JPH0523674B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electronic still camera that photographs a subject using an imaging means such as a solid-state imaging device and records the imaging signal on a rotating recording medium such as a magnetic disk. , relates to program exposure control in the still continuous shooting mode of an electronic still camera.

[Background of the invention]

Recently, imaging devices such as solid-state image sensors and image pickup tubes,
In combination with a recording device that uses a rotating recording medium such as a magnetic disk that is inexpensive and has a relatively large storage capacity,
Electronic still cameras have been developed that take still images of subjects purely electronically, record them on a rotating recording medium, and reproduce the images using a separate television, printer, or the like.

In addition to the original still camera mode, which takes single shots, this type of electronic still camera has a still continuous shooting mode that takes advantage of the characteristics of the imaging element and built-in recording disk to take a large number of frames in succession. ing. Still continuous shooting modes include continuous shooting mode in which images are taken by opening and closing the shutter (referred to here as ``mechanical still continuous shooting mode''), and continuous shooting mode in which images are taken by reading out an image sensor such as a CCD while the shutter is open. mode (herein referred to as "electronic still continuous shooting mode").

However, let us consider the number of frames taken per second when program exposure control is adopted in still continuous shooting mode. If you set this number of frames to a certain degree, you will be able to take pictures with the quick return mirror in the viewfinder optical system raised, but this will require additional time for charging the shutter, metering, correcting aperture errors, and reading out the image sensor. If the shutter time is considerably long, the number of frames captured will be less than the number of frames on the magnetic disk, and the desired number of frames cannot be recorded.

If the subject is dark and the shutter speed is slow, you can be instructed to stop using continuous shooting mode, but even if the color conditions deteriorate, such as when shooting to correct the form of a sports photo, There may be times when you want to use continuous shooting mode, and in that case, the user's desire should be prioritized.

[Purpose of the invention]

The present invention has been made in view of these circumstances, and aims to ensure the maximum number of frames to be taken while respecting the photographer's intentions in both mechanical still continuous shooting mode and electronic still continuous shooting mode. The purpose of the present invention is to provide a programmable exposure control electronic still camera.

[Summary of the invention]

In order to achieve the above object, the present invention includes a photographing optical system including an aperture mechanism, an imaging means for converting a subject image formed by the optical system into an electrical video signal and storing it, and a rotating recording medium for transmitting the video signal. a shutter placed between the photographing optical system and the imaging means, a single still mode, a mechanical still continuous shooting mode that takes pictures by opening and closing the shutter, and a shutter placed between the photographing optical system and the imaging means; a photographing mode switching means for switching between an electronic still mode and a movie mode for photographing by reading; an aperture and a shutter; an imaging means; and recording control means for controlling the recording means, reading the video signal obtained by exposing the imaging means, and recording it on a rotating recording medium, and the recording control means for controlling the recording means to read out the video signal obtained by exposing the imaging means and record it on a rotating recording medium, and the recording control means responds to an instruction of a mechanical still continuous shooting mode. while fixing the lower limit speed of the shutter.
The present invention is characterized in that it includes a circuit that fixes the number of frames to be photographed per unit time in accordance with an instruction for electronic still continuous shooting mode.

In the present invention, for example, in a mechanical still continuous shooting mode of 10 frames per second, the lower limit of the shutter speed is fixed at 1/125 seconds, while in an electronic still continuous shooting mode, the number of frames to be taken is fixed at 15 frames. As a result, the entire system can operate normally and the number of captured images will not be less than the number of recorded images.

〔Example〕

Preferred embodiments of the electronic still camera according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an electronic still camera according to the present invention. In the figure, the photographing optical system includes, for example, a zoom lens system 10 as a foreground lens system, an aperture 12, and a master lens system 14.
also serves as a beam splitter for the photometric optical system 24. Reference numeral 16 denotes a mirror for the viewfinder optical system, which is flipped up out of the optical path during photographing. 18 is an optical filter, and 20 is a shutter. Shyatsuta 20
In the still mode, the mirror is flipped up and the aperture is closed for a predetermined period of time, but in the movie mode, it remains open. 22 is a CCD of an image sensor.

