JPS63287181A - Image recording method - Google Patents

Abstract

PURPOSE:To realize the broad-band recording of a still picture by storing one- field-length of video signals from an image pickup means in a memory, and recording the signals stored in said memory repeatedly in a recording medium. CONSTITUTION:The image pickup elements of an image pickup circuit 50 are scanned by means of clocks from a clock generator 52, and R, G, B signals are outputted which are converted to Y, (R-Y), (B-Y) signals by a matrix circuit 51. During normal recording of moving image, switches 56, 72, 73 are connected to (a) contact side, and data are written in memories 54, 64, 65 sequentially and they are updated. When the shutter mechanism of a camera part is activated, the switches 56, 72, 73 are converted to (b) contact side by means of control signals from a system controller 121. The stored signals in the memories 54, 64, 65 at this point of time are read out repeatedly. In such a way, one image signal is divided into three fields, and recorded in a magnetic tape repeatedly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image recording method, and more specifically to a recording method that enables both still image recording and moving image recording.

[Conventional technology]

Camera-integrated VTRs are widely used as image recording and reproducing devices, and the general configuration of the recording system is shown in Fig. 7, and the reproducing system is shown in Fig. 8. The imaging circuit 10 is composed of
Driven by the clock of the clock generation circuit 12, R
, G, B signals are output. The matrix circuit 14 is
,G.

From the B signal, the luminance signal Y (・0.3R+0.59G+0
．． IIB) and two color difference signals (R-Y), CB-
Y) is formed. The Y signal is frequency modulated by an FM modulator 16. On the other hand, the color difference signals (R-Y) and (B-Y) are band-limited by low pass filters (LPF) 18 and 19, respectively, to θ to about 500 KHz. The quadrature two-phase modulator 20 receives a low carrier wave (V
629 KHz in the H3 system) and the phase shift circuit 22
The output of LPFlB, 19 is quadrature two-phase modulated by the signal whose phase is shifted by 90''.

The mixer 24 performs frequency multiplexing (so-called color multiplexing) on the FM modulated Y signal and the low carrier color signal from the quadrature two-phase modulator 20.
Under one type). The switch 26 switches every reciprocal of the field frequency (1/60 seconds), so that the mixer 2
The output of 4 is sent to a magnetic head 29A for both recording and reproduction, or to a recording amplifier 28 via a recording amplifier 28A for each field.
The signal is applied to the magnetic head 29B for both recording and reproduction via the signal line B, and is recorded on the magnetic tape 30.

When reproducing the recorded signals on the magnetic tape 30, the reproducing system shown in FIG. 8 is used. Magnetic head 29. A reproduction signal from the magnetic head 29B is supplied to one contact of the switch 32 via the reproduction amplifier 31A, and a reproduction signal from the magnetic head 29B is supplied to the other contact of the switch 32 via the reproduction amplifier 31B. The switch 32 is 17 in the same way as the recording system switch 26.
Switches alternately every 60 seconds. FM modulator 34 is high
The target F extracted by the pass filter (HPF) 33
Demodulate the M modulated luminance signal component to the original base band. On the other hand, the low carrier color signal component is extracted by the LPF 35, and the frequency converter 36 converts the carrier frequency to 3.58M.
1 (frequency conversion to a carrier color signal of z.

A sync separation circuit 38 separates the horizontal sync signal from the reproduced signal, and a burst separation circuit 39 extracts a color burst signal from the output signal of the frequency converter 36. AFC/APC
The circuit 40 receives the horizontal synchronization signal from the synchronization separation circuit 38 and the color burst signal from the burst separation circuit 39, forms a clock that follows the time axis fluctuation of the reproduction output, and supplies the clock to the frequency converter 36 as a carrier. .

The mixer 41 combines the output of the FM demodulator 34 and the frequency converter 36.
The output of the output terminal 42 is mixed and outputted to the output terminal 42.

