JPH04261258A - Color picture reader - Google Patents

Abstract

PURPOSE:To realize an inexpensive color picture reader with high resolution by forming a green color filter onto CCD elements of the same number as picture elements and forming red, blue filters onto CCD elements whose number is less than the picture elements. CONSTITUTION:Light receiving sections 135-137 in which red, green and blue color filters are respectively formed are provided onto a CCD image sensor. One set of the light receiving sections 135, 136 and one set of the light receiving sections 136, 137 correspond respectively to one picture element and the picture element area and the area of the light receiving section are made coincident. The electric charged generated from the light receiving sections 135, 137 and 136 receiving light is transferred to CCD channels 51, 52 via transfer gates 141, 142. Then an electric signal corresponding to the red blue color filters is subject to interpolation arithmetic calculation by a signal conversion circuit (not shown) and the result is outputted. Through the constitution above, the CCD image sensor with a larger area than that of a conventional light receiving section is used to obtain a same resolution as that for the conventional system.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading device for converting color images into electrical signals.

0002

2. Description of the Related Art FIG. 8 is a block diagram showing a general color image reading device. In the figure, 1 is a sensor substrate, 2 is a lens as an imaging means, 3 is a fluorescent lamp as an illumination means for illuminating an original 4, and 5 is an original table.

In this configuration, an original 4 placed on an original table 5 is illuminated by a fluorescent lamp 3, and an image on the original 4 is formed on a sensor substrate 1 by a lens 2. The sensor board 1, lens 2, and fluorescent lamp 3 move together in the direction of arrow A relative to the document 4 and document table 5, and the image information on the document 4 is converted into electrical signals sequentially for each scanning line. is converted to

FIGS. 9 and 10 are, for example,
184402 and a plan view schematically depicting the periphery of a light receiving section on the sensor substrate 1. FIG. In FIG. 9, 11 is an insulating substrate, and 12 is a CCD image sensor arranged in a straight line on the insulating substrate 11. In FIG. In FIG. 10, 13 is one pixel, 131 to 1
34 is a light receiving section arranged on the CCD image sensor 12. The light receiving section 131 is a light receiving section without a color filter,
The light receiving sections 132, 133, and 134 have yellow, green, and cyan color filters formed on their surfaces, respectively, and the four light receiving sections 131 to 134 correspond to one pixel.

[0005] Furthermore, 141 and 142 are the light receiving section 13.
1 and 132 and the light receiving sections 133 and 134 from the incident light are transferred to the CCD channels 151 and 15.
This is a transfer gate for transferring to 2.

Further, FIG. 11 is a time chart showing the general operation of such a CCD image sensor 12.

Next, the operation of the CCD image sensor 12 will be explained. When the transfer gate 141 is in an off state, light incident on the light receiving sections 131 and 132 is converted into electric charge and accumulated in the light receiving sections 131 and 132. Next, when the transfer gate 141 is turned on, the accumulated charge is transferred to the CCD channel 151. C
There is a potential well (not shown) in the CD channel 151 corresponding to each of the light receiving sections 131 and 132, and by applying two-phase clocks Φ1 and Φ2, the charges transferred from the light receiving sections are The signal is sequentially transferred to the adjacent potential well, and taken out as an analog signal to the outside of the CCD image sensor by a floating diffusion amplifier (not shown) in the final stage. Here, C
The total number of wells existing in the CD channel 151 is defined as the number of stages of the CCD image sensor. In reality, the transfer gate pulse ΦT is input at a period of time TS while continuously applying the two-phase clocks Φ1 and Φ2 (Fig. 11).
. In this case, the charge transferred to the CCD channel 151 by the second transfer gate pulse ΦT is
It is equal to the charge accumulated in the light receiving sections 131 and 132 during S. Therefore, from the floating diffusion amplifier at the final stage of the CCD channel, signals proportional to the amount of light incident on the light receiving section 131 without a color filter and the light receiving section 132 on which a yellow color filter is formed are alternately extracted as time-series signals. Can be done. The other light receiving section 133, 134, transfer gate 142, CCD
The operation of channel 152 is also similar to that described above.

