JP2000032356A - Ccd image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a signal shading when a sweep out transfer is performed and to make it a fixed value by performing read-out of the picture element signal and transfer of a read picture element signal by vertical and horizontal registers after an empty transfer of the vertical and horizontal registers is performed at the beginning of a picture element read-out period of term. SOLUTION: This device has a photoelectric conversion part PEC, a CCD imaging device 1, a CCD driving circuit 2 and a mechanical shutter. In this device, at the beginning of a picture element read-out period of term in which the mechanical shutter is in a closed state after an exposure period of term in which the mechanical shutter is in an open state, an empty transfer of a vertical register VR and a horizontal register HR is performed for more than one vertical cycle period of time. Then, after that, the CCD imaging device 1 is controlled by the CCD driving circuit 2 so as to perform reading of a picture element signal from plural photoelectric conversion part PEC and transfer the picture element signal read out by the vertical register VR and the horizontal register HR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD image pickup device of an interline transfer system and a CCD image pickup device having a light shielding means such as a mechanical shutter and a liquid crystal shutter.

[0002]

2. Description of the Related Art First, with reference to FIG. 3, a CCD image pickup apparatus using an IT (interline transfer type) CCD (charge coupled device) image pickup device will be described. Reference numeral 1 denotes a CCD imaging device of an IT system, and reference numeral 2 denotes a CCD driving circuit that drives the CCD imaging device 1. The CCD image pickup device 1 is composed of a large number of photoelectric conversion units (composed of photodiodes) PEC arranged in a matrix on which a subject image forming an image unit is projected, and one column of photoelectric conversion units PEC.
The pixel signals obtained by the light reception in the field period are simultaneously transferred and read in each of the vertical blanking periods, and are read out from each column of vertical registers VR (each of which is composed of multi-stage CCDs) shielded by an aluminum thin film. ) And one horizontal register HR (comprising a multistage CCD) in which pixel signals for each line from the vertical register VR of each column are transferred for each horizontal blanking period. Output a video signal for each field.

In the CCD image pickup apparatus shown in FIG. 1, although not shown, light from a subject passes through an objective lens, an iris, and a mechanical shutter (other light shielding means such as a liquid crystal shutter can be used). One light receiving surface is irradiated. The mechanical shutter is controlled by a system control device (with a built-in CPU). The above-described CCD drive circuit 2 is also controlled by this system controller.

In this CCD image pickup device, field readout is adopted, and two consecutive pixel signals of the photoelectric conversion unit PEC of each column are transferred to a single stage CCD of the vertical register VR. Therefore, the photoelectric conversion units PEC of each column
Is R, the number of CCD stages of the vertical register VR is R /
It becomes 2. In this case, the combination of two consecutive pixel signals of the photoelectric conversion unit PEC in each column is changed in an odd field and an even field. Of course, frame reading is also possible.

[0005] Next, referring to FIG.
A dark signal in the image sensor will be described. V in FIG. 4A
φ indicates a clock related to the vertical register VR, and this clock Vφ is a read clock RCK of a pixel signal from the photoelectric conversion unit PEC of each column to the vertical register VR of each column.
And the pixel signal accumulated in the vertical register VR of each column,
The vertical transfer clock VTCK is line-shifted toward the horizontal register HR every horizontal blanking period.

FIG. 4B shows that the power of the CCD imaging device is turned on (the power is turned on) immediately before the generation of the read clock RCK, and thereafter, the read clock RCK is generated.
This shows the state of the pixel signals stored in the vertical register VR immediately after the pixel signals from the photoelectric conversion units PEC of each column that have not been received are read by the vertical register VR of each column.
It is assumed that two consecutive pixel signals of the photoelectric conversion unit PEC in each column are transferred to the one-stage CCD of the vertical register VR. CR2 and CR1 indicate pixel signals of a light-shielding region having b and a pixels in the upper and lower vertical directions, respectively. PR indicates a pixel signal of an effective pixel area having n pixels in the vertical direction. In this case, the number of stages of the vertical register in each column is (n + a
+ B) / 2.

