Digital video camera for processing analog luminance signal and digital color information signal

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital video camera and, more particularly, to an apparatus suitably used in a video camera apparatus for converting an analog video signal obtained by an image pickup element into a digital video signal and performing digital signal processing.

2. Related Background Art

FIGS. 1A and 1B show a conventional video camera apparatus for A/D-converting an analog signal output from a solid-state image pickup element, and performing signal processing in a digital form. Referring to FIGS. 1A and 1B, a video signal obtained via a lens element 1, a solid-state image pickup device 2, a correlation double sampling circuit 3, and a gain adjustment circuit 4 is sampled by an A/D converter 5 to be converted into a digital signal.

The sampled digital signal is supplied to a digital signal processing circuit 6. The digital signal processing circuit 6 generates a digital luminance signal and digital color-difference signals from the input digital signal. The digital luminance signal generated by the digital signal processing luminance signal via a D/A converter 12 and a low-pass filter 13.

The digital color-difference signals are converted into band-limited analog color-difference signals via D/A converters 35 and 36 and low-pass filters 37 and 38. Furthermore, the analog color-difference signals are supplied to a modulation circuit 39 to be converted into an analog chrominance signal. The analog chrominance signal is supplied to a digital signal recording device 21 together with the analog luminance signal. The processing so far is executed at the sampling frequency of the image pickup element.

When YC-separated input signals are externally input as a video signal, these signals are respectively input to switch circuits 8 and 9. When a composite video signal VIDEO is input, the signal VIDEO is separated into luminance and chrominance signals by a luminance/chrominance separation circuit 7, and the separated signals are input to the switch circuits 8 and 9. One of these YC-separated input signals and the composite video signal is selected by the switch circuits 8 and 9.

The analog luminance and color-difference signals from a camera and externally input analog luminance and color-difference signals are selected by switch circuits 14 and 15. The frequency band of the analog luminance signal is limited by a low-pass filter 17. The band-limited analog luminance signal is supplied to an A/D converter 18 to be converted into a digital luminance signal.

The analog chrominance signal is converted into analog color-difference signals by a demodulation device 40, and the analog color-difference signals are then converted into digital color-difference signals by A/D converters 41 and 42. In this case, the A/D conversion is performed at the sampling frequency of a digital VTR.

The digital signal recording device records the digital luminance and color-difference signals, which are converted, as described above, on a magnetic tape 22. Thus, a digital video signal is recorded.

At this time, switch circuits 25 and 26 are switched to the REC side, and the analog luminance and chrominance signals are selected and output by the switch circuits 25 and 26. An EVF 33 performs a display operation based on the output luminance and chrominance signals for monitoring an image pickup operation.

In a reproduction mode, the digital signal recording device 21 generates digital reproduced luminance and color-difference signals from a signal reproduced from the magnetic tape 22. Of these signals, the reproduced luminance signal is converted into an analog luminance signal by a D/A converter 23 which operates at the sampling frequency of the digital VTR, and thereafter, the frequency band of the analog luminance signal is limited by a low-pass filter 24, thus obtaining an analog reproduced luminance signal.

On the other hand, the digital color-difference signals are converted into analog color-difference signals by D/A converters 28 and 29 which operate at the sampling frequency of the digital VTR. The frequency bands of these analog color-difference signals are then limited by low-pass filters 30 and 31 to obtain an analog reproduced color-difference signal. Furthermore, the analog reproduced color-difference signal is modulated by a modulation device 32.

At this time, the switch circuits 25 and 26 are switched to the PB side, selecting the modulated analog reproduced color-difference signals together with the analog reproduced luminance signal, and output these signals as a reproduced video signal.

In the case of the conventional digital video camera apparatus shown in FIGS. 1A and 1B, in order to allow recording/reproduction of both digital luminance and color-difference signals from the camera and external analog luminance and color-difference signals, many A/D converters, D/A converters, and the like are required. For this reason, the circuit scale constituting the digital video camera apparatus becomes large, and it is difficult to reduce cost.

In conventional image pickup recording apparatuses adopting a digital signal processing system, an image pickup signal processing circuit is an analog circuit, and an output signal from the analog processing circuit is converted into a digital signal. For this reason, due to a large circuit scale, the number of components becomes large, and current consumption undesirably increases. Also, it is difficult to make the apparatus compact, and to reduce cost.

