JPH0435176A - Electronic still camera - Google Patents

Abstract

PURPOSE:To prevent disturbance of a picture by outputting a picture signal stored in a memory to an electronic view finder when a shutter mode is set. CONSTITUTION:A video signal from an image pickup element 3 is processed by a video signal processing section 5 and fed to a memory 18. Moreover, a switching signal from a control section 15 is fed also to a changeover switch 19, which selects a video signal output from a video signal processing section 5 and the memory 18 and the selected signal is fed to an EVF 7, in which the signal is displayed. A photometry element 11, a sample-and-hold circuit 12 and a comparator 13 are controlled by a photometry exposure control section 14. The control section 14 gives a command of aperture control to the aperture mechanism 12 and gives a command of shutter speed control to an image pickup element drive signal generating section 4 for the element 3. Furthermore, a system control section 15 sends a changeover command as to whether shutter operation synchronously with a vertical synchronizing signal of a picture signal 3 or asynchronous shutter operation is to be implemented to the control section 14 and the signal generating section 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention uses an electronic still camera, more specifically, a solid-state image sensor (hereinafter abbreviated as an image sensor) such as a CCD, and uses an EvF (
The present invention relates to an electronic still camera that captures and records still images while monitoring them with an electronic viewfinder.

[Prior Art] As is well known, there are two types of shutter modes in electronic still cameras that capture and record still images using an image sensor: a shutter mode that is synchronized with a vertical synchronization signal of an image signal, and a shutter mode that is asynchronous. .

In the former type of electronic still camera, which operates the shutter with a shutter speed synchronized with the vertical synchronization signal of the image signal, the image sensor output is used as a recording signal for imaging and recording, as well as a non-recording signal for distance measurement, photometry, etc. Since it can also be used as a signal, it not only simplifies the circuit by eliminating the need for a distance measurement sensor or photometry sensor, but also eliminates the need for a distance measurement optical system or photometry optical system, making the entire camera more compact. be able to.

However, if you try to perform all camera operations in shutter mode synchronized with the vertical synchronization signal of the image signal,
The repetition period of the vertical synchronization signal is 1/6 not only during non-recording operations such as distance measurement and photometry, but also during recording operations for main exposure.
Since the shutter operation must be performed in 0 seconds, it is not possible to perform an exposure operation using so-called direct photometry, in which the exposure operation ends when the total exposure amount of subject light incident on the image sensor reaches a predetermined value, for example.

On the other hand, in the latter type of electronic still camera, which operates the shutter in a shutter mode asynchronous to the vertical synchronization signal of the image signal, the exposure time can be set regardless of the period of the vertical synchronization signal of the image signal, which is 760 seconds. Direct photometry becomes possible. However, if you try to perform all camera operations in a shutter mode that is asynchronous to the vertical synchronization signal of the image signal, you will need sensors and optical systems for distance measurement and photometry in addition to the image sensor, which will require a large size. Not only that, but the cost also increases. Therefore, an electronic still camera that uses the electronic shutter operation of the image sensor differently depending on the purpose of using the image output from the image sensor, thereby effectively utilizing the output of the image sensor to perform smooth image capturing operations, has been developed. Proposed by the applicant. That is, this electronic still camera uses the image output in the shutter mode synchronized with the vertical synchronization signal of the image signal as a non-recording signal, and uses the image output in the shutter mode asynchronous with the vertical synchronization signal as the recording signal. It is characterized by By the way, there are two types of means for checking the subject image in this type of electronic still camera: an optical viewfinder and an electronic viewfinder.In recent years, the performance of electronic viewfinders using liquid crystals has improved and they have become smaller. As a result, many examples using electronic viewfinders have been proposed.

[Problems to be Solved by the Invention] However, in electronic still cameras that capture images while displaying the subject image on a monitor such as an EVF, when not recording distance measurement, photometry, etc., the subject is captured in a shutter mode synchronized with the vertical synchronization signal of the image signal. When an image is continuously displayed on the EVF and recording exposure, etc., a shutter mode that is asynchronous to the vertical synchronization signal is used.For example, if an electronic shutter operation is performed by direct photometry, the shutter mode is asynchronous to the vertical synchronization signal of the image signal. Sometimes, the subject image is missing, so the image on a display monitor such as an EVF is distorted or missing, giving the photographer a sense of discomfort or anxiety.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and even if an electronic shutter operation is performed in a shutter mode asynchronous to a vertical synchronization signal of an image signal such as direct photometry
An object of the present invention is to provide an electronic still camera that does not cause disturbances or omissions on monitor images that may give a photographer a sense of discomfort or anxiety.

