JPH0516229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a still image recording device that records a still image video signal using an image sensor.

In addition to image pickup tubes, which are currently widely used as image pickup devices, solid-state image pickup devices (area image sensors) have recently come into use. These solid-state image sensors include MOS, CCD, CPD, and BBD.
These devices have many superior features compared to the above-mentioned image pickup tubes, such as small size, light weight, semi-permanent lifespan, and low power consumption, and are therefore expected to find a wide range of applications in the future.

By the way, using the solid-state image sensor described above, optical changes are converted into video signals that are electrical signals,
In many cases, images are played back on a television monitor according to the electrical signal, or the video signal is recorded on a VTR or the like. Furthermore, when converting the above-mentioned optical change, that is, change in field light, into a video signal, especially a still image video signal, conventionally the conversion was performed in fixed time units of 1/30 seconds or 1/60 seconds. I was doing it. In other words, the exposure time of the solid-state photographic element was fixed at 1/30 second or 1/60 second. Therefore, if the field light is too strong and exceeds the saturation exposure amount, blooming occurs, and even if the field light is within the saturation exposure amount, vertical smearing occurs.

Furthermore, the same problem as described above occurs not only when using a solid-state image pickup device but also when a general image pickup tube is used.
In other words, since the time for integrating field light in the image pickup tube is fixed as described above, there will be insufficient light for dark subjects, and conversely, there will be too much light for bright subjects. .

The present invention has been made in view of the above conventional problems, and provides a still image recording device that does not cause blooming, vertical smear, or excess or deficiency of light amount when recording still image video signals using an image sensor. The purpose is to provide

To achieve this objective, the present invention includes an image sensor, an aperture that opens and closes a field light optical path incident on the image sensor, and a vertical synchronization signal and a horizontal synchronization signal that are sent to the image sensor at regular intervals. a drive circuit; an exposure control circuit that outputs an exposure time control signal to open the aperture for an exposure time corresponding to the brightness of field light; a recording member that records a video signal from the image sensor; While the exposure time control signal is output, the operation of the drive circuit is stopped, and further, in synchronization with the vertical synchronization signal immediately after the exposure time elapses, reading out of the accumulated charge in the image sensor is started, and A still image control circuit for starting recording of a video signal onto the recording member.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings. Incidentally, the same members are given the same reference numerals and their explanations will be omitted.

FIG. 1 is a block diagram showing one embodiment of the present invention. First, an aperture 2, a lens 3, and an image sensor 4 are arranged on the optical axis. The image sensor 4 includes the solid-state image sensor described above and a general image sensor. A drive circuit 7 is provided which sends a vertical synchronization signal and a horizontal synchronization signal to the image sensor 4 at regular intervals, and is configured to send an exposure time control signal Sv to the image sensor 4 to control the exposure time according to the field light. An exposure control circuit 10 is provided. Note that 1 is the subject.

Furthermore, a recording member 6 for recording the video signal VS passed from the image sensor 4 via the signal processing circuit 5 is provided,
This recording member 6 may be a video tape recorder, a video disk, or the like. Further, a still image control circuit 8 is provided. This still image control circuit 8 stops the operation of the drive circuit 7 within the exposure time, and starts reading out the accumulated charge in the image sensor 4 in synchronization with the vertical synchronization signal immediately after the exposure time has elapsed. At the same time, the recording member 6 starts recording the video signal VS. The start of recording operation of this video signal VS is
This is done using the recording start signal SS.

FIG. 2 mainly shows a specific circuit of the still image control circuit 8. As shown in FIG. First, AND circuit 11
is adapted to receive vertical synchronization ΦV1 or ΦV2 from the synchronization signal generation circuit 9 and a signal from the exposure control circuit 10 via the inverter 12. Here, the vertical synchronization signals ΦV1 and ΦV2 are applied to the image sensor 4.
These signals are generated corresponding to every other row of pixels in the image plane, and are used to improve image quality by performing interlacing, and both of these signals are represented as ΦV in FIG. The output of the AND circuit 11 is connected to the drive circuit 7.

The AND circuit 13 receives the above vertical synchronization signal ΦV,
It is connected to receive the non-inverted output signal of the D flip-flop 14, and the output signal is sent to the recording member 6 as a recording start signal SS. The D flip-flop 14 has its C input terminal connected to the exposure control circuit 10 via an inverter 16, and its non-inverting output terminal connected to the D input terminal of another D flip-flop 17. The inverter 15 is connected between the synchronous signal generating circuit 9 and the C input terminal of the D flip-flop 17.

The OR circuit 20 receives the non-inverted output signal of the D flip-flop 17 and the signals from the differentiating circuits 18 and 19, and sends an output signal to the reset terminal R of the D flip-flop 14.

FIG. 3 is a time chart of the above embodiment.

