JPH0713322Y2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A Industrial Field of Application The present invention relates to an image pickup apparatus, and is particularly suitable for application to an image pickup apparatus having a shutter function.

B Outline of the Invention The invention is to visually reduce the pulsation of the brightness level and the color temperature of a captured image by setting the timing of the shutter opening to an irregular timing asynchronous with the vertical synchronization signal in the imaging device. You can

C. Related Art Conventionally, in this type of image pickup device, there is one in which the charge accumulation time of the light receiving portion is switched to obtain a shutter function (Japanese Patent Laid-Open No. 56-8966).

That is, as shown in FIG. 3, reference numeral 1 denotes a frame interline transfer type CCD solid-state image pickup device as a whole, and a plurality of light receiving portions 2 formed of photoelectric conversion elements for accumulating charges according to the amount of incident light are arranged in a matrix. It is located in.

The light receiving section 2 has a transfer gate 3 and an overflow control gate 4, respectively, and transfers the accumulated charges to the vertical transfer register section 5 and the drain section 6, respectively.

That is, as shown in FIG. 4, in the image pickup apparatus, based on the field determination signal S _F (FIG. 4A) in which the logical level is inverted every field in synchronization with the vertical synchronization signal, the field determination signal is generated. The gate switching signal S _VAA (FIG. 4 (B)) that rises to the logic “H” after the logic level falls to the logic “L” with the time point t1 at which the logic level of S _F is inverted interposed therebetween, A gate control signal S _XSG (fourth falling pulse P1 falling at time t1 and a second falling pulse P2 falling at a timing advanced by a predetermined period from the first falling pulse P1) (C) is generated.

While the transfer gate 3 transfers the charge of the light receiving section 2 to the vertical transfer register section 5 at the timing when the gate control signal S _XSG falls while the logic level of the gate switching signal S _VAA is logic “L”. The overflow control gate 4 transfers charges to the drain section 6 at the timing when the gate control signal S _XSG falls while the logic level of the gate switching signal S _VAA is logic “H”.

As a result, in the light receiving section 2, the period from the fall of the first falling pulse P1 during the period of one field to the fall of the second falling pulse P2 in synchronization with the vertical synchronizing signal. While the electric charge accumulated during T2 is transferred to the drain portion 6 and discharged, after the fall of the second falling pulse P2 and until the fall of the first falling pulse P1. The charges accumulated during the period T1 are transferred to the vertical transfer register unit 5
Transferred to.

The storage unit 7 takes in the charges transferred to the vertical transfer register unit 5, and then sequentially transfers the charges to the horizontal transfer register unit 8 at a cycle of horizontally scanning the light receiving units 2 arranged in a matrix.

The horizontal transfer register unit 8 sequentially outputs the transferred charges, and thus the charges accumulated in the light receiving unit 2 during the period T1 are
The data can be sequentially output at the timing of raster scanning (FIG. 4 (C)).

Therefore, by setting the timing of the second falling pulse P2 with respect to the first falling pulse P1 to a predetermined timing, after the second falling pulse falls at the timing synchronized with the vertical synchronizing signal, It is possible to obtain a captured image in which the shutter is opened during the period T1 until the trailing pulse of 1 falls.

D is a problem to be solved by the present invention. However, in this type of image pickup device, when the shutter opening time (that is, period T1) is shortened and a subject is imaged by a high-speed shutter, the brightness level and color of the picked-up image are reduced. There is a problem that the temperature changes.

That is, since the shutter opens at the timing synchronized with the vertical synchronizing signal, for example, the field frequency is 60 [H
z], the shutter opens regularly at a 1/60 second cycle.

On the other hand, when the subject is illuminated by, for example, a fluorescent lamp driven by a commercial power source, the fluorescent lamp is repeatedly lit at the frequency of the commercial power source. Inevitably, the frequency of the commercial power source changes.

Therefore, when a subject whose brightness level and color temperature change in this way is imaged with a high-speed shutter, the difference frequency between the frequency of the commercial power supply and the field frequency of the shutter opening,
There is an unavoidable problem that the brightness level and color temperature of the difference image fluctuate.

In particular, the shutter opens regularly at a cycle of 1/60 second, but the frequency of the commercial power source cannot avoid pulsation, so in the captured image, the brightness level and color temperature are accompanied by the pulsation of the frequency of the commercial power source. It will pulsate.

Therefore, particularly when illuminated with a commercial power source with a frequency of 60 Hz, there is a problem that the brightness level and color temperature of the captured image pulsate at a frequency that is extremely low, and the captured image becomes visually unsightly. .

The present invention has been made in consideration of the above points, and an object thereof is to propose an image pickup apparatus capable of visually reducing the pulsation of the brightness level and the color temperature of a picked-up image.

E Means for Solving the Problems In order to solve the problems, in the present invention, based on the charges obtained from the photoelectric conversion elements 2 arranged in a matrix during a predetermined period T1 during one field period. hand,
In the image pickup apparatus 10 configured to form a picked-up image, the predetermined period T1 is set at a timing asynchronous with the vertical synchronization signal.

