JPS6249786A - Electronic still camera - Google Patents

Abstract

PURPOSE:To decrease power consumption by supplying driving power to all the circuits and means by depressing of a shutter switch, photographing an object after an image pickup means goes to a stable state, then the object is recorded after a recording medium goes to a stable state, to limit the supplying period of the driving power supply to respective circuits and means, to the necessary minimum. CONSTITUTION:When a power supply source switch 12 closes under an instruction fro a system control circuit 10, the drive power from a power source 11 is supplied to all the circuitries and devices of the titled still camera. The state of the recording medium is detected by the first state-detector 8 and the second state-detector 9. When the medium 5 goes to a stable state, a shutter 2 is released until a prescribed period of exposure lapses, and the object is photographed. Thereafter, the object stored in the image pickup device 3 is read out, subjected to a signal processing circuit 4, and recorded in a recording medium 5. When the recording ends at a time T8, the switch 12 accepts an instruction to open, and the power supply to respective components of the titled camera is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic still camera that takes and records still images, and particularly to power saving of an electronic still camera.

Conventional technology Conventional examples of power saving for electronic still cameras include:
There are two main types, typified by JP-A-58-33370 and JP-A-68-96475. The former is the first. 2nd 1. Provide a switch, 1st
By operating the switch, power is supplied to all the circuits of the electronic still camera, and the rotation of the disk motor (drive means that drives the recording medium), which has the largest electrical inertia among the parts that make up the electronic still camera, is in a steady state. The second after stabilizing
It is configured to photograph and record a subject by operating a switch (corresponding to a shutter switch). In the latter case, by operating the shutter switch, power is immediately supplied to all circuits and the subject is photographed, the subject image is held in the imaging device, and after the disk motor reaches steady rotation,
The camera is configured to read out this subject image from an imaging device and record it.

Problems to be Solved by the Invention However, the conventional example of the above configuration has the following problems.

First of all, the problem with the former is that power is supplied to all circuits by operating the first switch, so the period of power supply is longer than the period required for actual shooting and recording, and the power saving effect is small. There is.

In the latter case, after photographing the subject, it is necessary to hold the subject image in the image sensor until the motor reaches steady rotation and can be recorded.This period is relatively long, so There is a problem in that the SN ratio of the recorded image deteriorates due to dark current generated in the image sensor. By the way, the time required for the disk motor to reach steady rotation is generally about 0.3 seconds or more, and in current image sensors, the value of dark current generated during this time is extremely large, and the image quality is The deterioration of the SN ratio cannot be ignored.

Means for Solving the Problems In order to solve the above problems, the present invention provides an imaging means for converting optical information into an electrical signal, a signal processing circuit for processing an output signal of the imaging means, and a recording medium. A drive means for driving, a synchronization signal generation circuit for generating a synchronization signal for synchronizing the imaging means, the signal processing circuit, and the drive means, and a control circuit, and the control circuit is configured to, by pressing a shutter switch, Drive power is supplied to all the circuits and means, and after a certain period of time has elapsed since the imaging means has reached a stable state, an image of the subject is photographed and stored and held in the imaging means, and the recording medium is The stored subject image is controlled to be recorded on the recording medium after stabilization, and the certain period starts from a first time required for the recording medium to reach a stable state after the start of supply of driving power. , after the imaging means starts supplying driving power,
The value is the value obtained by subtracting the second time required to reach a stable state and the third time smaller than the maximum charge storage time of the imaging means.

Effects of the Invention With the above-described configuration, the present invention can minimize the period during which driving power is supplied to each circuit/means of the electronic still camera, making it possible to save power in the electronic still camera.

Embodiment FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, 1 is a lens, 2 is a shutter, 3 is an imaging device, 4 is a signal processing circuit, 5 is a recording medium, 6 is a recording medium drive device, 7 is a synchronization signal generation circuit, and 8 is a first recording medium 9 is a state detector for the recording medium of pJ2, 1o is a system control circuit, 11 is a power supply, 12 is a power switch circuit, and 13 is a shutter switch. Next, the operation will be explained using the timing chart shown in FIG. Time T1
When the shutter switch 13 is pressed, the system control circuit 10 detects this and issues a command to close the power switch 12, and the power source 11 supplies driving power to all circuits and devices of the electronic still camera. . The imaging device 3, signal processing circuit 4, synchronizing signal generating circuit 7, etc. other than the recording medium 5 and its driving device 6 start up in a short time as shown in FIG. 2d and reach a steady state at time T2. The time from T1 to T2 can be shortened to about 20 to 30 msec, and is generally about 60 msec.