[Means for Solving the Problems] An electronic still camera of the present invention has a memory that stores a readout signal from a means for accumulating and reading out an image signal in synchronization with a vertical synchronization signal of the image signal. The image signal stored in the EVF is output to the EVF asynchronously with the vertical synchronization signal when the shutter mode is set.

[Function] In this electronic still camera, image information in a shutter mode synchronized with a vertical synchronization signal of an image signal is sequentially written into a memory capable of storing one field or one frame of image information, and the vertical synchronization signal When the asynchronous shutter mode is set, the stored information is read from the memory and E
Output to VF.

[Example] The present invention will be specifically described below with reference to the drawings. 1st
FIG. 1 is a block diagram of an electronic still camera showing an embodiment of the present invention. Subject light collected by the photographic lens 1 is imaged on the light receiving surface of the image sensor 3 via the diaphragm mechanism 2 . The video signal photoelectrically converted by the element 3 is subjected to camera processing in a video signal processing section 5, and then supplied to a memory 8 capable of storing image information for one field or one frame. This memory 8 is a memory input/output controller controlled by a switching signal from a system control section 15, which will be described later.・Roll part 17
This controls switching between writing and reading from memory. Further, the switching signal from the system control section 15 is also supplied to the through/memory changeover switch 19, thereby selecting between the video signal output of the video signal processing section 5 and the video signal output temporarily stored in the memory 18. - and supplies it to an external device (not shown), and also supplies it to an EVF 7 composed of a liquid crystal display monitor such as an LCD or a cathode ray tube, etc., to display the subject image on a monitor.

On the other hand, the output of the video signal processing section 5 is also supplied to the AF calculation section 8, and the calculation section 8 controls the photographic lens 1 via the lens drive section 9 so that, for example, the contrast information of the subject image is maximized. This causes the focus to be set.

A photometric element 11 that measures the illuminance of the subject. A sample and hold circuit 12 that samples and holds this photometric output. When the above photometric output exceeds the predetermined threshold level, 'L'
→The comparator 13 that becomes "H" is controlled by a photometric exposure control section 14 that performs photometric control, exposure calculation, shutter speed control, etc.

The control unit 14 instructs the aperture mechanism 2 to perform aperture control, takes in the aperture information obtained as a result, and also drives the image sensor to cause the image pickup element 3 to perform an electronic shutter operation at a predetermined shutter speed. The signal generator 4 is then commanded to control the shutter speed. Further, upon receiving a shutter trigger signal from the shutter trigger switch 16, the system control unit 15, which controls the entire operation sequence of the electronic still camera, performs a shutter operation at a movie rate synchronized with the vertical synchronization signal of the image signal 3. A switching command for performing an asynchronous still shutter operation is sent to the photometry/exposure control section 14 and the image pickup device drive signal generation section 4.

Next, the synchronous or asynchronous shutter operation in the electronic still camera according to the present embodiment configured as described above will be explained below based on the timing chart shown in FIG. At time t1, when the trigger switch] 6 (see Figure 1) is pressed halfway and the first stage trigger signal is taken into the system control section 15, the control section 15 synchronizes with the field rate of 60 Hz using the vertical blanking signal. This command instructs each part of this camera system to start the shutter operation according to the formula. The photometric element 11 starts photometry after being reset by an integral reset signal 21 output from the photometric exposure control section 14 and synchronized with the vertical blanking signal. Then, by gradually integrating the light intensity, the photometric element output level rises as shown by the straight line Ω1, and after one field period has passed, the photometric exposure control section 14 sends the photometric element output level to the sample hold circuit 1.
For the direction 2, the output sample hold signal 35 causes
The output level is sampled and held in the control section 1.
Incorporated into 4. This photometric amount is calculated during the next transmission period of the vertical blanking signal 22, and the shutter speed is determined thereby.

That is, in an element shutter of an image pickup element in an electronic still camera, the time difference between unnecessary charge discharge 33 and accumulated charge readout 34 from the element becomes the exposure time. Therefore, in the synchronous shutter operation using the first stage trigger signal, the photometric element 11 is operated at the field rate or movie rate of the vertical blanking signal, and the exposure time of the synchronous shutter is determined by the photometric value. Therefore, the output of the image sensor corresponds to the shutter speed.

This output is written in the memory 18 (see FIG. 1), is sent to an external device through the through output side of the changeover switch 19, and is also displayed on the monitor screen of the EVF 7. In other words, if the video signal output ■ in Figure 2 is output and the next field outputs ■, ■ sequentially, the external device or EVF7 will obtain continuous image information output in the order ■, ■, ■. However, the memory information is sequentially updated in the memory 18, and the latest information for one field or one frame is always stored. Next, the asynchronous still shutter operation using the second stage trigger signal will be explained.