A portion of the subject light taken into the photometric optical system 24 is received by a photometric sensor 26, amplified by a photometric amplifier 28, and input to an arithmetic/control circuit 32 via an A/D converter 30. The arithmetic/control circuit 32 controls the shutter and the diaphragm through the shutter drive circuit 34 and drive mechanism based on information such as the brightness of the subject that has been taken in, thereby obtaining an appropriate amount of exposure.

40 is a CCD drive circuit/preamplifier that drives the CCD, reads out and amplifies the charge, 42 is an encoder that converts it into a video signal, and 44 is a recording amplifier that amplifies the video signal. An encoder 42 provides an output to an electronic viewfinder or monitor, and a recording amplifier 44 provides an output to an external video adapter. The recording amplifier 44 is also connected to a recording head 48 via a recording/playback switch 46. 50 is a magnetic disk for recording video signals, 52 is a disk motor, 54
56 is a servo circuit for rotating the disk 50 at a constant speed; and 58 is a drive circuit for the motor 60 that feeds the recording head 48.

70 is a control circuit that receives signals from each circuit section and controls the overall operation; 72 is a control circuit that generates timing pulses under its control; Reference numeral 74 indicates a release timing pulse generating circuit, 76 indicates a switching means for switching between still mode and movie mode, and 78 indicates a display unit for displaying the operating status of the camera, etc.

The switching means for switching between still mode and movie mode is specifically a multi-connector for attaching accessories, and has a function of obtaining a signal to automatically switch to movie mode when an electronic viewfinder or video adapter is attached.

The operation of the electronic still camera according to the present invention configured as described above in still mode, movie mode, and still continuous shooting mode will be explained with reference to FIGS. 3, 4, and 5.

FIG. 3 is a timing chart during still mode photography. In the figure, VD is a synchronization signal created by inverting the vertical synchronization signal. Therefore, the pulse rate is 60pps. In this case, since the camera is in the still mode, the signal from the still/movie switching means 76 remains at a low level.
After checking the shutter movement and pressing the release button (switch) 74, commands from the control circuit 70 and calculation/exposure control circuit 32 cause the aperture to
2 is open, the A/D converter 30 sends photometric data to the calculation/exposure control circuit 32. Based on the data, the calculation/exposure control circuit 32 calculates a combination of an appropriate shutter speed and an appropriate aperture value according to the program exposure method, and first sends a pulse to the stepping motor drive circuit 36. The stepping motor drive circuit 36 operates the stepping motor using, for example, a two-phase excitation method to narrow down the aperture 12 to the calculated value. Therefore, the photometry calculation system performs photometry again using the aperture photometry method. The reason why photometry is performed again in this way is because the photographing element of an electronic still camera has a narrower latitude than that of a silver halide still camera, and requires more accurate exposure control. Based on this re-measured light value, the shutter speed is finally determined, and a pulse corresponding to the exposure time is output to the shutter drive circuit 34 for exposure.

In Figure 3, the blank space from after exposure to opening the aperture is
This is the time taken to return the mirror 16 of the viewfinder optical system to its home position and to open the aperture, and corresponds to the time taken to wind up the camera in a silver halide still camera. Note that although the mirror 16 is flipped up in response to pushing up the release button 74, in the case of this embodiment, the photometric light beam is taken in from before the mirror 16, so re-photometry is not affected in any way.

FIG. 4 is a timing chart when shooting in movie mode. In this case, since the electronic viewfinder or video adapter is attached to the multi-connector when the accessory is attached, the still/movie switching signal becomes high level. Therefore, the release signal is ignored and photometry is started. The optical viewfinder mirror 16 remains raised. The stepping motor is driven based on the photometry result, but since photometry and aperture value control are performed with the aperture stopped down, compared to still mode,
The stepping motor 36 only needs to compensate for variations in brightness, and the amount of operation is generally small.
When the aperture correction is completed, exposure is performed. Note that movie mode may be driven at the same pulse rate as still mode, but since the previous state narrowed down at each correction is used as the starting point,
Since the amount of aperture correction is small, the stepping motor pulse rate is lowered than in still mode.
It is also possible to achieve smooth control with even less overshoot and ringing.

