JPS59132287A - Image pickup device - Google Patents

Abstract

PURPOSE:To suppress the generation of smear by driving independently and sequentially transfer electrodes arranged in the direction of charge transfer and providing a shutter. CONSTITUTION:The transfer electrodes n1-n4 of an image pickup section 3 of a frame transfer type charge coupling element 1 being an image pickup element are connected independently to a scanning circuit 7 and driven sequentially. Further, in transferring the stored charge from the image pickup section 3 to a memory section 4, the shutter 8 operated in this case is provided. Thus, after the charge under the electrode n1 is transferred to the electrode n2, no driving pulse is impressed to the electrode n1 and similarly, as the charge is transferred from the n2 to the n3 and from the n3 to the n4, the next driving pulse is not impressed and the storage potential state is kept. Thus, the generation of smear is halved. Then, the generation of smear is suppressed.

Description

Detailed Description of the Invention Technical field to which the invention of this application pertains The invention of this application relates to an imaging device using an imaging element having a charge transfer function, which suppresses the occurrence of smear with a simple configuration, and can achieve high speed. The objective is to find a means to enable shutter control.

2. Description of the Related Art A conventional frame transfer solid-state imaging device, such as a frame transfer charge-coupled device (FT-CCD), has a structure as shown in FIG. That is, the imaging device 1 includes an imaging section 6 that combines an imaging cell 2 for converting an optical image from a subject into charges and storing them, a memory section 4 that temporarily stores the accumulated charges of the imaging section 3, and a memory section 4. horizontal register section 5 for reading charges from the horizontal register section 5;
It consists of an output amplifier 6 that amplifies the charge from. Note that φPIIφps and φB in the figure indicate drive pulses for accumulating, storing, and horizontally transferring charges, respectively. FIG. 2 is an explanatory diagram of the electrode arrangement for applying the driving pulse φP to the imaging section 6 and the driving pulse φps to the memory section 4 in the apparatus shown in FIG. A portion shows an electrode provided on an imaging cell and a memory cell.

To explain the occurrence of smear in the image sensor having the electrode structure described above, FIG. 3(a) shows a state in which the image sensor 6 is in the accumulation state and a portion of the image sensor 3 is irradiated with high-intensity incident light. , and FIG. 4(b) shows a state in which the charges accumulated in FIG. 3(a) are vertically transferred to the memory section 4. In this case, even during vertical transfer, since the imaging unit 3 is in the process of photoelectric conversion, smear occurs in its SA area, and smear also occurs in the SB area of the memory unit 4 that has been vertically transferred.

After this SB region smear is read out from the output amplifier 6, it appears below the high brightness region L' on the display surface (not shown). Figure (c) shows the state of the charge image after the second vertical transfer, and as shown in the figure, smears are observed above and below the high-brightness area L' on the display surface in the second and subsequent transfers. . As described above, in the conventional vertical transfer means, it is impossible in principle to eliminate smear because the charge image is transferred during photoelectric conversion.

Such smearing also occurs in the interline type COD. In other words, although the vertical transfer path of an interline type COD is shielded from light by a light shielding layer, light in the long wavelength region can also enter the semiconductor substrate under this light shielding layer, so in reality it is similar to a frame transfer type COD. smear occurs.

Therefore, in order to prevent the occurrence of smear as described above, it is possible to consider means for blocking the incident light to the imaging section during the vertical transfer period. However, in order to block such incident light, a shutter with good responsiveness must be used, and realizing this with a physical shutter such as a liquid crystal requires the relationship between responsiveness and light transmittance. It is extremely difficult,
On the other hand, in order to obtain such high-speed response with a mechanical shutter, for example, a two-blade configuration is required, which makes the configuration extremely complicated.

OBJECTS OF THE INVENTION OF THIS APPLICATION Accordingly, the first invention of this application aims to eliminate the above-mentioned drawbacks of the prior art and provide an imaging device capable of suppressing the occurrence of smear with a simple configuration.

A further object of the first invention is to provide an imaging device that achieves the above object and also enables control of storage time in an imaging section.

A second invention of this application provides an imaging device that achieves the first object of the first invention and has an effect of offsetting unevenness in accumulation time due to transfer in an imaging section of an imaging device (e.g., uneven exposure of a shutter means). The purpose is to provide.

