JP2994427B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that reads an image with a color image sensor and converts the image into an electric signal.

[Conventional technology]

Conventional full-color reading systems of this type include a light source switching system, a prism separation system, a color filter switching system, an on-chip color filter system, and the like. On-chip color filters in terms of high-speed reading and color separation accuracy are available. The scheme seems to be optimal.

FIG. 7 shows a conventional color CC of an on-chip color filter system.
4 shows a configuration example of a D linear image sensor. This conventional color CCD linear image sensor 700 is composed of a plurality of color CCDs (charge coupled devices) using on-wafer color filters.
This is a color contact type CCD linear image sensor in which chips are arranged in a staggered manner as shown in this figure, for example, five color CCD image sensors (chips) 701 to 705 are arranged.

FIG. 8 shows a circuit configuration example of each chip of the color CCD linear image sensor 700 described above. Photodiode section 801
Between the horizontal CCD register 810 and seven horizontal line shift gates # 1 to # 7 (802 to 808) are disposed as analog memories. The line shift gates 802 to 808 are used to correct a spatial shift between the chips and align output signals of the chips on the same line. The number of effective pixels of this chip is 2928 bits (976 bits x 3
Color), the pixel size is 63.5 μm × 20 μm, and a resolution of 400 dots / inch can be obtained by reading at the same magnification.

The horizontal CCD register 810 is driven by two-phase clocks φ _1A and φ _2A , and one electrode at the last stage of the horizontal CCD register 810 is independently driven for high-speed transfer. The output signal OS of the chip is output through a source follower amplifier (amplifier) 811. OD is the barrier electrode 812, storage electrode 813,
And a power supply terminal for applying a bias to the source follower amplifier 811 and the like.RS is a reset clock terminal for resetting the residual charge after reading the output signal OS.
_{V1 to} φ _V7 are line shift gates # 1 to # 7 (802 to 808)
, And SH is a shift pulse terminal for transferring the charge accumulated in the shift gate 809 to the horizontal CCD register 810.

FIG. 9 schematically shows the appearance of the pixels of the above color CCD linear image sensor. These pixels have a sequential arrangement of G (green), B (blue), and R (red), and in order to minimize the dead zone in each color, each pixel is inclined by 45 °, thereby generating moire fringes. Is suppressed.

[Problems to be solved by the invention]

However, in the above-described conventional example, pixels having a sequential arrangement of G, B, and R color filters are provided, and electric charges accumulated in each pixel are transferred by a single horizontal CCD register. If the transfer efficiency of the CCD register is low, there is a problem to be solved that color mixing occurs between the color signals. In addition, even when the transfer efficiency of the horizontal CCD register is high to some extent, as the number of transfer stages of the horizontal CCD register to be transferred increases, the degree of color mixing between the respective color signals increases. There is a problem to be solved in that a problem of color mixing, which has an extremely small effect on an image, newly occurs.

An object of the present invention is to solve the above-described problems and to provide an image reading device capable of obtaining a higher quality image.

[Means for solving the problem]

In order to achieve the above object, an image reading apparatus according to the present invention includes:
A plurality of color filters for separating light from a subject into a plurality of colors including a first color and a second color; and a photoelectric conversion unit for converting light transmitted through the plurality of color filters into an electric signal;
A first shift register for transferring the signal of the first color from the photoelectric conversion unit to a first output unit; and a second shift register for transferring the signal of the second color from the photoelectric conversion unit to a second output unit. A color linear image sensor comprising: a shift register; and a transfer gate provided between the first shift register and the second shift register.
The signal of the second color is transferred from the photoelectric conversion unit to the second output unit via the first shift register, the transfer gate, and the second shift register, respectively. .

Here, the plurality of color filters may be mixedly formed on at least one photoelectric conversion unit, and may include a shift gate between the photoelectric conversion unit and the shift register.