Since the apparatus includes both an analog signal processing circuit and a digital signal processing circuit, a sufficient S/N ratio cannot often be obtained due to interference such as mixing of a digital signal into an analog signal, and the apparatus cannot be rendered compact.

Since the image pickup signal processing circuit adopts analog processing, image quality is determined by performance such as the frequency characteristics, noise characteristics, a change in performance due to a change in temperature, a variation in characteristics in units of circuits, and the like, and it is difficult to achieve high image quality.

In order to attain special effects using a frame memory and a digital calculation, a still larger number of circuit components are required. As a result, it is difficult to make the apparatus compact, and power consumption undesirably increases.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the above-mentioned problems, and has as its object to simplify the circuit arrangement of a digital video camera apparatus which selects one of a video signal from a digital video camera and a video signal from an external input terminal, and records the selected video signal on a recording medium.

The present invention has been made to solve the above-mentioned problems, and has as its another object to provide a digital video camera apparatus having a small number of components.

The present invention has been made in consideration of the above-mentioned problems, and has as its still another object to simplify the circuit arrangement of an apparatus for digitally recording an image pickup signal.

In a digital video camera apparatus according to an aspect of the present invention, which comprises a digital signal processing circuit and a digital signal recording device and in which an analog video signal supplied from an image pickup element is converted into a digital video signal, the converted digital video signal is supplied to the digital signal processing circuit, and the digital signal recording device records the digital video signal on a recording medium after predetermined signal processing, and of signals to be supplied from the digital signal processing circuit to the digital signal recording device, a luminance signal is supplied in a state of an analog signal and a chrominance signal is supplied in a state of a digital signal.

According to another aspect of the present invention, the chrominance signal is supplied in a state of a digital signal sampled at the frequency of clocks of the image pickup element.

According to still another aspect of the present invention, an externally input luminance signal is supplied in a state of an analog signal, and an externally input chrominance signal is supplied in a state of a digital signal which is sampled at a frequency four times that of a subcarrier.

Therefore, when a signal from a solid-state image pickup element is A/D-converted and processed in a digital region, and the processed signal is then connected to an existing digital recording device, a luminance signal supplied from the solid-state image pickup element and an externally input luminance signal are supplied in an analog state, color-difference signals are supplied to the digital recording device in a state of digital color-difference signals at the sampling frequency of the solid-state image pickup element, and an externally input chrominance signal is supplied after it is sampled at a frequency four times that of the subcarrier, and the sampled signal is converted into digital color-difference signals. Therefore, the arrangement of the circuit required for selecting one of a video signal input from the digital video camera and a video signal input from the external. input terminal, and recording the selected signal on a recording medium can be simplified.

According to still another aspect of the present invention, when a signal from a solid-state image pickup element is A/D-converted and processed in a digital region, and the processed signal is then connected to an existing digital signal recording device, an externally input luminance signal to be supplied to the digital signal recording device is A/D-converted at the sampling frequency of the digital signal recording device, and an externally input chrominance signal to be supplied to the digital signal. recording device is A/D-converted at, e.g., a frequency four times the subcarrier frequency.

According to still another aspect of the present invention, when a signal from a solid-state image pickup element is A/D-converted and processed in a digital region, and the processed signal is then connected to an existing digital signal recording/reproduction device, digital color-difference signals from a camera unit are supplied to a modulation circuit without changing their sampling frequency, e.g., four times the subcarrier frequency, and color-difference output signals from the digital signal recording/reproduction device are frequency-converted and are then modulated in the digital region.

According to still another aspect of the present invention, when a signal from a solid-state image pickup element is A/D-converted and processed in a digital region, and the processed signal is then connected to an existing digital signal recording/reproduction device, the sampling frequency of digital color-difference signals from a camera unit is converted, and color-difference signals to be output are modulated in an analog region.

In this manner, the number of components can be decreased, and an existing digital signal processing camera and an existing digital VTR can be easily connected.

