JP2706095B2 - Image storage device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image storage device, and more particularly, to an image storage device suitable for storing an image synchronized with a strobe.

BACKGROUND OF THE INVENTION There are the following devices for freezing (fixing) an image from a video camera in synchronization with strobe light.

The strobe light is detected by a sensor (strobe tuner),
A device that records an image from a video camera in a still video recording device using the detection result as a trigger.

The strobe light is detected by a sensor (strobe tuner),
A device that stores an image from a video camera in a semiconductor memory using the detection result as a trigger.

(Problems to be Solved by the Invention) The above-described devices have the following disadvantages.

When using a still video recorder, only 50 screens can be stored per video floppy. Therefore, it is inconvenient when performing a large amount of processing. Further, a detector for detecting strobe light is required.

When a semiconductor memory is used, the number of screens is not limited by increasing the capacity of the memory. However, as in the above case, a strobe light detector is required. If the detector is not used, the flash emission timing is controlled from the memory side, but a flash emitting at an arbitrary timing cannot be used.

In order to update the frozen screen, it is necessary to clear the contents of the stored memory in a fixed time or to press a reset switch. In this case, it is important how long the certain time is set. Further, it is troublesome to press the reset switch every time the screen is updated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to freeze an image from a video camera in a memory in synchronization with a strobe that emits light at an arbitrary timing. It is an object of the present invention to realize an image storage device capable of re-freezing each time light is emitted.

(Means for Solving the Problems) The present invention for solving the above problems includes an image pickup means for photographing a subject and outputting a video signal, and an image storage means for storing a video signal output from the image pickup means. An image storage device which has a video signal output from the imaging unit and stores the video signal in the image storage unit in synchronization with the emission of a strobe, wherein a horizontal / vertical synchronization signal in the video signal output from the imaging unit is A sync separation circuit to be extracted, a comparator for comparing the video signal obtained by the imaging means with a threshold value to detect a video signal irradiated with strobe light, an output signal of the comparator and an output signal from the sync separation circuit. Control signal generating means for generating a write control signal for determining a write period of a video signal based on the horizontal / vertical synchronization signal and supplying the control signal to the image storage means. The image of the field is frozen in the image storage means.

(Operation) The comparator compares the video signal obtained by the imaging means with a threshold to detect a video signal irradiated with strobe light. The control signal generation means creates a write control signal for determining a write period of the video signal based on the output signal of the comparator and the horizontal / vertical synchronization signal output from the sync separation circuit, and supplies the write control signal to the image storage means. As a result, the image of the field irradiated with the strobe light is frozen in the image storage means.
Thereafter, the stored image is read.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing the configuration of one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a video camera for photographing a subject and outputting a video signal. 2 is a DC component reproducing circuit for reproducing a DC component in the video signal, 3 is a sync separation circuit for extracting a sync signal (vertical (V) sync signal and horizontal (H) sync signal) in the video signal, and 4 is a memory for storing images. Field memory for performing 5 is a comparator for comparing the video signal whose DC component is reproduced with a certain reference voltage, and 6 and 7 are D
It is a type flip flop.

FIG. 2 is a waveform diagram showing waveforms at various parts of the device shown in FIG. 1, and FIG. 3 is an enlarged waveform diagram of the portion shown in FIG.

Hereinafter, the operation of this embodiment will be described with reference to FIGS.

First, it is assumed that a strobe light is emitted at an arbitrary timing (FIG. 2A). As a video signal output from the video camera 1, a bright image can be obtained by flash irradiation in one field after flash emission (FIG. 2 (b)). In other periods, the subject is dark, so the level of the video signal is small,
It is almost black (zero) level. Assuming that the light amount difference between flash emission and non-flash emission is 10 times (3 stops), the voltage value of the video signal also has a 10 times difference. Assuming that the peak value of the video signal at the time of flash emission is 0.7 V, the peak value at the time of no flash emission is 0.07 V, which is extremely small.

Therefore, it is possible to determine a certain threshold value Vth and determine that the strobe light is emitted if the video signal is at a level higher than this.

The output of the video camera 1 is a DC component reproducing circuit 2, which accurately reproduces the DC component in the video signal. This is because the output level of the video signal needs to be accurately reproduced in order to detect strobe light emission at the level of the video signal. Therefore, the black level of the video signal is set to a constant value in the DC component reproducing circuit 2. The video signal whose DC component has been accurately reproduced in this way (FIG. 2 (b)) is supplied to one input terminal of the comparator 5.

