JP3618372B2 - Imaging device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an image pickup apparatus such as an image scanner that obtains image data using an image pickup device typified by a CCD such as an area sensor and a line sensor.
[0002]
[Prior art]
In general, a CCD imaging device is used in an imaging device such as an image scanner. For example, as shown in FIG. 19, a conventional imaging apparatus has a lens 1 that collects light to form an image, a diaphragm 2 that optimally adjusts the amount of light passing through the lens 1, and imaging light obtained by the lens 1. CCD 3 for converting to an electrical signal, CDS circuit 4 for performing double correlation sampling on the output signal from the CCD 3, A / D converter 5 for converting analog data output from the CDS circuit 4 to digital data, and the converted digital A low-pass filter (LPF) 6 that limits the high-frequency component of data, a process circuit 7 that processes video data that has passed through the LPF 6, a memory 8 that stores data processed by the process circuit 7, and is stored in the memory 8 A timing computer that outputs a drive control signal for driving the personal computer (PC) 9 for processing the data and the CCD 3 It is constituted by a regulator (TG) 10 and the like. Here, the CCD 3 is a line sensor.
[0003]
The schematic configuration of the above-described CCD 3 is the same as that shown in FIG. The CCD 3 includes a light receiving unit 31 that is a photosensor unit in which a plurality of photodiodes (indicated by A, B, C,...) That convert received light into electric signals are arranged in a line, and the photoelectric conversion unit A transfer gate unit 32 that transfers photocharges to a transfer register unit 33, which will be described later, and a transfer register unit 33 that sequentially transfers charges transferred through the transfer gate unit 32 to the output side.
[0004]
Now, when light hits the photodiodes A, B, C, D,... Of the light receiving unit 31, electric charges photoelectrically converted according to the intensity of the light are stored in the storage electrodes (not shown) of the respective photodiodes. Is done. The electric charges accumulated in the light receiving unit 31 are transferred to the transfer register unit 33 through the transfer gate unit 32 controlled by the gate control signal φTG output from the timing generator 10. Thereafter, each time the transfer path driving pulses φS1 and φS2 repeat the inversion operation, the charges in the transfer register unit 33 are sequentially transferred to the output side. When the transfer of the charge in the transfer register unit 33 is completed and the imaging signal received by the light receiving unit 31 is output, the charge of the light receiving unit 31 is prepared for the next light reception by the Vsub signal as an unnecessary charge discharging control signal. Discharged for.
[0005]
The electrical signal output from the CCD 3 in this manner is then processed by each processing circuit as shown in FIG.
[0006]
[Problems to be solved by the invention]
However, since the conventional imaging apparatus requires the LPF 6 for band-limiting the high-frequency component of the A / D converted digital data in hardware, the hardware scale increases and the size can be reduced. There is a problem that there is a disadvantage.
[0007]
In view of such problems of the conventional imaging apparatus, the present invention provides an imaging apparatus that does not require a hardware LPF, does not increase the scale of hardware, and is advantageous in terms of miniaturization. It is the purpose.
[0008]
[Means for Solving the Problems]
The present invention condenses light to form an image, a photosensor unit that photoelectrically converts the light imaged by the lens, and the photoelectrically converted charge that is input via a transfer gate and sequentially transferred. An image sensor having a transfer register unit and a timing generator that outputs a drive control signal for the image sensor. The timing generator transfers the charge of the transfer register unit for a predetermined number of pixels so that the image sensor is subjected to multiple exposure. This is an image pickup apparatus that filters the image pickup signal by the image pickup device by outputting a drive control signal so that the photocharge of the photo sensor portion is input to the transfer register portion each time.
[0009]
[Action]
In the present invention, imaging is performed so that the timing generator inputs the photocharge of the photosensor unit to the transfer register unit every time the charge of the transfer register unit is transferred by a predetermined number of pixels so that the image pickup device performs multiple exposure. An element drive control signal is output. As a result, the charge transferred by the transfer register unit and the photocharge input from the photosensor unit are mixed, and as a result, the same filtering as the low-pass filter is performed on the imaging signal.