An image pickup recording apparatus according to still another aspect of the present invention has an electronic zoom circuit for electronically enlarging or reducing an image. The apparatus has a first clock for operating an image pickup unit, and a second clock, having a frequency different from that of the first clock, for operating a recording unit. In the electronic zoom circuit, image pickup video signal data at the first clock rate is converted into video signal data at the second clock rate.

According to still another aspect of the present invention, a circuit for separating and forming a luminance signal and a chrominance signal from a digital signal obtained by A/D-converting a color image pickup element output signal is constituted by a plurality of stages of delay circuits, a plurality of coefficient multipliers for respectively multiplying the outputs from the plurality of stages of delay circuits with predetermined coefficients, an adding up circuit for adding up the outputs from the plurality of coefficient multipliers, and a chrominance signal forming circuit for forming a chrominance signal using some of signals output from the plurality of stages of delay circuits.

Therefore, since image pickup video signal data at the first clock rate for operating the image pickup unit and video signal data at the second clock rate for operating the recording unit are converted in the electronic zoom circuit, a video signal formed by a camera can be recorded by a digital recorder without being D/A converted, thus minimizing deterioration of image quality. In addition, since the number of digital circuit portions increases, high integration, low power consumption, and high precision can be realized.

The above and other objects and features of the present invention will become apparent from the following description of the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 which is comprised of FIGS. 1A and 1B is a block diagram showing the arrangement of a conventional digital video camera apparatus;

FIG. 2 which is comprised of FIGS. 2A and 2B is a block diagram showing a digital video camera apparatus according to the first embodiment of the present invention;

FIG. 3 which is comprised of FIGS. 3A and 3B is a block diagram showing a digital video camera apparatus according to the second embodiment of the present invention;

FIG. 4 is a block diagram showing the third embodiment of the present invention;

FIG. 5 is a block diagram showing the fourth embodiment of the present invention;

FIG. 6 is a block diagram showing the fifth embodiment of the present invention;

FIG. 7 is a block diagram showing the sixth embodiment of the present invention;

FIG. 8 which is comprised of FIGS. 8A and 8B is a block diagram showing an image pickup recording apparatus according to the seventh embodiment of the present invention;

FIG. 9 is a circuit diagram showing in detail the arrangement of an electronic zoom circuit in FIGS. 8A and 8B;

FIG. 10 is a circuit diagram showing in detail another arrangement of the electronic zoom circuit in FIGS. 8A and 8B;

FIG. 11 which is comprised of FIGS. 11A and 11B is a block diagram showing the eighth embodiment of the present invention;

FIG. 12 is a block diagram showing in detail main part of an electronic zoom circuit in FIGS. 11A and 11B;

FIG. 13 is a block diagram showing the ninth embodiment of the present invention;

FIG. 14 is a circuit diagram showing in detail the arrangement of a filter color separation block in FIG. 13; and

FIG. 15 is a circuit diagram showing in detail another arrangement of the filter color separation block in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of a digital video camera apparatus according to the present invention will be described hereinafter with reference to the accompanying drawings. FIGS. 2A and 2B are a block diagram showing the arrangement of a video camera apparatus according to the first embodiment of the present invention.

As shown in FIGS. 2A and 2B, a video signal obtained via a lens element 1, a solid-state image pickup device 2, a correlation double sampling circuit 3, and a gain adjustment circuit 4 is sampled by an A/D converter 5 at a clock frequency (MCLK) of the solid-state image pickup device 2 to be converted into a digital signal.

A digital signal processing circuit 6 generates a digital luminance signal and digital color-difference signals. Thereafter, the digital luminance signal is supplied as a band-limited analog luminance signal to a switch circuit 14 via a D/A converter 12 and a low-pass filter 13. The digital color-difference signals are supplied to switch circuits 15 and 16.

When YC-separated input signals are externally input as a video signal, these signals are directly input to switch circuits 8 and 9. When a composite video signal is input as an externally input video signal, the composite video signal is separated into luminance and chrominance signal by a luminance/chrominance separation circuit 7, and the separated signals are input to the switch circuits 8 and 9. Of these switch circuits 8 and 9, the switch circuit 8 is arranged for selecting a luminance signal Y, and the switch circuit 9 is arranged for selecting a chrominance signal C.

