JPH057345A - Image pickup device - Google Patents

Abstract

PURPOSE:To make the deterioration of picture quality due to the diffraction phenomenon of light difficult to occur, and in addition, to prevent the motion of an image picked up picture from becoming unnatural. CONSTITUTION:An image pickup element 13 is made to execute discretely accumulation plural times in one field period, and the overall accumulation time i.e., the sum of accumulation time of plural times is controlled so as to be prescribed time. In a range in which the opening amount of an iris 12 is larger than a prescribed value, by controlling, at least, one of the opening amount of the iris 12 and the overall accumulation time of the image pickup element 13, proper exposure is obtained. In the range in which the opening amount of the iris 12 is smaller than the prescribed value, by fixing the opening amount of the iris 12 at the prescribed value, and controlling the overall accumulation time, the proper exposure is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera, and more particularly to its exposure control.

[0002]

2. Description of the Related Art Conventionally, as means for realizing a function called exposure control in a video camera or the like, one using a diaphragm blade or the like for directly controlling the amount of light incident on an image sensor,
Some have used a so-called electronic shutter function, which controls the charge storage time of the image sensor.

A method using the electronic shutter function will be described below. Fig. 5 shows an interline transfer type C
In the conceptual diagram of a CD, 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. 6 is a sectional view and a potential view taken along the line AA ′ in the figure. In FIG. 6, 6 is a channel stop (CS) for pixel separation, 7 is a read-out gate (ROG) for transferring charges accumulated in the sensor unit 1 to the vertical transfer register 2, 8 is a substrate, and 9 is an oxide film. Is.

The operation of the electronic shutter will be described with reference to FIGS. 6 and 7. FIG. 7 is a diagram for one field of the standard television signal. ΦROG is a pulse applied to the lead-out gate 7, and when the logic level is “H”, the potential of the lead-out gate 7 is lowered and the sensor unit 1 The charges are transferred to the vertical transfer register 2. The removal pulse φSUB is a pulse applied to the substrate 8, and the charge accumulated in the sensor unit 1 when it is “H” is φS.
Sweep it out through the UB terminal.

In this conventional example, in FIG. 7, φROG is in the vertical blanking period and φSUB is in the horizontal blanking period. After the electric charge of the sensor unit 1 is read out at time t0, the next period starts, but φS during the horizontal blanking period until time t1.
Since UB = “H”, the charge from t0 to t1 does not remain in the sensor unit 1. Since φSUB = “L” from the time t1 to t2, the charges in this period are accumulated in the sensor unit 1 and transferred to the vertical transfer register 2 by the φROG = “H” pulse at the time t2. After all, the exposure time in this case becomes (t2-t1).

[0006]

However, in the operation of the conventional electronic shutter described above, although the function as the electronic shutter is sufficiently fulfilled, when this is used as the exposure correction, the exposure time is continuously changed especially. However, there is a problem in that the difference in the dynamic resolution at each exposure time appears on the screen as it is, resulting in a very unsightly image.

On the other hand, among the conventional examples, in the method using the diaphragm blade, when the incident light amount is large, the opening amount of the diaphragm blade becomes small (small diaphragm), a diffraction phenomenon occurs, and the image quality is easily deteriorated. There is a point. In order to solve this, a method of activating the electronic shutter function when the opening amount of the diaphragm blade becomes small has been proposed, but as described above, when the conventional electronic shutter function is used, the movement of the captured image There is a problem that it becomes unnatural.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to prevent deterioration of image quality due to a diffraction phenomenon of light and to make movement of an imaged image unnatural. An object of the present invention is to provide an image pickup apparatus that does not occur.

[0009]

In order to solve the above-mentioned problems and to achieve the object, an image pickup device of the present invention includes a sensing means for receiving an optical signal, performing photoelectric conversion, and accumulating information, and the sensing means. A diaphragm blade means for controlling the amount of light incident on the means and the sensing means are caused to discretely accumulate a plurality of times within one field period, and a total accumulation time obtained by summing the times of the plurality of accumulations. In a range in which the opening amount of the diaphragm blade means is larger than a predetermined value. By controlling at least one of the static accumulation times, an appropriate exposure is obtained, and the opening amount of the diaphragm blade means is set to the predetermined value in a range in which the opening amount of the diaphragm blade means is smaller than a predetermined value. Solid And, by controlling the overall storage time, it is characterized in that the way to obtain the proper exposure.

Further, in the image pickup apparatus according to the present invention, the predetermined value is an opening amount of the diaphragm blade means on the small diaphragm side, which is less likely to cause image deterioration due to a diffraction phenomenon of light.