(Operation)

According to the present invention, a plurality of color filters for separating light from a subject into a plurality of colors including a first color and a second color, and a photoelectric conversion unit for converting light transmitted through the plurality of color filters into an electric signal are provided. A first shift register for transferring the first color signal from the photoelectric conversion unit to the first output unit, and a second shift register for transferring the second color signal from the photoelectric conversion unit to the second output unit. , A color linear image sensor having a transfer gate provided between the first shift register and the second shift register, wherein a signal of a second color is supplied from the photoelectric conversion unit to the first shift register, the transfer gate, and the second shift register. Since the configuration is such that the signals are transferred to the second output unit via the two shift registers, it is possible to eliminate the occurrence of color mixing between the color signals, and to obtain a high-quality image. Further, according to the present invention, it is not necessary to extremely increase the transfer efficiency of the shift register, and the manufacturing cost can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment FIG. 1 shows a circuit configuration of a color CCD linear image sensor of an image reading apparatus according to a first embodiment of the present invention.

In this figure, reference numeral 100 denotes the entire color CCD linear image sensor. A light receiving unit 101 performs photoelectric conversion according to the amount of incident light. In the present embodiment, the light receiving unit 101 includes dummy pixels D _{1 to} D ₆₀ not connected to the CCD shift registers (108 to 113) and a black reference for detecting dark output by shielding the photodiode with an aluminum pattern. Pixel D ₆₁
~ D ₁₅₀ and color filters B, G,
Effective pixel portions (B _{1 to} B ₅₀₀₀ , G _{1 to} G
_5000, and R ₁ to R _5000), and a rear dummy pixel D ₁₅₁ to D ₁₈₀ Prefecture.

Shift gates 102 and 103 transfer the charge accumulated in the light receiving unit 101 to the CCD shift registers 108 to 113 in accordance with the shift gate pulse SH. D of light receiving unit 101
_{3m + 1} , D _{3m + 2} , D _{3m + 3} (where m = 0,2,4,…, 48) and B
Charges accumulated in pixels of _{2n + 1} , G _{2n + 1} , R _{2n + 1} (where n = 0, 1,..., 2499) are transferred by shift gate 103 to CCD shift registers 111, 112, 113 for odd-numbered pixels. You. On the other hand, D _{3m + 1} , D _{3m + 2} , D _{3m + 3} (where m = 1,3,
, 49) and B _2n , G _2n , R _2n (n = 1, 2,..., 2500) are transferred to the CCD shift registers 108, 109, 110 for even-numbered pixels by the shift gate 102.

Reference numerals 104, 105, 106, and 107 denote transfer gates (TR). Of the charges transferred by the shift gates 102 and 103 in response to the transfer gate pulses TR1 and TR2, D _{3m + 1} and D _{3m + 2} (where m = 0, 1,2,…, 49), B _{2n + 1} , G
_{2n + 1} (however, n = 0,1, ... 2499), B _2n , G _2n (where n = 1,
2, ..., 2500) by the CCD shift registers 109,110,
It works to transfer to 112,113.

That is, in the pixel transferred by the shift gate 102, D _{3m + 3} (where m = 1,3, ..., 49) and R _2n (where n = 1,2, ..., 2500) are the CCD shift registers. 108, D _{3m + 2} (m = 1,3,…, 49), G _2m (However,
n = 1, 2,..., 2500) are the CCD shift register 108 and the transfer gate 10 according to the transfer gate pulse TR1.
The data is transferred to the CCD shift register 109 after passing through 4. Further, D _{3m + 1} (where m = 1,3, ..., 49), B _2n (where n = 1,
2, ..., 2500) are CCD shift registers 108,109 and transfer gates according to the transfer gate pulses TR1, TR2.
After passing through 104 and 106, the data is transferred to the CCD shift register 100.

Similarly to the above, in the pixel transferred by the shift gate 103, D _{3m + 3} (where m = 0, 2,... 48), R
_{2n + 1} (where n = 0,1, ..., 2499) is a CCD shift register
111, D _{3m + 2} (m = 0,2,…, 48), G
_{2n + 1} (where n = 0, 1,..., 2499) is transferred to the CCD shift register 112 through the CCD shift register 111 and the transfer gate 105 according to the transfer gate pulse TR1. Furthermore, D _{3m + 1} (where m = 1,2,…, 48), B
_{2n + 1} (where n = 0, 1,..., 2499) is transferred to the CCD shift register 113 through the CCD shift registers 111 and 112 and the transfer gates 105 and 107 according to the transfer gate pulses TR1 and TR2.

