JP2004112797A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high quality image with an apparatus of a low cost by performing processing such as dark current correction in real time with a simple circuit configuration. <P>SOLUTION: Sensors 18A and 18B for dark current detection of which photo-detection planes are shielded are provided near photo-detection parts 11A and 11B linearly arraying photo-sensors for photo-detecting image light, electric charges stored in the sensors 18A and 18B for dark current detection are outputted from dummy output parts 15 and 16 as dummy signals, and the dummy signals are subtracted from image signals outputted from image output parts 13 and 14, such that an image signal in which a dark current component is corrected is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus applied to a film scanner, a copying machine, a facsimile machine, and the like.

Conventionally, there are various methods for correcting a dark current in an image signal obtained from a solid-state imaging device such as a CCD. For example, a light receiving surface of a specific photosensor in a photosensor is shielded, and an output of the photosensor is output. The dark current component is stored in the memory, and the dark current component stored in advance is subtracted from the image signal including the dark current component, thereby obtaining an image signal in which the dark current is corrected.

On the other hand, in order to read a color image, some linear sensors are composed of two or more lines provided with different color filters. In this case, sufficient image quality is obtained due to a spatial line shift. I can't. Therefore, conventionally, in order to correct a spatial shift between lines, a digital signal is used to delay an image signal obtained from one line, or a delay line provided outside with an image signal obtained from one line. The image signal is corrected by correcting the spatial deviation between the lines.

However, the conventional dark current correction method needs to capture the dark current in advance, and when correcting the spatial deviation between the lines, it is necessary to use digital processing or an external delay line. There was a problem that the circuit scale became large.

The present invention has been made in view of such circumstances, and can correct dark current and synchronize image signals obtained from each line in real time with a simple circuit. An object of the present invention is to provide an image reading apparatus capable of obtaining the above image.

In order to achieve the above object, the invention according to claim 1 is directed to a light receiving unit in which photosensors for receiving image light are arranged in a line, and charges read from each photosensor arranged in parallel to the light receiving unit. In an image reading apparatus having a transfer unit that transfers and an image output unit that outputs electric charges sequentially sent from the transfer unit as an image signal, a light receiving surface provided adjacent to a position different from the line of the light receiving unit Output from the image output unit, a dark current detection sensor that is shielded from light, a dummy output unit that is different from the image output unit that simultaneously outputs the charge accumulated in the dark current detection sensor as a dummy signal, and the image signal. Subtracting means for subtracting a dummy signal output simultaneously with the image signal from the dummy output unit from the image signal.

That is, a dark current detection sensor having a light receiving surface shielded in the vicinity of the light receiving portion is provided, and the electric charge accumulated in the dark current detecting sensor is output as a dummy signal from the dummy output portion, and the image output portion and the dummy output portion By subtracting between the image signal and the dummy signal that are output simultaneously, the image signal with the dark current corrected can be obtained in real time.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect of the present invention, an electronic shutter for removing a substrate for sweeping out unnecessary charges accumulated in the light receiving unit is provided. This makes it possible to control the accumulation time of charges to be taken out from the light receiving unit.

According to a third aspect of the present invention, there is provided a first light receiving unit in which photosensors that receive image light via a G filter are arranged in one row, and a second row in a row arranged in parallel with the first light receiving unit. A second light receiving section in which photosensors that receive image light via an R filter and photosensors that receive image light via a B filter are alternately arranged; and An analog memory that is arranged in parallel with the light receiving unit and delays charges read from the respective photosensors in correspondence with a spatial line shift between the first and second light receiving units, and a parallel arrangement in the first light receiving unit. A first transfer unit that transfers charges read from the photosensors, a second transfer unit that is arranged in parallel with the analog memory and transfers charges that are input via the analog memory, and the first transfer unit. Charges that are sequentially sent out from the transfer unit An image reading apparatus comprising: a first image output unit that outputs a signal as a signal; and a second image output unit that outputs, as R / B image signals, the charges sequentially sent from the second transfer unit. A dark current detection sensor provided adjacent to a position different from the line of the first and second light receiving portions and having a light receiving surface shielded from light, and charges accumulated in the dark current detection sensor as dummy signals. A dummy output unit different from the first image output unit and the second image output unit that outputs simultaneously with the image signal and the R / B image signal, and the dummy from the G image signal output from the first image output unit A first subtracting means for subtracting a dummy signal output simultaneously with the G image signal from the output unit; and a dummy signal output from the dummy output unit corresponding to the dark current accumulated through the analog memory. An amplifying means for amplifying with a gain; and a second for subtracting a dummy signal output simultaneously with the R / B image signal amplified by the amplifying means from the R / B image signal output from the second image output section. And subtracting means.