Structure of the invention of this application A first invention of this application is an image sensor having a charge transfer function, which includes a plurality of transfer electrodes arranged in the direction of charge transfer (in the specific example described later, for example, Frame transfer type charge-coupled device 1) comprising transfer electrodes n1 to n4 shown in FIG.
(means for sequentially driving the image pickup device by the vertical transfer pulse φP shown in FIG. The present invention is characterized by an imaging device comprising: means for operating the shutter plate 8 in response to a start signal S which is the output of the timer circuit 16 shown in FIG. 4;

A second aspect of the present invention is an image sensor having a charge transfer function, comprising a plurality of transfer electrodes arranged in the direction of charge transfer; a driving means for independently and sequentially driving the plurality of transfer electrodes; Shutter means for gradually shielding the light-receiving surface of the image sensor in the direction corresponding to the driving order of the transfer electrodes by the driving means (also the imaging section 3 of FIG. 4 in the direction of the driving order of the transfer electrodes n1 to n4 of FIG. 5) The imaging device is characterized by comprising: a shutter plate 8) that gradually shields the image;

The image sensor in the invention of this application is COD or BBD.
Any material having an equal charge transfer function may be used, and the transfer function may be either a frame transfer type or an interline transfer type.

In the above, the citation of specific examples described later does not limit the scope of the invention of this application in any way, and the invention of this application can be modified as appropriate within the scope of the claims.

The configuration and operation of an imaging device embodying the invention of this application will be described in detail below with reference to the drawings. In the following explanation, the image sensor is a frame transfer type COD (hereinafter referred to as F-TC).
It is abbreviated as CD. ) for an example.

Configuration of an imaging device embodying the invention of this application (Figs. 4 to 4)
FIG. 6) FIG. 4 shows an imaging device embodying the invention of this application,
FIG. 5 and FIG. 6 show the electrode arrangement in the image sensor.

In FIG. 4, reference numerals 1 to 6 have basically the same structure and function as the parts indicated by the same reference numerals in FIG. 1, but the electrode arrangement is similar to that in FIG. 2 as shown in FIG. This is different from the conventional electrode arrangement shown. That is, in FIG. 2, a plurality of transfer electrodes are commonly connected in the vertical direction for each imaging section and memory section, but in FIG. 5, the horizontal transfer electrodes (n
1 to 4) are independent from each other, and are connected independently to the scanning circuit 7 in FIG. 4. In FIG. 6, the imaging section 3 is the same as in FIG. , the horizontal transfer electrodes of the memory section 4 are also independent of each other, and are connected to the scanning circuit 7' independently of each other.

The electrode arrangement will be explained below using the arrangement shown in FIG. 5 as an example, and the differences in the operation and effect of the arrangement shown in FIG. 6 will be supplementarily explained later. In addition, in FIGS. 5 and 6, only four horizontal transfer electrodes are shown in both the imaging section 6 and the memory section 4 for the sake of simplicity. In Figure 1, it is possible to provide as many horizontal columns as 2).

Returning to FIG. 4, reference numeral 8 denotes a shutter plate, which is driven by a drive source such as a motor or a spring, and shields at least the imaging section 3 of the FT-CCD 1. The figure shows an example in which the shutter shutter 8 is driven by a motor 9, and 10 is a driving circuit thereof, which is controlled by a start signal S which is an output of a timer circuit 16, which will be described later. Although not shown in the figure, instead of the motor 9, a spring is attached to the shutter plate 8 in advance.
Alternatively, the shutter plate 8 may be stored in energy and locked, and then released from the lock in response to the start signal S to cause the shirt cover plate 8 to run in a direction that shields the imaging section 3. Further, in the second invention of this application, the shutter plate 8 may be one that causes exposure unevenness, such as a single blade, and a simple structure is sufficient. Its effect will be described later. Furthermore, the shutter plate 8 in the second invention may be a physical shutter such as liquid crystal, and may be configured to intentionally cause exposure unevenness.

A clock oscillator 11 generates a clock signal for synchronizing the timing of the entire system. 12
is a synchronizing signal generating circuit, which forms pulses for controlling the FT-CCD j based on the aforementioned clock signal. Reference numeral 16 denotes a COD drive circuit, which generates a pulse signal of a level necessary for driving CCD 1<hs, φPI tφ based on the output pulse of the synchronization signal generation circuit 12.
PB, φS, etc. are formed. Here, φvs is a vertical synchronizing signal, and its period is selected to be, for example, one field period of a standard television signal. φAE is a vertical transfer pulse in the imaging section 6, and is outputted as shown in FIG. 7 in synchronization with the pulse φvs. Note that symbols n1 to n4 in FIG. 7 indicate transfer pulses for the horizontal transfer electrodes n1 to n4 of the imaging section 6 in FIG. 5, respectively. φps is a vertical transfer pulse in the memory section 4, φS
is the horizontal transfer pulse in register 5.

A trigger signal forming circuit 14 generates a trigger signal TR for starting a shutter operation in still photography in conjunction with a button (not shown). Reference numeral 15 denotes an AND gate, which activates the timer circuit 16 by logical product of the vertical synchronization signal φvs, which is the output of the COD drive circuit 16, and the trigger signal TR. A predetermined accumulation time information T is stored in the timer circuit 16 in advance by a setting means (not shown).

is set. The timer circuit 16 is an AND gate 15
This set accumulation time T
When M has elapsed, the start signal S mentioned above is output.