The charges sent from the light receiving unit 101 to the CCD shift registers 108 to 113 are transferred by CCD to the output unit (complete transfer), and two-phase driving is performed by driving clocks φ ₁₁ , φ ₂₁ , φ ₁₂ , φ ₂₂ , φ _ABC , φ _DEF Have been. Output gates 114 to 119 serve to send charges from the CCD shift registers 108 to 113 to the floating diffusion regions (output capacitance units) 120 to 125. The floating diffusion regions (output capacitance units) 120 to 125 convert the transferred charges into voltages. Reference numerals 126 to 131 denote source follower amplifiers (amplifiers) which reduce output impedancelessness and prevent noise from being added to output signals.

OSA, OSB, OSC, OSD, OSE, OSF are the odd pixel output signal of B signal, the odd pixel output signal of G signal, the odd pixel output signal of R signal, the even pixel output signal of B signal, and the even signal of G signal, respectively. The pixel output signal is an even pixel output signal of the R signal. RS _ABS and RS _DEF are reset pulses, φ ₁₁ , φ ₂₁ , φ ₁₂ , φ
₂₂ , φ _ABC and φ _DEF are CCD shift register clocks, SH is a shift gate clock, TR1 and TR2 are transfer gate clocks, and OD is a drain. SS is a ground terminal.

FIG. 2 shows the timing of each drive clock in FIG.

In the color CCD linear image sensor 100 configured as described above, the reflected light from the document incident on the light receiving unit 101 is color-separated into three colors of B, G, and R by a color filter on the light receiving unit. Is converted into electric charge proportional to the amount of light in a pixel corresponding to the color filter of FIG. As described above, this charge is generated by the CCD shift registers 108, 109, 110, and by the shift gate pulse SH and the transfer gate pulses TR1 and TR2.
In addition, the data is separately transferred to the CCD shift registers 111, 112, and 113 for each separated color and for each even-numbered pixel and each odd-numbered pixel.

Next, the above-described electric charges transferred separately for each separated color and for each even-numbered pixel and odd-numbered pixel are used as drive clocks φ ₁₁ , φ ₂₁ ,
According to φ ₁₂ , φ ₂₂ , φ _ABC , φ _DEF , at the timing shown in FIG. 2, the data is output bit by bit to the floating diffusion regions 120 to 125 through the output gates 114 to 119, and the charge output is converted into a voltage. Then, the signals are separately output for the separated colors, even pixels, and odd pixels through the source follower amplifiers 126 to 131 and the output terminals (OSA to OSF).

However, regarding the output signals of OSC and OSF, the OSC and OSF are determined by the relationship between the drive clocks φ ₁₁ , φ ₁₂ , φ _ABC and φ ₂₁ , φ ₂₂ , φ _DEF.
The output timing is shifted by one pixel compared to the output signals of A, OSB, OSD, and OSE.

Second Embodiment FIG. 3 shows a circuit configuration of a color CCD linear image sensor of an image reading apparatus according to a second embodiment of the present invention.

This embodiment differs from the first embodiment of the present invention shown in FIG. 1 in the structure of the image reading section, and is different from the conventional color CCD linear image sensor shown in FIG. This is a configuration in which a circuit is added.

That is, in the conventional example, the number of horizontal CCD registers is one, but in the color CCD linear image sensor 300 of the present embodiment, three horizontal CCD registers 312, 313, 314 are provided, one for each color (R, G, B). Provided. In addition, since the number of horizontal CCD registers becomes three, each horizontal CCD register 312,31
Source follower amplifier (amplifier) corresponding to 3,314
26 and 325 are respectively connected, and output signals are output to output terminals OSR, OSG, and OSB for each color. Further, similarly to the first embodiment, in the present embodiment, the electric charges for each color accumulated under the photodiode are transferred to the horizontal CCD registers 312, 31 corresponding to each color.
In addition to the shift gate 311, a transfer gate 315 for transferring the G and B color signals to the horizontal CCD registers 313 and 314, and a transfer gate for transferring the B color signal to the horizontal CCD register 314. A gate 316 is provided.