That is, two lines of the first light receiving unit and the second light receiving unit are provided, and an analog memory is provided between the second light receiving unit and the second transfer unit in order to synchronize the image signal obtained from each line. Is provided. Then, this analog memory appropriately delays the charge transferred from the second light receiving unit and transfers it to the second transfer unit to correct the spatial deviation between the lines. The charge transferred through the analog memory is deteriorated in S / N by the analog memory, but the analog memory is on the R / B channel side because the S / N of the image quality is influenced by the G channel. To be provided. Also in the case of this two-line image reading apparatus, a dummy that outputs a dummy signal separately from the first image output unit that outputs a G image signal and the second image output unit that outputs an R / B image signal. By providing an output unit and subtracting between the G image signal, R / B image signal and dummy signal output simultaneously from the first and second image output units and the dummy output unit, the dark current is corrected. The obtained G image signal and R / B image signal can be obtained in real time.

According to a fourth aspect of the present invention, in the image reading device according to the third aspect of the present invention, unnecessary charges that are provided between the first and second light receiving units and are accumulated in the first and second light receiving units are swept out. And a shutter drain. That is, a shutter gate and a shutter drain for sweeping out unnecessary charges accumulated in the first and second light receiving portions are provided so that the accumulation time of charges to be taken out from the first and second light receiving portions can be controlled. .

According to a fifth aspect of the present invention, in the image reading device according to the third or fourth aspect, when the image is read by scanning in the direction opposite to the normal scanning direction, the second transfer unit corresponds to one line. Fast transfer in the analog memory when transferring the charge stored in the second light receiving unit to the second transfer unit via the analog memory from the end of transfer to the start of transfer of the next line, It is characterized in that no substantial delay is caused by the analog memory. That is, when reading an image by scanning in the direction opposite to the normal scan direction, the analog memory delays in the direction opposite to the direction in which the spatial deviation of each line is corrected. The charge stored in the second light receiving unit is transferred to the second transfer unit via the analog memory from the end of the transfer of one line in the transfer unit to the start of the transfer of the next line. There is no typical delay.

According to the present invention having the above-described configuration, the dark current detection sensor whose light receiving surface is shielded is provided in the vicinity of the light receiving section, and the electric charge accumulated in the dark current detection sensor is output as a dummy signal, from the image output section. Since the dummy signal is subtracted from the output image signal, the dark current can be corrected with a simple circuit. In addition, the accumulation time of charges to be taken out from the light receiving unit can be controlled.

In addition, when configured with two lines of a G channel light receiving unit and an R / B channel light receiving unit, as a delay means for synchronizing image signals obtained from each line, a light receiving unit on the R / B channel side An analog memory is provided between the transfer unit and the circuit for synchronization can be simplified, and when the image is scanned in the direction opposite to the normal scan direction, the analog memory is used. As a result, the analog memory can be prevented from being substantially delayed, thereby preventing the adverse effect of the analog memory during reverse scanning. It should be noted that the spatial line shift cannot be corrected at the time of reverse scanning, but an index image that does not care about film image shooting conditions and image quality can be obtained.

Hereinafter, preferred embodiments of an image reading apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a principal block diagram showing a first embodiment of an image reading apparatus according to the present invention. The linear sensor 10 shown in the figure is packaged as a single component, and mainly includes light receiving units 11A and 11B, shift registers 12A and 12B, image output units 13 and 14, dummy output units 15 and 16, and analog memories M1 and M2. , A shutter drain 17 and dark current detection sensors 18A and 18B.