As shown in FIG. 10, the pixel 13 is composed of a plurality (n≧3) of light receiving portions each having a different color filter. Therefore, the light-receiving area of the pixel is n times the area of the unit light-receiving section.

[0009]

[Problem to be Solved by the Invention] In such a color image reading device, improving the resolution, which is a standard for fine line reading accuracy, means reducing the area of the pixel. becomes even smaller. Therefore, high-resolution CCD image sensors require micromanufacturing techniques. Furthermore, since the area of the light receiving section becomes smaller, a highly sensitive CCD image sensor is required. As a result, there was a problem of high cost. Also, CC
Color image reading devices using D image sensors also have the problem of being relatively expensive. Furthermore, reducing the area of the light receiving section increases the number of CCD channels, resulting in a problem that the transfer efficiency of the entire CCD image sensor decreases. Further, even with a reduced-sized CCD image sensor, there is a problem that the chip length is long and the cost is high.

That is, conventional color image reading devices with high resolution reading accuracy have high production costs and C
There was a problem that the overall transfer efficiency of the CD image sensor was low.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a color image reading device that has high resolution, high transfer efficiency, and is inexpensive.

0012

[Means for Solving the Problems] The present invention has been made to achieve the above object, and includes a plurality of light receiving elements that perform photoelectric conversion, and a plurality of types of light receiving elements having different spectral characteristics formed on the light receiving elements. A color filter, an illumination means for illuminating the document, an imaging means for forming an image of the document on the light receiving element, and a signal conversion means for converting the electric signal from the light receiving element into a three primary color signal. , in the color image reading device that decomposes one scanning line of the document into a plurality of pixels and outputs a color signal for each pixel, a first color filter is formed on the same number of light receiving elements as the number of pixels;
Color filters other than the first color filter are formed on each of the light receiving elements smaller than the number of pixels, and the signal conversion means converts an electrical signal corresponding to the color filter other than the first color filter. , the configuration is a means for performing interpolation calculations.

[0013] According to a second aspect of the present invention, a first light receiving element row in which the first color filter is green and the color filter is formed, and a second light receiving element row in which red and blue color filters are formed are arranged alternately. The structure has a light-receiving element array. Image reading device.

In claim 3, the signal converting means is connected to a first latch to which electrical signals from the light receiving element in which color filters other than the first color filter are formed are sequentially input, and the first latch. a second latch, an adder/divider receiving the electrical signal and the output of the second latch;
The configuration includes a first output terminal for taking out the output of the first latch to the outside, and a second output terminal for taking out the output of the adder/divider to the outside.

[0015]

[Operation] In this invention, since the area of the pixel and the area of the light-receiving part match, the light-receiving part having an area n times that of the light-receiving part in the conventional example can have the same resolution as the conventional example, improving the resolution. Even if this is done, the number of stages of light receiving elements will be equal to the total number of pixels.

[0016]

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, 13 is one pixel, and 135 to 1
37 is a light receiving section disposed on the CCD image sensor 12. The light receiving sections 135, 136, and 137 are light receiving sections each having red, green, and blue color filters formed on their surfaces. A set of light receiving sections 135 and 136, light receiving section 136,
One set of 137 corresponds to one pixel. Also, 14
1 and 142 are light receiving sections 135, 137 and light receiving section 1
36 is a transfer gate for transferring charges generated by the incident to the CCD channels 151 and 152.

FIG. 2 is a time chart showing the setting of the accumulation time of each column for the two light receiving sections shown in FIG. FIG. 3 is a graph showing the positional relationship between the original 4 and each light receiving section row.

FIG. 4 shows a block that performs signal processing for each light receiving section in a row of light receiving sections in which different color filters are alternately formed as shown in FIG. This signal processing section is
A plurality of units, for example, two sets of latches 611 and 612, one adder/divider 62, one input terminal 63, and two output terminals 641.
, 642. One input terminal 63 is directly connected to the input terminal of the latch 611 and also to the input terminal of the adder/divider 62 . An output terminal of latch 611 is connected to an output terminal 641 and an input terminal of adder/divider 62. An output terminal of the adder/divider 62 is connected to an output terminal 642.