FIG. 4C shows a horizontal signal in the 1f (field) period when the pixel signals accumulated in the vertical register VR of each column are transferred (line shifted) toward the horizontal register HR in each horizontal blanking period. Register HR
Shows the dark signal output waveform (dark shading) of
As time elapses, the level has a characteristic that the level increases in proportion to the accumulation time of the pixel signal in the vertical register VR.

FIG. 4D shows a pixel signal from the photoelectric conversion unit PEC in each unreceived column immediately after the second read clock RCK is generated after the power is turned on, by the vertical register VR in each column. Shows the state of the pixel signals stored in the vertical register VR immediately after the operation. The pixel signals stored in the vertical register VR of each column include the vertical register V formed at the time of the line shift in the previous one field period.
A dark signal indicated by a characteristic S whose level linearly increases from the upper end to the lower end of R is included.

FIG. 4E shows a second read clock RC.
Immediately after K, when the pixel signals accumulated in the vertical registers VR of each column are transferred (line-shifted) toward the horizontal registers HR in each horizontal blanking period, the darkness of the horizontal registers in the 1f (field) period 4 shows a signal output waveform (dark shading). This waveform has a characteristic that the level increases in proportion to the accumulation time of the pixel signal in the vertical register as time passes.
D is a signal obtained by adding a dark signal whose level linearly increases from the upper end to the lower end of the vertical register as shown by the characteristic S shown in FIG.
Has constant characteristics of level. The dark signal output waveform of the horizontal register after the third and subsequent read clocks RCK after the power is turned on is similar to that of FIG. 4E.

In an electronic still camera using a mechanical shutter, a frame reading method of a CCD image pickup device or an all-pixel reading method in which signals are not mixed in a vertical register is adopted. In the frame reading method, in order to obtain a video signal for one frame, a video signal for two fields is required. When a video signal for one image is obtained by one exposure as in an electronic still camera, Needs to be shielded by a mechanical shutter or the like after the exposure is completed in order not to change the video signals of the images of the first and second fields.

Next, with reference to FIG. 5, a dark signal of an interline CCD image pickup device using a conventional mechanical shutter will be described. FIG. 5A shows the open / closed state of the mechanical shutter. ΦSUB in FIG. 5B indicates a substrate clock, which is a clock for operating the electronic shutter. The signal charge is discharged by the electronic shutter according to the substrate clock φSUB, and the end of the substrate clock φSUB is a start point of the exposure period. VC in FIG. 5C indicates a clock relating to the vertical register VR, and this clock Vφ is a clock RC for reading VR pixel signals from the photoelectric conversion unit PEC of each column to the vertical register of each column.
K and a vertical transfer clock VTCK for transferring the pixel signals accumulated in the vertical registers VR of each column toward the horizontal registers HR for each horizontal blanking period. SO
T indicates sweep transfer of the vertical register of each column, and here, the sweep transfer is performed immediately before the read clock RCK.

Next, with reference to FIGS. 5D to 5G, how the dark signal in the IT type CCD image sensor changes will be described. As shown in FIG. 5C, at the same time when the power of the CCD imaging device is turned on, the mechanical shutter shifts from the open state to the closed state after the end of the exposure period, and the sweeping out transfer SOT is performed to remove the smear signal and the like. Be started. In the case of the all-pixel reading method, a video signal for one image can be obtained by one exposure without using a mechanical shutter. Then, the same sweep transfer may be performed.

FIG. 5D shows the state of the pixel signals stored in the vertical register VR after the first sweep transfer SOT after the power is turned on, and the sweep transfer SOT is much less than the line shift by the vertical clock. Since the operation is performed at high speed, the level of the dark signal indicated by the characteristic S caused by the stagnation of the pixel signal in the vertical register of each column is negligibly low unlike the case of the line shift. That is, there is almost no signal accumulated in the vertical register VR.

FIG. 5E shows a dark signal output waveform of the horizontal register during the first field period, and the level increases in proportion to the residence time of the effective pixel signal of the dark signal in the vertical register. Since it differs depending on the position of the screen, when a black object or a dark place is imaged, the image looks slightly different depending on the screen position.
For this reason, an electronic still camera that requires higher image quality may have a problem.