The linear sensor 10 is composed of two lines of a G channel and an R / B channel, and the photosensor 11A for the G channel has photosensors that receive image light via a G filter arranged in a row, In the light receiving unit 11B of the B channel, photosensors that receive image light via the R filter and photosensors that receive image light via the B filter are alternately arranged. The photosensors of the light receiving unit 11A and the light receiving unit 11B accumulate an amount of charge corresponding to the intensity of the image light incident on each light receiving surface.

A shutter drain 17 is provided between the light receiving unit 11A and the light receiving unit 11B via a shutter gate SG. The shutter gate SG is driven by a shutter gate pulse (not shown). The charges accumulated in the light receiving unit 11A and the light receiving unit 11B can be swept out to the shutter drain 17. That is, the linear sensor 10 has a so-called electronic shutter function that controls charges accumulated in the light receiving portions 11A and 11B according to the shutter gate pulse.

The space line difference between the light receiving portion 11A and the light receiving portion 11B is two lines in this embodiment because the shutter drain 17 and the like are between them.

On the other hand, a lead-out gate OG is provided between the light receiving unit 11A and the shift register 12A. When a read gate pulse having a one-line cycle is applied to the lead-out gate OG, the charge accumulated in the light receiving unit 11A. Is transferred to the shift register 11A. Similarly, a lead-out gate OG is provided between the light-receiving unit 11B and the analog memory M1, and when a read-gate pulse having a one-line cycle is applied to the lead-out gate OG, the read-out gate OG is accumulated in the light-receiving unit 11B. The charge is transferred to the analog memory M1.

The analog memories M1 and M2 are for correcting the above-described spatial line difference between the light receiving unit 11A and the light receiving unit 11B, and are driven by an analog memory pulse (not shown) having a cycle of one line. The charge obtained from 11B is delayed by two line times and transferred to the shift register 12B.

The charge transferred to the shift register 12A sequentially flows into the floating capacitor 13A of the image output unit 13 by a known register transfer pulse. The preamplifier 13B of the image output unit 13 outputs the voltage of the floating capacitor 13A as a G image signal. The voltage of the floating capacitor 13A is returned to the initial state, and a reset pulse is applied so that a voltage corresponding to the charge of the next pixel can be taken out. The charge transferred from the analog memory M2 to the shift register 12B is transferred to the image output unit 14 by a register transfer pulse, and the image output unit 14 outputs an R / B image signal in the same manner as the image output unit 13. .

On the other hand, the dark current detection sensor 18A is a photosensor equivalent to the photosensor of each pixel of the light receiving unit 11A, and its light receiving surface is shielded from light, and the charges accumulated therein are floating in the dummy output unit 15. It is transferred to the capacitor 15A. The preamplifier 15B of the dummy output unit 15 outputs the voltage of the floating capacitor 15A as a dummy signal indicating the dark current. The dark current detection sensor 18B and the dummy output unit 16 are configured in the same manner as the dark current detection sensor 18A and the dummy output unit 15, respectively.

FIG. 2 is a principal block diagram of a film scanner using the linear sensor 10.

In the figure, a central processing unit (CPU) 30 controls and controls each circuit, and a CCD drive circuit 32 linearly outputs the shutter gate pulse, read gate pulse, analog memory pulse, register transfer pulse, reset pulse, etc. described above. The linear sensor 10 outputs a G image signal and an R / B image signal from the image output units 13 and 14, respectively, and outputs a dummy signal from the dummy output units 15 and 16. When the image is read by scanning in the normal scanning direction (that is, when the image light of a certain line is incident on the light receiving unit 11B first), the R / B image signal is the analog memory M1, Since the signal is delayed via M2, the G image signal and the R / B image signal are synchronized and output from the linear sensor 10.

The G image signal output from the linear sensor 10 is clamped by the CDS clamp 34 and output to the correction circuit 44, the R / B image signal is clamped for each color by the color separation CDS clamp 36, and the B image signal is corrected by the correction circuit 46. The R image signal is output to the correction circuit 48.