By setting the F action period T1 to a timing asynchronous with the vertical synchronizing signal, the shutter can be opened at irregular timing, and as a result, the pulsation of the brightness level and color temperature can be effectively reduced visually.

G Embodiment One embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 denotes an image pickup apparatus as a whole, and by controlling the image pickup device 1 based on a drive signal output from a drive circuit 11, the shutter opening timing is controlled to be a timing asynchronous with the vertical synchronizing signal. It is something that is done.

That is, as shown in FIG. 2, the drive circuit 11 has a random number generating circuit, and based on the random number generated by this random number generating circuit, the field discriminating signal S _F (second The logic level in the figure (A)) is at time points t3, t4, t5 ...
After reversing with ..., the gate switching signal S _VAA (Fig. 2 (B))
Period until the logic level of T3, T4, T5 ……
However, the gate switching signal S that changes irregularly for each field
Generate _VAA .

Further, in the gate control signal S _XSG1 (FIG. 2 (C)), the first falling pulse P1 falls while the logic level of the gate switching signal S _VAA falls to the logic "L", and The second falling pulse P2 is made to fall at a timing earlier than the falling pulse P1 by the period T1.

Therefore, in the image pickup device 1, the shutter is opened during the period T1 at irregular timing asynchronous with the vertical synchronizing signal during each one field period (FIG. 2 (D)), and the light is received during the period T1. The charges accumulated in the section 2 are transferred to the vertical transfer register section 5 via the transfer gate 3 (FIG. 3).

The drive circuit 11 further controls the transfer of the charges transferred to the vertical transfer register unit 5 to the storage unit 7 at the timing at which the logical level of the field determination signal S _F is inverted, and the charges transferred to the storage unit 7 are horizontally transferred. Transfer control to the transfer register unit 8 is performed in a horizontal scanning cycle.

Thus, by sending out the charges via the horizontal transfer register unit 8, it is possible to obtain a picked-up image in which the shutter is opened at irregular timings that are asynchronous with the vertical synchronizing signal for each field.

Therefore, for example, in a commercial power source with a frequency of 60 [Hz],
Since the frequency pulsates at a frequency almost equal to the field frequency, opening a regular timing shutter in synchronization with a vertical synchronizing signal for an object under a fluorescent lamp using such a commercial power source causes pulsation of the commercial power source. Depending on the brightness level and color temperature, the image is very ugly and pulsating, and the image is very unsightly.On the other hand, if the shutter is opened at an irregular timing that is asynchronous to the vertical sync signal,
It is possible to obtain a captured image in which the brightness level and the color temperature change irregularly at the field frequency regardless of the pulsation of the commercial power supply.

As a result, the brightness level and color temperature vary irregularly at the field frequency even under lighting conditions where only a visually unsightly captured image is obtained due to pulsation of the brightness level and color temperature. As a result, it is possible to obtain a captured image in which the change in the brightness level and the color temperature can hardly be visually sensed.

Thus, the pulsation of the brightness level and color temperature of the captured image can be significantly reduced visually.

In the above configuration, the drive circuit 11 controls the overflow control gate 4 and the transfer gate 3 to open the shutters at irregular timings asynchronous with the vertical synchronization signal for each field, and the opening time of the shutters. After controlling the transfer of the charge accumulated during (that is, in the period T1) to the vertical transfer register unit 5,
These are controlled so as to be sent out from the horizontal transfer register section 8 at the timing of raster scanning.

According to the above configuration, the pulsation of the brightness level and the color temperature can be visually reduced by opening the shutter at irregular timings that are asynchronous with the vertical synchronization signal for each field.

In the above-described embodiment, the present invention is applied to an image pickup device that obtains a shutter function by discharging the electric charge accumulated in the light receiving portion to the drain portion during the period other than the period in which the shutter is opened. Although the present invention has been described above, the present invention is not limited to this, and can be widely applied, for example, to the case of using an image pickup device which controls the light receiving element to the active state only during the period when the shutter is opened.

H Effect of the Invention As described above, according to the present invention, the pulsation of the brightness level and the color temperature of the captured image is visually recognized by setting the timing for opening the shutter to an irregular timing that is asynchronous with respect to the vertical synchronization signal. Can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image pickup device according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation, FIG. 3 is a schematic plan view showing an image pickup device, and FIG. FIG. 7 is a signal waveform diagram for explaining the operation. 1 ... Image sensor, 2 ... Light receiving part, 3 ... Transfer gate, 4 ... Overflow control gate, 10 ...
… Imaging device, 11 …… Drive circuit.

Claims (1)

[Scope of utility model registration request] 1. A photoelectric conversion means converts incident light incident within a photoelectric conversion period having a fixed time length into signal charges,
An image pickup unit that outputs the signal charges accumulated in the photoelectric conversion period as an image pickup signal, and a control unit that starts the photoelectric conversion period at an irregular timing that is asynchronous with the vertical synchronization signal. Image pickup device.