JP2695520B2 - Driving device for solid-state image sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a driving device for a solid-state image sensor used in, for example, a video camera.

[Prior art] Conventionally, as means for realizing a function called exposure compensation in a video camera or the like, a device using an aperture blade or the like that directly controls the amount of light incident on an image sensor, or controlling the charge accumulation time of the image sensor Some use a so-called electronic shutter function.

[Problems to be Solved by the Invention] However, among the above-mentioned conventional examples, the method using diaphragm blades requires diaphragm blades and mechanical members around them, thus increasing the size and cost of the video camera. There was a problem of inviting. In addition, the technique using the electronic shutter function has a problem that the movement of the captured image becomes unnatural.

Hereinafter, among the above problems, the problems in the method using the electronic shutter function will be described in more detail.

FIG. 7 is a conceptual diagram of an interline transfer CCD, in which 1 is a sensor unit for photoelectric conversion, 2 is a vertical transfer register, 4 is a horizontal transfer register, and 5 is an output amplifier. FIG. 8 is a sectional view and a potential view taken along the line AA ′ in the figure.

In FIG. 8, 6 is a channel stop (C) for pixel separation.
S) and 7 are readout gates (ROG) for transferring the electric charges accumulated in the sensor unit 1 to the vertical transfer register 2, 8 is a substrate, and 9 is an oxide film.

The operation of the conventional electronic shutter will be described with reference to FIGS. 8 and 9. FIG. 9 is a diagram for one field of the standard television signal, where φROG is a pulse applied to the readout gate 7, and when the logic level is “H”, the potential of the readout gate 7 is lowered and the sensor The charges of the section 1 are transferred to the vertical transfer register 2. The removal pulse φSUB is a pulse applied to the substrate 8 and charges the electric charge accumulated in the sensor unit 1 at “H” by φSUB
Sweep out (remove) through the terminal.

In this conventional example, in FIG. 9, φROG is in the vertical blanking period and φSUB is in the horizontal blanking period. Time t0
After the electric charge of the sensor unit 1 is read out, the next period starts, but during the horizontal retrace period until time t1, φSUB = “H”, so that the electric charge from t0 to t1 is applied to the sensor unit 1. Not left. Since φSUB = “L” during the period from time t1 to t2, the electric charge during this period is accumulated in the sensor unit 1, and φROG at time t2
== “H” pulse, transfer to vertical transfer register 2 As a result, the exposure time in this case is (t2−t1).

Therefore, although the function as an electronic shutter is sufficiently performed, when the conventional electronic shutter function is used as exposure compensation, particularly when the exposure time is continuously varied, the difference in dynamic resolution at each exposure time is reduced. There is a problem that the screen appears as it is, and the screen becomes very unsightly, such that the dynamic resolution changes every field.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to realize an electronic shutter function with a constant dynamic resolution and capable of exposure compensation suitable for the condition of the subject. The present invention is to provide a drive device for a solid-state image sensor.

[Means for Solving the Problems] In order to solve the above problems and achieve the object, a driving device for a solid-state imaging device according to the present invention receives an optical signal, performs photoelectric conversion, and stores information. Means, first storage means for reading information from the sensing means, and the first storage means.
Second storage means for storing information from the storage means, and removal means for removing information from the sensing means,
A driving device of a solid-state imaging device, which controls information storage time by intermittently removing information of the sensing means by the removing means twice or more within one field period. After the first predetermined time T1 from the synchronization signal, the operation of the removing means is changed to the second predetermined time T2.
The information from the sensing means is read into the first storage means after a third predetermined time T3 from the end of the operation every predetermined number N of the operations of the removing means. And a static mode for capturing an image of a subject having a small amount of movement, and a first predetermined predetermined in the dynamic mode and the static mode. It is characterized by including a control means for switching the time T1.

Further, in the solid-state imaging device driving device according to the present invention, the timing of moving the information from the sensing means to the first storage means and the timing of removing the information of the sensing means are the horizontal return of the standard television signal. It is characterized by being in or near the line period.

[Operation] In the above configuration, the present invention operates so that the dynamic resolution can be made constant by discretely accumulating within one field period. Also, by having a mode in which the number of times of accumulation differs depending on the brightness, it is possible to control the total accumulation time and perform exposure correction suitable for the condition of the subject.

Further, by switching the first predetermined time T1 between the time of capturing a subject with little motion and the time of capturing a subject with large motion, it is possible to prevent the dynamic resolution from being lowered easily even for a subject with large motion, and , It is possible to make it difficult to change the dynamic resolution depending on the screen.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a conceptual diagram of a CCD sensor used in this embodiment. This sensor is called a frame interline transfer type CCD, and the difference from FIG.
(Second storage means). The number of storage cells in the storage unit 3 is the same as the number of cells in the sensor unit 1 (sensing means). The electric charge from the sensor unit 1 is transferred to the vertical transfer register 2 (first storage unit), then to the storage unit 3 during the vertical retrace period, and then to the horizontal transfer register 4 at a predetermined timing. , Through the output amplifier 5.