[Problem that the invention seeks to solve]

In recent years, in VTRs, high resolution has been actively achieved by increasing the carrier frequency when FM modulating the luminance signal, such as high band β and 5-VH3. - It has become possible to record and play back images that are comparable to still images taken by video cameras.

With the spread of camera-integrated VTRs, the joy of video creation has become widely recognized, and in addition to recording and playing back video, parts of it can also be played back as still images, and even mixed with video recording. Requests to record still images have begun to be heard. However, with current VTRs, it is possible to virtually freeze part of the video for viewing using the still playback mode, but this requires operating the still key at the point where you want to freeze the image. However, the operation tends to be cumbersome. Furthermore, the image quality deteriorates to some extent due to the stoppage of the capstan motor when transitioning from normal playback to still playback, and the S/N decreases at the top and bottom of the screen due to not being able to just trace due to the difference in the inclination of the head scanning trajectory. Due to these problems, it is not possible to observe high-quality still images. Furthermore, there is still no recording method that enables mixed recording of moving images and still images on magnetic tape.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image recording method that realizes broadband recording of still images while maintaining compatibility with moving image recording formats.

[Means for solving problems]

The image recording method according to the present invention is a method for recording a still image by storing one field worth of video signal from an imaging means in a memory, and repeatedly recording the stored signal in the memory on a recording medium. After subsampling the signal in the band band f [Hz] at a sampling frequency of 2 f/n [Hz] that shifts the phase of each field by 360°/n (n is an integer) and making one cycle in n fields, the signal is subsampled in the baseband band f/n. It is characterized by recording with the band limited to n [Hz].

[Effect]

With the above means, high-definition still images can be recorded in the same format as the recording format of moving images. Although it is the same as the video recording format, still images can be viewed without special operations such as the still key. By detecting that the image is a still image, high-definition still images can be easily reproduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a recording system in which one still image is developed into three-field video signals for recording and reproduction according to the present invention, and FIG. 2 is a block diagram showing the configuration of the reproduction system.

In FIG. 1, 50 is an imaging circuit having a high-resolution imaging element, 51 is a matrix circuit that forms Y, (RY), and (B-Y) signals from the RlG and B signals from the imaging circuit 50, and 52 is a clock generator that generates a driving clock for the imaging circuit 50. 53 is an A/D converter with a sampling frequency of 3 f sc (f 5c = 3° 58 MHz) and 8-bit quantization; 54 is a memory with a storage capacity for one field; and 55 is a D/A that operates with a clock having a frequency of 3 fsc. Converter, 56 is a switch connected to the a contact side in the video recording mode and connected to the b contact side in the still image recording mode, 57 is a switch with a frequency deviation of 5.4 to
It is a 7.0 MHz FM modulator.

58 and 59 are the (RY) signal and (
B-Y) Cuff to band limit the signal) Off frequency 0.5M
Hz LPF, 60.61 is cutoff frequency 1.5M
Hz LPF, 62.63 is sampling frequency 3.0
MHz, 8-bit quantization A/D converter, 64.65, memory with storage capacity for one field, 66.6
7 is a sub-sampling circuit, 68.69 is a D/A converter operated with a 1.0 MHz clock, and 70.71 is an LPF with a cutoff frequency of 0.5 MHz. 72.73 is
Similar to the switch 56, the switch is connected to the a contact side in the video recording mode and to the b contact side in the still image recording mode. 74 is a quadrature two-phase modulator, and 75 is a 900 phase shift circuit.

Mixer 76, switch 77, recording amplifier 78A.

78B and magnetic heads 79A and 79B for both recording and reproduction are the same as the mixer 24, switch 26, recording amplifiers 28A and 28B, and magnetic heads 29A and 29B shown in FIG. 7, respectively.