[0010]
【Example】
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
[0011]
FIG. 1 is a configuration diagram of an image pickup apparatus according to a first embodiment of the present invention. That is, the imaging device includes a lens 1 that collects light to form an image, a diaphragm 2 that optimally adjusts the amount of light passing through the lens 1, and an imaging device that converts imaging light obtained by the lens 1 into an electrical signal. CCD 3, a CDS circuit 4 that performs double correlation sampling of an output signal from the CCD 3, an A / D converter 5 that converts analog data output from the CDS circuit 4 into digital data, and processing of the converted digital data A process circuit 7 to be performed, a memory 8 for storing data processed by the process circuit 7, a personal computer (PC) 9 for processing data stored in the memory 8, and a timing generator (TG) for driving the CCD 3 10 or the like. The present embodiment is an image pickup apparatus using a film scanner as an example, and the CCD 3 is a line sensor. As is apparent from FIG. 1, the present embodiment does not require the LPF 6 required in the conventional example shown in FIG. 19, and controls the drive control signal of the CCD 3 output from the timing generator 10. The feature of the LPF 6 is that the function of the LPF 6 is performed inside the CCD 3.
[0012]
Next, the operation of the image pickup apparatus of the above embodiment will be described with reference to the drawings.
[0013]
Here, the schematic configuration of the CCD 3 is shown in FIG. 2 as described above. FIG. 3 is a diagram for explaining an example of the drive timing of the CCD 3 in this embodiment. In FIG. 3, the φTG signal is a control pulse (gate control signal) of the transfer gate unit 32, the φS1 signal and the φS2 signal are transfer path drive pulses, and the φTG signal is the light accumulated in the light receiving unit 31 in the [HI] period. The charge is transferred to the transfer register unit 33, and this operation is stopped during the “LO” period. On the other hand, the φS1 signal and the φS2 signal change the charge accumulated in the transfer register unit 33 every time the level is inverted. To the output unit). Further, a Vsub signal as a control signal for discharging unnecessary charges is a generally known vertical control pulse of a photodiode, and this Vsub signal is extracted in the vertical direction which is “HI” and is in the substrate direction. The charge is discharged, and the state is held at “LO”. Also, the timing positions shown from “a” to “g” in FIG. 3 correspond to the times “T = a” to “T = g” shown in FIG. Further, in FIG. 4, A, B, C, D, E, F, G,... In the uppermost stage correspond to the respective photodiodes of the light receiving unit 31 shown in FIG. Each stage up to “= g” indicates the state of the transfer register unit 33 at each time.
[0014]
First, at time “T = a”, the charges accumulated in the photodiodes A, B, C, D,... Are transferred by the transfer gate unit 32 being turned on (the φTG signal is “HI” immediately before). Is transferred to the unit 33 (indicated by A1, B1, C1, D1,...). Next, at “T = b”, since the φS1 signal and the φS2 signal are inverted, the charge of the transfer register 33 is in a state in which one pixel has moved to the right in the drawing. In this state, next, at “T = c”, the φTG signal becomes “HI”, and the charges (A2, B2, C2, D2,...) Accumulated in the photodiodes A, B, C, D,. Are transferred to the transfer register unit 33. As a result, the charges moved earlier and the charges from the respective photodiodes are mixed, and the charges in the transfer register section 33 are A2, A1 + B2, B1 + C2, C1 + D2,.
[0015]
Next, at “T = d”, after the φS1 signal and the φS2 signal are inverted, the φTG signal becomes “HI”, the charges of the transfer register unit 33 move by one pixel, and the photodiodes A, B, Charges stored in C, D,... (Indicated by A 3, B 3, C 3, D 3,...) Are transferred to the transfer register unit 33. As a result, the charges moved earlier and the charges from the respective photodiodes are mixed, and the charges in the transfer register section 33 are A3, A2 + B3, A1 + B2 + C3, B1 + C2 + D3,. Here, the charge of the photodiode is inputted every time the charge of the transfer register section 33 is transferred for one pixel. However, for example, the charge of the photodiode may be inputted every time it is transferred for a plurality of pixels. Good.