The dummy signal output from the dummy output unit 15 of the linear sensor 10 is clamped by the CDS clamp 38 and output to the other input of the correction circuit 46. The dummy signal output from the dummy output unit 16 is the CDS clamp. After being clamped by 40 and then multiplied by a factor of 3 by amplifier 42, it is output to the other inputs of correction circuits 46 and 48. The reason why the dummy signal is amplified three times by the amplifier 42 is that the dark current included in the R / B image signal includes the dark current in the analog memories M1 and M2.

The correction circuits 44, 46 and 48 are each composed of a subtraction circuit, which subtracts a dummy signal from each image signal, and subtracts the subtracted G, B, R image signals (signals corrected for dark current), respectively, as variable amplifiers 50, 52. And 54. Each of the variable amplifiers 50, 52, and 54 is supplied with a gain control signal from the CPU 30, and adjusts the white balance by applying a necessary gain to the input G, B, and R image signals.

The G, B, and R image signals output from the variable amplifiers 50, 52, and 54 are dot-sequentially converted by the multiplexer 56, converted into digital signals by the A / D converter 58, and then added to the image memory 60.

The image memory 60 stores R, G, B image signals for one frame, the stored R, G, B image signals are repeatedly read and converted into analog signals by a D / A converter (not shown). After that, it is converted into an NTSC composite video signal by an encoder and output to a monitor TV (not shown). As a result, the film image can be viewed on the monitor TV.

In order to capture a good image signal, the film is scanned in advance (pre-scan) to detect shooting conditions such as the brightness of each frame of the film, and then scanned again (main scan) according to the shooting conditions. It is necessary to capture an image signal with adjusted exposure and white balance.

Here, if the scanning direction of the film is changed between the pre-scan and the main scan, it is possible to capture an image signal whose exposure is adjusted by reciprocating the film once.

When the scan direction is changed between the pre-scan and the main scan, the normal scan direction described above is the main scan and the opposite direction is the pre-scan. In the pre-scan, the linear sensor 10 in FIG. The image light of the line enters the light receiving unit 11A before the light receiving unit 11B.

Then, when the R / B image signal on the light receiving unit 11B side that is incident later is delayed by the analog memories M1 and M2, the G image signal and the R / B image signal having a spatial line shift are further expanded in time. It will be.

Therefore, at the time of pre-scanning, a substantial delay is not performed by the analog memories M1 and M2. That is, at the time of pre-scanning, the charges stored in the light receiving unit 11B are stored in the analog memories M1 and M2 between the end of the transfer of one line in the shift register 12B and the start of the transfer of the next line. Then, the data is immediately transferred to the shift register 12B. Note that such transfer can be performed by controlling the read gate pulse and the analog memory pulse. In addition, the spatial line shift between the light receiving unit 11A and the light receiving unit 11B cannot be corrected at the time of the pre-scanning. However, in the pre-scanning, an index image that does not care about shooting conditions such as the brightness of the film image or image quality. Therefore, there is no problem due to the spatial line shift.

Incidentally, the charge accumulation time can be controlled by controlling the shutter gate pulse output to the linear sensor 10 during the main scan based on the luminance signal of the image signal obtained during the prescan. Similarly, an average value for each color of the R, G, and B image signals obtained at the prescan is obtained, and the gains of the variable amplifiers 50, 52, and 54 at the main scan are controlled so that these average values are equal. The white balance can be adjusted.

When the scanning operation is not performed, the power consumption can be reduced by stopping the drive system of the linear sensor 10. Further, when the scanning operation is performed from the stopped state, the influence on the image quality can be eliminated by starting the image signal reading after the warm-up driving is performed first. The CPU 30 controls the CCD driving circuit 32 according to the scanning direction, the exposure time, etc., and realizes the driving of the linear sensor 10 suitable for the purpose.

FIG. 3 is a principal block diagram showing a second embodiment of the image reading apparatus according to the present invention. In addition, the same code | symbol is attached | subjected to the part which is common in the linear sensor 10 shown in FIG. 1, and the detailed description is abbreviate | omitted.

The linear sensor 10 shown in FIG. 1 is provided with a shutter gate SG and a shutter drain 17 between the light receiving part 11A and the light receiving part 11B. However, the linear sensor 20 shown in FIG. The light receiving part 11A and the light receiving part 11B are in contact with each other. As a result, the line difference in space between the light receiving unit 11A and the light receiving unit 11B shown in FIG. 3 is one line, and the charge accumulated in the light receiving unit 11B is delayed by one line by one analog memory M to be a shift register. 12B is transferred.