As shown in FIG. 5C, the second sweep transfer after the power is turned on is performed, the dark signal is removed together with the smear signal, and the second read clock RCK immediately after the second sweep transfer SOT is completed. Occurs.

FIG. 5F is similar to FIG. 5D and shows that little signal is stored in the vertical register VR.

FIG. 5G shows a dark signal output waveform of the horizontal register during the second field period, and the level increases in proportion to the residence time of the effective pixel signal of the dark signal in the vertical register. Since it differs depending on the position of the screen, when a black object or a dark place is imaged, the image looks slightly different depending on the screen position.
For this reason, an electronic still camera that requires higher image quality may have a problem.

Since the sweep transfer is only required to remove the smear component during the exposure period, it is not always necessary to perform the sweep transfer immediately before reading the second field as shown in FIG. 5C.

FIG. 6 shows an example in which the sweep transfer is not performed immediately before the reading of the second field. In addition, FIG.
G is a figure respectively corresponding to FIGS. FIG. 6F
The vertical register immediately after the second read clock RCK after the power is turned on and the pixel signal from the photoelectric conversion unit PEC of each column that has not received light has been read by the vertical register VR of each column. This shows the state of the pixel signal stored in VR. As shown in FIG. 4D, the pixel signals stored in the vertical register VR of each column include, from the upper end to the lower end of the vertical register VR, as shown in the characteristic S, which was formed during the line shift of the previous one field period. , A dark signal whose level increases linearly is included.

FIG. 6G shows a characteristic in which the level increases in proportion to the accumulation time of the pixel signal in the vertical register VR over time, as shown in FIG. 4F, and a characteristic S shown in FIG. A signal to which a dark signal whose level linearly increases from the upper end to the lower end of the vertical register VR is added, and has a characteristic that the level is constant as time passes. The rest is the same as in FIG.
Description is omitted.

[0021]

SUMMARY OF THE INVENTION In view of the above, the present invention corrects signal shading when performing sweep transfer in a CCD imaging device having an interline CCD imaging device and a mechanical shutter.
It is intended to propose something that can be made a constant value.

[0022]

SUMMARY OF THE INVENTION The present invention provides a plurality of photoelectric conversion units arranged to form a plurality of columns, and a plurality of photoelectric conversion units provided corresponding to the plurality of columns of the plurality of photoelectric conversion units, respectively. An interline transfer type CCD image sensor including a plurality of vertical registers for transferring pixel signals read from the photoelectric conversion units of a column, and a horizontal register for transferring pixel signals from the plurality of vertical registers, and the CCD image sensor In a CCD imaging device having a CCD driving circuit for driving an element and light blocking means for controlling light incidence on the CCD imaging element, at the beginning of a pixel reading period after the end of an exposure period, for at least one vertical period, After performing the idle transfer of the vertical register and the horizontal register, the pixel signals are read from the plurality of photoelectric conversion units and the image read by the vertical register and the horizontal register is read. As the transfer of signals, CCD
The driving circuit controls the CCD image pickup device.

According to the present invention, after the end of the exposure period in which the mechanical shutter is in the open state, at the beginning of the pixel reading period in which the mechanical shutter is in the closed state, the vertical register and the horizontal register are maintained for at least one vertical cycle period. After performing the idle transfer of the register, the CCD driving circuit controls the CCD image pickup device so as to read the pixel signals from the plurality of photoelectric conversion units and transfer the pixel signals read by the vertical register and the horizontal register. To do it.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a plurality of photoelectric conversion units arranged to form a plurality of columns, and a plurality of photoelectric conversion units provided in correspondence with the plurality of columns, respectively. An inter-line transfer type CCD imaging device including a plurality of vertical registers for transferring pixel signals read from the photoelectric conversion unit, and a horizontal register for transferring pixel signals from the plurality of vertical registers, and the CCD imaging device. In a CCD imaging device having a driving circuit for driving a CCD and light blocking means for controlling incidence of light to the CCD imaging device, a vertical register is provided for at least one vertical cycle period at the beginning of a pixel reading period after an exposure period. And after performing idle transfer of the horizontal register, reading pixel signals from the plurality of photoelectric conversion units and reading pixel signals read by the vertical register and the horizontal register. As performs transmission, by a CCD drive circuit, CCD which is adapted to control the CCD image sensor
An imaging device.

