JPH0545119B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color television communication device, and in particular, a device for receiving a composite video signal captured by a color camera built into a doorway handset on a color monitor built into a living room unit. The present invention relates to a color television communication device.

[Prior Art] As shown in FIG. 2, a conventional color television communication device receives a composite video signal captured by a color camera 20 built into an entrance handset on a color monitor 21 built into a living room unit. Color camera 20 has lens 2
A subject is imaged by an imaging section 2 comprising a color filter 2b and a CCD 2c. The imaging unit 2 includes a timing pulse generator 6, a camera synchronization signal generator 5,
It is controlled by driver 4. With this control, the signals captured by the imaging unit 2 are transmitted to the amplifier 3, 3MHz low-pass filter 11, yellowness signal detector HDYe, green chromaticity signal detector HDG, and cyan chromaticity signal detector.
The signal is sent to the luminance signal processor PY, red processor PR, green processor PG, and blue processor PB via HDCy. The signals processed by the red processor PR, green processor PG, and blue processor PB are sent to R-Y via matrix 12.
The color difference signal and the B-Y color difference signal are passed through low-pass filters 13 and 14 and combined with the luminance signal formed by the luminance signal processor PY in an encoder 15 to form a composite video signal. The composite video signal is composed of a luminance signal, a synchronization signal, and a 3.58 MHz color burst signal, and the color monitor 21 identifies whether it is a composite video signal or not based on the presence or absence of the color burst signal organized in the back porch of the horizontal retrace period.

The color monitor 21 has the same configuration as a normal color television, and detailed description thereof will be omitted. In the figure, 22 is a first video amplifier, 23 is a delay circuit, 24 is a second video amplifier, 25 is a band amplifier, 26 is a color demodulator, 27 is a matrix circuit, 28 is a color cancellation circuit, 29 is a burst gate amplifier, 30 is a gate pulse delay circuit, 31 is a synchronous separation circuit, 32 is a color synchronous phase detector, 33 is a vertical deflection circuit, 34 is a horizontal deflection circuit, 35 is a high voltage rectifier circuit, 36 is a convergence circuit, and 37 is a picture tube. .

[Problems to be Solved by the Invention] A conventional color TV communication device processes a signal captured by the imaging unit 2 in a very bright daytime condition, and
At night, the subject must be imaged in dim light. Since this change between bright and dark states is extremely large, the signal-to-noise ratio (S/N
ratio) becomes worse. A composite video signal with a poor S/N ratio has a disadvantage in that color reproducibility deteriorates, and the color tone becomes dull, especially in shadow areas. Furthermore, when attempting to capture an image by illuminating a subject with infrared light in an environment such as nighttime where subject illumination is not available, the color camera 20 has the disadvantage of compiling a composite video signal with unnatural colors.

[Object of the Invention] The present invention has been made in view of the above-mentioned difficulties, and it is possible to improve the S/
It is an object of the present invention to provide a color television communication device that automatically cuts out the harsh colors of the subject and switches to black and white video when the N ratio decreases.

[Means for Solving the Problems] A color television communication device according to the present invention is a color television communication device that is equipped with a color camera provided in an entrance handset and a color monitor that receives a composite video signal generated by the color camera. , a reference voltage generator that generates a reference signal of a predetermined level of the composite video signal captured by the color camera, a rectifier that rectifies the composite video signal, and a rectifier that converts the output from the rectifier into a reference voltage generator. It is equipped with a comparator that compares the level, and a switching circuit that deletes the 3.58MHz color burst signal from the composite video signal when the composite video signal becomes below a predetermined level and the S/N ratio decreases. be.

[Embodiment of the Invention] Hereinafter, an embodiment of a color television communication device according to the present invention will be described in detail with reference to FIG.

Components that are the same in FIG. 1 and FIG. 2 are designated by the same reference numerals, so their explanation will be omitted.

In FIG. 1, numeral 1 is a color camera built into the entrance cordless handset. The color camera 1 has a lens 2a,
Imaging unit 2 equipped with color filter 2b and CCD 2c
The imaging unit 2 that captures an image of a subject (not shown) is controlled by a timing pulse generator 6, a camera synchronization signal generator 5, and a driver 4, and an amplifier 3.
Outputs the imaged video signal.