[0016]
Thereafter, this operation is repeated in the same manner, and finally the state of “T = g” shown in FIG. 4 is obtained. This gives the same result as that of the circuit configuration shown in FIG. 5 and is equivalent to the basic configuration of the digital filter, whereby the effect of the filter inside the CCD 3 can be obtained. The subscripts in A1, A3, A6, etc. shown here indicate the number of times of exposure in the multiple exposure. In this embodiment, the number of exposures is six. In FIG. 5, each block indicated by “T” serves as a delay means for delaying by one data, and the delayed data is finally added and output.
[0017]
Here, by using the CCD 3 in which the transfer register unit 33 has a storage capacity at least multiple times the number of multiple exposures with respect to the storage capacity of the light receiving unit 31, each light receiving unit, transfer register unit, and each dynamic range can be sufficiently provided. It can be used, and S / N can be improved and dynamic range can be increased.
[0018]
Further, by controlling the exposure time of each of the multiple exposures, the filter characteristics can be changed, and a general example of an equivalent filter configuration is shown in FIG. That is, the timing of the φTG signal, φS1 signal, φS2 signal, and Vsub signal shown in FIG. 3 can be changed to a configuration equivalent to that of the digital filter shown in FIG. 8 by controlling the timing as shown in FIG. it can. In FIG. 8, k0, k1, k2, k3, k4 are coefficients indicating how much weight is given to the data at that time, and correspond to k0, k1, k2, k3, k4 shown in FIG. T1, T2, T3, and T4 are delay blocks that delay data. Thus, by applying the timing pulse shown in FIG. 7 to the CCD 3, the filter characteristics as shown in FIG. 8 can be obtained. Therefore, the filter characteristics can be made variable by controlling the timing of each drive control signal of the CCD 3. I can do it.
[0019]
Moreover, the exposure time T shown in FIG. 7 is the total time of each exposure time at the time of multiple exposure, and this exposure time is made equal to the normal exposure time. This normal exposure time is the exposure time T in driving the normal CCD shown in FIG. 18, and the normal exposure time T is the capacity of the well of the transfer register unit and the photosensor unit as shown in FIG. Can be used enough. As described above, by making the total exposure time T equal to the normal exposure time T, the dynamic range of the transfer register unit can be sufficiently used, and the dynamic range and the S / N can be improved. FIG. 9B is an image diagram of the well capacity of the first transfer register section at the time of multiple exposure.
[0020]
Each exposure time at the time of multiple exposure shown in FIG. 7 is determined by a ratio with respect to a preset normal exposure time T. Therefore, for example, even when the total exposure time changes, each exposure time is determined by the ratio, so that it can be controlled without changing the filter characteristics. As a result, the exposure amount can be varied, and the filter characteristics do not change with changes in the exposure amount.
[0021]
FIG. 10 is a configuration diagram of the image pickup apparatus according to the second embodiment of the present invention. In FIG. 10, the difference between the present embodiment and the image pickup apparatus of the first embodiment in FIG. 1 is that the averaging circuit 13 that calculates the average value of the digital data output from the A / D converter 5 and its calculation are obtained. On the basis of the average value, there is provided a microcomputer 11 for outputting a timing judgment result of the drive control signal for the CCD 3 to the timing generator 10, whereby automatic exposure adjustment (AE) operation can be performed. Thus, the total exposure time T at the time of multiple exposure can be obtained. Also connected to the PC 9 is a storage device 12, which is generally provided such as a hard disk device or a magneto-optical disk device. Further, in front of the lens 1 (on the left side in the drawing), a film to be imaged and a light source for irradiating the film with light are drawn.
