JPH0454061A - Image reading device - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the S/N due to the reduction in the size of a picture element in the main scanning direction by using a picture element corresponding to a 3rd filter, a picture element corresponding to a 1st filter at the same position of the 3rd filter in the main scanning direction and a picture element corresponding to the 2nd filter adjacent to the former picture elements as one picture element. CONSTITUTION:A 1st sensor having a 1st filter B and a 2nd filter R and a 2nd sensor having a 3rd filter L different from the filters are arranged in parallel on a photoelectric conversion section. The photoelectric conversion means on which the 1st sensor having the 1st filter B and the 2nd filter R and the 2nd sensor having the 3rd filter L different from the 1st and 2nd filters are arranged in parallel uses a 1st picture element corresponding to the 3rd filter, a 2nd picture element corresponding to the 1st filter on the same position with the 3rd filter in the main scanning direction and a 3rd picture element corresponding to the 2nd filter adjacent to the 2nd picture element to form one picture element and to read picture information thereby applying prescribed signal processing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that reads image information using a plurality of lines of image sensors and performs signal processing.

[Prior art] Conventionally, as an image sensor that reads color image information, ■ It has multiple color filters (R/G-B filters) in the main scanning direction, and when reading image information, it is dot-sequential from the image sensor. One configured to output as a color signal, ■ Equipped with a multiple line (R-G-83 line) image sensor with different color filters in the sub-scanning direction, and when reading image information, each line's image sensor may be A configuration is used in which the R-G-B signals are output in the main scanning direction as the same time-base signal, and in the sub-scanning direction, reading and positioning is performed using a line buffer memory or the like.

[Problems to be Solved by the Invention] However, among the conventional examples described above, in an image sensor having a plurality of different color filters in the main scanning direction, one pixel signal is composed of pixel signals corresponding to each color filter. Therefore, when high-resolution reading is aimed at, the pixel size in the main scanning direction must be reduced, which reduces the aperture area and reduces the S/N ratio of the output signal. This problem becomes even more pronounced when high-speed reading is performed.

In addition, among the conventional examples mentioned above, in the case of a multi-line type image sensor having a plurality of different color filters in the sub-scanning direction, when reading color image information, a small amount of image information (three lines are required), This method not only increases the cost of the sensor, but also requires multiple stages of line buffer memory to align each color signal in the sub-scanning direction, leading to an increase in the cost of the entire device.

SUMMARY OF THE INVENTION Therefore, in view of the above points, an object of the present invention is to provide an image reading device that does not cause deterioration of the S/N ratio of an output signal due to a reduction in the aperture area of a sensor (and can be constructed at a low cost). It's about doing.

[Means for Solving the Problems] An image reading device according to the present invention includes a first sensor having first and second filters, and a third filter having a third filter different from the first and second filters. a photoelectric conversion means in which two sensors are arranged in parallel, a first pixel corresponding to the third filter, and a first pixel corresponding to the first filter located at the same position in the main scanning direction as the third filter. A second pixel and a third pixel adjacent to the second pixel corresponding to the second filter form one pixel, and are equipped with signal processing means for reading image information and performing predetermined signal processing. be.

[Function] According to the present invention, an image sensor is provided in which a sensor having first and second filters on a photoelectric conversion section and a sensor having a third filter different from the above filter are arranged in parallel. However, the pixel corresponding to the third filter, the pixel corresponding to the first filter located at the same position in the main scanning direction, and the pixel corresponding to the second filter adjacent to that pixel are treated as one pixel, and the image is By reading information and performing signal processing, the pixel density of the sensor with the third filter is twice that of the sensor with the first and second filters, and the number of lines in the sub-scanning direction is 2.
You can get away with just a line.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color image reading device to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 1 shows an example of a signal processing block included in a color image reading device according to this embodiment.

FIG. 2 shows the filter arrangement when the sensor 6 shown in FIG. 1 is viewed from above. As shown in FIG. 2, a first filter (B) and a second filter (R) are placed on the photoelectric conversion section.
A first sensor having a filter (L) and a second sensor having a third filter (L) different from the filter described above are arranged in parallel.