Further, the sectional view and the potential diagram along the line AA ′ in FIG. 2 are the same as those in FIG. 8, and the above-mentioned charge sweeping mechanism and the charge reading mechanism from the sensor unit 1 to the vertical transfer register 2 are also included. It is the same.

FIG. 1 is a diagram for explaining the operation of the present embodiment, and explains a driving method when the CCD sensor itself shown in FIG. 2 performs exposure correction.

At the time F1, the electric charge accumulated in the sensor unit 1 until immediately before is sent from the sensor unit 1 to the vertical transfer register 2, and the electric charge for one field from the vertical transfer register 2 is rapidly supplied during the vertical flyback period. It is sent to the storage unit 3 (vertical transfer period in the figure). Thereafter, as shown in the figure, the φSUB removal pulse is generated m times at intervals of a second predetermined time T2 in one field at times S1, S2,..., Sm, and the electric charge accumulated in the sensor unit 1 is the φSUB removal pulse. It is swept out (removed) every time it occurs.

The φROG transfer pulse starts at time R1, R2,..., RN and the pulse intervals K1 × T2, K2 × T2,
…, KN-1 × T2 [where K1, K2,…, KN-1 are positive integers]
Is driven at the timing shown in FIG. Φ just before the first pulse R1
As shown in the drawing, the SUB removal pulse is delayed from the time F1 by a first predetermined time T1. Third predetermined time T3 which is a time difference between the φSUB removal pulse and the φROG transfer pulse
Are the actual sensor accumulation periods a1, a2,.
Becomes That is, in one field period, the charges accumulated in the sensor unit 1 in N small accumulation periods a1, a2, ..., AN are sequentially transferred to the vertical transfer register at times R1, R2 ,. Accumulated.

Accordingly, the sum of the charges generated in the sensor unit 1 during N fine accumulation periods having a time length of T3 within one field period, that is, the charges accumulated during the total accumulation time T0 = N × T3 Are added and mixed in the vertical transfer register, and then vertically transferred at a time at high speed and stored in the storage unit 3.

Here, φSUB removal pulse generation timings S1, S2,.
Sm and φROG transfer pulse generation timing R1, R2, ..., RN
Is set in or near the horizontal retrace period of the standard television signal. This is because if the φSUB removal pulse or the φROG transfer pulse is generated at a timing other than the above, it appears as noise on the screen.

After that, the process in which the charges accumulated in the storage unit 3 are transferred to the horizontal transfer register 4 at a predetermined timing and taken out as an output signal through the output amplifier 5 is the same as in the interline transfer CCD of FIG. .

FIG. 3 is a block diagram showing a process of processing the output signal taken out from the CCD 11. The output signal extracted from the CCD 11 is subjected to corrections such as γ correction, knee correction, automatic gain correction, etc. in the process circuit 12 and encoded to be the video signal Vo.
It is output as ut. On the other hand, the luminance signal Y being output from the process circuit 12 is input to the arithmetic circuit 14 via the averaging circuit 13 and subjected to arithmetic processing. The arithmetic circuit 14 uses the CCD driver 16 to drive the CCD 11, that is, T1 to T3.
Control.

The mode setting circuit 15 has a plurality of modes according to the conditions of the subject, and functions to select and switch one of them. Here, the plurality of modes include, for example, two modes, one is a moving mode applied to a fast moving subject, and the other is a static mode applied to a slow moving subject. Arithmetic circuit 14 receives the selection signal from mode setting circuit 15, and sets T1, T2, and T3 to predetermined values. The driver circuit 16 drives the CCD 11 according to the set values of T1, T2, and T3 set by the arithmetic circuit.

Next, a method of changing T1, T2, and T3 according to the condition of the subject will be described.

FIG. 4 is a flow chart showing an example of the algorithm of the arithmetic circuit 14. First, determine whether it is the dynamic mode or the static mode. For the dynamic mode, T1 = t1, T2 = t2, T3
= T3, Kj = kj (kj is a positive integer), for static mode, T
1 = t1 ', T2 = t2, T3 = t3, Kj = ij (ij is a positive integer)
Set T1, T2, T3 and Kj. However, t1 ′ <t1, kj <ij
It is.

This is because if T1 is set to a small value for a moving subject, the image will be blurred like a strobe action, so T1 should be increased and the accumulation of the sensor unit 1 within one field period should start. Shorten the time to end,
This is because the blur is reduced.

Next, if the level of the averaged luminance signal is greater than the reference value Y1, that is, if the subject is brighter than a certain level, Kj = kj '(kj <kj') in the dynamic mode, and Ij in the static mode. = Ij '(ij <ij'). Also, the reference value
If it is smaller than Y2 (Y2 <Y1), that is, if the subject is darker than a certain level, Kj = kj ″ in the dynamic mode, and Kj = ij ″ (kj> kj ″, ij> ij ″) in the static mode. I do. After that, the program returns to the beginning and repeats the above operation.