[0022]
Here, the ratio of each exposure time is determined by the system mode. As shown in FIG. 11, there are A, B, C, and D modes. For example, in the A mode, k0 = ka0, k1 = ka1, k2 = ka2, k3 = ka3, k4 = ka4, and so on. Similarly, an optimum ratio is determined in advance for each mode. Then, one of the modes A, B, C, and D is selected. Then, an optimum filter characteristic according to a desired mode can be selected by performing an exposure operation with a coefficient corresponding to the selected mode.
[0023]
In this case, if the system mode is determined by the necessary pixels of the subsequent system, the optimum filter characteristics based on the desired necessary pixels can be selected, so that false signals can be suppressed. At this time, by changing the sampling frequency for A / D conversion depending on the necessary pixels, it is possible to control the necessary data amount based on the necessary number of pixels. Furthermore, the data amount can be changed by simultaneously switching the resampling frequency on the subsequent process circuit 7 side. This resampling is limited in band by the output of the CCD 3 itself, so even if the data rate is up to a high frequency range, the band that has it is suppressed in the first place. Sampling does not cause aliasing and can be performed without problems, and by performing resampling according to the filter characteristics, the data rate and the number of data can be suppressed, and the capacity of the recording system can be reduced. .
[0024]
Further, if the ratio of the system mode is set according to the type of the pattern, the optimum filter corresponding to the desired pattern type can be selected by switching the system mode according to the type of pattern. For example, when a person is copied as a design, it is better to hold down the high range to make the picture softer. Optimal filter characteristics can be set.
[0025]
Also, as shown in FIG. 10, when the imaging target is a film, if the ratio of the system mode is set according to the type of film, the type of film can be changed by switching the system mode according to the type of film. The optimum filter can be selected according to This type of film can be reproduced, for example, in the case of ISO sensitivity with a low ISO sensitivity, even finer, but with a high ISO sensitivity, the grain becomes coarser and the phenomenon that it floats occurs. For this reason, it is possible to set the high ISO sensitivity so that the high frequency is lowered, and the low ISO sensitivity is not lowered for the low ISO sensitivity.
[0026]
In the above description, each exposure time is controlled by controlling the timing of the φTG signal of the transfer gate. As shown in FIG. 12, there are the φTG signal, φS1 signal, and φS2 signal. Each exposure time can be controlled by setting only a fixed pulse and controlling only the Vsub signal. In this case, the signal timing can be controlled only by the Vsub signal, so that the control can be easily performed.
[0027]
Further, as shown in FIG. 13, by performing the read transfer in the transfer register section within the first exposure time T0, that is, the charge discharge time of the transfer register section is set to the first exposure among the exposure times at the time of multiple exposure. By making it within the time, there is no wasted time, and the capture time can be set to the shortest.
[0028]
Further, by changing the number of times of multiple exposure (6 in the embodiment shown in FIG. 4), the filter characteristics can be made variable. In the digital filter shown in FIG. 6, the number of taps is made variable. The filter characteristics can be changed by changing the number of taps. In this case, if the number of times of multiple exposure is set as four system modes A, B, C, and D as shown in FIG. 14, for example, this mode is selected. An optimum filter characteristic according to a desired mode can be obtained. For example, in FIG. 14, when the B mode is selected, nb is selected as the number of exposures.
[0029]
FIG. 15 is a block diagram of the image pickup apparatus according to the third embodiment of the present invention. In FIG. 15, the imaging apparatus includes a lens 1 that collects light and forms an image, an aperture 2 that optimally adjusts the amount of light that passes through the lens 1, and an area that converts image light obtained by the lens 1 into an electrical signal. The CCD 103 of the sensor, the CDS circuit 4 that performs double correlation sampling of the output signal from the CCD 103, the A / D converter 5 that converts the analog data output from the CDS circuit 4 into digital data, and the horizontal of the converted digital data It comprises a horizontal filter 104 for limiting the direction band, a process circuit 7 for processing the filtered data, a timing generator (TG) 110 for driving the CCD 103, and the like.