The chrominance signal separated by the switch circuit 9 is supplied to an A/D converter 10. The chrominance signal is converted into a digital signal by the A/D converter 10 at a frequency four times the subcarrier frequency, and the digital chrominance signal is supplied to a demodulation device 11. The digital chrominance signal is converted into digital color-difference signals by the demodulation circuit 11.

The analog luminance signal and the digital color-difference signals from the camera, and the externally input analog luminance signal and digital color-difference signals are respectively selected by switch circuits 14 to 16. The frequency band of the analog luminance signal is limited by a low-pass filter 17, and the band-limited signal is supplied to an A/D converter 18 to be converted into a digital luminance signal. At this time, sampling is performed at the sampling frequency of a digital VTR.

The frequencies of the digital color-difference signals are converted by sampling frequency conversion circuits 19 and 20 from the clock frequency (MCLK) of the solid-state image pickup device 2 or the frequency four times the subcarrier frequency to the sampling frequency of the digital VTR.

The converted digital luminance and color-difference signals are supplied to a digital signal recording device 21, and are recorded on a magnetic tape 22 by the digital signal recording device 21. Thus, a digital video signal is recorded.

At this time, switch circuits 25 to 27 are switched to the REC side, and the analog luminance signal is directly output. The digital color-difference signals are converted into analog color-difference signals by D/A converters 28 and 29 which operate at the sampling frequency of the digital VTR, and the analog color-difference signals are modulated and converted into a chrominance signal by a modulation device 32. The chrominance signal is output. An EVF 33 performs a display operation using the output luminance and chrominance signals, and a displayed image is utilized for monitoring in an image pickup operation.

In a reproduction mode, the digital signal recording device 21 receives a signal reproduced from the magnetic tape 22, and generates digital reproduced luminance and color-difference signals. Of these reproduced signals, the reproduced luminance signal is converted into an analog luminance signal by a D/A converter 23 which operates at the sampling frequency of the digital VTR. Thereafter, the frequency band of the analog luminance signal is limited by a low-pass filter 24, thus obtaining an analog reproduced luminance signal.

The second embodiment of the present invention will be described below with reference to FIGS. 3A and 3B. The same reference numerals in FIGS. 3A and 3B denote the same parts as in FIGS. 2A and 2B.

A video signal obtained via a lens element 1, a solid-state image pickup device 2, a correlation double sampling circuit 3, and a gain adjustment circuit 4 is sampled by an A/D converter 5 at a clock frequency (MCLK) of the solid-state image pickup device 2 to be converted into a digital signal.

A digital signal processing circuit 6 generates a digital luminance signal and digital color-difference signals. Thereafter, the digital luminance signal is supplied as a band-limited analog luminance signal to a digital signal recording device 21 via a D/A converter 12 and a low-pass filter 13 together with the digital color-difference signals.

When YC-separated input signals are externally input as a video signal, these signals are input to switch circuits 8 and 9. When a composite video signal is input as an externally input video signal, the composite video signal is separated into luminance and chrominance signal by a luminance/chrominance separation circuit 7, and the separated signals are input to the switch circuits 8 and 9. One of these video signals is selected by the switch circuits 8 and 9, and the selected video signal is supplied to subsequent circuits.

Thereafter, the chrominance signal is converted into a digital signal by an A/D converter 10 at a frequency four times the subcarrier frequency, and the digital signal is converted into digital color-difference signals by a demodulation device 11.

The analog luminance signal and the digital color-difference signals from a camera and the externally input analog luminance signal and digital color-difference signals are supplied to switch circuits 14 to 16, and signals selected by these switch circuits are supplied to subsequent circuits.

The frequency band of the analog luminance signal is limited by a low-pass filter 17, and the band-limited signal is converted into a digital luminance signal by an A/D converter 18. At this time, sampling is performed at the sampling frequency of a digital VTR.

The frequencies of the digital color-difference signals are converted by sampling frequency conversion circuits 19b and 20b from the clock frequency (MCLK) of the solid-state image pickup device 2 or the frequency four times the subcarrier frequency into the sampling frequency of the digital VTR.