In the present embodiment, the dark current detection sensor and the dummy output unit are provided for each line, but only one of them may be provided. The linear sensor for correcting the dark current in the present invention is not limited to the two-line linear sensor of the above-described embodiment, and can be applied to a one-line linear sensor.

FIG. 1 is a principal block diagram showing a first embodiment of an image reading apparatus according to the present invention. FIG. 2 is a block diagram of a main part of a film scanner using the linear sensor of FIG. FIG. 3 is a principal block diagram showing a second embodiment of the image reading apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20 ... Linear sensor, 11A, 11B ... Light-receiving part, 12A, 12B ... Shift register, 13, 14 ... Image output part, 15, 16 ... Dummy output part, 17 ... Shutter drain, 18A, 18B ... For dark current detection Sensor, M1, M2, M ... Analog memory, 30 ... Central processing unit (CPU), 32 ... CCD drive circuit, 42 ... Amplifier, 44, 46, 48 ... Correction circuit

Claims (5)

A light receiving section in which photosensors that receive image light are arranged in a line, a transfer section that is arranged in parallel with the light receiving section and transfers charges read from each photosensor, and charges that are sequentially sent out from the transfer section. In an image reading apparatus having an image output unit that outputs an image signal,
A dark current detection sensor that is provided adjacent to a position different from the line of the light receiving unit and whose light receiving surface is shielded;
A dummy output unit different from the image output unit that outputs the charge accumulated in the dark current detection sensor as a dummy signal simultaneously with the image signal;
Subtracting means for subtracting a dummy signal output simultaneously with the image signal from the dummy output unit from the image signal output from the image output unit;
Subtracting means to
An image reading apparatus comprising: 2. The image reading apparatus according to claim 1, further comprising an electronic shutter for removing a substrate for sweeping out unnecessary charges accumulated in the light receiving unit. A first light receiving unit in which photosensors that receive image light via a G filter are arranged in one row, and a second light receiving unit in a row arranged in parallel with the first light receiving unit, wherein R A photosensor that receives image light through a filter and a photosensor that receives image light through a B filter, and a photosensor arranged in parallel with the second photoreceiver. An analog memory that delays the electric charge read from the sensor in accordance with a spatial line shift between the first and second light receiving units, and the photosensor that is arranged in parallel with the first light receiving unit. A first transfer unit that transfers the charges, a second transfer unit that is arranged in parallel with the analog memory and transfers charges that are input via the analog memory, and a charge that is sequentially sent from the first transfer unit. First output as G image signals respectively An image reading apparatus comprising an image output unit, and a second image output section for outputting the successively fed out charges from the second transfer unit respectively as R / B image signals,
A dark current detection sensor that is provided adjacent to a position different from the line of the first and second light receiving portions and whose light receiving surface is shielded;
A dummy output unit that is different from the first image output unit and the second image output unit that outputs the charge accumulated in the dark current detection sensor as a dummy signal simultaneously with the G image signal and the R / B image signal;
First subtracting means for subtracting a dummy signal output simultaneously with the G image signal from the dummy output unit from a G image signal output from the first image output unit;
Amplifying means for amplifying the dummy signal output from the dummy output unit with a gain corresponding to the dark current accumulated through the analog memory;
Second subtracting means for subtracting a dummy signal output simultaneously with the R / B image signal amplified by the amplifying means from the R / B image signal output from the second image output section;
An image reading apparatus comprising: 4. The image reading apparatus according to claim 3, wherein a shutter gate and a shutter drain are provided between the first and second light receiving units and sweep out unnecessary charges accumulated in the first and second light receiving units. An image reading apparatus comprising: 5. The image reading apparatus according to claim 3, wherein when reading an image by scanning in a direction opposite to a normal scan direction, the next transfer line starts from the end of transfer of one line in the second transfer unit. When the charge stored in the second light receiving unit by the start of the transfer is transferred to the second transfer unit via the analog memory, the transfer in the analog memory is performed quickly, An image reading apparatus characterized by preventing delay.

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