As video signal level detection means for detecting the level of this video signal, a reference voltage generator 10 that generates a reference signal of a predetermined level of the composite video signal captured by the color camera 1; A rectifier 8 for rectification and a comparator 9 for comparing the output from the rectifier with the level from the reference voltage generator 10 are provided.

Further, a switching circuit 7 is provided as a color killer means for erasing the 3.58 MHz color burst signal from the composite video signal when the composite video signal becomes lower than a predetermined level by the comparator and the S/N ratio decreases. When normally closed, the switching circuit 7 sends the 3.58MHz color burst signal generated by the camera synchronization signal generator 5 to the yellowness signal detector HDYe, the green chromaticity detector HDG, and the cyan chromaticity signal detector HDCy. . When opening, the 3.58MHz color burst signal is cut off. The switching circuit 7 is opened by the output of the comparator 9 when the level of the video signal output from the amplifier 3 falls below the level determined by the reference voltage generator 10.

When switching circuit 7 is opened, the red processor
PR, Green Processor PG, Blue Processor
The output of PB is matrix 12, which is the R-Y color difference signal,
Since it is not organized as a B-Y color difference signal, only the luminance signal processor PY operates.

[Operation of the invention] When imaging a bright subject, the reference voltage generator 10
The comparator 9 does not operate because the amplifier 3 outputs a video signal that is higher than the level determined by . Therefore, a 3.58 MHz color burst signal is sent from the camera synchronization signal generator 5 via the switching circuit 7 to the yellow color signal detector HDYe, the green color signal detector HDG, and the cyan color signal detector HDCy. Therefore, from the terminal 1a of the color camera 1 to the terminal 21 of the color monitor 21 of the room unit shown in FIG.
A composite video signal is sent to a. The color monitor 21 that has received the composite video signal is connected to the first video amplifier 22.
The color burst signal separated from the color burst signal is sent to the color synchronization phase detector 32 via the burst gate amplifier 29. The picture tube 37 allows color images to be monitored.

When imaging a dark object, a video signal lower than the level determined by the reference voltage generator 10 is output from the amplifier 3, so the comparator 9 operates and the switching circuit 7 is opened. Therefore, the 3.58 MHz color burst signal is blocked and a composite video signal without the color burst signal is sent out from the terminal 1a. Color monitor 2 that received this composite video signal
1, since there is no color burst signal, the color erasing circuit 28 operates, and a monochrome image can be monitored on the picture tube 37. Therefore, when the composite video signal falls below a predetermined level and the S/N ratio decreases, the unnatural dull colors of a dark subject disappear, resulting in an easy-to-see video.

[Effects of the Invention] According to the color television communication device according to the present invention,
In a color television communication device equipped with a color camera installed in the entrance handset and a color monitor that receives the composite video signal generated by the color camera, the predetermined level of the composite video signal captured by the color camera a reference voltage generator that generates a reference signal, a rectifier that rectifies the composite video signal, a comparator that compares the output from the rectifier with the level from the reference voltage generator, and a comparator that lowers the composite video signal below a predetermined level. Equipped with a switching circuit that erases the 3.58MHz color burst signal from the composite video signal when the S/N ratio decreases due to low subject illuminance such as at night. Since the color signal component in the composite video signal is essentially cut out, a clear black-and-white image can be obtained without unnatural dull colors when the subject illuminance is low. A similar effect can also be obtained by using infrared illumination at night.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a color television communication device according to the present invention, and FIG. 2 is a block diagram of a conventional color television communication device. 1... Color camera, 7... Switching circuit, 8... Rectifier, 9... Comparator, 10...
...Reference voltage generator.

Claims (1)

[Claims] 1. In a color television communication device equipped with a color camera 1 provided in an entrance handset and a color monitor 21 that receives a composite video signal generated by the color camera, a preview of the composite video signal captured by the color camera is provided. a reference voltage generator 10 that generates a reference signal of a predetermined level; a rectifier 8 that rectifies the composite video signal; and a comparator 9 that compares the output from the rectifier with the level from the reference voltage generator 10. When the comparator determines that the composite video signal falls below a predetermined level and the S/N ratio decreases, the comparator determines that the composite video signal
A color television communication device characterized by comprising a switching circuit 7 for erasing a 3.58MHz color burst signal.