JP2790294B2 - Electronic still camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic still camera that magnetically records a video signal obtained by a solid-state imaging device on a floppy disk.

[Prior Art] Conventionally, photometry is performed by an external photometric sensor, the aperture and shutter speed are determined based on the values, and a temporary exposure (hereinafter, pre-exposure) is performed before performing exposure for recording (hereinafter, main exposure). There is known an electronic still camera that performs exposure) and corrects the exposure level at the time of main exposure according to the level of the video signal.

In the pre-exposure in this case, an electronic shutter function is used.

[Problems to be solved by the invention]

However, there is a problem that the relationship between the shutter speed of the electronic shutter and the output video signal level is not linear during pre-exposure. In other words, there is a defect that a difference between the position of the electronic shutter pulse with respect to the “charge readout pulse” and the exposure time occurs, and a proper exposure cannot be obtained.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an electronic still camera configured to always obtain an appropriate exposure in view of the above points.

[Means for solving the problem]

In order to achieve such an object, an electronic still camera according to the present invention includes a photometric operation unit that performs a photometric operation based on the output of a photometric element to determine an aperture value and an electronic shutter speed, and a shutter speed obtained by the photometric operation. The apparatus includes a correction unit for adding a correction term, and an exposure unit for performing exposure corresponding to shutter speed information obtained from the correction unit.

(Operation)

According to the present invention having such a configuration, it is possible to obtain an appropriate video signal level even with a faster shutter speed (short-time side) by adding an offset to the accumulation time at the time of the electronic shutter and correcting it. Become.

〔Example〕

 Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a block diagram showing one embodiment of an electronic still camera to which the present invention is applied. In this figure, 1 is a CPU for controlling the system of the entire camera, 2 is a driver for driving a mechanical mechanism of a lens, an aperture and a shutter, 3 is a dimmable flash device, and 4 is a distance measuring sensor (hereinafter referred to as an AF sensor) ), 5 is an automatic exposure sensor (hereinafter referred to as AE sensor), 6 is a light control sensor (hereinafter EF)
Reference numeral 7 denotes a colorimetric sensor (hereinafter, referred to as an AWB sensor) that measures the color temperature of external light.

8 is shooting mode, track number, time, date, ID
It is a liquid crystal display for displaying information such as. A driver 9 drives a sheet motor for rotating a video floppy disk as a recording medium and a magnetic head for recording. Reference numeral 10 denotes an image sensor, 11 denotes a signal processing circuit, and 12 denotes an image recording circuit.

13 is an input / output interface circuit composed of a group of mechanical switches, 14 is a battery, and 15 is a lithium battery for a liquid crystal display and a clock. 16 is a sheet motor for rotating the video floppy disk, 17 is a lens, 18 is an aperture, and 19 is a shutter. 20, 21 are release switches SW1 and SW2.

22 is a setting mode selection switch for shooting mode, exposure compensation, time, date, ID, etc., 23 is a field / frame switch, 24 is a selection switch for setting time, date, ID, etc., 25, 26 are time, date , An up / down switch for setting an ID.

27, 28 are shooting mode selection switches for signal, continuous shooting, self-timer, etc. 29 is a lock switch for inhibiting camera operation, 30, 31 is a switch for selecting the flash shooting mode, 32 is an instant exposure compensation switch for backlighting Reference numeral 33 denotes a write protect switch for detecting that the erroneous write prohibition is broken, reference numeral 34 denotes a load completion switch for detecting that a video floppy disk has been inserted, and reference numeral 35 denotes a switch for detecting the head position.

Reference numerals 36, 37, 38 denote code plates for detecting the position of the lens.
Reference numerals 39 and 40 denote tele and wide switches, respectively.

 First, a normal shooting sequence will be described.

When the ON operation of SW1 20 is detected, CPU 1
To measure the distance to the subject, and perform photometry by the AE sensor 5. When the combination of the aperture and the shutter speed is determined according to the program diagram (see FIGS. 6 and 8) provided in advance based on the photometric value,
The color measurement is performed by the AWB sensor 7.

Next, when the ON operation of SW221 is detected, the CPU 1 sends the lens through the driver 2 based on the distance information from the AF sensor 4.
17 is driven to the in-focus position. At the same time, the aperture 18 is set to the aperture value determined by the photometric calculation. Then, the user drives the shutter 19 to expose the surface of the CCD 10.

After the exposure, the CCD surface information is recorded from the recording system 12 through the signal processing system 11 to the video floppy disk via the head.

Next, the pre-exposure performed before the main exposure using the aperture and the shutter speed determined by the output obtained from the AE sensor 5 will be described.

After setting aperture 18 by metering calculation, shutter 19
Is half-opened (not shown) so that exposure is performed on the surface of the CCD 10. At this time, pre-exposure is performed by the electronic shutter function of the CCD.

FIG. 2 is a waveform diagram showing the timing of the electronic shutter and the obtained pre-exposure output (hereinafter referred to as ALC-OUT).

Figure 3 is a diagram showing a range in which the ALC-OUT is obtained on one screen, the video signal up to 227.5 _H from 99.5 _H is integrated ALC-OUT is formed.