At time t2, when the trigger switch 16 is fully pressed and the second stage trigger signal is received by the system control unit 15, the control unit 15 applies an asynchronous still shutter operation using the direct metering method to each part of this camera system. command.

That is, from the control section 15 to the photometric exposure control section 14
and activates the still shutter command supplied to the image sensor drive signal generation unit 4, that is, sets its logic level to “L”→
The signal is set to "H", thereby sending out the still shutter command 23 in the asynchronous operation mode. Then, the output level of the 71Ilj optical element 11 is reset as shown by the straight line Ω2 by the integral reset signal 24, and the image sensor 3 discharges unnecessary charges 25. In other words, the photometric element]
1 and the image sensor 3 are reset at the same time, and from this time t2, the photometry element 11 performs direct photometry.
Exposure by the image sensor 3 or the asynchronous shutter is started.

In the photometric element 11, the amount of light is gradually integrated and its output level rises as shown by the straight line ρ3, and when it reaches the threshold level of the comparator 13 (see FIG. 1) at time t3, the comparator output signal 26 becomes active "H".
As a result, the still shutter command 23 becomes non-active L". Then, the imaging element 11 starts reading out the charge 27 from the element, so the exposure time by the asynchronous shutter is changed from the above time t to t3. becomes.

By the way, since no synchronous shutter output is generated from the image sensor 3 during this period from time t to t3, if this continues, the image information displayed on the monitor on the EVF 7 will be missing or distorted, causing confusion to the operator. I end up giving. Therefore, the system control section]
At time t2, at time t2, the through/memory changeover switch 19 is switched to the memory side or the memory 8 is switched to the read operation mode, respectively, and thereby the imaging probe output information ■, ■, . . . Memory 8 instead of...
The latest image information for one field (E
), G are repeatedly read out and displayed on the EVF 7 on the monitor. In other words, at time t2, the information written up to that point is O, and the missing information is O, so in order to display it on the EVF7 monitor, in order to compensate for the missing information O, the previous busy field information ◎ must be used. The part corresponding to O, that is, information 0, is read out and combined with O to obtain output information. Therefore, at the point where the synchronous shutter output is missing in the period from time t to t3, the memory 8 is switched from the write operation mode to the read operation mode, and the memory information O2 for one field immediately before time t2 is
By applying this to the EVF 7 as a video signal output, continuous monitor images can be obtained with the EVF 7. When the direct photometry ends at time t3, the asynchronous shutter output 29 is read out in the next field and recorded on a recording medium (not shown) using the still recording signal 30.

Thereafter, the system control unit 15 sets one through/memory selector switch to the through side and returns the memory 18 to the write operation mode to set the synchronous shutter mode, and activates the synchronous shutter mode similar to the synchronous shutter output 28 described above. The outputs 31, 32°, . . . are continuously output to external equipment and displayed on the monitor on EVFl.

According to the above-described embodiment, by providing the memory 18, it is possible to eliminate the loss or disturbance of the image output that normally occurs when an electronic shutter operation is performed in a shutter mode asynchronous to the vertical synchronization signal of the image signal during direct photometry. Since it can be supplemented with the image information written in the memory immediately before direct left photometry, image information without disturbances or omissions can be displayed on a finder such as an EVF. This prevents the photographer who is monitoring the image on the EVF from feeling uncomfortable or anxious. Such an effect is particularly noticeable during continuous shooting or when the shutter speed is slow.

[Effects of the Invention] As described above, according to the present invention, the image signal in the shutter mode synchronized with the vertical synchronization signal of the image signal is stored in the memory, and the image information stored in this memory is stored in the asynchronous shutter mode. Since the output is output to the EVF, even if the electronic shutter is operated asynchronously with the vertical synchronization signal due to direct metering, etc., there will be no disturbances or omissions on the monitor image of the EVF, etc. that may make the photographer feel uncomfortable or uneasy. This has the remarkable effect of not causing any problems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electronic still camera showing an embodiment of the present invention. FIG. 2 is a timing chart showing the operation of each part in FIG. 1. 3... Image sensor 7... EVF 18... Memory

Claims (1)

[Claims] (1) It has a memory that stores a readout signal from a means for accumulating and reading out an image signal in synchronization with a vertical synchronization signal of the image signal, and the image signal stored in the memory is read out asynchronously with the vertical synchronization signal. An electronic still camera characterized by outputting to an EVF when a shutter mode is set.