At this time, a switch circuit 34 selects whether a connected device is a digital camera or an external input, and the sampling frequency conversion circuits 19b and 20b change coefficients based on the selection result so as to convert the clock frequency (MCLK) into the sampling frequency of the digital VTR or to convert the frequency four times the subcarrier frequency into the sampling frequency of the digital VTR.

Thus, even when the clock frequency. (MCLK) is not equal to the frequency four times the subcarrier frequency (for example, in the case of an NTSC device using a solid-state image pickup element having 250,000 pixels), frequency conversion can be appropriately performed.

The digital signal recording device 21 records the converted digital luminance and color-difference signals on a magnetic tape 22. Thus, a digital video signal is recorded. At this time, switch circuits 25 to 27 are switched to the REC side, and the analog luminance signal is directly output.

The digital color-difference signals are converted into analog color-difference signals by D/A converters 28 and 29 which operate at the sampling frequency of the digital VTR, and thereafter, the frequency bands of the analog color-difference signals are limited by low-pass filters 30 and 31. The band-limited signals are modulated by a modulation device 32 to be converted into a chrominance signal. Thus, the chrominance signal is output. An EVF 33 performs a display operation using the output luminance and chrominance signals, and a displayed image is utilized for monitoring in an image pickup operation.

Furthermore, in a reproduction mode, the digital signal recording device 21 receives a signal reproduced from the magnetic tape 22, and generates digital reproduced luminance and color-difference signals. 0f these reproduced signals, the reproduced luminance signal is converted into an analog luminance signal by a D/A converter 23 which operates at the sampling frequency of the digital VTR. Thereafter, the frequency band of the analog luminance signal is limited by a low-pass filter 24, thus obtaining an analog reproduced luminance signal.

At this time, the switch circuits 25 to 27 are switched to the PB side, and the analog luminance signal is directly output. The digital color-difference signals are converted into analog color-difference signals by the D/A converters 28 and 29 which operate at the sampling frequency of the digital VTR. Thereafter, the analog color-difference signals are modulated by the modulation device 32 into a chrominance signal. The chrominance signal is output as a reproduced video signal together with the luminance signal.

In each of the embodiments of the present invention, as described above, when a video signal obtained by A/D-converting a signal output from the solid-state image pickup element and processing the digital signal on a digital region, and a video signal input from an external input terminal are supplied to the digital signal recording device, and are recorded on a recording medium, a luminance signal and an externally input luminance signal are supplied to the digital signal recording device in a state of analog signals, and a chrominance signal is supplied thereto in a state of a digital signal. For this reason, the circuit arrangement of the digital video camera apparatus, which can select one of a video signal form the digital video camera and a video signal from the external input terminal, and can record the selected signal on a recording medium, can be simplified, and cost can be reduced.

FIG. 4 shows the third embodiment of the present invention. Referring to FIG. 4, a video signal obtained via a lens element 101 and a solid-state image pickup element 102 is converted into a digital signal by an A/D converter 105 via a correlation double sampling circuit 103 and a gain adjustment circuit 104. The video signal is sampled by the A/D converter 105 at a clock frequency (MCLK) of the solid-state image pickup element 102. A digital signal processing circuit 106 generates a digital luminance signal Y and a digital chrominance signal C from the camera input signal.

The frequency of the digital luminance signal Y is converted by a frequency converter 134 from the clock frequency (MCLK) of the solid-state image pickup element 102 into a sampling frequency (about 13.5 MHz) of a digital signal recording/reproduction device (digital recorder) 113. Thereafter, the digital luminance signal is supplied to a selector 135.

The luminance signal Y from an external input terminal 110 is sampled at the sampling frequency (about 13.5 MHz) of the digital recorder 113 by an A/D converter 136 so as to be A/D-converted into a digital signal. Thereafter, the digital luminance signal is supplied to the selector 135. The selector 135 selects one of the camera input luminance signal Y and the externally input luminance signal Y, and supplies the selected luminance signal to the digital recorder 113.