On the other hand, in the case of an electronic still camera using a magnetic recording method, the recording medium 5 and its driving device 6 are composed of, for example, a magnetic fan sheet and a disk motor for rotating it.
Since the inertia is large, it takes a considerable amount of time to rise, and the steady state is finally reached at time T6, as shown in FIG. 2C. Note that the steady state of this recording medium is a state in which signals can be recorded normally, and in the case of the magnetic disk described above, it rotates at a steady rotational speed and the rotational phase is also a predetermined phase. refers to the state in which

This rising period (period T1 to T6) has a value of about 0.2 to 0.3 seconds at the shortest at the current technological level. The state of the recording medium 5 is detected by a first state detector 8 and a second state detector 9, and the first state detector 8 detects that the recording medium 6 is in a steady state as shown in FIG. The second state detector 9 is set to generate a detection signal when the steady state is reached (time T6), while the second state detector 9 reaches the steady state by, for example, detecting the rotational speed of the recording medium 5. The detection signal is set to be generated in a state a certain period of time ago (time T3). Then, in synchronization with the synchronization signal (generated from the synchronization signal generator 7 in order to synchronize the entire system) immediately after the signal is generated from the second state detector 9, As shown in FIG. 2q, the shutter 2 is activated at time T4 after a predetermined exposure period, at time T5.
The light from the subject is guided to the imaging device 3 through the lens 1, and an image of the subject is photographed. Thereafter, this subject image is accumulated and held within the imaging device until the synchronization signal generation time T7 immediately after the recording medium 5 reaches a steady state. Then, during the period from time T to T8, a recording gate is generated as shown in the second diagram, and the subject image stored and held in the imaging device 3 is read out and sent to the recording medium via the signal processing circuit 4. 6 is recorded. When recording is completed at time T8, the power switch 12 receives an opening command, and the power supply to each part of the electronic still camera is stopped.
The shooting operation ends. The time T3 at which the signal is generated from the second state detector 9 will be further explained. Generally, in a still camera, the shorter the period from when a photographing command is issued until the photograph is actually taken (in the above embodiment, the period from T1 to T4), the better.

Therefore, from the viewpoint of this characteristic, it is better to make T3 as close to T1 as possible. However, during the period during which the subject image is accumulated and held in the imaging device after shooting (the period from T4 to T7 in the above embodiment), the subject image is recorded as explained in the conventional example section. In terms of the signal-to-noise ratio of the image, the shorter the better. Therefore, from the viewpoint of this characteristic, it is better to make T3 as close to T6 as possible. However, since the imaging device has the ability to accumulate and hold the charge of the subject image in principle, this ability can be used to reduce T3 to T1 as long as the deterioration of the S/N ratio is not visually noticeable. If you move it closer, the performance of the electronic still camera as a whole will improve. The present invention is constructed from this point of view, and as described above, the S of an image is
Let T1 be the maximum charge accumulation period during which the N ratio deterioration falls within the allowable limit (referred to as the maximum allowable charge accumulation period), T2 be the period from T1 to T6, and T3 be the period from T1 to T2.
, let T4 be the period from T1 to T3, and T5 be the period from T2 to T3, then τ 〉τ −τ ・・・・・・・・・・・・・・・・・・
...(1) Therefore, τ5=τ4-τ3〉τ2-(τ1+τ3)...
If time T3 is selected so as to satisfy (2), an electronic still camera with good performance balance can be achieved.

With the above configuration, for example, the period τ2 from T to T is generally 0.2 to 0.3 seconds,
Since T1 is 0.06 to 0.1 seconds for a CCD solid-state image sensor, the time delay from when a photographing command is given until actual photographing is performed can be approximately 0.1 to 0.26 seconds. , it is possible to suppress the power consumption to an allowable value for a normal electronic still camera, and to reduce the power consumption of the electronic still camera.

As described in detail, according to the present invention, it is possible to save power by minimizing the driving period of each circuit and device inside the electronic still camera without interfering with other performances of the electronic still camera. This has great practical effects.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a timing diagram. 1...Lens, 2...Shutter, 3
...imaging device, 4...signal processing circuit,
5... Recording medium, 6... Recording medium drive device, 7... Synchronization signal generation circuit, 8.9...
... Status detector, 10 ... System control circuit, 11 ... Power supply, 12 ... Power switch, 13 ... Shutter switch.

Claims (1)

[Claims] an imaging means for converting optical information into an electrical signal; a signal processing circuit for processing an output signal of the imaging means; a recording medium for recording an output signal of the signal processing circuit; and a driving means for driving the recording medium. , a synchronization signal generation circuit that generates a synchronization signal for synchronizing the imaging means, the signal processing circuit, and the drive means, and a control circuit, the control circuit controlling all the circuits and the drive means by pressing the shutter switch. A driving power is supplied to the imaging means, and after a certain period of time has elapsed since the imaging means has reached a stable state, a subject image is photographed and stored in the imaging means, and after the recording medium has stabilized, the Control is performed to record the accumulated and held subject image on the recording medium, and the certain period of time starts from the first time required for the recording medium to reach a stable state after the start of supply of driving power. The second time required for the means to reach a stable state after the start of supply of driving power
An electronic still camera characterized in that the value is a value obtained by subtracting the time of 1 and a third time smaller than the maximum allowable charge accumulation time of the imaging means.