Other configurations are the same as those of the conventional example shown in FIG.
1 is a photodiode portion as a light receiving portion, 302 is a barrier electrode, and 303 is a storage electrode.
The charge generated in 01 is stored under the storage electrode 303 through the barrier electrode 302. 304 to 310 are line shift gates # 1 to # 7 as analog memories, and 311 are shift gates. OD is a power supply terminal for applying a bias to the inside of the CCD. φ _1A, φ _2A, φ _2B is a two-phase clocks for driving the horizontal CCD register 312, 313, 314, RS the reset clock for resetting the residual charge after the output signal read, phi _V1 to [phi] _V7
Is a line shift gate pulse for driving the line shift gates # 1 to # 7 (304 to 310), and SH is a shift gate pulse. SS is a grant terminal, and OSB, OSG, and OSR are output terminals corresponding to each color B, G, and R.

FIG. 4 shows the color CCD linear image sensor 300 of FIG.
Shows the timing of each drive clock for driving.

In the color CCD linear image sensor 300, light incident on the light receiving unit (photodiode unit) 310
The color filters are separated into three colors of B, G, and R by the upper color filter, and are converted into charges proportional to the amount of light in the pixels corresponding to the respective color filters. This charge is delay-controlled by the line shift gates # 1 to # 7 (304 to 310) as described above, and is then shifted by a plurality of horizontal CCD registers 312, 313, 31 by the shift gate pulse SH and the transfer gate pulses TR1, TR2.
Separately transferred to 4 for each separation color. Then, this decomposition Color of charge, two-phase clock phi _1A in the horizontal CCD register 312, 313, 314, phi _2A, follow the timing of phi _2B are horizontal transfer me, read one bit output terminal OSR, OSG, from OSB It is.

Third Embodiment FIG. 5 shows a circuit configuration of a color CCD linear image sensor of an image reading apparatus according to a third embodiment of the present invention.

The color CCD linear image sensor 500 of the image reading apparatus according to the present embodiment has two lines, a first light receiving unit 501 in which light receiving units are alternately arranged with B filters and R filters, and a second light receiving unit 502 in which G filters are arranged on the entire surface. It is a configuration, this 2
The color signals of three colors are read by the R, G, B filters on the light receiving units 501, 502 of the line.

The first light receiving unit 501 has 2500 effective B pixels and 2500 effective R colors as effective pixels.
The second light receiving section is composed of 5000 pixels in total.
502 is composed of 5000 pixels of G color, and the two light receiving units 501 and 502 are arranged adjacent to each other and shifted by 1/2 pixel. Therefore, charge transfer of the light receiving units 501 and 502 cannot be performed unless a single-line CCD shift register is used. Therefore, the charge of B and R of the first light receiving portion 501 is transferred to the CCD shift register 505 through the shift gate 503 and the transfer gate 509, and B is transferred to the CCD shift register 506, as shown in FIG. The data is transferred from the registers 505 and 506 to the output unit separately.

On the other hand, the charge of G of the second light receiving unit 502 passes through the shift gate 504 and the transfer gate 510, the even-numbered pixels are transferred to the CCD shift register 508, and the odd-numbered pixels are transferred to the CCD shift register 507. Even and odd pixels are separately transferred to the output unit.

In the output unit, each charge transferred from the CCD shift register is converted into a voltage by the floating diffusion region 511 to 514, the output impedance is lowered by the corresponding source follower amplifier 515 to 518, and the output terminals OSA, OSB, Output to OSC and OSD.

Note that φ ₁₁ and φ ₁₂ and φ ₂₁ and φ ₂₂ are two-phase driving pulses for driving the CCD shift registers 507 and 508 and CCD shift registers 505 and 506, respectively, and φ _AB and φ _CD are high-speed charges at the last stage of the CCD shift register. A high-speed transfer clock for transferring to the floating diffusion regions 511 to 514, RS _AB and RS _CD are reset clocks for resetting residual charges after reading signals from the floating diffusion regions 511 to 514, and SH and TR1 are shift gates 50, respectively.
3,504, a shift gate clock for driving the transfer gates 509, 510, and a transfer gate clock. OD is a power supply terminal for applying a bias to the CCD, SS is a ground terminal, OSA, OSB, OSC, and OSD are G odd-numbered pixel output terminals, G even-numbered pixel output terminals, B output terminals, and R output terminals, respectively. is there.