As is clear from FIGS. 1 and 2, the present embodiment includes a first sensor having first and second filters, and a second sensor having a third filter different from the first and second filters. a photoelectric conversion means in which the sensor is arranged in parallel;
A first pixel corresponding to the third filter, a second pixel corresponding to the first filter located at the same position in the main scanning direction as the third filter, and a second pixel adjacent to the second pixel.
The third pixel corresponding to the filter forms one pixel, reads image information, and performs predetermined signal processing. Here, the pixel dimensions of the first sensor and the second sensor in the main scanning direction are the same.

Further, in addition to using a blue (B) filter as the first filter, a red (R) filter as the second filter, and an all-wavelength transmission filter as the third filter, Blue (B) as a filter
) as the second filter, red (R
) as the third filter, green (
It is also possible to use the filter of G).

FIG. 3 shows a detailed configuration of the analog signal processing circuit shown in FIG. 1. Further, FIG. 4 is a waveform diagram showing the operation of FIG. 3.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 to 4.

The document is first illuminated by an exposure lamp (not shown);
The reflected light is separated into colors for each image and read by a color reading sensor 6 in the document scanning unit 3, and amplified to a predetermined level by an amplifier circuit (preamplifier) 8. Here, 7 is a CCD driver that supplies a pulse signal to drive the color reading sensor 6, and the necessary pulse source is the system control bulb generator 17.
is generated.

A color signal 502 and a luminance signal 503 are independently outputted from the sensor 6 in synchronization with the drive pulse, each amplified to a predetermined voltage value by an independent amplifier circuit (preamplifier) 8, and then sent to the video via coaxial cables 504 and 505. It is input to the processing unit 4.

The color signal and brightness signal (color signal and brightness signal obtained by reading the original in the main scanning direction) input to the video processing unit 4 are input to the analog signal processing circuit 9 (see FIG. 3), respectively. That is, the color signal 5iGC is input to the buffer 19 and impedance-converted. Next, the output signal of the buffer 19 is processed by an S/H (sample/hold) circuit 2o, in which the reset portion of the composite signal is removed according to the S/H pulse, and the S/HB output signal is obtained by removing waveform distortion caused by high-speed driving. (S/H0UT in Figure 3). Since the R signal is the same as the B signal processing system, the B signal system will be explained here.

The S/H B signal contains unnecessary components at the frequency of the sampling pulse, so in order to remove them,
Next, the signal is input to a low pass filter (LPF) 21. The B signal from which unnecessary sampling frequency components have been removed is sent to amplifier 2.
2 and is amplified to a specified signal output, at the same time, the DC level fluctuation of the analog color signal whose DC level fluctuates in an AC manner is removed, and the DC level of the image signal is fixed at the optimum operating point of the amplifier 22. Therefore, it is clamped to zero level by the feedback clamp circuit 23.

The feedback clamp circuit 23 is composed of an S/H circuit 23a and a comparison amplifier 23b, and the output level of the dark output portion (optical black) of the B signal output from the amplifier 22 is detected by the S/H circuit 23a.
It is input to the inverting input terminal of the comparison amplifier 23b. G
It is compared with the ND (ground) level, and the difference is fed back to the amplifier 22, so that the dark output portion of the output of the amplifier 22 is always fixed at the ground level. here,
This is a signal indicating the section of the dark output part of the DK double signal analog color signal, and by supplying it to the S/H circuit 23a, the B
The DC level of the dark output portion of the signal is detected once during the horizontal scanning period (IH). Further, this zero clamp circuit also has the purpose of eliminating the disturbance of the voltage control amplifier circuit (VCA) 24 in the next stage.

The signal whose dark output part of the B signal is zero-clamped is then applied to the VC
It is input to A24. Here, gain adjustment is performed under CPU control. Data is set in the D/A converter 25 via the data bus 524 of the CPU. D/A
The conversion output V6ut is ■. ut=-Vrec+/
N (0<N<1)
becomes. where N is the binary fractional value of the input digital code.