As shown in FIG. 1, a signal Vpulse is input to the CPU 1 from the signal processing system 11. At the timing of the pulse called Vpulse, the charges exposed and accumulated on the surface of the CCD 10 are read. Here, when the E-shutter-Pulse is output from the CPU 1 to the signal processing 11, the charges accumulated up to that point are read and discarded, and the accumulation time becomes the accumulation time until the next Vpulse comes, and the charge accumulated by the Vpulse. Only read.

Therefore, the shutter speed of this electronic shutter is from E-shutter-Pulse to the next Vpulse. At this time, since the ALC-OUT is output from the signal processing system 11 after 99.5 _H after Vpulse, the CPU 1 reads the A / D converted at a certain timing.

Next, Vpulse and E-shutter-Pulse are described using the timing chart shown in FIG. 4 and the flowchart shown in FIG.
(Electronic shutter pulse) and offset will be described. In particular, a case where an electronic shutter pulse is used at the time of pre-exposure will be described.

When the ON operation of SW120 is detected in step # 1, the process proceeds to step # 2, and the AF sensor 4 performs distance measurement. Next, proceeding to step # 3, photometry by the AE sensor 5 and colorimetry by the AWB sensor 7 are performed. Here, AE calculation is performed (see FIGS. 7 and 9), and the aperture and shutter speed are determined.

Next, when the ON operation of SW221 is detected in step # 4, the process proceeds to step # 5.

On the other hand, if the ON operation of SW221 is not detected in step # 4, the process returns to step # 3 to perform photometry and colorimetry.

Proceeding to step # 5, focus drive is performed based on the distance measurement result of step # 2. Next, the process proceeds to step # 6, and the diaphragm is driven based on the photometric result of step # 3.

Next, the process proceeds to step # 7, where a calculation for pre-exposure is performed. Here, 10 _H after the rise of Vpulse in FIG.
Is read out, so E-shutter
If the -Pulse came out, T _V of the figure corresponds to the shutter speed.

Here, the following operation is performed to obtain T _V ′.

_{T V '= 1V-T V} +10 H Then, post-rise T _V of V _P' after, put E-shutter-Pulse to the signal processing system 11 from CPU 1. At this time, in the present embodiment so as subtracting the offset value of [Delta] T _V as _{T V '= 1V-T V} +10 H -ΔT V.

Thus, the value of T _V + ΔT _V is as shutter speed.

When the calculation for the pre-exposure in step # 7 is completed,
Proceeding to step # 8, pre-exposure is performed. Here, the ALC-OUT is read from the exposure obtained by the electronic shutter pulse, and the shutter speed is corrected. Then, in step # 9, the mechanical shutter is driven based on the recalculation.

In steps # 10 and # 11, main exposure is performed, and recording is performed on a floppy disk.

As for the program diagram for determining the aperture value and the shutter time based on the photometric value, the shutter time at the time of the electronic shutter is the reading interval of the image sensor (Vp in this embodiment).
Since a high-speed time of less than 1 cycle (usually 1/60 second (1 V period)) can be realized, the diagram of FIG. 7 is different from that of the mechanical shutter (FIG. 6) at the time of the electronic shutter.

Further, in a camera in which the iris can take only discrete values such as a turret type, the diagram of FIG. 8 is used for a mechanical shutter, and the diagram of FIG. 9 is used for an electronic shutter. To determine.

Also, these program diagrams are only examples, and other diagrams can of course be used.

In the embodiments described so far, the correction term is a fixed value. However, it is possible to correct the variation included in the video signal output circuit by writing the value for each camera (for each imaging element) in an E ² PROM or the like. Becomes possible.

〔The invention's effect〕

As described above, according to the present invention, when the electronic shutter function is operated, an appropriate exposure can be obtained by adding a correction term to the shutter speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic still camera to which the present invention is applied, FIG. 2 is a timing diagram when an electronic shutter is used, and FIG. 3 shows an effective portion of an ALC-OUT signal in one screen. FIG. 4 is a timing chart of an electronic shutter pulse, FIG. 5 is a flowchart showing a control procedure of the present embodiment, and FIG. 6 determines an aperture value and a shutter time for a photometric value at the time of a mechanical shutter. FIG. 7 is a program diagram for determining an aperture value and a shutter speed for a photometric value at the time of an electronic shutter, and FIG. 8 is a camera having an aperture that can only take a discrete aperture value. Fig. 9 is a program diagram for determining an aperture value and a shutter time for a photometric value at the time of a mechanical shutter in Fig. 9. Fig. 9 is an electronic diagram of a camera having an aperture that can only take a discrete aperture value. Is a program diagram for determining when the aperture value and shutter speed with respect to the photometric value at Yatta. 1 ... CPU, 2 ... Driver, 3 ... Dimmable flash device, 4 ... Distance sensor, 5 ... Automatic exposure sensor, 6 ... Dimmable sensor, 7 ... Colorimetric sensor, 8 ... Liquid crystal display, 9 Driver, 10 Image sensor, 11 Signal processing circuit, 12 Image recording circuit, 13 Input / output interface circuit.

Claims (1)

(57) [Claims] 1. A photometric calculation means for performing a photometric calculation based on an output of a photometric element to determine an aperture value and an electronic shutter speed; a correction means for adding a correction term to the electronic shutter speed obtained by the photometric calculation; An electronic still camera, comprising: an exposure unit that performs exposure corresponding to electronic shutter speed information obtained from a correction unit.