The imaging device shown in FIG. 4 can be constructed in the same manner as described above by using an interline COD and driving the transfer electrodes of the vertical transfer path independently.

Functions of the imaging device embodying the invention of this application (Figs. 4 to 4)
(FIG. 8) Next, the operation of the imaging apparatus shown in FIGS. 4 to 6 will be explained. Based on the pulses from the synchronization signal generation circuit 12, the COD drive circuit 13 generates a vertical synchronization pulse φVS and a vertical transfer pulse φPI in the imaging section 3 at the timing shown in FIG.
, outputs a vertical transfer pulse φPB in the memory section 4 and a horizontal transfer pulse φS in the register 5. As a result, for example, at time t5, the image pickup unit 5 of the FT-CCD 1
The charges accumulated from ~t2' to time t5 to t4'
The data is transferred to the memory section 4 over the period of time. In the invention of this application, the transfer electrodes n1 to n4 of the imaging unit 6 are configured so that voltages are applied to them independently of each other, so as shown in the pulse φP in FIG. n2
After transferring to electrode n1, no driving pulse is applied to electrode n1, and as the data is transferred from n2 to n3 and from n3 to n4, the accumulated potential state is maintained without applying the next driving pulse. become.

Therefore, the first effect of the apparatus embodying the first and second inventions of this application is that the occurrence of smear can be suppressed to half that of conventional apparatuses. That is, when there is no output from the trigger signal forming circuit 14, the state shown in FIG.
As shown in (a), the L portion of the imaging unit 3 is illuminated by high-intensity incident light, but even if the charges in the imaging unit 3 are vertically transferred to the memory unit 4 in this state, the image (b) ), smear occurs only in the SB region and does not occur elsewhere. In this respect, there is a marked difference from the manner in which smear occurs in the conventional apparatus shown in FIG. Furthermore, after a predetermined period of time has elapsed, the imaging unit 3
Even if the charges of 1 are vertically transferred to the memory section 4, the area where smear occurs does not spread to areas other than the BB area, as shown in FIG. That is, compared to the case using conventional electrode arrangement and driving means, the occurrence of smear can be suppressed to half.

A second effect is that the shutter mechanism becomes extremely simple. In other words, when used as an electronic still camera that captures instantaneous images of a subject, conventional imaging devices open the shutter once to accumulate charge in order to prevent smearing.
A mechanism for closing the shutter before vertical transfer is required, but since no smear remains in the FT-CCD imaging section in common in the imaging devices embodying the first and second inventions of this application, Since it is only necessary to close the shutter when vertically transferring data to the memory section, the shutter mechanism becomes very simple.

Furthermore, a third effect is that power consumption is reduced to H of conventional devices. In other words, power consumption P in transfer is P=f
cv2, where f is the repetition frequency of the vertical transfer pulse, and since smear is normally inversely proportional to this frequency, high-speed repetition is desirable, but due to the structure of the element, 2 MH
z is the current level. C is the interelectrode capacitance, which is approximately 8000 PF in a conventional COD. Further, V is a transfer voltage and is approximately 15V. Therefore, when constantly driven at 2 MH2, the calculated power consumption is 3.6 W, but the actual transfer period is 245 (pulses) x 6 in the case of TV mode.
0 (frame), so the actual output is about 26 mW. On the other hand, according to the driving methods of the first and second inventions of this application, the number of transfer pulses is approximately % of that of the conventional method, as shown in n1 to n4 in FIG. The power consumption is also almost 2%, about 13mW in the numerical example above.
become. In the electrode arrangement shown in FIG. 6, the transfer electrodes of the memory section 4 are also independently connected to the scanning circuit 7', so that power consumption can be further reduced.

Next, the operation timing of the still photography mode will be explained. As a specific example of the first invention of this application, FT-C
Imaged periodically using CD 1.

When a button (not shown) is pressed at time t1 in FIG. 7 while transfer and reading are being performed, the trigger signal forming circuit 14 generates a pulse TR having a pulse width slightly longer than 1 TV. The timer circuit 16 is actuated by the AND of this pulse and the vertical synchronizing pulse φVS, and when the time TM has elapsed, it outputs a signal S to start closing the shutter plate 8.

In response to this signal S, the shutter plate 8 travels at high speed to shield the imaging section 3 from light. Since the above-mentioned time T can be set in advance as accumulation time information as described above, according to the first invention of this application, this accumulation time can be controlled, and in particular, this accumulation time can be controlled. It can be shortened to the required range.