Next, the operation of the recording system shown in FIG. 1 will be explained. The image sensor of the image sensor 50 is scanned by the clock from the clock generator 52 and outputs R, G, and B signals, which are converted into Y, (RY), and (B-Y) signals by the matrix circuit 51. Convert to

In the normal video shooting state, Y from the matrix circuit 51 is
The signal is applied to an FM modulator 57 via a switch 56, and at the same time is quantized to 8 bits by an A/D converter 53. The output of the A/D converter 53 is written into the memory 54 and read out, and is supplied to the b contact of the switch 56 via the D/A converter 55. FM modulator 57 performs FM modulation on the luminance signal from switch 56 and supplies it to mixer 76 . On the other hand, PF5B and 59 respectively input the (RY) and (B-Y) signals from the matrix circuit 51 to Q and 5M.
) (band limited to z, see FIG. 3(d)), its output is supplied to the quadrature two-phase modulator 74 via switches 72 and 73, and at the same time, the LPF 60°61
), the (B-Y) signal is band-limited to 1.5MHz.
(see Figure (a)), A/D converters 62 and 63 digitize it. Figure 3 (mountain) is the A/D converter 62.63
shows the frequency distribution of the output.

The outputs of the A/D converters 62 and 63 are sequentially stored in the memories 64 and 65.
written to and read from.

The sub-sampling circuits 66 and 67 sub-sample the output of the memories 64 and 65 using a clock having a frequency of 173 of the clock of the A/D converter 62 and 63.

In other words, the sub-sampling circuits 66 and 67 sample one pixel per three pixels from the outputs of the memories 64 and 65, as shown in FIG.
Take out the pixel signal. In Fig. 5, ■ is a sample pixel of the nth field, ■ is a sample pixel of the (n+1)th field, ■ is a sample pixel of the (n+2)th field, f
, is 3. The sampling frequency is OMHz. Due to this inter-field 120@shift subsampling, the output of the subsampling circuit 66°67 contains the original signal up to 0.5 MHz, the first harmonic, and The first harmonic is multiplexed with a signal obtained by folding back from the baseband. The outputs of the sub-sampling circuits 66 and 67 are converted into analog signals by D/A converters 68 and 69, and the L
Limited to 0.5 MHz with PF70.71. LPF
The frequency distribution of the output of 70.71 is shown in FIG. 3(e).

Quadrature two-phase modulator 74 quadrature two-phase modulates the color difference signals from switches 72, 73 in a manner similar to that described in connection with FIG. 7 and supplies the same to mixer 76. A mixer 76 multiplexes the output of the FM modulator 57 and the output from the quadrature two-phase modulator 74, and the output of the mixer 76 is sent to the magnetic head 78A for each field.
, 78B on the magnetic tape 80.

A memory controller 120 drives the memories 54, 64, and 65 according to the oscillation output of the clock generator 52. A system controller 121 controls each part of the circuit, and is composed of a so-called microcomputer. 122 is a still/movie selection switch.

Next, we will explain the still image recording operation. During normal video recording, the switches 56, 72, and 73 are connected to the a contact side as described above, and the memories 54, 64, and 65 are sequentially written and updated. . When the shutter mechanism (not shown) of the camera unit is activated, the so-called system controller 121
A control signal from the switch 54.64.65 turns b
At the same time as switching to the contact side, the memory controller 120
The memory 54, 64, 65 is prohibited from being rewritten, and thereafter, the stored signals in the memory 54, 64, 65 at that time are repeatedly read out in the pattern shown in FIG. This results in
The signal of one image is divided into three fields and repeatedly recorded on the magnetic tape 80. FIG. 4 shows the recording pattern of the magnetic tape recorded in this way. The 0MV section is the moving image recording area, and the SV is indicated by diagonal lines.
The area is the still image recording area. In this case, the system
A control signal indicating whether still image recording or moving image recording is being performed by the controller 121 may also be recorded.

The reproduction system shown in FIG. 2 will be explained. 80 is a magnetic tape 81A with the recording system shown in Figure 1, on which still images are also recorded.

