JPS6132670A - Image pickup device - Google Patents

Abstract

PURPOSE:To control exposure within the limit of exposure control by decreasing exposure at the prescribed rate by exposure control means as well as increasing sensitivity only at the prescribed rate out of limit of exposure control. CONSTITUTION:An arithmetic control circuit 8 operates photographing conditions from output condition of a photometric circuit 12, a shutter second time set circuit 13, a stop set circuit 14, a mode selection circuit 15, and integration circuit 17, etc. The integration circuit 17 is for the purpose of integrating a video signal through a gain control circuit 6. The arithmetic control circuit indicates exposure information in the input terminal of a gate circuit 23 as well as controlling stop driving circuit 9 for driving stop 2 based on the photographic condition operated, a shutter driving circuit 10 for driving shutter, a clock driver 11 for driving an image pickup element, a gain control circuit 6, an oscillator 19 and a switch circuit 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an imaging device capable of controlling the sensitivity of an imaging means.

(Prior art) When photographing using a conventional imaging device, the sensitivity of the existing imaging device is not sufficient for objects with low brightness.As a countermeasure for this, artificial lighting or electrical signal processing is required. The sensitivity of the image sensor is improved by increasing the gain of the system, which is being done in the four nose bases. The latter case, that is, the case of electrically increasing the sensitivity of the imaging device, will be described in detail. 1For example, some conventional video cameras 2 are equipped with an ALO circuit that automatically controls the aperture according to the output of the imaging means. In such a camera, when the aperture reaches its maximum aperture and the average output level of the imaging means is lower than the appropriate value, the gain is automatically increased.

On the other hand, in recent years, imaging devices for capturing still images have come into consideration, and in such still image capturing devices, exposure control and sensitivity control must be performed in a short time.

Therefore, servo control of exposure is unsuitable because it requires a long time, and continuous control of sensitivity is also unsuitable in terms of time and structure.

That is, if you try to control the sensitivity continuously, the control signal t
-The disadvantage is that the configuration becomes complicated because the image must be converted to V, and if you try to control it discretely to simplify this, conventionally it takes a long time to follow up with the servo for exposure control such as aperture. It had the disadvantage of being too wide.

(Objective) It is an object of the present invention to eliminate such drawbacks of conventional devices.

Another object of the present invention is to relate to an imaging device that can simplify the configuration of sensitivity control means. Another object of the present invention is to obtain an imaging device with good exposure control responsiveness.

(Example) The contents will be explained in detail below based on embodiments of the present invention.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 is an optical system for forming a subject image, 2.3 is an aperture 9.3 serving as an exposure control means, respectively. Shutter.

4 is an image pickup device as an image pickup means such as a CCD image pickup tube; 5
1 is a process processing circuit, 6 is a gain control circuit as a sensitivity control means, and 7 is a recording section.

8 is an arithmetic control circuit; a photometric circuit 12. Shutter time setting circuit 13. Aperture set circuit 14° mode selection circuit 1
5. Photographing conditions are calculated from the output state of the integrating circuit 17 and the like.

Here, the integration circuit 17 is for integrating the video signal passed through the gain control circuit 6f.

The arithmetic control circuit adjusts the aperture lens 2 based on the calculated shooting conditions.
Aperture drive circuit for driving 9. Shutter drive circuit for driving the shutter 10° Clock driver for driving the image sensor 11° Gain control circuit 6
1 oscillator 19. Switch circuit 21. In addition to controlling
Exposure information and the like are displayed on the input terminal of the gate circuit 23.

Incidentally, 19 is an oscillator for causing the display device 24t to blink. 20 is a frequency divider, 21 is a switch circuit, 22 is a NAND gate, and 23 is a gate circuit. Also 18
is a resistance for forming a high-level potential. or,
DI+Y is a display section as a display means.

Next, the operation of the arithmetic control circuit 8 of this embodiment is shown in FIG. 2(a).
, (b), (Q) will be explained based on the 70-chart.

In FIG. 2(a), when the power supply (not shown) is turned on, the program in the arithmetic control circuit starts (step (1)).
), reads the setting mode of the mode selection circuit 15. (
Step (2)) Then, it is determined in step (3) whether or not the aperture priority mode is selected, and if so, the process proceeds to a subroutine for the aperture priority mode in step (4).

Further, if it is determined in step (3) that the mode is not the aperture priority mode, it is first determined in step (5) whether or not the mode is the shutter priority mode. If it is not the shutter priority mode, the process proceeds to step (6) K advance, manual mode subroutine.

Further, in the case of the shutter priority mode, the process proceeds to step (7).In the embodiment, the case of the shutter priority mode will be explained.

From FIG. 2(b) onwards, the flowchart of the shutter priority mode is shown. In the figure, first, the shutter time TV set in the shutter time setting circuit 15 is read. (Step (8)) Here, TV is a type of exposure amount, and Ap
0 then step (
9) reads the photometric value Bv from the photometric circuit 12, where By is MUFI! Corresponds to the brightness value in the method, and
For example, the photometry circuit 12 converts a part of the luminous flux behind the aperture 2 into sp
0, which is detected at step a, etc. Then, at step θ, Av==Bv−Tvt− is calculated. Here, A is a type of old exposure amount and corresponds to the aperture value in the 5PBX method.

Furthermore, in step 01), it is determined whether or not the aperture value Avd is greater than or equal to the aperture value AVO (exposure control limit) in the open state of the lens. If not.

That is, if the aperture value is smaller than the fully open state, the aperture value is decreased by one step in step (12).

That is, the aperture -it, which is reduced by one step of the diaphragm, is set to the H value. Also, in step θ9, the gain control circuit 6
Double the gain of ・Also, along with this, step (1
4), convert the arithmetic control circuit 8O output (xl”2) to (1, o)
In this case, the aperture display value on the upper display device 24 is made to blink.

That is, the output (X+, x2) is normally (o, o), and in this state the oscillation of the oscillator 19 is stopped and the switch 21 is connected to the a side. Therefore, at this time, the output of the NAND gate 22 is at a high level, and the input signal of the SIGUT circuit 230 is output as is as an output signal.

Further, various calculation results of the mining calculation control circuit are inputted as input signals to the gate circuit 2S.

- Therefore, this is normally displayed as is on the display device 24.

However, when x1=1 in step θ4), oscillator 1
9 starts oscillation, and the gate circuit 23 is closed in accordance with the division frequency f7 of this oscillation signal, so that the displayed value on the display flashes.

Note that since the shutter priority mode is selected here, the aperture value is displayed as the display value.

Next to this step θ4), in step θ5), it is determined whether the aperture value V is smaller than the aperture value VVO when the lens is open, and if not, the aperture value AV is set as VVO. (Step θ6)) Step θ1)
In addition, in the case θ5), V≧V.

In this case, or if MuV=MuVO is set in step 06), the process moves to the next step θ7).

That is, from step 0υ onwards, in the sequence for shooting, it is first determined in step θ8) whether or not the release switch (not shown) is turned on, and if it is turned on, the process proceeds to the next step θ9). The aperture drive circuit 9 is driven by the output of the arithmetic control circuit 8, and the aperture 2 is stopped down to the aperture value AV.

Then, in step (2), the integral output of the integrating circuit 17 is inputted.Actual aperture photometry using the virtual image element 4 is thereby performed with the aperture aperture being stopped down to the aperture value AV.

Next, in step (21), this actual aperture photometry result B
Using V and the set value TV of the shutter time setting circuit 13, the aperture value is reset.

That is, the recalculated aperture value is determined as m'v=%-TV.

Furthermore, the aperture error, mv=4-Av, is determined.

Next, in step (22), this dV is added to control the aperture aperture value to become AV.

Next, in step (2), it is determined whether the modified aperture aperture value I'-1) is smaller than the aperture value 'vo of the E lens, and if it is smaller, the process proceeds to step (24) and the gain control circuit has already been used. It is determined whether the gain has increased by one step.

If the gain has not been increased yet, the gain is doubled in step (25), and accordingly.

The throttle opening value AIv at this time is made to blink in the same manner as in step θ4). (Step (26)) Further step (2
In step 7), the aperture value is increased by one step (the diaphragm is closed down by one step).It is determined in step (28) whether this aperture value Av1 is smaller than aVO.

If Av'≧mm7°, exposure control is possible within the range of aperture values larger than the lens aperture value mu7°, so the process proceeds to step (31).

If it is determined in step (24) that the gain has already been increased, or if it is determined in step (2B) that WAv□, it is determined that proper mist control is impossible; In step (29), the blinking cycle of the displayed value is changed.

That is, the output of the arithmetic control circuit 8 ("l #" is (1, 1)
By doing so, the switch 21 is connected to the b side.

A signal is input to the input of the HAND gate 22 at a high frequency. Therefore, the blinking cycle of the displayed value on the display device 24 becomes faster.

Also, once after that, in step (5), the aperture value A of the aperture
After closing ~ at 7 degrees, proceed to step (Sl).

Note that even if it is determined in step (2) that A'v, ≧'vo, appropriate exposure control is possible, so the process proceeds to step (6).

Step (in step 3, correct the aperture value of the diaphragm so that it becomes 4).

After that, in step (32), the shutter is operated to open for a predetermined time to perform exposure, and in step (35)
The image formed by this exposure is then read out, processed by a processing circuit 5, and recorded in a recording section 7 via a cane control circuit 6 having a constant gain of 7fr.

After that, if the power is turned on, the process returns to step (1) again and the same control is performed. As explained above, according to this embodiment, even if the sensitivity of the imaging device changes unexpectedly due to exposure conditions, the operator can accurately grasp this change, making it possible to prevent the failure of taking an image unexpectedly. .

For example, instead of increasing the apparent sensitivity by increasing the gain and performing imaging, it is possible to perform imaging with priority on image quality, such as changing the illumination state and performing imaging.

In addition, in order to perform such a display, since the gain-up state is indicated by blinking the display on the first display device, there is no need to increase the number of display elements, and the display can be performed with a simple configuration. can. Furthermore, if the exposure cannot be optimized even after the gain is increased, the blinking cycle is changed, which has the effect of simplifying the structure of the display device. The oscillation (blinking) period may be changed by changing the amount of increase in sensitivity of the image sensor according to the amount of underexposure (for example, increasing by one step or increasing by two steps). Also, in this example, we have explained the aperture V priority mode, but the same applies to shutter priority mode, program mode, etc. At that time, the displayed aperture value (or chasse,
Of course, it is also possible to make changes similar to those described above (stepwise) to increase the sensitivity and issue an underexposure warning.

Further, in this embodiment, a gain control circuit is used as the sensitivity control means, but the present invention is not limited to this, and it may be possible to change the bias of the target electrode of the image pickup tube, for example. This includes everything that can adjust the gain of the image sensor.

Further, in the embodiment, the operating state of the sensitivity control means is displayed by the blinking period, but for example, the sensitivity value may be displayed numerically, or the change in sensitivity may be made to correspond to a change in color of another display. Further, in the embodiment, if it is determined that the exposure is outside the limits of exposure control.

Since the sensitivity is increased by a predetermined percentage and the exposure amount is controlled to be decreased according to the predetermined percentage, the exposure amount can be kept within the limits of exposure control, and the responsiveness of exposure control can also be improved. Since the target value is fixed, it becomes faster.

Therefore, even if sensitivity control is performed discretely, the time required for corresponding exposure control is short, so the responsiveness of the imaging device is not impaired and the configuration for sensitivity control can be simplified.

In the example, the exposure control amount is set to H when the sensitivity is doubled, but in general, the aperture value and the actual aperture value may deviate slightly near the aperture value when the lens is open. There is. In that case, if you increase the sensitivity by n times and set the exposure control amount strictly to 1/n, you will not be able to obtain an appropriate exposure level.Therefore, in the above case, the exposure amount should be adjusted taking into account the amount of error. Just control it.

It also includes things similar to the present invention.

Further, in the embodiment, an aperture is used as an exposure control means, but a shutter may be used, or a combination of both may be used.

In addition, in the example, the sensitivity is increased by one step (2 steps) to simplify the explanation.
(double), but you can also increase it by two steps or more.

(Effects) As explained above, the imaging device of the present invention increases the sensitivity by a predetermined percentage outside the limits of exposure control, and accordingly, the exposure amount is decreased by approximately the predetermined percentage by the exposure control means. This allows the calculated amount to be kept within the limits of exposure control.

Moreover, sensitivity control can be controlled discretely.

Therefore, the configuration of the sensitivity control means can be simplified. Furthermore, the responsiveness of exposure control is also improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of an imaging device according to the present invention;
FIGS. 2(a) to 2(0) are 70-charts showing the operation of the imaging apparatus of the present invention. 60.・Gain control circuit as sensitivity control means

Claims (1)

[Scope of Claims] Imaging means for converting an optical image into an electrical signal; exposure control means for controlling the exposure state of the imaging means; sensitivity control means for controlling the sensitivity of the imaging device; and the exposure control. an arithmetic control means for controlling the sensitivity control means to increase the sensitivity by a predetermined proportion and to reduce the exposure amount by the exposure control means by approximately the predetermined proportion outside the limits of exposure control by the means; Device.