[0030]
On the other hand, as shown in FIG. 20, the conventional imaging apparatus corresponding to this is provided with a vertical filter 105 for limiting the band of the digital data in the vertical direction between the horizontal filter 104 and the process circuit 7. The filter 105 is connected to a line memory 106 for storing data of the line. That is, in the present embodiment, the vertical filter 105 and the line memory 106 that are conventionally required are unnecessary.
[0031]
Here, a general operation of the CCD 103 of the area sensor will be described. As shown in FIG. 16, the CCD 103 includes a photosensor unit in which a plurality of photodiode columns arranged in a vertical direction are arranged in a horizontal direction, a vertical transfer register unit arranged in parallel with the photodiode columns, and The horizontal transfer register unit is arranged in the horizontal direction so as to join the end of the vertical transfer register unit. With the above configuration, light entering the photosensor unit is converted into an electric signal, and the electric charge is sent to the vertical transfer register unit by a control signal of a transfer gate (not shown). The charges sent to the vertical transfer register unit are transferred to the horizontal transfer register unit by the vertical transfer pulse, and the charges transferred to the horizontal transfer register unit are output by the horizontal transfer pulse. As shown in FIG. 17, the flow of data in the CCD output at this time is 1-1, 2-1, 3-1, 4-1,..., 9-1 in the horizontal direction. Advances one pixel in the vertical direction and flows in the horizontal direction as 1-2, 2-2, 3-2, 4-2,..., 9-2, and so on. Is transferred.
[0032]
In this embodiment, the vertical filter 105 and the line memory 106 after the horizontal filter 104 are not necessary by performing filtering in the vertical direction in the same manner as in the first or second embodiment. The circuit scale can be considerably reduced. Here, when comparing the area sensor and the line sensor, in the case of the line sensor, since there is no photo sensor in the adjacent part, the transfer register part can be easily configured large, so that the capacity of the transfer path can be increased and the dynamic range can be increased. This contributes to improvement of S and N.
[0033]
In each of the above embodiments, either one of the exposure time and the number of exposures in multiple exposure is changed. However, the present invention is not limited to this, and both the exposure time and the number of exposures may be changed at the same time. .
[0034]
In the above-described embodiments, an image scanner such as a film scanner has been described as an example. However, the present invention is not limited to this, and may of course be applied to other imaging devices such as an electronic digital camera.
[0035]
【The invention's effect】
As is apparent from the above description, the present invention transfers the photo charge of the photo sensor unit every time the charge of the transfer register unit is transferred for a predetermined number of pixels so that the image pickup device performs multiple exposure. Since the image pickup signal is filtered by the image pickup device by outputting the drive control signal so as to be input to the register unit, a hardware LPF is not required, the hardware scale is not increased, and the size is reduced. This also has the advantage of being advantageous.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image pickup apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram schematically showing a general CCD (line sensor).
FIG. 3 is a diagram showing timings of CCD drive control signals in the first embodiment.
FIG. 4 is a diagram showing an operation of a transfer register unit in the first embodiment.
FIG. 5 is a block diagram showing a digital filter equivalent to the filter characteristic in the first embodiment.
FIG. 6 is a configuration diagram of a filter generally showing filter characteristics in which the number of exposures is controlled.
FIG. 7 is a diagram showing an example of exposure time control in the first embodiment;
8 is a configuration diagram of a filter showing the filter characteristics of FIG.
FIG. 9 is a diagram illustrating an image of a well capacity of a transfer register unit;
FIG. 10 is a configuration diagram of an image pickup apparatus according to a second embodiment of the present invention.
FIG. 11 is a diagram showing an example of selection of filter characteristics in the second embodiment.
FIG. 12 is a diagram showing an example of exposure time control in the second embodiment.
FIG. 13 is a diagram showing an example of transfer control of a transfer register unit in the second embodiment.
FIG. 14 is a diagram showing an example of exposure number selection in the second embodiment.
