JP2695519B2 - Imaging device and solid-state imaging device driving device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device such as a solid-state imaging device used for a video camera and the like, and a driving device of the solid-state imaging device.

[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 the diaphragm blades, 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. 8 is a conceptual diagram of an interline transfer type CCD, wherein 1 is a sensor unit for performing photoelectric conversion, 2 is a vertical transfer register, 4 is a horizontal transfer register, and 5 is an output amplifier. FIG. 9 is a sectional view and a potential diagram along the line AA ′ in the figure.

In FIG. 9, 6 is a channel top (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. 9 and 10. FIG. FIG. 10 is a diagram for one field of the standard television signal, φROG is a pulse applied to the readout gate 7, and when the theoretical 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. 10, φROG is during a vertical flyback period, and φSUB is during a horizontal flyback 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.

Accordingly, the present invention has been made in view of the above-described problems, and has as its object to realize an electronic shutter function capable of performing exposure correction with a constant dynamic resolution and suitable for the conditions of a subject. It is an object of the present invention to provide an imaging device and a driving device for a solid-state imaging device.

[Means for Solving the Problems] In order to solve the above problems and achieve the object, the image pickup apparatus according to the present invention discretely accumulates a predetermined time T3 a predetermined number of times N, thereby performing a predetermined total operation. Accumulation time T0 = N × T3
And a first drive mode in which the predetermined number of times N is changed while keeping the predetermined time T3 constant in order to change the total accumulation time T0 according to the brightness, Even if the predetermined number of times N is set to 1 and the brightness is too high, the predetermined time T3 is set to T3 '(T3'
<T3) and a second drive mode.

Further, the solid-state image pickup device driving apparatus of the present invention receives a light signal, performs photoelectric conversion, and stores information, sensing means, first storage means for reading information from the sensing means, and the first storage means. It has a second storage means for storing information from the storage means and a removing means for removing the information of the sensing means, and intermittently removes the information of the sensing means two or more times within one field period. In the driving device of the solid-state image pickup device for controlling the information storage time by removing the data by the means, the operation of the front-back removing means is performed by the second predetermined time after the first predetermined time T1 from the vertical synchronizing signal within one field period. The operation is performed every time T2, and every time the operation of the removing means is performed a predetermined number of times N, the information from the sensing means is stored in the first storage means after a third predetermined time T3 from the end of the operation. Read into Allowed, if the predetermined number N is 1, in which the manner decreases the third predetermined time T3.

[Operation] In the above configuration, the present invention operates so that the dynamic resolution can be kept constant by performing discrete accumulation within one field period. In addition, by providing a mode in which the number of times of accumulation is changed according to the brightness, it is possible to control the overall accumulation time and perform exposure correction suitable for the conditions of the subject. Furthermore, by having a mode in which the accumulation time is shortened when the brightness is equal to or higher than a predetermined level, proper exposure can be obtained even for a subject having high brightness.

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.

The sectional view and the potential diagram along the line AA 'in FIG. 2 are the same as those in FIG. 9, and the mechanism for sweeping out the charges and the mechanism for reading out the charges from the sensor unit 1 to the vertical transfer register 2 are also included. The same is true.

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.

Further, the φROG transfer pulse starts from the middle of one field from the time F1, and the time R1, R2, ..., RN and each pulse interval 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
However, as shown in the figure, the actual sensor accumulation times a1, a2, ..., aN
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.

Thereafter, the process of transferring the electric charge stored in the storage unit 3 to the horizontal transfer register 4 at a predetermined timing and extracting it as an output signal through the output amplifier 5 is the same as that of the interline transfer CCD shown in FIG. .

FIG. 3 is a block diagram showing a process of processing an output signal extracted from the CCD 11. The output signal extracted from the CCD 11 is subjected to corrections such as γ correction, near correction, automatic gain correction, etc. in the process circuit 12, and is encoded into a video signal.
It is output as V _out . 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 drives the CCD 11 via the CCD driver 16, that is, T 1 to T
Control 3

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. Here, the arithmetic circuit 14 has a first drive mode and a second drive mode,
The second drive mode is a mode applied when the subject is extremely bright, and the first drive mode is a mode applied when the subject has other brightness. The switching between the first drive mode and the second drive mode is performed by the second drive mode when the output signal from the averaging circuit 13 is> Y0, and by the first drive mode otherwise. This is automatically determined and performed inside the arithmetic circuit 14.