On the other hand, the digital chrominance signal C generated by the digital signal processing circuit 106 is supplied to a selector 137. A chrominance signal C from an external input terminal 118 is sampled at a sampling frequency 4f.sub.sc four times a subcarrier frequency f.sub.sc by an A/D converter 138 so as to be converted into a digital signal. The selector 137 selects one of the camera input chrominance signal C and the externally input chrominance signal C. The output from the selector 137 is demodulated by a demodulator 119, thus obtaining digital color-difference signals R-Y and B-Y. At this time, the sampling frequency of each color-difference signal is 4f.sub.sc, but the sampling frequency of the digital recorder 113 is about 13.5 MHz. Thus, the color-difference signals R-Y and B-Y are subjected to frequency conversion by frequency converters 139a and 139b. Thus, the digital color-difference signals having the sampling frequency of 13.5 MHz are input to the digital recorder 113, and are recorded on a tape 114 together with the digital luminance signal Y.

In a reproduction mode, a digital video signal recorded on the tape 114 is reproduced by the digital recorder 113. The digital reproduced luminance signal is converted into an analog signal by a D/A converter 141 at the sampling frequency of the digital recorder 113 via a selector 140, and the analog signal is output from an output terminal 125 as a luminance signal Y via a low-pass filter 142. Note that, in a recording mode, the output from the selector 135 is directly supplied to the selector 140 to monitor the luminance signal Y at the output terminal 125.

On the other hand, the reproduced digital color-difference signals R-Y and B-Y are subjected to frequency conversion by frequency converters 143 and 144, respectively. At this time, the sampling frequency is converted from the sampling frequency (13.5 MHz) of the digital recorder 113 to 4f.sub.sc. The frequency-converted color-difference signals are respectively supplied to selectors 145 and 146. These signals are modulated by a digital modulator 147 into a digital chrominance signal. The digital chrominance signal is converted into an analog signal by a D/A converter 148 at the sampling frequency 4f.sub.sc, and the analog chrominance signal is output from an output terminal 132 as a chrominance signal C via a low-pass filter 149. Note that, in the recording mode, the outputs from the demodulator 119 are directly supplied to the selectors 145 and 146 without converting their sampling frequency from 4f.sub.sc, thus monitoring the chrominance signal C at the output terminal 132.

FIG. 5 shows the fourth embodiment of the present invention. The same reference numerals in FIG. 5 denote the same parts as in FIG. 4.

In this embodiment, the arrangement and operation in the recording mode, the arrangement and operation associated with the luminance signal Y in the reproduction mode are the same as those in FIG. 4. Therefore the arrangement-and-operation associated With the chrominance signal in the reproduction mode will be explained below.

Digital reproduced color-difference signals R-Y and B-Y reproduced by a digital recorder 113 are respectively supplied to selectors 145 and 146. These signals are respectively converted into analog signals by D/A converters 150 and 151 at the sampling frequency of the digital recorder 113, and the analog signals are analog-modulated by a modulator 130 via low-pass filters 152 and 153, thus obtaining a chrominance signal C to be output to an output terminal 132. In the recording mode, the outputs from frequency converters 139a and 139b are supplied to the selectors 145 and 146, and after they are subjected to D/A conversion and modulation, the chrominance signal C at the output terminal 132 is monitored.

FIG. 6 shows the fifth embodiment of the present invention. The same reference numerals in FIG. 6 denote the same parts as in FIGS. 1A to 5. Referring to FIG. 6, a digital signal converted by an A/D converter 105 at a clock frequency (MCLK) of a solid-state image pickup element 102 is supplied to a digital signal processing circuit 106, thus generating a digital luminance signal Y and digital color-difference signals R-Y and B-Y.

The digital luminance signal Y is converted into an analog signal by a D/A converter 154 at the sampling frequency MCLK, and the analog signal is input to a selector 156 via a low-pass filter 155. A luminance signal Y at an external input terminal 110 is input as an analog signal to the selector 156. The selector 156 selects one of the camera input luminance signal Y and the externally input luminance signal Y. The selected signal is filtered through a low-pass filter 157, and is then converted into a digital signal by an A/D converter 158 at the sampling frequency (about 13.5 MHz) of a digital recorder 113. The digital signal is supplied to the digital recorder 113.