Furthermore, as a specific example of the second invention of this application, the direction in which the plurality of transfer electrodes n1 to n4 are sequentially driven and the shutter plate 8 are explained.
Since the zero running direction is the same, the following effects are achieved. That is, in the above specific example, the FT-CCD
1, since the vertical transfer pulses are sequentially stopped from the top in FIG. 4, unevenness in accumulation time occurs in the vertical direction in the imaging section 3. In terms of a monitor screen, this means that the lower part of the screen is brighter and the upper part is darker.
For movie shooting, the vertical transfer time is at most 0.1
Since 5 melons θθC, the accumulation time for one field is 16.7
With respect to XIBθC, the error at the top and bottom ends of the screen falls within a range of 0.7%, and has almost no effect. However, if the accumulation time is shortened by using the shutter plate 8 as in the specific example shown in FIG. 4, the influence of this error may increase. Therefore, as a means for embodying the second invention of this application, the shutter plate 8 is made into a separate root, and the imaging unit 3
When the lens is changed from the open state to the closed state, an additional exposed area 2 is formed within the imaging plane. Then, the running direction of the shutter plate 80 is made to coincide with the direction of vertical transfer so that the distribution of this exposure unevenness cancels out the unevenness of accumulation time due to the vertical transfer. Furthermore, the closer the running speed of the shirt flap plate 8 is to the vertical transfer speed, the more pronounced the above-mentioned canceling effect becomes.If both speeds match, it is theoretically possible to completely suppress the above-mentioned unevenness in the accumulation time. Furthermore, the structure of the shutter for preventing smear generation or shortening the storage time can be significantly simplified.

In order to embody the second invention of this application, it is sufficient that the shutter intentionally causes unevenness in exposure time, and it is sufficient if it has a characteristic that cancels out unevenness in storage time due to vertical transfer. Therefore, a simple structure such as a single-blade shutter may be used, or a physical shutter such as a liquid crystal as described above may be used to intentionally cause exposure unevenness.

It is clear from the above description that the various effects described above can be similarly expected in an imaging apparatus configured using an interline transfer type imaging element.

The invention of Cotton 1 of the present application is such that a plurality of transfer electrodes of an image sensor are driven independently and sequentially, and the image sensor is periodically driven (by a driving means) for a predetermined period of time. Since the shutter is activated later, firstly, with a simple configuration, the occurrence of smear can be minimized, for example, to about H compared to the conventional device, and the shutter mechanism can be made extremely simple. Furthermore, the power consumption of the transfer end can be reduced, and secondly, the storage time can be controlled in the imaging section of the imaging device, and in particular, it can be shortened within the range set by the setting means.

Further, the second invention is configured to drive the plurality of transfer electrodes of the image sensor independently and sequentially, and to provide a shutter means for gradually shielding the light receiving surface of the image sensor in a direction corresponding to the order in which the transfer electrodes are driven by the drive means. Therefore, the above-mentioned first invention of the first invention
In addition, unevenness in storage time due to transfer can be offset by unevenness in exposure time of the shutter.
Furthermore, the structure of the shutter for suppressing thismia or shortening the storage time can be significantly simplified.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional image sensor, Figure 2 is a diagram of the electrode arrangement in the image sensor shown in Figure 1, and Figures 6 (a) and (b).
? (0) is an explanatory diagram showing the mode of smear generation in the image sensor of FIG. 1, and FIG. 4 is a block diagram of the configuration of the image sensor in the image sensor embodying the invention of this application, and a block diagram of the driving section of the image sensor. 5 is a diagram showing an example of the electrode arrangement of the imaging element in the imaging device shown in FIG. 4, FIG. 6 is a diagram showing another example of the electrode arrangement in the imaging device shown in FIG. FIGS. 8(a), 8(b), and 8(c) are explanatory diagrams of the timing of drive pulses, and are explanatory diagrams showing aspects of smear suppression in the imaging apparatus of FIG. 4. In the figure, 1...frame transfer type charge-coupled devices 6 and 4, which are imaging devices; respectively, their imaging section and memory section 7;
...Scanning circuit 8...Shutter board 9...Motor 10...Morph drive circuit 16...CCD drive circuit 14...Trigger signal forming circuit 15...AND gate 16...Timer circuit n1Hn2 H”5 and n4-transfer electrode and 7°

Claims (1)

[Scope of Claims] (Li) An imaging device having a charge transfer function, comprising a plurality of transfer electrodes arranged in the direction of charge transfer, and a driving means for independently and sequentially driving the plurality of transfer electrodes. , means for activating a shutter after a predetermined period of time in a state in which the image sensor is periodically driven by the driving means. (2) An image sensor having a charge transfer function, the image sensor having a charge transfer function. a plurality of transfer electrodes arranged in a direction; a drive means for independently and sequentially driving the plurality of transfer electrodes; and a light-receiving surface of the image sensor in a direction corresponding to the order in which the transfer electrodes are driven by the drive means. (3) The imaging device according to claim (2), wherein the transfer speed of the drive means and the running speed of the shutter means are made close to each other.