[0011]

As described above, since the image pickup apparatus according to the present invention is configured, when the amount of light from the subject is large and the opening amount of the diaphragm is smaller than a predetermined value in which image deterioration due to the diffraction phenomenon is small, By fixing the aperture opening amount to this predetermined value and performing discrete accumulation within one field period so as to compensate for it, the deterioration of image quality due to light diffraction phenomenon can be avoided by controlling the accumulation time. Also, it works so that the movement of the captured image does not become unnatural.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the arrangement of an image pickup apparatus according to an embodiment. The configuration of the imaging device will be described based on FIG.

Reference numeral 11 is an image pickup lens for forming an image of light from a subject on an image pickup device 13 which will be described later, 12 is an iris for limiting the amount of light incident on the image pickup device 13 through the image pickup lens 11, and 13 is a subject. Image pickup device for converting the light of the above into an electric signal, 14 is a sample hold circuit (S / H
Circuit), 15 is an AGC circuit, 16 is a signal processing circuit, 17
Is a detection circuit, 18 is a system control circuit for controlling the overall operation of the image pickup apparatus 10, 19 is an image pickup element drive circuit for driving the image pickup element 13, and 20 is an iris drive circuit for driving the drive motor 12a of the iris 12. , 12b are Hall elements for detecting the rotation angle of the iris motor 12a.

Next, FIG. 2 is a conceptual diagram of an image pickup element used in the image pickup apparatus of one embodiment. Image sensor 1 shown in FIG.
1 is called a frame interline transfer type CCD, and the difference from the interline transfer type CCD shown in FIG. The number of memory cells in the memory unit 3 is the same as the number of sensor units 1. The charges accumulated in the sensor unit 1 are transferred to the vertical transfer register 2 and then transferred to the storage unit 3 during the vertical blanking period, and thereafter, the horizontal transfer register 4 is transferred at a predetermined timing.
And is read out through the output amplifier 5.

FIG. 3 is a diagram for explaining an operating state of the frame interline transfer type CCD shown in FIG. The so-called multi-exposure operation using the frame interline transfer type CCD will be described with reference to FIG. At 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 of the vertical transfer register 2 is rapidly stored in the storage unit 3 during the vertical blanking period. Sent (vertical transfer period in the figure). Thereafter, as shown in the figure, the φSUB removal pulse is driven m times at a predetermined time interval t2 in 1 field with S1, S2, S3, ..., Sn, and the φROG transfer pulse is pulse R1 from the middle of 1 field from time F1. R
2, R3, ..., Rn and each pulse interval K1 × t2, K2 ×
t2, ..., K (n-1) × t2 (however, K1, K2,
, (K (n-1) is a positive number). The φSUB removal pulse immediately before the first pulse R1 is
As shown in the figure, the relationship is delayed by t1 from time F1. As shown by the time difference t3 between the φSUB removal pulse and the φROG transfer pulse, the actual storage time t of the sensor is t.
This corresponds to the periods a1, a2, a3, ... Then, the total sum of the charges accumulated in the sensor unit 1 in the small accumulation periods a1, a2, a3, ..., An within this one field period is added and mixed, and the charges are vertically transferred at once at a high speed to the storage unit 3. Will be transferred. In this way, by accumulating multiple times discretely within one field period, it becomes possible to control the total amount of charges accumulated within one field period, and evenly within one field period. Since we are accumulating charges,
It is possible to provide an image with a constant dynamic resolution.

Next, the operation of the image pickup apparatus of one embodiment will be described. In FIG. 1, the light from the subject that has passed through the image pickup lens 11 is imaged on the image pickup device 13 after the light amount is limited by the iris 12. The image sensor 13 is the frame interline transfer CCD described above.
Then, the electric charge is normally accumulated for 1/60 seconds (one field period in the case of the NTSC system), transferred to the storage unit 3 during the vertical blanking period, and then the electric charge is read out through the output amplifier 5. The output signal of the image pickup device 13 (the output signal from the output amplifier 5) is sampled by the S / H circuit 14, and the AGC is performed.
After being processed by the circuit 15 and the signal processing circuit 16, the video signal is output from the output terminal 22 to the outside of the imaging device 10. On the other hand, the output signal of the S / H circuit 14 is the detection circuit 1
7, and the output signal from the detection circuit 17 is input to the system control circuit 18.