On the other hand, the digital color-difference signals R-Y and B-Y generated by the digital signal processing circuit 106 are respectively supplied as digital signals to selectors 159 and 160. A chrominance signal C at an external input terminal 118 is converted into a digital signal by an A/D converter 161, and the digital signal is input to a demodulator 162, thus generating externally input color-difference signals R-Y and B-Y. The selectors 159 and 160 select either the camera input color-difference signals or the externally input color-difference signals. At this time, the sampling frequency of each of the color-difference signals output from the selectors 159 and 160 is 4f.sub.sc, but the sampling frequency of the digital recorder 113 is 13.5 MHz. For this reason, the color-difference signals R-Y and B-Y are subjected to frequency conversion by frequency converters 139a and 139b, respectively. Thus, the digital color-difference signals having the sampling frequency of 13.5 MHz are input to the digital recorder 113, and are recorded on a tape 114 together with the luminance signal Y.

In a reproduction mode, a digital reproduced luminance signal reproduced from the tape 114 by the digital recorder 113 is converted into an analog signal by a D/A converter 122 at a sampling frequency (about 13.5 MHz), and the analog signal is input to a selector 140 via a low-pass filter 123. Then, the analog luminance signal is output from an output terminal 125 as a luminance signal Y. In a recording mode, the output from the selector 156 is directly supplied to the selector 140, thus monitoring the luminance signal Y at the output terminal 125.

On the other hand, the frequencies of reproduced digital reproduced color-difference signals R-Y and B-Y are converted by frequency converters 143 and 144 from the sampling frequency of 13.5 MHz to 4f.sub.sc. The frequency-converted color-difference signals are respectively supplied to selectors 145 and 146, and are modulated by a digital modulator 147, thus obtaining a chrominance signal. The chrominance signal is converted into an analog signal by a D/A converter 148 at the sampling frequency 4f.sub.sc, and the analog signal is filtered through a low-pass filter 149, thus obtaining a chrominance signal C at an output terminal 132. In the recording mode, the outputs from the selectors 159 and 160 are supplied to the selectors 145 and 146 without converting their sampling frequencies from 4f.sub.sc, thus monitoring the chrominance signal C at the output terminal 132.

FIG. 7 shows the sixth embodiment of the present invention. The same reference numerals in FIG. 7 denote the same parts as in FIGS. 1A to 6.

In this embodiment, the arrangement and operation in the recording mode, the arrangement and operation associated with the luminance signal Y in the reproduction mode are the same as those in the fifth embodiment. Therefore, the arrangement and operation associated with the chrominance signal in the reproduction mode will be explained below.

Referring to FIG. 7, digital reproduced color-difference signals R-Y and B-Y reproduced by a digital recorder 113 are input to selectors 145 and 146. These signals are converted into analog signals by D/A converters 150 and 151 at a sampling frequency of 13.5 MHz, and the analog signals are filtered through low-pass filters 152 and 153. The filtered signals are then modulated by a modulator 130, and the modulated signal is output to an output terminal 132. In a recording mode, the outputs from frequency converters 139a and 139bare directly supplied to the selectors 145 and 146, thus monitoring a chrominance signal C at the output terminal 132.

As described above, in the third embodiment, an externally input luminance signal to be supplied to the digital recorder is A/D-converted at the sampling frequency of the digital recorder, and an externally input chrominance signal to be supplied to the digital recorder is A/D-converted at a frequency four times the subcarrier frequency.

In the fourth embodiment, color-difference signals from a camera unit are supplied to the modulator without changing their frequency from the sampling frequency 4f.sub.sc. When a video signal is output, the sampling frequency of color-difference output signals from the digital recorder is converted into 4f.sub.sc, and these color-difference signals are modulated in a digital region to generate a chrominance signal.

In the fifth embodiment, the sampling frequency of input color-difference signals R-Y and B-Y is converted from 4f.sub.sc into the sampling frequency of the digital recorder. In addition, when a video signal is output, digital color-difference signals are D/A-converted at the sampling frequency, and the analog color-difference signals are modulated in an analog region to generate a chrominance signal.

Therefore, according to these embodiments, the number of components can be decreased, and an existing digital camera and an existing digital signal recording/reproduction device such as a digital VTR can. be easily connected.

FIGS. 8A and 8B are a block diagram showing the arrangement of an image pickup recording apparatus according to the seventh embodiment of the present invention. Referring to FIGS. 8A and 8B, an image pickup lens 201 includes a diaphragm and an optical filter.