Next, the operation of this embodiment will be explained. φ1 and φ1 in FIGS. 2A and 2B are two-phase clocks applied to the CCD channels 151 and 152 in FIG.
Continuously applied at all times. φ in FIGS. 2(c) and (d)
TGA and φTGB are transfer gates 14, respectively.
1, 142, and this transfer gate pulse φTGA, φT
The cycles TSA and TSB of GB are the accumulation time.

In FIG. 1, if the area below the center line L is the A channel and the area above it is the B channel, it can be said that the storage time of the A channel is TSA and the storage time of the B channel is TSB. Period TSA in this example,
Although the TSBs are equal, the start times of each channel differ by TD. Therefore, the output signals DA, DB from each channel are the transfer gate pulse φ
Immediately after TGA and φTGB are applied, DA is applied in the order of A1g, A2g, A3g, etc., and DB is applied in the order of A1r, A2b, A3r, A.
4b... are output in the order shown in (e) and (f) of FIG.

Next, the relationship between the reading positions of each light-receiving array of the image sensor in this embodiment will be explained. Figure 3
P indicates the position (in the sub-scanning direction) of the document where the A-channel and B-channel light-receiving sections of the color image reading device are located with respect to time, and P is the sub-scanning pitch. Assume that at time t0 shown in FIG. 3, the A channel light receiving section 136 is at position y0, and the B channel light receiving sections 135 and 137 are at position y0-(P/2). In the color image reading device, each light receiving section 135 to 1
37 moves relative to the document 4. S1 in FIG. 3 shows the moving state of the light receiving section 136 of the A channel, and S2 shows the moving state of the light receiving sections 135 and 137 of the B channel. Assuming that the accumulation starts from time t0, the accumulation time TSA
The light incident on the light receiving section 136 of the A channel during this period is the reflected light of the image of the portion from y0 to y0 +P on the fourth surface of the document. At this time, if the difference TD between the A channel's accumulation start time and the B channel's accumulation start time is (TSA/2), then FIG.
As is clear from the above, the B channel also photoelectrically converts the reflected light of the image of the portion from y0 to y0 +P on the fourth side of the document, which is the same as the A channel. In this way, by making the start times of the accumulation times of the respective light receiving section rows different from each other, the plurality of light receiving sections can read images at the same position in the sub-scanning direction.

Next, the operation of the signal processing section of this embodiment will be explained with reference to the time chart of FIG. The input terminal 63 of the signal processing section 6 receives the signals of the light receiving sections 135 and 137 in which alternately different color filters of the B channel are formed, so the time chart of the input signal DIN is as follows...Ri-2, Bi-1, Ri, Bi+1...
(Ri has the meaning of the signal value of the light receiving section in which the red filter of the i-th pixel is formed. The same applies to the others). Output signal DO of output terminal 641
Since UT1 is the output signal of the latch 611, it is a signal delayed by one clock with respect to the input signal DIN. The adder/divider 62 receives both the signal that has passed through the latches 611 and 612, that is, the signal delayed by two clocks with respect to the input signal DIN, and the input signal DIN. Therefore, the output signal DOUT2 of the output terminal 642, which is the output signal of the adder/divider 62, is as shown in FIG.
The time chart will look like the one shown.

Next, the physical meaning of FIG. 5 will be explained with reference to FIG. 6. The output signals DOUT1 and DOUT2 at time t0 in FIG. 5 are Ri and (Bi
−1 +Bi+1 )/2. Bi-1, Bi+
1 is the signal value of the light receiving sections 137 on both sides of the light receiving section 135, as shown in FIG. 6(a). This Bi-1, Bi+
Adding 1 and dividing by 2 means finding a value corresponding to the B signal at the position of the central light receiving section 135 ((b) in FIG. 6).

Next, the relationship between the area of the light receiving section and the resolution in this embodiment will be explained with reference to FIG. The pixel 13 of the color image reading device in this embodiment is shown in FIG.
), the area of the pixel and the area of the light receiving section match. This means that the resolution is determined by the area of only one light receiving section, and it is possible to have the same resolution as the conventional example with a light receiving section that is n times the area of the conventional light receiving section. .