5 and 6 are timing charts showing T1, T2, T3 and Kj set by the algorithm of the arithmetic circuit 14 for each mode. FIG. 5 shows the case of the dynamic mode, and FIG. 6 shows the case of the static mode.

First, in the dynamic mode of FIG. 5, (a) shows that Y1 <
In the case of, that is, when the subject is bright to some extent or more, T1 = t1, T2 = t2, T3 = t3, Kj = kj '. That is, the total accumulation time is reduced by extending the accumulation interval and setting the number of accumulations N within one field period to N = n2 (n2 <n1).

(B) shows a case where Y2 ≦≦ Y1, that is, a case where the brightness is normal, and T1, T2, T3, and Kj are set at the beginning of the algorithm, and T1 = t1, T2 = t2, T3 ＝ t3, K
j = kj. At this time, the number of accumulations N within one field period is N = n1.

(C) shows that when Y2>, that is, when the subject is dark to some extent, T1 = t1, T2 = t2, T3 = t3, Kj
= Kj ″. That is, the total accumulation time is increased by shortening the accumulation interval and setting the number N of accumulations within one field period to N = n3 (n3> n1).

For the static mode of FIG. 6, except that the initial settings of the algorithm are T1 = t1 ', T2 = t2, T3 = t3, Kj = ij
This is the same as in the case of the operation mode. Therefore, (a) Y1
When <2, T1 = t1 ′, T2 = t2, T3 = t3, Kj = ij ′, and when Y2 ≦≦ Y1 in (b), T1 = t1 ′, T2 = t
2, T3 = t3, Kj = ij, and when Y2> in (c), T
1 = t1 ', T2 = t2, T3 = t3, Kj = ij ".

In the method described above, the accumulation interval (Kj × T2) (where Kj is a positive integer) is changed within one field period to change the number of accumulations N, thereby obtaining a total of one field. The accumulation time T0 can be controlled. That is, it can be changed and controlled according to the brightness of the subject, and the condition and environment of the subject.

Also, by changing the time T1 until the start of accumulation of one field according to the speed of movement of the subject, the dynamic resolution is less likely to decrease even for fast-moving subjects, and the dynamic resolution is improved on the screen. It is possible to realize an electronic shutter function whose movement does not change.

Further, the present invention can be applied to a modification or a modification of the above embodiment without departing from the gist thereof.

For example, in the present embodiment, the case where one field period is 1/60 second has been described, but the present invention is not limited to this case. Further, the present invention may be applied not only to a two-dimensional sensor but also to a one-dimensional sensor.

[Effects of the Invention] As described above, according to the present invention, there is an effect that the dynamic resolution can be made constant by discretely accumulating within one field period. In addition, by having a mode in which the number of times of accumulation differs depending on the brightness, there is an effect that the total accumulation time can be controlled and exposure correction suitable for the condition of the subject can be performed.

Further, by switching the first predetermined time T1 between the time of capturing a subject with little motion and the time of capturing a subject with large motion, it is possible to prevent the dynamic resolution from being lowered easily even for a subject with large motion, and , It is possible to make it difficult to change the dynamic resolution depending on the screen.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the operation of the embodiment of the present invention, FIG. 2 is a conceptual diagram of a frame interline transfer type CCD used in the embodiment, and FIG. 3 is a diagram for processing an output signal extracted from the CCD. FIG. 4 is a flow chart showing the algorithm of the arithmetic circuit, FIG. 5 is a timing chart showing dynamic mode operation, and FIG. 6 is a static mode operation. Fig. 7 is a timing chart, Fig. 7 is a conceptual diagram of an interline transfer CCD, Fig. 8 is a sectional view and a potential diagram taken along the line AA 'in Fig. 7, and Fig. 9 is a conventional electronic shutter. FIG. 7 is a diagram illustrating the operation of FIG. In the figure, 1 is a sensor unit (sensing unit), 2 is a vertical transfer register (first storage unit), 3 is a storage unit (second storage unit).

Claims (2)

(57) [Claims] 1. A sensing means for receiving an optical signal, performing photoelectric conversion, and accumulating information, a first storage means for reading information from the sensing means, and storing information from the first storage means. A second storage means and a removing means for removing the information of the sensing means, and by intermittently removing the information of the sensing means by the removing means twice or more within one field period, A drive device for a solid-state image sensor for controlling information storage time, comprising: a first predetermined time from a vertical synchronization signal within one field period.
After T1, the operation of the removing means is performed every second predetermined time T2, and after every predetermined number N of the operations of the removing means, the third predetermined time T3 after the end of the operation. A control unit that reads information from a sensing unit into the first storage unit, and has a moving mode for capturing a subject with large motion and a static mode for capturing a subject with little motion, A driving device for a solid-state image pickup device, comprising a control means for switching the first predetermined time T1 between the dynamic mode and the static mode. 2. The timing of moving information from the sensing means to the first storage means and the timing of removing information from the sensing means are in or near the horizontal blanking period of a standard television signal. The drive device for a solid-state image pickup device according to claim 1, wherein the drive device is a solid-state image pickup device.