The apparatus shown in FIGS. 8A and 8B includes a CCD 202 as a color image pickup element, and a camera timing generator 203. The camera timing generator 203 generates timing pulses necessary for the CCD 202, a signal processing circuit (to be described later), and the like. The outputs from the CCD 202 are converted into a continuous output by a sample & hold (S/H) circuit 204.

The apparatus includes A/D converters 205, 213, 215, and 216, and a camera signal processing circuit 206. The camera signal processing circuit 206 performs filtering, color separation, gamma correction, gain adjustment, clipping, and the like by digital calculations. The apparatus includes an electronic zoom circuit 207 for enlarging/reducing an image using a memory, Y (luminance)-C (chrominance) separated external video signal input terminals 208, and an external video input terminal 209 for a composite video signal.

The apparatus includes a YC separation circuit 210 for extracting Y and C signals from an input composite video signal, switch circuits 211 and 212 for switching the types of externally input signals in accordance with YC-separated (S) signals/composite (CO) signal, and a color demodulation circuit 214 for separating and demodulating color-difference signals R-Y and B-Y from the input C signal.

The apparatus includes a zoom terminal 217 for inputting a zoom signal ZOOM, switch circuits 218, 219, and 220 for switching the types of input signals in accordance with a switching signal CAMERA (image pickup signal)/LINE (external input), and a digital recorder circuit 221 for performing signal processing such as data compression/expansion, digital modulation/demodulation, and the like.

The apparatus includes a recording/reproduction head (magnetic head) 222, a digital video tape 223, switch circuits 224, 225, and 226 for switching the types of output signals in accordance with a switching signal REC (recording)/PB (reproduction), D/A converters 228, 229, and 230, low-pass filters 231, 232, and 233, a color modulation circuit 234 for receiving color-difference signals R-Y and B-Y and outputting a modulated chrominance signal C, and YC separated video output terminals 235.

In the image pickup recording apparatus of this embodiment with the above-mentioned arrangement, when the switch circuits 218, 219, 220, 224, 225, and 226 are switched in accordance with signals CAMERA/LINE and REC/PB generated by a control signal (not shown) in FIGS. 8A and 8B, three major modes, i.e., camera recording, external input recording, and reproduction modes are realized. Operations in these modes will be described in turn below.

The camera recording mode will be described below. In this mode, the switch circuits 218, 219, and 220 are connected to the CAMERA (C) side, and the switch circuits 224, 225, and 226 are connected to the REC (R) side.

An object image formed on the image pickup surface of the CCD 202 by the image pickup lens 201 is photoelectrically converted by the CCD 202 into electrical signals, and the electrical signals are sequentially read out according to a driving signal generated by the camera timing generator 203, thus obtaining image pickup signals. The image pickup signals are converted by the S/H circuit 204 into a continuous image pickup signal, and this signal is converted into a digital image pickup signal by the A/D converter 205.

The digital image pickup signal is subjected to the above-mentioned signal processing, i.e., filtering, color separation, gamma correction, clipping, and the like, by the camera signal processing circuit 206, thus. obtaining a luminance signal Y and color-difference signals R-Y and B-Y. These signals are then input to the electronic zoom circuit 207, and are subjected to enlargement or reduction processing according to a zoom signal ZOOM input from the zoom terminal 217. The processed signals are then input to the digital recorder circuit 221 via the switch circuits 218, 219, and 220.

In the digital recorder circuit 221, the input signals are subjected to processing such as data compression, digital modulation, and the like. The digital recording signal output from the circuit 221 is recorded on the digital video tape 223 via the magnetic head 222.

The outputs from the switch circuits 218, 219, and 220 are respectively supplied to the D/A converters 228, 229, and 230 via the switch circuits 224, 225, and 226, and are D/A-converted by these D/A converters 228, 229, and 230.

The D/A-converted outputs from the switch circuits 218, 219, and 220 are supplied to the low-pass filters 231, 232, and 233, and low-frequency signals are extracted therefrom. The output from the low-pass filter 231 is directly output as a luminance (Y) signal from the corresponding output terminal 235 to an external device such as a television monitor (not shown) as a monitor signal.

The outputs from the low-pass