[Specific Example of the Embodiment of the Invention] The CCD image pickup device according to the specific example of the embodiment of the present invention has a plurality of photoelectric elements arranged so as to form a plurality of columns as described with reference to FIG. A plurality of vertical registers VR which are provided corresponding to the conversion units PEC and the plurality of columns of the plurality of photoelectric conversion units PEC and transfer pixel signals read from the photoelectric conversion units of the respective columns; An interline transfer type CCD image sensor 1 including a horizontal register HR for transferring a pixel signal from a register VR, a CCD driving circuit 2 for driving the CCD image sensor 1, and a CCD image sensor 1
In a CCD imaging device having a mechanical shutter (another light-shielding unit such as a liquid crystal shutter is also possible) as a light-shielding unit for controlling the incidence of light on the mechanical shutter after the end of the exposure period in which the mechanical shutter is in the open state, At the beginning of the pixel reading period in which the shutter is in the closed state, the vertical register VR and the horizontal register HR are kept for one vertical cycle period or more (1, 2, 3, ‥‥‥ times the vertical cycle period).
After the idle transfer, the CCD driving circuit 2 reads out the pixel signals from the plurality of photoelectric conversion units PEC and transfers the pixel signals read out by the vertical register VR and the horizontal register HR. The element 1 is controlled.

Next, with reference to FIG. 1, a dark signal of an interline CCD image pickup device using a mechanical shutter of a specific example will be described. FIG. 1A shows the open / closed state of the mechanical shutter. In FIG. 1B, φSUB indicates a substrate clock, which is a clock for operating the electronic shutter. The signal charge is discharged by the electronic shutter according to the substrate clock φSUB, and the end of the substrate clock φSUB is a start point of the exposure period. FIG. 1C
Vφ indicates a clock related to the vertical register VR,
This clock Vφ is a read clock R of the VR pixel signal from the photoelectric conversion unit PEC of each column to the vertical register of each column.
CK and a vertical transfer clock VTCK for transferring the pixel signals stored in the vertical register VR of each column toward the horizontal register HR every horizontal blanking period. SO
T indicates sweep transfer of the vertical register of each column, and here, the sweep transfer is performed immediately before the read clock RCK.

Next, with reference to FIGS. 1D to 1G, how the dark signal in the IT type CCD image sensor changes will be described. As shown in FIG. 1C, at the same time when the power of the CCD imaging device is turned on, the mechanical shutter shifts from the open state to the closed state after the end of the exposure period, and the sweeping transfer SOT is performed to remove the smear signal and the like. Be started. In the case of the all-pixel reading method, a video signal for one image can be obtained by one exposure without using a mechanical shutter. Then, the same sweep transfer may be performed.

FIG. 1D shows the state of the pixel signals stored in the vertical register VR after the first sweep transfer SOT after the power is turned on, and the sweep transfer SOT is much smaller than the line shift by the vertical clock. Since the operation is performed at high speed, unlike the line shift, the level of the dark signal indicated by the characteristic S caused by the stagnation of the pixel signal in the vertical register of each column is negligibly low. That is, there is almost no signal accumulated in the vertical register VR.

FIG. 1E shows a dark signal output waveform when a line shift due to idle transfer is performed. The level of the dark signal increases in proportion to the residence time of the dark signal in the vertical register. It depends on the position.

As shown in FIG. 1C, a plurality of photoelectric conversion units PE are supplied by the first read clock RCK after the power is turned on.
The pixel signal is read from C.

FIG. 1F shows a pixel signal from the photoelectric conversion unit PEC of each column that has not received light immediately after the first read clock RCK is generated after the power is turned on by the vertical register VR of each column. Shows the state of the pixel signals stored in the vertical register VR immediately after the operation. The pixel signals accumulated in the vertical register VR of each column include, from the upper end to the lower end of the vertical register VR, as shown by the characteristic S, formed during the idle transfer in the previous one field period.
A dark signal whose level increases linearly is included.