81B is a magnetic head for both recording and reproduction, 82B is a reproduction amplifier, and 83 is a switch that is switched every 1760 seconds.

84 is a HPF for extracting the FM modulated luminance signal component from the reproduced signal, 85 is an FM demodulator, 86 is an LPF for extracting the low frequency carrier color signal component, 187 is a quadrature two-phase demodulator, 88.89 is a sampling frequency 1 .0MHz, quantized 8-bit A/D converter, 90.91 has a memory that can store 3 fields of digital signals from A/D converter 88.89, 92.93 operates with a 3.0MHz clock. The D/A converter 94.95 is an LPF with a cutoff frequency of 1.5 MHz.

96 is a moving image/still image detection circuit that determines whether the reproduced image is a moving image or a still image, and 97 and 98 are switches that are switched based on the detection result of the moving image/still image detection circuit 96. Switches 97 and 98 are connected to the a contact side in the case of a moving image, and connected to the b contact side in the case of a still image. The moving image/still image detection circuit 96 may be a circuit that records a signal for determining moving image recording/still image recording on the magnetic tape 80 during recording, and detects it from the reproduced signal.

99 is a quadrature two-phase modulator, 100 is a clock generator that generates a clock therefor, and 101 is a 90" phase shift circuit. 102 is a signal output from the modulator 99, which removes unnecessary components. BPF for, 103 is mixer, 104
1 is an output terminal; 105 is a sync separation circuit that separates the horizontal sync signal from the reproduced signal; 106 is a burst separation circuit that extracts the color burst signal from the output of the BPF 102;
07 is an APC/AFC circuit having a PLL configuration.

Next, the operation of the reproduction system shown in FIG. 2 will be explained. A switch 83 causes the recording signal of the magnetic tape 80 to be reproduced from the magnetic head 81A or 81B for each field. HPF84
extracts the FM modulated luminance signal component from the reproduced signal, and
The M demodulator 85 demodulates it, and the moving image/still image detection circuit 9
6 and mixer 103.

On the other hand, the LPF 86 extracts the low frequency carrier color signal component from the reproduced signal, and the demodulator 87 extracts the APC/A FC circuit 1.
The low frequency carrier color signal is demodulated using the clock from 07 and a clock phase-shifted by 90 degrees, and two color difference signals are output. During video playback, the video/still image detection circuit 9
Switches 97 and 98 are connected to the a contact side by the output of 6, and (R-Y) and (B-
Y) signals are respectively applied to a quadrature two-phase modulator 99 via switches 97,98. At the same time, the output of the demodulator 87 is also applied to the A/D converter 88.
．． 91. The write addresses are every third as shown in FIG. That is, the signal of the n-th field is stored at the address (2), the signal of the (n+1)th field is allocated to the address (2), the signal of the (n+2) field is allocated to the address (2), and so on. Memory 90.
Continuation of 91 is performed using a clock having a frequency three times that of writing. The subsequent signal is converted into an analog signal by a D/A converter 92.93, band-limited to 1.5 MHz by an LPF 94.95, and supplied to the b contact of a switch 97.98.

When playing still image recording area S■, LPF, 94.9
The output of No. 5 is exactly restored to a signal with the frequency distribution shown in FIG. 3(a).

When reproducing the moving image recording area MV, the switches 97 and 98 are connected to the a contact side, so the color difference signal output of the demodulator 87 is supplied to the quadrature two-phase modulator 99 via the switches 97 and 98, and the modulator 99 3. from clock generator 100;
The color difference signal is modulated into a carrier color signal by using a 58 MHz clock and a clock whose phase is shifted by 90 degrees by a 900 phase shift circuit 101, and a mixer 103 mixes the luminance signal and the carrier color signal.