Figure 5 shows continuous shooting by opening and closing the shutter.
This is a timing chart when shooting in mechanical still continuous shooting mode, which records on the camera's built-in magnetic disk. When the release button 74 is pressed, photometry is started and the images are narrowed down based on the results. At the same time, the quick return mirror 16 is flipped up. Once the aperture is complete, the light is measured again, and the error is absorbed by correcting the shutter speed. Exposure is then performed, and charge is transferred from the photographing element 22. The first photograph is now taken, and in preparation for the next shot, the shutter 20 is wound up and the mirror 16 is returned to its normal position. Since the aperture 12 remains closed, the light is immediately measured again, and exposure, transfer, and shutter winding are repeated to take continuous pictures. As is clear from the figure, it takes six synchronization signals to take one photo. Therefore, at 60/6, it is possible to take 10 images per second. In this case, if the shutter speed is slow (the exposure time is long), the time taken to take one image increases, making it impossible to take a predetermined number of images per unit time.

Therefore, in the present invention, a lower limit value is set for the shutter speed, and only short-time exposures exceeding the lower limit value are permitted.

On the other hand, when shooting in electronic still continuous shooting mode, the quick return mirror is flipped up, the shutter is held open, and the charge is read out from the image sensor. time is necessary. Therefore, in the electronic still continuous shooting mode, we decided to set an upper limit on the number of frames that can be taken.

FIG. 2 shows an example of a program diagram. In the figure, the lower limit of shutter speed in mechanical still continuous shooting mode is fixed at 1/125 seconds. On the other hand, in the electronic still continuous shooting mode, it takes one synchronization signal to transfer the charge and three synchronization signals to feed the magnetic disk head, so the number of frames is 60/(1+3)=15. If higher-speed shooting is required, connect an external video recorder to record.

Note that a signal instructing to fix the lower limit value of the fixed shutter speed or to specify the number of frames is issued from the control device.

〔Effect of the invention〕

As explained above, the present invention fixes the lower limit of shutter speed in mechanical still continuous shooting mode, while in electronic still continuous shooting mode,
Since the number of frames to be photographed is fixed, an electronic still camera can be obtained in which charge transfer and video recording are performed at appropriate timings.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an electronic still camera according to the present invention, FIG. 2 is a program diagram showing an example of the program exposure method used in the present invention, and FIG. 3 is a diagram showing the still mode shooting mode. 4 is a timing chart when shooting in movie mode, and FIG. 5 is a timing chart when shooting in mechanical still continuous shooting mode. 10...Front group lens system, 12...Aperture, 14...
... Master lens system, 16 ... Mirror, 20 ... Shutter, 22 ... Image sensor (CCD), 24 ... Photometry optical system, 26 ... Photometry sensor, 28 ... Photometry amplifier, 30 ... A/D conversion device, 32... calculation/exposure control circuit, 34... shutter drive circuit, 36...
... Stepping motor drive circuit, 38 ... Stepping motor, 40 ... CCD drive circuit/preamplifier, 70 ... Control circuit, 72 ... Timing pulse generation circuit, 74 ... Release, 76 ... Still/movie mode switching means.

Claims (1)

[Scope of Claims] 1. a photographing optical system including an aperture mechanism; an imaging means for converting a subject image formed by the photographing optical system into an electrical video signal and storing it; and recording the video signal on a rotating recording medium. a shutter disposed between the photographing optical system and the imaging means; a single still mode, a mechanical still continuous shooting mode in which images are taken by opening and closing the shutter, and a shutter disposed between the photographing optical system and the imaging means; a photographing mode switching means for switching between an electronic still continuous shooting mode and a movie mode to be photographed by readout; and controlling the aperture and shutter according to the brightness of the subject taken in from the photographing optical system and a switching signal from the photographing mode switching means; An electronic still camera comprising an imaging means and a recording control means for controlling a recording means, reading out a video signal obtained by exposing the imaging means, and recording it on the rotating recording medium, wherein the recording control means is a mechanical The electronic camera is characterized by comprising a circuit that fixes the lower limit speed of the shutter in accordance with an instruction for an electronic still continuous shooting mode, and fixes the number of frames to be taken per unit time in accordance with an instruction for an electronic still continuous shooting mode. still camera. 2 The fixed circuit changes the shutter speed by 1/2 in response to an instruction for a mechanical still continuous shooting mode of 10 frames per second.
The electronic still camera according to claim 1, characterized in that the circuit fixes the number of frames per second to 125 seconds, and fixes the number of frames to be taken at 15 frames per second according to an instruction for an electronic still continuous shooting mode. .