Based on the detection signal output from the detection circuit 17, the system control circuit 18 controls the iris 12 so that an appropriate exposure can be obtained when the exposure time of the image pickup device 13 is 1/60 second described above. Calculate the proper opening amount, and iris 1
It outputs an iris control signal for driving 2. This iris control signal is input to the iris drive circuit 20,
The iris drive circuit 20 drives the iris motor 12a to drive the iris 12 so that the iris 12 has an appropriate opening amount.
At this time, the opening amount of the iris 12 is determined by the Hall element 12b.
Then, the system control circuit 18 determines whether or not the iris 12 is in a predetermined small aperture state from the detection signal from the Hall element 12b. System control circuit 1
When the iris 12 is in a predetermined small aperture state and it is determined by the detection signal from the detection circuit 17 that the exposure amount of the image pickup device 13 is still large, the driving state of the image pickup device 13 is normally stored. The image pickup device drive circuit 19 is controlled so as to change the operation (the above-described operation in which the exposure time is fixed to 1/60 seconds) to the multi-exposure operation. In the multi-exposure operation, the image sensor 13 is driven so that the charge accumulation time (exposure time of the image sensor 13) is 1/60 seconds or less (in the case of the NTSC method), and as a result, the image sensor 13 is driven.
The exposure level of the signal output from the
The opening amount of the iris 13 is controlled so as not to become smaller than a predetermined small aperture state.

In the above-mentioned method, the accumulation time t3 is fixed, and the time t1 until the first accumulation starts in one field and the accumulation interval (Ki × t2) (Ki is a positive integer) are respectively set.
Alternatively, the total accumulation period as a total of one field can be controlled by changing the combination. In addition, the defect that the change in the dynamic resolution is felt like the conventional electronic shutter function is also improved.

FIG. 4 is a timing chart showing a state in which the accumulation time t1 and the accumulation interval (Ki × t2) are actually changed, and FIG. 4 (a) shows the state t shown in FIG.
Only 1 is changed. In addition, FIG.
Only (Ki × t2) is changed, and FIG.
(C) is obtained by changing both t1 and (Ki × t2).

As described above, according to one embodiment,
If the iris small aperture state is detected and it is detected that the iris is in the predetermined small aperture state, multi-exposure is performed to make sure that the iris has a smaller aperture than the predetermined small aperture state. It is possible to avoid the deterioration of image quality due to the diffraction phenomenon associated with the small aperture. Also,
In the multi-exposure operation, the accumulation periods a1, a2, a
Since 3, ..., An are evenly distributed within one field period, it is possible to perform natural exposure compensation without feeling a change in dynamic resolution.

The present invention can be applied to a modified or modified version of the above embodiment without departing from the spirit of the invention.

[0022]

As described above, according to the image pickup apparatus of the present invention, when the light amount from the subject is large and the aperture opening amount is smaller than the predetermined value in which the deterioration of the image quality due to the diffraction phenomenon is small, By fixing the aperture opening amount to this predetermined value and performing discrete accumulation within one field period so as to compensate for it, and by controlling the accumulation time, deterioration of image quality due to light diffraction phenomenon is avoided, Moreover, there is an effect that the movement of the captured image does not become unnatural.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of an image pickup apparatus according to an embodiment.

FIG. 2 is a conceptual diagram of a frame interline transfer CCD used in the image pickup apparatus of FIG.

FIG. 3 is a diagram illustrating an operation of the image pickup apparatus.

FIG. 4 is a diagram illustrating a method of changing a storage time of an image sensor.

FIG. 5 is a conceptual diagram of an interline transfer CCD.

FIG. 6 is a sectional view and a potential view taken along the line AA ′ of FIG.

FIG. 7 is a diagram illustrating a conventional electronic shutter operation.

[Explanation of symbols]

1 sensor 2 Vertical transfer register 3 storage 4 Horizontal transfer register 5 output amplifier 11 lenses 12 Iris 13 Image sensor 14 S / H circuit 15 AGC circuit 16 Signal processing circuit 17 Detection circuit 18 System control circuit 19 Image sensor drive circuit 20 Iris drive circuit

Claims (2)

[Claims] 1. A sensing means for receiving an optical signal and performing photoelectric conversion for accumulating information, a diaphragm blade means for controlling the amount of light incident on the sensing means, and the sensing means are discrete within one field period. A plurality of times, and an accumulation time control means for controlling so that a total accumulation time obtained by summing the times of the plurality of accumulations becomes a predetermined time. In a range in which the opening amount of the blade means is larger than a predetermined value, at least one of the opening amount of the diaphragm blade means and the total accumulation time is controlled to obtain an appropriate exposure. In the range where the opening amount of is smaller than the specified value,
An image pickup apparatus, characterized in that an appropriate amount of exposure is obtained by fixing the opening amount of the diaphragm blade means to the predetermined value and controlling the total accumulation time. 2. The image pickup apparatus according to claim 1, wherein the predetermined value is an opening amount of the aperture blade unit on the small aperture side, in which image deterioration due to a diffraction phenomenon of light is small.