The driver circuit 16 has T1, T2, T3 set by the arithmetic circuit 14.
The CCD 11 is driven according to the set value of.

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

FIG. 4 is a flowchart showing an example of the algorithm of the first drive mode of the arithmetic circuit 14 in a flowchart. First,
It is determined whether the mode 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 the static mode, T1 = t1 ', T2 = t2, T3 = t3, Kj = ij
T1, T2, T2 and Kj are set like (ij is a positive integer). Here, t1 ′ <t1, kj <ij.

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.

FIGS. 5 and 6 are timing charts showing T1, T2, T3 and Kj set by the algorithm of the first driving mode 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 other words, when the subject is brighter than a certain level, T1 = t1, T2 = t2, T3 = t3, and 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) is a case of Y2 ≦≦ Y1, that is, a case of normal brightness, and T1, T2, T3, and Kj are set as T1 = t1, T2 = t2, T3 = t3, Kj
= Kj. At this time, the number of accumulations N within one field period is N = n1.

(C) shows a case where Y2>, that is, a case where the subject is darker than a certain level, and T1 = t1, T2 = t2, T3 = t3, and Kj = k.
That is, the total accumulation time is increased by shortening the accumulation interval and setting the number of accumulations N 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 ".

FIG. 7 is a diagram showing the operation in the second drive mode. In the algorithm of the first driving mode of the arithmetic circuit 14 described above, as the brightness of the subject increases, φRO
The number of G transfer pulses is reduced, and as a result, the number N of times of accumulation within one field period is reduced to make the output of the output amplifier 5 constant. However, when the subject is extremely bright, that is, when the averaged luminance signal is larger than Y0, the output of the output amplifier 5 is too large even if the number of accumulations N in one field period is 1. There is.
In such a case, the second mode shown in FIG. 7 is selected inside the arithmetic circuit 14, and T3 = T3 '(T3'<T3) is set, and the accumulation time is set short.

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 moving speed of the subject, the moving resolution does not easily decrease even for a fast moving subject, and the moving resolution varies depending on the screen. An electronic shutter function that does not change can be realized.

Furthermore, the first drive mode in which the storage time T3 is constant and the second drive mode in which the storage time T3 is changed for an extremely bright subject
With this driving mode, it is possible to widely cope with the conditions of the subject.

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. Also, by having a mode in which the number of accumulations is changed according to the brightness, there is an effect that it is possible to control the total accumulation time and perform exposure correction suitable for the condition of the subject. Furthermore, by having a mode in which the accumulation time is shortened when the brightness is equal to or higher than a predetermined value, it is possible to obtain an appropriate exposure even for a subject having high brightness.

[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 block diagram showing a process, FIG. 4 is a flow chart showing an example of an algorithm of the first driving mode of the arithmetic circuit, and FIG. 5 is a timing chart showing the operation of the dynamic mode. FIG. 6 is a timing chart showing the operation in the static mode, FIG. 7 is a view showing the operation in the second drive mode, FIG. 8 is a conceptual diagram of the interline transfer CCD, and FIG. FIG. 8 is a sectional view and a potential diagram taken along the line AA ′ in FIG. 8, and FIG. 10 is a diagram for explaining the operation of the conventional electronic shutter. 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 (3)

(57) [Claims] 1. An image pickup device for obtaining a predetermined total storage time T0 = N × T3 by discretely storing a predetermined time T3 a predetermined number of times N, wherein the total storage is performed according to brightness. In order to change the time T0, the first drive mode in which the predetermined number of times N is changed while keeping the predetermined time T3 constant, and when the predetermined number of times N is set to 1 and the brightness is too bright The predetermined time T3 to T3 '(where T3'<
An image pickup apparatus including a control unit having a second drive mode defined as T3). 2. 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 a first storage means for storing information from the first storage means. 2 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 two or more times within one field period, A drive device for a solid-state image sensor for controlling 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 for each of a predetermined number N of the operations of the removing means,
Information from the sensing means is read into the first storage means after a third predetermined time T3 from the end of the operation, and the third predetermined time T3 is decreased when the predetermined number N is 1. A drive device for a solid-state image pickup device characterized by the above. 3. A timing for moving information from said sensing means to said first storage means and a timing for removing information from said sensing means are within or near a horizontal retrace period of a standard television signal. 3. The driving device for a solid-state imaging device according to claim 2, wherein: