JP2531668B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus called program automatic exposure, which performs exposure control for determining an aperture value and a shutter speed depending on the brightness of a subject.

〔Technical field〕

Conventionally, there was no electronic still camera capable of both field recording and frame recording. Further, even in a camera using a silver salt film, the program line was switched by a manual operation, or by the open F value of the lens, the focal length of the lens, etc., but the switching of the program line by the field resolution was not considered. . Further, in the silver-salt film camera, there is no means for detecting the film resolution, and there is no relation between the resolution and the number of frames that can be photographed, so switching the program line depending on the resolution has little meaning.

[Problems to be solved by the invention]

With the objective of automatically enabling exposure control that takes advantage of the high resolution of frame images and the number of frames that can be captured on the medium of field images, and selecting the field recording according to various imaging conditions. There is.

[Means for solving problems]

In an image pickup apparatus capable of frame recording and field recording, the exposure constant determination program diagram is changed depending on whether the recording mode is frame recording or field recording.

[Work]

This makes it possible to select the optimum program diagram for both the frame recording mode and the field recording mode.

〔Example〕

FIG. 1 is a block diagram of an electronic still camera of one embodiment of the image pickup apparatus of the present invention. FIG. 2 is an exposure determination program diagram of the embodiment of the present invention, where a is a frame recording and b
Is at the time of field recording. FIG. 3 is a flow chart when the control block 14 of FIG. 1 is realized by a CPU, and FIG. 4 is a control block of FIG.
14 is another flowchart when 14 is realized by a CPU.

In FIG. 1, 1 is an optical system for forming a subject image on an image pickup device 4, 2 is a diaphragm for the image pickup lens 1,
3 is a shutter, 4 is an image pickup device such as a MOS or CCD, 11 is a driver for operating the device 4, 7 is a device 4
Is a sample and hold circuit for sample-holding the output of the above and distributing it to the first field and the second field. 8a and 8b are process circuits for converting R, G and B signals into luminance signals Y and color difference signals, 9a and 9b are modulation circuits, and 10a and 10b
Is a recording amplifier, 6a and 6b are recording heads, 12 is a circuit 11,
Synchronous signal generation circuit for supplying operation clock to 7, 8a and 8b, 13 driver for diaphragm 2 and shutter 3, 15 compression circuit for logarithmically compressing output of light receiving element 5, 16 digital signal for analog signal of circuit 15 A / D converter for converting to, 14
Is a controller for controlling the operation sequence of the entire circuit and is realized by a CPU or the like.

17 is a photometric circuit composed of circuit elements 5, 15 and 16;
Reference numeral 18 is a recording block circuit, and 19 is a color temperature detection circuit for detecting the color temperature of a light source illuminating a subject. 20 is a release signal from a release button, continuous shooting for setting the number of frames to be shot, a signal from a single-shot switching switch, a signal for instructing whether or not to record sound, a signal for instructing an electronic shutter operation of an imaging device, and field shooting. , A selector circuit for inputting a signal or the like for instructing which mode of frame photographing is to be performed and sending it to the controller 14.

Reference numeral 21 is a microphone, and 22 is a light source such as a flash light source, which emits light in response to a trigger signal from the controller 14 and sends to the controller 14 a light emission preparation for the light source, for example, a charge completion signal for a capacitor in the power supply.

A distance measuring circuit 23 measures the distance to the subject by a known method and inputs this to the controller 14. Reference numeral 24 is a display circuit that performs various displays according to signals from the controller 14.

 The operation of FIG. 1 will be described below.

When a release signal is input from a release button (not shown) during recording, the controller 14 will cause the heads 6a, 6b to
The disk-shaped recording medium (not shown) facing the
The field recording mode or the frame recording mode is selected according to the output of the selector circuit 20 and the like, and a drive pulse is given to the imaging device via the driver 11.

Further, the controller 14 obtains the Av value and the Tv value for giving an appropriate exposure according to the subject brightness information obtained from the photometry circuit 17 and the above-mentioned fields / frames, and according to this, the aperture and the shutter (or Controls the storage time of the imaging device). In addition, Av and Tv have shown the opening value and time value in APEX calculation here.

A method of determining Av and Tv will be described later. The controller 14 uses the determined Av and Tv data to control the diaphragm and the shutter (or the imaging device via the driver 11 when controlling the accumulation time) via the driver 13 to perform a predetermined imaging. The image pickup result is read and recorded on the medium by the sample hold circuit 7, the process circuit 8, the modulation circuit 9, the recording circuit 10, and the head 6.

In the field recording mode, the circuits of 8, 9 and 10 are 8a, 9a,
10a works, 8b, 9b, 10b does not work. In the frame recording mode, 8a, 8b, 9a, 9b, 10a, 10b operate and heads 6a, 6b
Signals of odd and even fields are recorded via.

Considering the difference between the characteristics of the frame recording and the field recording, although the frame recording has a high resolution, it is one frame with two fields, so the number of recordable frames per medium is small. On the other hand, in field recording, conversely, the resolution is low, but the number of recordable frames is large.

Considering this characteristic, it is desirable to select an aperture value and shutter time at the time of frame recording so as to make use of high resolution as compared with the field recording. That is, in the embodiment of the present invention, a region near a wide open area with a relatively large aberration and a shallow depth of field and a small aperture area where the influence of the diffraction of the aperture is large are avoided, and the intermediate aperture is used, whereby the characteristics of the frame recording are improved. The exposure that makes the best use of is obtained.

Further, in the field recording, when the same image pickup device is used as compared with the frame recording, the sensitivity is 1 Ev higher in principle. Therefore, in the embodiment, a high-speed shutter time is used so as to make use of this. Since there are many frames that can be recorded during field recording, it is highly likely to be used for continuous shooting, and it is rational to use such high-speed shutter seconds.

Next, the program diagram of this embodiment having such a device will be described with reference to FIG. FIG. 2a shows a program curve at the time of frame recording, but this curve is divided into four regions according to the subject brightness.

The first is the area from darkness to Bv2, where the intermediate aperture value is used, the shutter time becomes longer and camera shake easily occurs, so it is open. Since the open aperture of the lens is assumed to be 1.4, 1/60 corresponds to Bv2. (Here, the sensitivity of the imaging device is ISO100 when recording frames.
(Sv = 5), ISO200 (Sv = 6) is assumed during field recording. ) Next, in the brighter region from the brightness when the shutter speed becomes 1/60, the constant aperture control is performed until the intermediate aperture is reached. In this diagram, it is assumed that the aperture area where the best image is obtained with this lens is F4 to F8.
Up to Bv5, which is 4 or 1/60, becomes the shutter priority control area. Next, in the area brighter than F4 and 1/60 (Bv5), it is a diagram that connects straight lines until it reaches F8 with the fastest shutter. At brightness of F8, 1/2000 (Bv12) or higher, the shutter speed cannot be shortened any further, so the aperture is controlled.

On the other hand, during field recording, the curve is switched to the curve b in FIG. 2, and this curve is divided into three areas.

In other words, it is an open area from darkness to Bv3, a fixed area at 1/2000 second when brighter than Bv13 or more, and a program area in which a relatively straight line connects these areas.

As described above, this program takes advantage of the high sensitivity of field recording to cut off high-speed shutter.

From the Bv value obtained from the photometric circuit 17, the Av value as shown in FIG.
An algorithm as shown in FIG. 3 can be considered to obtain the combination of Tv values.

That is, after reading Bv data from the photometric circuit in S1,
The field recording mode or the frame recording mode is determined in S2, and the Bv value read in the frame recording mode is 2, 5, 12
And S3, S4, and S5 respectively, and select the formula for determining the Av value and Tv value by the Bv value. The formula (1) is Is. The equations S6, S7, S8 and S9 give Av and Tv on the curve as shown in FIG.

On the other hand, when recording a field, the Bv value is 3,13 and S10,
The comparison is made in S11, and the arithmetic expressions of S12, S13, and S14 are selected according to the comparison result.

The formula (2) is Is.

Instead of calculating Av and Tv by calculating in this way, a ROM is built in the controller 14 or the like to determine the field / frame and Av, Tv previously stored in the ROM by the Bv value.
The table may be addressed.

Next, FIG. 4 is a diagram showing a configuration example of an image pickup device, and an example of an interline CCD will be described. That is, 25 is a pixel cell arranged in a matrix, 26 is a vertical transfer register for vertically transferring the signal of each pixel, and 27 is a horizontal shift register for horizontally transferring the signal of each vertical shift register.

After the exposure for a predetermined time by the shutter, the image pickup device is shielded from light. After that, in the field recording (shooting) mode, the signals of a pair of vertically adjacent pixels are added by the vertical shift register, and a signal of half the number of rows is added as a whole, and then read by the horizontal shift register for each row.

Further, in the frame mode, pixel signals of odd rows are transferred to the vertical shift registers after the light is shielded, and then vertically transferred row by row and horizontally transferred by the horizontal shift register to output as odd field signals. Next, pixel signals of even rows are similarly transferred to the vertical shift register, and then vertically and horizontally transferred to be read out as even field signals.

Therefore, in the frame mode, the signal of each pixel is read as it is, whereas in the field mode, the signals of two pixels are added and then read, so that the sensitivity is doubled.

That is, the sensitivity is increased by 1 Ev as compared with the frame mode.

5 to 7 are program diagrams of another embodiment of the present invention, where a is for the frame mode and b is for the field mode.

As in the case of FIG. 2, the diagram of FIG. 5 controls the aperture intermediately during the frame, and controls the shutter speed to be faster in the field mode.

Further, FIG. 6 shows an example in which an intermediate diaphragm is used in both modes, but the field mode makes the shutter speed faster.

Further, in FIG. 7, bending points and slopes are changed as compared with those in FIG. In both cases, the aperture is emphasized during the frame, and the aperture is changed smoothly, and conversely, the shutter speed is faster during the field.

In the above embodiment, an example is shown in which one program diagram is provided for each of the frame mode and the field mode, but a plurality of program diagrams that are switched according to various conditions in each mode may be provided. Not to mention good things.

As described above, according to the present embodiment, since the exposure characteristics are positively changed so as to make the best use of the respective characteristics in the frame mode and the field mode, optimum exposure is possible. It should be noted that almost the same image is obtained in the frame mode and the field mode only by adjusting the sensitivity so that the amount of signals formed by the imaging device becomes equal by the Tv, Av, or the gain controller according to the switching of the field and the frame. In contrast to the above, only the image obtained based on the optimum exposure characteristic can be obtained according to the configuration of the present embodiment.

Next, FIG. 8 is an operation flow chart showing another characteristic of the electronic camera shown in FIG. 1. Even if the frame mode and the field mode are preselected by the selector 20, the recording mode can be changed according to other conditions. It has a feature in that is automatically changed to the optimum mode.

That is, to explain with reference to FIG. 8, the program starts when the power supply (not shown) is turned on, and it is determined in S26 whether or not a release signal is received, and if not, the process proceeds to S37. S
At 37, it is determined whether the input of the selector 20 has changed, and if so, the counter in the controller 14 is reset at S38 and then the process returns to S26. If the input of the selector 20 does not change, the process directly returns to S26.

When the release signal comes, it is checked in S27 whether it is the field mode or not. In the field mode, the field recording operation is performed in S36.

If the frame mode is selected in S27, then it is determined whether or not the continuous shooting mode is selected in S28. If it is the continuous shooting mode, the process automatically advances to S36 to perform the field recording operation. In continuous shooting mode, the number of frames that can be recorded will be halved in frame mode even if the frame mode is set in advance.
This is because, considering operability and practicality, priority should be given to increasing the continuous shooting effect by increasing the number of frames even if the resolution is slightly reduced.

If it is the single shooting mode, it is determined in S29 whether or not it is the voice recording mode, and in the voice recording mode, the field recording is automatically set.

This is because the audio track is required separately from the video track, and the number of recordable frames is prevented from being extremely reduced even during audio recording, which has a great practical effect.

If the voice recording mode is not set in S29, it is determined in S30 whether or not the electronic shutter mode is set. Here, the electronic shutter mode is a mode in which the electronic still camera is controlled so that the shutter 3 is opened and an image is formed by the accumulation time of the diaphragm and the imaging device according to the brightness of the subject. In this mode, since the shutter is open, the image is deteriorated due to smear when trying to read in the frame mode. Therefore, the image quality can be maintained by automatically switching to the field mode and transferring the pixel signal to the vertical shift register (FIG. 4) shielded from light so that smear does not occur.

 Next, in S31, it is determined whether or not the strobe mode is set.

When a strobe switch (not shown) is turned on, this strobe signal is input to the controller 14 via the selector 20,
The power source of the light source 22 is turned on, and charging of the capacitor in the power source is started.

In strobe mode, see the output of the distance measuring circuit 23 in 32,
Object distance D is determined not or away than the predetermined distance D _0, and when to S36 field recording mode of D> D _0.

This is because the ambient light is often relatively dark in the strobe mode, and the sensitivity is often insufficient when the subject distance is long. Of course, if the strobe guide number is large enough, the lack of sensitivity can be compensated, but there is a limit to that.
Further, if the gain of the output of the image pickup device is simply increased by an amplifier, the S / N is deteriorated. Therefore, in this embodiment, the field mode is set to improve the sensitivity without deteriorating the S / N.

Next, in S33, it is determined whether or not the charging to the capacitor is completed, and if not completed, the field recording mode is set. At this time, the display 24 also indicates that charging is not completed and that the field recording mode has been switched.

Similar to the case of S32, this is to effectively prevent the image from being extremely underexposed due to insufficient sensitivity when recording is performed by strobe emission in a state where charging is not completed.

When the strobe mode is not set in S31 and the charging is completed in S33, the count value T of the timer is set to the predetermined time T in S34.
_{If it is 0} (for example, 10 seconds) or more, and if T> T ₀ , it is automatically switched to the field recording mode. This is based on the statistic that the frame recording mode is a special recording mode in this electronic still camera, and usually the image is recorded and recorded in the field recording mode overwhelmingly.
This is to give priority to a mode with a high frequency. Since this is done, the operator can always perform field recording quickly, and the operability is significantly improved.

After the recording is completed, in S37, it is determined whether or not an operation member (release button, continuous shooting switch, voice recording switch, electronic shutter switch, field / frame switching switch, strobe mode switch, etc.) for input to the selector 20 is operated. If it is operated, the timer is reset. Here, since the timer is reset by the operation of the operation members other than the field / frame switching switch, the frame recording can be performed while the other operation members are variously operated for the frame recording mode. .

[Effect]

As described above, according to the present invention, optimum exposure characteristics can be obtained in the field recording mode and the frame recording mode.

Further, since field recording and frame recording are optimally selected under various conditions, it is possible to always record high quality images.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration example of an imaging device, FIG. 2 is a first embodiment diagram of a program diagram, FIG. 3 is a diagram showing an example of a control flow chart, and FIG. Is a diagram for explaining the driving of the image pickup device, FIGS. 5 to 7 are second to fourth examples of program diagrams, and FIG. 8 is a diagram for further explaining the operation of the first illustrated apparatus.

Claims (3)

(57) [Claims] 1. An imaging device capable of frame recording and field recording, wherein the exposure constant determining program diagram is changed depending on whether the recording mode is frame recording or field recording. 2. A program diagram in which a wide range of BV values that utilize AV in a range of good resolution among AV values of a lens is widened during frame recording, and a program diagram in which a speed is relatively high during field recording. The image pickup apparatus according to item 1. 3. The image pickup apparatus according to claim 1, wherein field recording is automatically selected according to various image pickup conditions.