When the still image recording area SV is reached, the switches 97 and 98 are switched to the b contact side by the output of the moving image/still image detection circuit 96, and from then on, the color difference signal is switched to the A/D until the moving image recording area MV is reached. Converters 88, 89, memories 90, 91, D/A converters 92, 93, LPF 94.
95 and switches 97 and 98 to a modulator 99.

Therefore, the modulator 99 is supplied with a color difference signal in a band of up to 1.5 Mb, and the mixer 103 repeatedly outputs a video signal of the same image, thereby realizing still image reproduction.

When the moving image recording area MV is reached, the switches 97 and 98 are switched to the a contact side by the output of the moving image/still image detection circuit 96, and normal moving image playback begins.

FIG. 6 shows an example of the moving image/still image detection circuit 96.
The reproduced luminance signal from the demodulator 85 is sent to the A/D converter 110.
and one input of the differential circuit 113. A/D
Converter 110 quantizes the input signal to 8 bits with a 3fsc clock. A memory 111 has a storage capacity for one field, and functions as a delay element for one field. The signal read out from the memory 111 one field before is converted into an analog signal by the D/A converter 112 using clocks 3f and c, and applied to the other input of the difference circuit 113. The output of the difference circuit 113 is the absolute value circuit 1
The signal is made into a positive signal at step 14, and integrated over one field by an integrating circuit 115. Partial integration circuit 115 is reset in synchronization with the vertical synchronization signal. The integral value by the integrating circuit 115 represents the movement of the image from the previous field signal, and when the integral value of the integrating circuit 115 is larger than a predetermined threshold TH, it can be determined that the image is a moving image, and when it is smaller than the predetermined threshold TH, it can be determined that the image is a still image. 116 is a comparison circuit for this purpose, and its output is applied to switches 97 and 98. In order to prevent malfunctions in moving/still image detection, the reference threshold TH is preferably as small as possible without being affected by noise.

In the above explanation, the magnetic tape 80 is running when reproducing the still image recording area SV, but of course the still image recording area is also recorded in a normal recording format, so it cannot be used in a conventional reproducing device. It is also possible to reproduce the still image recording area in the still reproduction mode.

In the above description, the magnetic tape was described as a representative recording medium, but the present invention is not limited thereto, and other recording media may be used.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, still images can be recorded without changing the conventional recording format. Furthermore, even if you do not specify the still playback mode during playback, the playback image will be a still image and a broadband image will be obtained, making it extremely practical.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording system according to an embodiment of the present invention.
Fig. 2 is a block diagram of the reproduction system, Fig. 3 is an explanatory diagram of the frequency characteristics of color difference signal processing in the embodiment of Fig. 1, Fig. 4 is an explanatory diagram of the recording pattern of the magnetic tape, and Fig. 5 is an explanatory diagram of the recording pattern of the magnetic tape. 6 is a concrete example of the moving/still image detection circuit 96 shown in FIG. 2, FIG. 7 is a block diagram of a conventional recording system, and FIG. FIG. 2 is a block diagram of a conventional reproduction system. 50-Imaging circuit 52.100...Clock generator 57--FM modulator 66.67--Subsample circuit 74.99--Quadrature two-phase modulator 76--Mixing circuit 78A, 78B・-Recording amplifier 79A, 79B
, 81A, 81B, ---Magnetic head 80--Magnetic tape 82A, 82B--Reproduction amplifier 85-FM demodulator 87-Right-angle two-phase demodulator 96--Movie/still image detection circuit 101, 108-- 90″ phase shift circuit 104-
...output terminal 113--differential circuit 121, Figure 3, Figure 6

Claims (1)

[Scope of Claims] A method for recording a still image by storing one field worth of video signal from an imaging means in a memory and repeatedly recording the stored signal in the memory on a recording medium, the method comprising: [Hz] signal in 36 field units
It is characterized by sub-sampling at a sampling frequency of 2f/n [Hz] with a phase shift of 0°/n (n is an integer) and making one cycle in n fields, and then band-limiting and recording to the baseband band f/n [Hz]. Image recording method.