Furthermore, since the A channel of the CCD image sensor is composed of a light receiving section with the same green color filter formed on its surface, each pixel receives a G signal corresponding to a luminance signal in the form of raw data. include.

Next, the relationship between the area of the light receiving section and the transfer efficiency in this embodiment will be described. As shown in FIG. 7B, the area of the pixel 13 and the area of the light receiving portion match. This shows that even if the resolution is improved, the number of stages of the CCD image sensor is equal to the total number of pixels. This means that the same resolution can be achieved with 1/n the number of stages of the conventional CCD image sensor.

In the above embodiment, the shape of the light receiving portion is rectangular, but the shape of the light receiving portion may be a parallelogram. Further, although the case where the storage times TSA and TSB of each channel are equal is shown, they may be different times. Further, although an example has been shown in which the color filters are arranged alternately, the arrangement is not limited to this example. Further, although an example of a CCD image sensor with two light receiving sections has been shown, it may be one row.

[0028]

Effects of the Invention As explained above, in this invention, the area of one pixel is equal to the area of one light-receiving section, so that a CCD with an area n times that of the conventional light-receiving section can be used to obtain the same resolution as the conventional one. It is possible to use an image sensor and obtain a color image reading device that is cheaper than conventional ones.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the vicinity of a light receiving section of a CCD image sensor according to an embodiment of the present invention.

FIG. 2 is a time chart showing a method of driving the CCD image sensor.

FIG. 3 is a diagram showing the relationship between each channel and a document in the above embodiment.

FIG. 4 is a block diagram of a signal processing section in the above embodiment.

FIG. 5 is a time chart of the signal processing section.

FIG. 6 is a diagram for explaining the physical meaning of the signal processing section.

FIG. 7 is an explanatory diagram of pixels in the above embodiment.

FIG. 8 is a diagram showing the main parts of a general color image reading device.

FIG. 9 is a diagram showing a sensor board.

FIG. 10 is a plan view showing the vicinity of a light receiving section of a CCD image sensor in a conventional example.

FIG. 11: CC in a conventional color image reading device
3 is a time chart showing a method of driving a D image sensor.

[Explanation of symbols]

1 Sensor board 2 Lens ３　　　　　　　　　　　Fluorescent lamp 4 Manuscript 5　　　　　　　　　　Manuscript table 6 Signal processing section 13 pixels 62 Adder/divider 135-137 Light receiving part 611, 612 latch 641, 642 Output terminal

Claims (3)

[Claims] [Claim 1] A plurality of light receiving elements that perform photoelectric conversion;
a plurality of types of color filters having mutually different spectral characteristics formed on the light receiving element; an illumination means for illuminating the original;
An image forming means for forming an image of the original on the light receiving element, and a signal converting means for converting the electric signal from the light receiving element into three primary color signals, converting one scanning line of the original into a plurality of pixels. In a color image reading device that decomposes and outputs a color signal pixel by pixel, a first color filter is formed on the light receiving elements of the same number as the above number of pixels, and color filters other than the first color filter are formed on the same number of light receiving elements as the above number of pixels. Each of the light receiving elements is formed on a smaller number of the light receiving elements, and the signal conversion means includes a circuit that performs an interpolation operation from an electric signal corresponding to a color filter other than the first color filter. Color image reading device. 2. A first light-receiving element row in which the first color filter is green and in which the color filter is formed, and a second light-receiving element row in which light-receiving elements in which red and blue color filters are formed are arranged alternately. 2. The color image reading device according to claim 1, further comprising: a color image reading device; 3. The signal converting means includes a first latch to which electrical signals are sequentially inputted from a light receiving element in which a color filter other than the first color filter is formed, and a second latch connected to the first latch. a second latch, an adder/divider that receives the electric signal and the output of the second latch, a first output terminal that takes out the output of the first latch to the outside, and an adder/divider that receives the output of the first latch; 3. The color image reading device according to claim 1, further comprising a second output terminal that is output to the outside.