FIG. 5 shows D/A set data and gain characteristics. The VCA 24 shown in FIG. 3 is a VCA with a multiplier configuration,
Control voltage■. The gain is controlled by ut.

A/ when the original scanning unit 3 reads the uniform white plate
D so that the D conversion output data becomes a predetermined value.
The data of the /A converter 25 is set via the data bus 524 of the CPU, and the level of the B signal is amplified. Next, the B signal is input to the amplifier 26, and the feedback clamp circuit 28 clamps the dark output portion to the output voltage value of the multiplier 32.

As shown in FIG. 6(A), the multiplier 32 includes a multiplying D/A converter 550, operational amplifiers 552, 556, resistors 553, 554 with a resistance value of R, and a resistor 55 with a resistance value of 2R.
It is a multiplier in all four quadrant modes consisting of 5 and 5.
According to 8-bit digital data set by the CPU, bipolar voltages are output as shown in FIG. 6(B).

The buffer 27 is a large-power buffer for the A/D converter 29, and has a low output impedance so that its output impedance is less than the reference resistance value of the A/D internal comparator that guarantees the linearity accuracy of the A/D converter. and is configured as a high-speed buffer.

The B signal amplified and DC-clamped to predetermined white and black levels is input to the A/D converter 29 and becomes digital data B A/D OUT. It is input to a latch circuit 30 for digital data transmission. The latch output data latched by the clock signal 0LACHCLK is output to 0LACHCLK by the next stage digital signal processing circuit lO.
By being latched with a latch clock of opposite polarity, digital data can be received with reliable timing.

The same applies to analog signal processing circuits for R signals and luminance (L) signals. Here, as for color signals, as shown in FIG. 4, the same color signal is processed for two pixels at a time, and the luminance signal is processed for one pixel at a time.

Digitally converted B, R, L signals 506.507.5
08 is input to the digital signal processing circuit IO, and the decoder 13 converts the B and H color signals and luminance signals into RG and B signals.

Next, each R-G-B digital color signal is subjected to black correction/
It is input to the white correction circuit 14. First, the black correction circuit will be explained.

When the amount of light input to the sensor is small, the black level output varies greatly between chips and pixels. If this is output as is and an image is output, streaks and unevenness will occur in the data portion of the image. Therefore, it is necessary to correct the output variation of this black part. In this embodiment, prior to the copying operation, the document scanning unit 3 is moved to the position of a black plate with uniform density located in the non-image area at the tip of the document table, and the halogen lamp (
(not shown) is turned on, and a black level image signal is input to this circuit. One line of this image data is stored in the black level memory and becomes the black reference value (hereinafter referred to as black reference value import mode).

When reading an image, for example, in the case of a blue signal, B, n (i) - DK (i) = black level data DK (i)
A black correction output is obtained as B and t(i) (black correction mode). green mouth. Similar control is performed for red R1H and black correction output G0. .

It becomes Rout.

Next, a white level correction (shading correction) circuit will be explained.

White level correction is to correct variations in sensitivity of the illumination system, optical system, and sensor based on white data obtained when the document scanning unit 3 is moved to the position of a uniform white plate and irradiated. The basic circuit configuration is the same as that of the black correction circuit, but the difference is that black correction uses a subtracter, whereas white correction uses a multiplier. During white correction, first, when the original scanning unit 3 is at the uniform white plate position (home position), that is, before copying or reading, the exposure lamp is turned on and one line of uniformly white level image data is Store in white level memory.

If the white board data of the i-th pixel is W(i), then this W(
For i), the read value o of the normal image of the i-th pixel
+n(t), the corrected image data is Dout(i
)"D+n(i)XFFH/W(i), and white correction is performed for each color of green (G), blue (B), and red (R).