If the background of the subject is a bright background such as an ID photo,
From 1H (horizontal scanning period) immediately after the vertical blanking period (FIG. 3A), there is a luminance change due to strobe irradiation. By comparing this video signal with an appropriate threshold value Vth, the video signal can be detected as a flash-irradiated video signal. FIG. 3B shows the output of the comparator 5 in which the video signal is compared with the threshold value Vth. Here, the high level is where the level of the video signal exceeds the threshold value Vth. This signal is applied to the flip-flop 6, rises at the same time as the rise of the output signal of the comparator 5, and creates a pulse until the start of the vertical synchronizing signal (FIG. 2 (c), FIG. 3 (c)). ). Since this pulse rises in the middle of the horizontal scanning cycle, it cannot be used as a memory write control signal. Therefore, the output pulse of the flip-flop 6 is supplied to the flip-flop 7, and pulses (FIGS. 2 (d) and 3 (d)) which rise in synchronization with the rise of the horizontal synchronizing signal are created. This pulse is supplied to the field memory 4 as a memory write / read control signal.

As a result, the image data cannot be stored in the field memory until the memory write control signal is output (here, during 1H). Therefore, it cannot be frozen and output. However, since this portion is the background portion of the image, there is no problem. Further, the missing area (horizontal scanning line) is not limited to 1H, and may be a plurality of Hs as long as there is no problem (a range where no effective image is lost).

FIG. 4 is a configuration diagram showing the configuration of another embodiment of the present invention,
FIG. 5 is a timing chart for explaining the operation. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this configuration, the video signal from the video camera 1 passes through the delay
At 12, the DC component is reproduced and written into the field memory 4. The synchronization signal applied to the field memory 4 is a delayed video signal (FIG. 5 (c)).
In the configuration shown in FIG. 1, 1H or more than one H is required until a change in the luminance of the video signal is detected, so that the upper background portion of the image stored in the field memory 4 is missing 1H or more than one H. Was. In this configuration, the delayed video signal is transmitted through the delay element 11 having a delay time equal to the time required to detect a luminance change of the video signal (the time required to generate the memory write control signal). Writing to the field memory 4 was performed. Therefore, the rise of the memory write control signal coincides with the start timing of the desired video signal (FIGS. 5 (c) and (d)). Therefore, the upper part of the stored image does not drop.

FIG. 6 is a block diagram showing the configuration of still another embodiment of the present invention, and FIG. 7 is a timing chart for explaining the operation. 6, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this circuit, the field memory 4a and the field memory 4b have the same storage capacity,
A period slightly longer than the horizontal scanning period required from the start of the video signal to detecting a change in the video signal is set to L horizontal scanning lines. The total storage capacity of the field memory 4a (field memory 4b) and the field memory 4c is
One field is set.

First, it is assumed that an image for one field has already been stored in the field memories 4b and 4c. In the B field, L horizontal scanning lines are stored in the field memory 4a regardless of the presence or absence of the memory write control signal (at this stage, the presence or absence of the occurrence of the memory write control signal is unknown) (FIG. 7 (f)). ). The counter 21 counts the horizontal synchronizing pulses, and outputs a high-level signal when the decoder 22 counts L lines (FIG. 7 (d)). The output of this decoder and the vertical synchronizing signal inverted by the inverter 23 are supplied to the NOR circuit 24 and output as a write control signal for L lines of the video signal. The write control signal for the L lines is supplied to the field memory 4a by the MPX circuit 25 in accordance with the output of the flip-flop 8.
And the field memory 4b. In this B field, the memory write control signal is given to the field memory 4a. Thereafter, the memory write control signal (the output of the flip-flop 7) supplied to the field memory 4c goes high, and the data after the (L + 1) th line is stored in the field memory 4c. In this way, the image at the moment when the strobe shines is frozen. In this example, no image is lost without using a delay element.

Thereafter (from the C field), writing to the field memory 4b is performed up to the L line, and when the strobe light is emitted, the data is also stored in the field memory 4c. Thereafter, this operation is repeated.

FIG. 8 is a block diagram showing the configuration of still another embodiment of the present invention, and FIG. 9 is a timing chart for explaining the operation. 8, the same elements as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. In this example, a detection window is provided to detect a luminance change of a video signal.
That is, a counter 21 and a decoder 22 for detecting the V direction and a counter 31 and a decoder 32 for detecting the H direction are provided.
An AND circuit 33 that creates a detection window by taking an AND output of the output of the decoder 22 and the output of the decoder 32;
An AND circuit 34 for ANDing the signal of the detection window with the comparison circuit 5 and a memory write / read clock 35 for generating a memory write / read clock pulse are provided.

FIG. 10 is a schematic diagram showing a screen area and a detection window area of a video signal. The hatched area in this figure, that is, A in the H direction
B to D in the directions C to V are the detection window regions.

