so-called document reading scanning.

〔Effect of the invention〕

According to the color image reading device according to the present invention, 1. Color images can be read at high speed.

2. There is no need to use a special fluorescent lamp as a light source.

3 Subtle color separation is possible simply by using different optical color filters.

You can obtain many excellent effects such as.

In this device, if the sole purpose is to increase the color image reading speed, there is nothing in this invention that uses a blue fluorescent lamp or a green fluorescent lamp, which have relatively excellent blinking response characteristics, as the light source. Don't deviate from the purpose. That is, in this case, an optical color filter is used for the purpose of producing only the color emitted by a color fluorescent lamp with poor blinking response characteristics, such as a red fluorescent lamp.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the schematic configuration of an example of a conventional color image reading device, Fig. 2 is a diagram showing the spectral characteristics of a blue fluorescent lamp and a red fluorescent lamp, and Fig. 3 is similar to Fig. 1. A timing chart showing a conventional color image reading method using the shown device;
FIG. 4 is a block diagram showing an embodiment of the color image reading device according to the present invention, FIG. 5 is a diagram showing the spectral characteristics of document irradiation light used in the embodiment shown in FIG. 4, and FIG. This figure is a timing chart showing an example of a color image reading operation of the embodiment shown in FIG. 4, and FIG. 7 is a color distribution diagram obtained by the embodiment shown in FIG. 4. 3... Lens, 4... Image sensor, 6... Optical color filter, 10, 20... Fluorescent lamp, 11, 21
...Lighting control unit, 12, 22...Lighting circuit, 40...Image sensor drive circuit, 50...Color discrimination circuit,
51...A/D conversion circuit, 52...Switch circuit, 5
3...Line memory, 54...Color information memory.

Claims (1)

[Scope of Claims] 1. A plurality of light sources for illuminating a document, and a light source disposed between at least one of these light sources and the document, in which light irradiated from the light source to the document is combined with light irradiated from another light source. an optical color filter having different predetermined spectral characteristics; an image sensor arranged to form an image of reflected light from the light irradiated onto the document from the plurality of light sources and reading and scanning an image of the document; a first lighting control means for blinking at least one of the plurality of light sources at a predetermined period corresponding to a period of document reading scanning by the image sensor; A color image reading device comprising: a second lighting control means for keeping the light on during the scanning period; and a determining means for determining the image color of the read and scanned document based on the level of the photoelectric conversion signal output from the image sensor. Device. 2. The image sensor is a sensor configured with a charge storage type photoelectric conversion element, and the predetermined period of blinking control by the lighting control means is synchronized with the charge storage period of this sensor.
The color image reading device described in Section 1. 3. The color image reading device according to claim 1, wherein the optical color filter is any one of a red transmission type, a green transmission type, a blue transmission type, a cyan transmission type, a magenta transmission type, and a yellow transmission type. .