Three-color image signal 512 that has been subjected to black correction and white correction
514 is then input to the image processing circuit 15, which processes the logarithmic conversion circuit for converting the luminance data into density data, the spectral characteristic correction of the color separation filter of the sensor, and the color toner transferred to the transfer paper in the color printer 2. (Y, M,
C) Color correction circuit (input masking/output masking) that corrects unnecessary absorption characteristics, each color component image data Y
,,M,,C,byM,,(Y,,M,,C,) (
The minimum value of Y, , M, , C) is calculated, this is used as a smear (black), and a black toner is added later. The image is processed through a color removal (UCR) circuit (51 in Figure 1).
5).

The three color image signals then enter the printer interface circuit 15. In addition to the digital video signal, the interface signals include a synchronization signal (I
TOP), synchronization signal (BD) in the raster scan direction (main scan direction) that occurs once per raster scan
, synchronous clock signal (VCLK) for sending the digital video signal to the color printer unit 2, synchronous signal (H3YNC) generated in synchronization with jitter-free VCLK based on the BD double signal, half-duplex bidirectional Consists of signals for serial communication (SRCOM). Image information and instructions are sent from the league section to the printer section through these signal lines, and the printer section sends printer status information (for example, if there is a jam).

(information such as no paper, weight, etc.) is exchanged.

Next, other embodiments will be described.

In the embodiments described so far, it has been explained that color image signal processing is performed, but in the case of the second embodiment, in which a document containing only black and white images is read, a sensor with a color filter is not used. By using only a sensor having an all-wavelength transmitting filter, there is no need to interpolate color signals using adjacent pixels, and high-resolution black-and-white image reading becomes possible.

In the case of reading density, the 1-line sensor configuration suppresses deterioration of the S/N ratio due to the reduction in pixel size in the main scanning direction, and the 3-line sensor configuration requires less line buffer memory for aligning each color signal in the sub-scanning direction ( In addition,
For the luminance signal, the pixel density is twice that of the color signal,
By performing adjacent interpolation on color signals that do not significantly affect the resolution, the cost of the apparatus can be reduced, thereby making it possible to achieve higher resolution through signal processing.

[Effect of the Invention 1 According to the present invention, the first . The image sensor includes a sensor having a second filter and a sensor having a third filter different from the above filter arranged in parallel, and a pixel corresponding to the third filter, a pixel corresponding to the third filter, and a sensor having a third filter different from the above filter. A pixel corresponding to a first filter located at the same position in the scanning direction and a pixel corresponding to a second filter adjacent to that pixel are read as one pixel, and a predetermined signal processing is performed. Because there is, it is the same

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a digital color copying machine according to an embodiment of the present invention, FIG. 2 is a diagram showing the arrangement of filters on the top surface of the sensor in an embodiment of the present invention, and FIG. A block diagram showing the details of the analog signal processing circuit 9 shown in FIG. 1, FIG. 4 is a waveform diagram showing the signal timing of each part in FIG. 3, FIG. This figure is a diagram showing the circuit configuration of the multiplier 32 shown in FIG. 3 and its code. 3... Original scanning unit, 4... Video processing unit, 6... Sensor, 9... Analog signal processing circuit, 10... Digital signal processing circuit. ΦΦ DA de throat 9-ノ勺小F disorder] Qi? 7 (S533

Claims (1)

[Claims] 1) a first sensor having first and second filters;
a photoelectric conversion means in which a second sensor having a third filter different from the first and second filters is arranged in parallel; a first pixel corresponding to the third filter; and the third filter. and a second pixel corresponding to the first filter located at the same position in the main scanning direction, and a second pixel adjacent to the second pixel.
1. An image reading device comprising a signal processing means for reading image information by forming one picture element with a third pixel corresponding to a filter, and performing predetermined signal processing. 2) The image reading device according to claim 1, wherein the first sensor and the second sensor have the same pixel size in the main scanning direction. 3) In the image reading device according to claim 1, a blue (B) filter is used as the first filter, a red (R) filter is used as the second filter, and a red (R) filter is used as the third filter. An image reading device characterized by using a wavelength-transmitting filter. 4) In the image reading device according to claim 1, the first filter is a blue (B) filter, the second filter is a red (R) filter, and the third filter is a green filter. An image reading device characterized by using the filter of (G).