The counter 21 counts the horizontal synchronization pulse, and
When a count corresponding to B is performed at 22, a high-level signal is output, and when a count corresponding to D is performed, a low-level signal is output again (FIG. 9 (c)). The counter 31 counts a pulse corresponding to a pixel in the horizontal direction supplied from the memory write / read clock 35. When a count corresponding to A is performed by the decoder 22, a high-level signal is output, and when a count corresponding to C is performed, a low-level signal is output again (FIG. 9 (d)). These decoders 21, 31
Is applied to an AND circuit 33, and an AND output is obtained (creation of a detection window). The output of the comparator 5 (FIG. 9B) and the output of the AND circuit 33 are applied to the AND circuit 34, and the output of the AND circuit 34 is applied to the flip-flop 6
Is applied to the input. Accordingly, the output of the flip-flop 6 becomes high level in a range where the video signal exceeds the threshold value Vth within the range of the detection window (FIG. 9 (e)). The output pulse of the flip-flop 6 is supplied to the flip-flop 7, and a pulse that rises in synchronization with the rise of the horizontal synchronization signal is created. This pulse is supplied to the field memory 4 as a memory write / read control signal.

As described above, since the detection window is created and the luminance change of the video signal is detected within the range of the detection window, it is possible to reliably detect the strobe irradiation to the subject.

Although the level of the video signal is compared with the threshold value Vth in order to detect the strobe light emission, the average value of the brightness level of the video signal and the sample and hold value of a specific point of the video signal in the previous field are used. It is also possible. With this configuration, malfunctions due to noise or the like become strong.
Also, it is possible to detect a slight change in luminance as compared with the previous field.

FIG. 11 is a configuration diagram showing a configuration in a case where a sample and hold value at a specific point of a video signal in a previous field is used instead of a threshold value. The same components as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. In this configuration, a fixed threshold V
Instead of th, the S / H amplifier 40 holds the luminance level at a specific point one field before, and inputs the luminance level to the comparator 5. Therefore, it is possible to detect a slight change in luminance of the video signal, and the detection accuracy is improved.

Also, instead of the counter used in the above embodiment,
It is also possible to use a mono-multi.

As described above, it is possible to automatically detect and store a subject that has become brighter due to the irradiation of strobe light.
Then, when the storage is completed, the reading is automatically performed. In this way, a freeze is performed. The update of the stored image is automatically performed every time the strobe light is emitted.

(Effect of the Invention) As described above in detail, in the present invention, the video signal output from the imaging unit is stored in the image storage unit in synchronization with the emission of the strobe light. By comparing the obtained video signal with the threshold value, the video signal irradiated with the strobe light is detected, and the control signal generating means is based on the output signal of the comparator and the horizontal / vertical synchronization signal output from the synchronization separation circuit. A writing control signal for defining a writing period of the video signal is created and supplied to the image storage means. As a result, it is possible to realize an image storage device that can freeze an image at the moment of being illuminated by a strobe that emits light at an arbitrary timing, and can freeze again each time the strobe shines.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention, FIGS. 2 and 3 are timing charts showing the operation state of the device of the present invention, and FIG. 4 is the configuration of another embodiment of the present invention. FIG. 5 is a timing chart showing an operation state of the device shown in FIG. 4, FIG. 6 is a block diagram showing a configuration of another embodiment of the present invention, and FIG. 7 is a diagram shown in FIG. FIG. 8 is a block diagram showing the configuration of another embodiment of the present invention, FIG. 9 is a timing chart showing the operation state of the apparatus shown in FIG.
FIG. 10 is an explanatory diagram showing a detection window area of a screen, and FIG. 11 is a configuration diagram showing still another configuration of the present invention. DESCRIPTION OF SYMBOLS 1 ... Video camera, 2 ... DC component reproduction circuit 3 ... Synchronization separation circuit, 4 ... Field memory 5 ... Comparator 6, 7 ... Flip-flop

Claims (1)

(57) [Claims] 1. An image pickup means for photographing a subject and outputting a video signal, and an image storage means for storing a video signal output from the image pickup means, wherein the video signal output from the image pickup means is provided. A synchronous separation circuit for extracting horizontal and vertical synchronizing signals in a video signal output from the imaging unit, wherein the synchronization separation circuit extracts a horizontal / vertical synchronization signal from the imaging unit. By comparing the video signal with the threshold,
A comparator for detecting a video signal irradiated with strobe light; and a write control signal for determining a write period of the video signal based on an output signal of the comparator and a horizontal / vertical sync signal output from the sync separation circuit. An image storage device, comprising: a control signal generating unit that supplies the image storage unit; and an image of a field irradiated with strobe light is frozen in the image storage unit.