FIG. 1G shows a first read clock RC.
Immediately after K, when the pixel signals accumulated in the vertical registers VR of each column are transferred (line-shifted) toward the horizontal registers HR in each horizontal blanking period, the darkness of the horizontal registers in the 1f (field) period 5 shows a signal output waveform (dark shading). This waveform has a characteristic in which the level increases in proportion to the accumulation time of the pixel signal in the vertical register as time elapses. From the lower end to the lower end, a dark signal whose level increases linearly is added, and the characteristic exhibits a constant level as time passes.

As shown in FIG. 1C, a plurality of photoelectric conversion units PE are supplied by a second read clock RCK after power-on.
The pixel signal is read from C.

Immediately after the generation of the second read clock RCK after the power is turned on, the photoelectric conversion unit P of each column that has not received light yet.
The state of the pixel signal stored in the vertical register VR immediately after the pixel signal from the EC is read by the vertical register VR of each column is the same as that in FIG. 1F. The pixel signal stored in the vertical register VR of each column includes the previous one.
The characteristic S formed during the line shift during the field period
As shown in FIG. 7, a dark signal whose level linearly increases from the upper end to the lower end of the vertical register VR is included.

FIG. 1H shows a second read clock RC.
Immediately after K, when the pixel signals accumulated in the vertical registers VR of each column are transferred (line-shifted) toward the horizontal registers HR in each horizontal blanking period, the darkness of the horizontal registers in the 1f (field) period 5 shows a signal output waveform (dark shading). This waveform has a characteristic in which the level increases in proportion to the accumulation time of the pixel signal in the vertical register as time elapses. From the lower end to the lower end, a dark signal whose level increases linearly is added, and the characteristic exhibits a constant level as time passes.

By the way, in the specific example of FIG. 1, during one vertical cycle period after the power is turned on, the pixel signals from the photoelectric conversion units PEC are not read out, and the vertical register VR and the horizontal register H are not read.
Since the idle transfer of R is performed, the smear signal can be removed during this time, so that the sweep transfer SOT of FIG. 1C in the specific example of FIG. 1 can be omitted, and a specific example in that case is shown in FIG. 2, A, B, and C in FIG. 1 correspond to A, B, and C in FIG. 2, respectively, and E, F, G, and
H corresponds to D, E, F, and G in FIG. 2, respectively.

FIG. 2D shows a dark signal output waveform when a line shift due to idle transfer is performed. The level of the dark signal increases in proportion to the residence time of the dark signal in the vertical register. It depends on the position.

As shown in FIG. 2C, the plurality of photoelectric conversion units PE are supplied by the first read clock RCK after the power is turned on.
The pixel signal is read from C.

FIG. 2E shows a pixel signal from the photoelectric conversion unit PEC of each column that has not received light immediately after the first read clock RCK is generated after the power is turned on, by the vertical register VR of each column. Shows the state of the pixel signals stored in the vertical register VR immediately after the operation. The pixel signals accumulated in the vertical register VR of each column include, from the upper end to the lower end of the vertical register VR, as shown by the characteristic S, formed during the idle transfer in the previous one field period.
A dark signal whose level increases linearly is included.

FIG. 2F shows a first read clock RC.
Immediately after K, when the pixel signals accumulated in the vertical registers VR of each column are transferred (line-shifted) toward the horizontal registers HR in each horizontal blanking period, the darkness of the horizontal registers in the 1f (field) period is reduced. 5 shows a signal output waveform (dark shading). This waveform has a characteristic in which the level increases in proportion to the accumulation time of the pixel signal in the vertical register as time elapses. From the lower end to the lower end, a dark signal whose level increases linearly is added, and the characteristic exhibits a constant level as time passes.

As shown in FIG. 2C, a plurality of photoelectric conversion units PE are supplied by a second read clock RCK after power-on.
The pixel signal is read from C.