Next, the operation of the above embodiment will be explained.

At some point, pressing the shutter button generates a shutter signal RE. Immediately after that,
Photometry is performed by a photometry device (not shown), and the exposure time tr is determined according to the field light. During this exposure time tr, the operation of the drive circuit 7 is stopped,
For this reason, the accumulated charge of the image sensor 4 is not read out. Then, when the exposure time tr has elapsed, readout of the accumulated charges in the image sensor 4 is started in synchronization with the vertical synchronization signal ΦV1 or ΦV2 that appears immediately after that. Also, at the same time,
The recording start signal SS also starts the operation of recording the video signal VS that has passed through the signal processing circuit 6 onto the recording member 6.

That is, by pressing the shutter button, the exposure time control signal Sv becomes H level for the exposure time tr in order to meter the appropriate exposure and open the aperture 2. During this exposure time, aperture 2 opens. Then, the H level signal is inverted by the inverter 12 and becomes L.
In this case, since the AND circuit 11 outputs an L level signal, the drive circuit 7 stops its operation. That is, during the exposure time tr, since the drive circuit is stopped, the accumulated charge in the image sensor 4 is not read out. As a result, appropriate exposure is performed according to the brightness of the subject.

On the other hand, since the pulses generated by the differentiating circuits 18 and 19 when the power is turned on are applied to the reset terminal R of the D flip-flop 14 via the OR circuit 20, the D flip-flop 14 is reset and its non-inverted output signal goes to the L level. has been done.

However, as mentioned above, the exposure time control signal Sv
When the signal goes to the H level and then to the L level, the L level signal is inverted to the H level by the inverter 16 and then applied to the C input terminal of the D flip-flop 14. As a result, the non-inverted output of the D flip-flop 14 also goes to H level and maintains that state for a while. Therefore,
An H level signal is applied to one input terminal of the AND circuit 13. Immediately after that, the synchronization signal generation circuit 9 generates a vertical synchronization signal ΦV (ΦV1 or ΦV2).
(This signal is designated as a) is sent to the other input terminal of the AND circuit 13. At this time, the AND circuit 13 outputs an H level signal, and this signal becomes the recording start signal SS and is sent to the recording member 6.
Therefore, the recording member 6 starts operating in synchronization with the vertical synchronization signal a generated immediately after the exposure time control signal Sv disappears. That is, the recording member 6 such as a magnetic tape or a magnetic disk starts recording the video signal VS from the image sensor 4.

Also, as mentioned above, the exposure time control signal Sv is
When the signal becomes L level, the L level signal is inverted to H level by inverter 12, and this H level signal is applied to one input terminal of AND circuit 11. Immediately thereafter, when the other input terminal of the AND circuit 11 receives the vertical synchronizing signal a, a drive signal is generated, and the drive circuit 7 starts operating, so that the image sensor 4 accumulates Charge reading is performed.
This reading is performed simultaneously with the start of recording.

Then, when the immediately following vertical synchronizing signal a disappears, the output signal of the inverter 15 becomes H level, and this H level signal is applied to the C input terminal of the D flip-flop 17, so that its non-inverted output signal becomes It becomes H level and resets the D flip-flop 14 via the OR circuit 20. As a result, the non-inverted output signal of the D flip-flop 14 becomes L level, and the output signal of the AND circuit 13 becomes L level, so the recording start signal SS disappears, the circuit returns to its initial state, and then Be prepared in case the shutter button is pressed.

As described above, when recording a video signal of a still image using an image sensor, the present invention can obtain an appropriate exposure time depending on the brightness of the subject, thereby preventing blooming, vertical smear, or excess or deficiency of light amount. The effect is that it does not occur.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit diagram specifically showing the still image control circuit in the above embodiment, and FIG. 3 is a time chart of the above embodiment. DESCRIPTION OF SYMBOLS 1...Subject, 2...Aperture, 4...Imaging element, 6...Recording member, 7...Drive circuit, 8...Still image control circuit, 9
...Synchronization signal generation circuit, 10...Exposure control circuit, VS
...video signal, Sv...exposure time control signal, SS...recording start signal.

Claims (1)

[Scope of Claims] 1. An image sensor, an aperture that opens and closes a field light path incident on the image sensor, a drive circuit that sends a vertical synchronization signal and a horizontal synchronization signal to the image sensor at fixed time intervals, an exposure control circuit that outputs an exposure time control signal to open the aperture for an exposure time corresponding to the brightness of field light; a recording member that records a video signal from the image sensor; and a recording member that records the video signal from the image sensor; While the video signal is being output, the operation of the drive circuit is stopped, and in synchronization with the vertical synchronization signal immediately after the exposure time has elapsed, reading out of the accumulated charge in the image sensor is started, and the recording of the video signal is started. A still image recording device comprising: a still image control circuit that starts recording on a member;