FIG. 6 shows the color CCD linear image sensor 500 of FIG.
Shows the timing of each drive clock for driving.

In the color CCD linear image sensor 500, light incident on the first and second light receiving units 501 and 502 is converted into B and R in the first light receiving unit 501 and G and G in the second light receiving unit 502 by color filters on the respective light receiving units. Each is color-separated. Then, the color-separated light is converted into a charge proportional to the amount of light in a pixel corresponding to each color filter, and then shifted by a shift gate pulse.
Due to SH and transfer gate pulse TR1, B and R charges become C
The charge of G is transferred to the CD shift registers 506 and 505, and the odd-numbered pixels are transferred to the CCD shift register 508, and the even-numbered pixels are transferred to the CCD shift register 507.

Next, the transferred charges of B, R, and G are horizontally transferred in accordance with the timings of the two-phase clocks φ ₁₁ , φ ₁₂ , φ ₂₁ , φ ₂₂ , φ _AB , φ _CD , and output terminals OSA, OSB, OSC, OSD
Is read for each color.

In the above embodiment, a CCD is used as the photoelectric conversion means. However, the present invention is not limited to this, and can be applied to other solid-state imaging devices. Further, the color filter is not limited to R, G, B, but may be, for example, four colors of Mg, G, Cy, Ye or W, G, Cy, Y
The four colors e may be used.

〔The invention's effect〕

As described above, according to the present invention, it is possible to eliminate the occurrence of color mixture between color signals, and to obtain a high-quality image. Further, according to the present invention, it is not necessary to extremely increase the transfer efficiency of the shift register, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a color CCD linear image sensor according to a first embodiment of the present invention, FIG. 2 is a diagram showing operation timing of the circuit of FIG. 1, and FIG. FIG. 4 is a diagram showing a circuit configuration of a color CCD linear image sensor according to an embodiment of the present invention; FIG. 4 is a diagram showing operation timing of the circuit of FIG. 3; FIG. 6 is a diagram showing an operation timing of the circuit of FIG. 5, FIG. 7 is a diagram showing an example of a circuit configuration of a color CCD linear image sensor in a conventional image reading apparatus, and FIG. FIG. 7 is a diagram showing a configuration of a chip of the color CCD linear image sensor of FIG. 7, and FIG. 9 is an enlarged view showing an external shape of a pixel of the color CCD linear image sensor chip of FIG. 100 color CCD linear image sensor 101 light receiving unit 102,103 shift gate 104,105,106,107 transfer gate (TR) 108,109,110,111,112,113 CCD shift register 114,115,116,117,118,119 output gate 120,121,122,123,124,125 floating diffusion area 126, 127, 128, 129, 130, 131 source follower amplifier, 312, 313, 314 horizontal CCD register, 315, 316 transfer gate, 325, 326, 327 source follower amplifier, 501 first light receiving section, 502 second light receiving section, 503, 504 shift gate, 505, 506, 507, 508 … CCD shift register, 509,510… Transfer gate, 516-518… Source follower amplifier.

Claims (2)

(57) [Claims] A plurality of color filters for separating light from a subject into a plurality of colors including a first color and a second color; and a photoelectric conversion unit for converting light transmitted through the plurality of color filters into an electric signal. Means, a first shift register for transferring the signal of the first color from the photoelectric conversion unit to a first output unit, and a unit for transferring the signal of the second color from the photoelectric conversion unit to a second output unit. A color linear image sensor comprising: a second shift register; a transfer gate provided between the first shift register and the second shift register; and a signal of the second color from the photoelectric conversion unit. Wherein the image data is transferred to the second output unit via the first shift register, the transfer gate, and the second shift register, respectively. 2. The apparatus according to claim 1, wherein said plurality of color filters are formed by being mounted on at least one photoelectric conversion means, and have a shift gate between said photoelectric conversion means and said shift register. The image reading device according to claim 1.