Immediately after the generation of the second read clock RCK after the power is turned on, the photoelectric conversion unit P of each column that has not received light yet
The state of the pixel signal stored in the vertical register VR immediately after the pixel signal from the EC is read by the vertical register VR of each column is the same as that in FIG. 2E. The pixel signal stored in the vertical register VR of each column includes the previous one.
The characteristic S formed during the line shift during the field period
As shown in FIG. 7, a dark signal whose level linearly increases from the upper end to the lower end of the vertical register VR is included.

FIG. 2G shows a second read clock RC.
Immediately after K, when the pixel signals accumulated in the vertical registers VR of each column are transferred (line-shifted) toward the horizontal registers HR in each horizontal blanking period, the darkness of the horizontal registers in the 1f (field) period 5 shows a signal output waveform (dark shading). This waveform has a characteristic in which the level increases in proportion to the accumulation time of the pixel signal in the vertical register as time elapses. From the lower end to the lower end, a dark signal whose level increases linearly is added, and the characteristic exhibits a constant level as time passes.

[0044]

According to the present invention, a plurality of photoelectric conversion units arranged to form a plurality of columns, and a plurality of photoelectric conversion units are provided corresponding to the plurality of columns, respectively. An inter-line transfer type CCD imaging device including a plurality of vertical registers for transferring pixel signals read from the photoelectric conversion unit, and a horizontal register for transferring pixel signals from the plurality of vertical registers, and the CCD imaging device. In a CCD imaging device having a driving circuit for driving a CCD and light blocking means for controlling incidence of light to the CCD imaging device, a vertical register is provided for at least one vertical cycle period at the beginning of a pixel reading period after an exposure period. And after performing idle transfer of the horizontal register, reading pixel signals from the plurality of photoelectric conversion units and reading pixel signals read by the vertical register and the horizontal register. As performs transmission, by a CCD driving circuit, since to control the CCD image sensor,
In a CCD imaging device having a mechanical shutter and an interline CCD imaging device, it is possible to obtain a CCD imaging device capable of correcting signal shading when sweeping transfer is performed to a constant value.

[Brief description of the drawings]

FIG. 1 shows a CC of an IT system according to a specific example of an embodiment of the present invention.
FIG. 3 is an explanatory diagram of shading correction of the CCD image pickup device in a CCD image pickup device having a D image pickup device and a mechanical shutter.

FIG. 2 is a CCD having an IT type CCD image pickup device and a mechanical shutter according to another specific example of the embodiment of the present invention;
FIG. 4 is an explanatory diagram of shading correction of the CCD image pickup device in the image pickup device.

FIG. 3 is a block diagram showing a CCD imaging device having an IT type CCD imaging device.

FIG. 4 is an explanatory diagram of a dark signal in the IT type CCD imaging device.

FIG. 5 shows a conventional example of an IT-type CCD imaging device and its CC in a CCD imaging device having a mechanical shutter.
FIG. 4 is an explanatory diagram of shading correction of a D imaging element.

FIG. 6 is an explanatory diagram of another conventional example of an IT-type CCD image pickup device and shading correction of the CCD image pickup device in a CCD image pickup device having a mechanical shutter.

[Explanation of symbols]

1 IT type CCD imaging device, 2 CCD drive circuit,
PEC photoelectric converter, VR vertical register, HR horizontal register.

Claims (1)

[Claims] 1. A plurality of photoelectric conversion units arranged to form a plurality of columns, and a plurality of photoelectric conversion units are provided corresponding to the plurality of columns of the plurality of photoelectric conversion units, and read from the photoelectric conversion units of each column. A plurality of vertical registers for transferring pixel signals from the plurality of vertical registers, and a horizontal register for transferring pixel signals from the plurality of vertical registers; a CCD imaging device of an interline transfer system; a CCD driving circuit for driving the CCD imaging device; A CCD imaging device having a light-blocking means for controlling the incidence of light on the CCD imaging device, wherein at the beginning of a pixel reading period after the end of an exposure period, the vertical register and the horizontal register After performing the idle transfer, the pixel signals are read from the plurality of photoelectric conversion units, and the read pixels are read by the vertical register and the horizontal register. A CCD image pickup apparatus characterized in that the CCD drive circuit controls the CCD image pickup device so as to transfer signals.