FIG. 15 is a configuration diagram of an image pickup apparatus according to a third embodiment of the present invention.
FIG. 16 is a block diagram schematically showing a CCD (area sensor) in the third embodiment;
17 is a diagram showing a data flow in the CCD output of FIG. 16. FIG.
FIG. 18 is a diagram illustrating an exposure time in normal CCD driving.
FIG. 19 is a configuration diagram of an imaging apparatus using a conventional line sensor.
FIG. 20 is a configuration diagram of an imaging apparatus using a conventional area sensor.
[Explanation of symbols]
1 Lens 2 Aperture 3 CCD (Line sensor)
4 CDS circuit 5 A / D converter 6 LPF
10, 110 Timing generator 31 Light receiving unit 32 Transfer gate unit 33 Transfer register unit 103 CCD (area sensor)

Claims (20)

A lens for condensing light to form an image, a photosensor unit for photoelectrically converting the light imaged by the lens, and a transfer register unit for inputting the photoelectrically converted electric charge via a transfer gate and sequentially transferring it. And a timing generator that outputs a drive control signal for the imaging device. The timing generator transfers the charge of the transfer register unit for a predetermined number of pixels so that the imaging device is subjected to multiple exposure. An image pickup apparatus that performs filtering of an image pickup signal by the image pickup element by outputting a drive control signal so that the photocharge of the photo sensor portion is input to the transfer register portion every time. The imaging apparatus according to claim 1, wherein the transfer register unit has a charge storage capacitor at least times the number of times of the multiple exposure with respect to the charge storage capacitor of the photosensor unit. The image pickup apparatus according to claim 1, wherein a filter characteristic of the image pickup device is changed by controlling each exposure time at the time of the multiple exposure. 4. The imaging apparatus according to claim 3, wherein each exposure time at the time of the multiple exposure is controlled so that a total of the exposure times at the time of the multiple exposure is equal to a normal exposure time. 5. The imaging apparatus according to claim 4, wherein each exposure time at the time of the multiple exposure is distributed at a preset ratio with respect to the normal exposure time. 6. The imaging apparatus according to claim 4, wherein the normal exposure time is obtained by an automatic exposure adjustment function. 6. The exposure time ratio is set as a system mode having a filter characteristic for each system as a ratio, and an optimum mode is selected from the system modes. The imaging device described. The imaging apparatus according to claim 7, wherein the system mode is determined by necessary pixels. The imaging apparatus further includes an A / D converter that converts an imaging signal from the imaging device into a digital signal, and a sampling frequency of the A / D converter is switched by the necessary pixel. The imaging device according to claim 8. 9. The imaging apparatus according to claim 8, further comprising a process circuit that processes an imaging signal from the imaging element, wherein a resampling frequency of the process circuit is switched by the necessary pixel. . The imaging apparatus according to claim 7, wherein the mode of the system corresponds to a type of pattern. The image pickup apparatus according to claim 7, wherein the mode of the system corresponds to a type of film to be imaged. 6. The imaging apparatus according to claim 5, wherein each exposure time at the time of the multiple exposure is controlled by a gate control signal for controlling the transfer gate. 6. The imaging apparatus according to claim 5, wherein each exposure time at the time of the multiple exposure is controlled by an unnecessary charge discharging control signal. 6. The imaging apparatus according to claim 5, wherein the charge discharge time of the transfer register unit is set to be within the first exposure time among the exposure times at the time of the multiple exposure. The imaging apparatus according to claim 1, wherein the filter characteristic is changed by controlling the number of times of the multiple exposure. The imaging apparatus according to claim 16, wherein the number of times of the multiple exposure is determined according to a mode of the system. The imaging apparatus according to claim 1, wherein the filter characteristic is changed by controlling each exposure time and the number of times of the multiple exposure during the multiple exposure. The imaging apparatus according to claim 1, wherein the imaging element is an area sensor. The imaging apparatus according to claim 1, wherein the imaging element is a line sensor.

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