JP3215509B2 - Contrast determination circuit for TV doorphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contrast determining circuit for a TV door phone.

[0002]

2. Description of the Related Art Conventionally, a visitor is imaged by a television camera,
In a TV door phone that can display visitors on a monitor TV, the ambient light is converted into an electric signal by a light intensity sensor attached to the door phone, and this converted electric signal is processed by an analog circuit. Then, the contrast in the video of the monitor television is controlled by brightening or darkening the original video data according to the surrounding brightness.

[0003]

However, in the above-described method of controlling contrast, an analog circuit is used as a circuit for setting contrast for input video data, so that a circuit used for a TV door phone is not used. There is a problem that it is too slow for a circuit used for a TV door phone that needs to determine the contrast of an image in real time.

[0004] Therefore, for example, the light of the sun hits,
It is difficult to determine and output an appropriate contrast when the contrast of the screen is large due to the movement of a point light source nearby. In addition, since the circuit is of the analog type, the current consumption increases and there is a problem when designing the circuit of the entire system.
For example, the present invention has been made in view of the above problems,
It is an object of the present invention to provide a contrast determination circuit for a video door phone that can determine a contrast at a high speed, can output appropriate video data in real time, has low current consumption, and can easily design a system.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is used for a TV door phone which images a visitor with a television camera and projects the visitor on a monitor television, and adjusts the ambient brightness. A light-amount sensor that senses and outputs an electric signal at a level corresponding to the brightness, a comparator that converts the electric signal from the light-amount sensor into a digital signal, and a digital signal that converts the video data from the TV camera into digital data.
A / D converter for converting data to a monitor
The above digital data for each area divided into a grid on the surface
Of the digital data and the digital data
A calculation unit that outputs a selection signal for determining the contrast according to the surrounding brightness in combination with the peripheral signal, for each of the divided ranges, and converts the selection signal into contrast determination data using the selection signal. And a storage device.

[0006]

According to the structure of the present invention, since the contrast can be determined by digital processing, the contrast can be determined at high speed, and the main subject can be displayed on the screen.
Screen even if it is unknown
Thus, an appropriate contrast determination output can be output simultaneously with the video data for each divided screen , so that real-time processing of the video data becomes possible. Further, by performing data conversion based on the contrast determination data stored in the storage device and digitizing the entire circuit, it is possible to use a CMOS with low current consumption, thereby facilitating system design.

[0007]

The present invention will be described below with reference to examples. FIG. 1 shows a configuration of an embodiment. A contrast determination circuit A of this embodiment includes an arithmetic unit 1, a ROM 2 storing contrast determination data, and a brightness around a door phone (not shown). Light quantity sensor 4 that senses and converts it into an electric signal
And a comparator 3 for converting an electric signal from the digital camera into a 2-bit digital signal. The arithmetic unit 1 converts video data from a television camera provided in a door phone (not shown) into digital video data via an A / D converter 5.
Convert and import. In this case, one pixel is constituted by a 6-bit digital signal and 256 × 120 pixels (one screen)
2 are sequentially input via the A / D converter 5, and at the same time, a 2-bit digital signal from the comparator 3 is input. From these input digital signals, as shown in FIG. Each contrast of the divided screens A to D is determined. FIG. 3 shows a flow of the processing operation of the arithmetic unit 1, in which the divided screens A to D
Each time the digital video data corresponding to is input, the contrast value of the divided screen is determined together with the 2-bit digital signal from the comparator 3 and the correction data is output corresponding to each pixel. I do.

After the contrast value of the final divided screen D is determined in this manner, an 8-bit selection signal based on the correction data is read out from the ROM 2 and is used as an address.
Give to 2. The ROM 2 stores 256 types of contrast determination data at each address determined by an 8-bit signal. When an address is given as described above, A / D-converted 6-bit video data is added to ambient brightness. The 8-bit contrast determination data to which the corresponding determined 2-bit contrast data is added is used for each of the divided screens A to D.
Is selected for each pixel and taken out simultaneously.

The extracted 8-bit contrast determination data is converted into an analog signal by the D / A converter 6, and a brightness corresponding to the brightness around the doorphone is obtained by the converted analog signal and the video signal. Thus, a corrected image can be obtained. In this embodiment, the entire circuit uses a CMOS which consumes a small amount of current to reduce the total current consumption.

[0010]

The present invention is used for a TV door phone that images a visitor with a television camera and displays the visitor on a monitor television, and detects an ambient brightness and outputs an electric signal of a level corresponding to the brightness. Light sensor, a comparator that converts an electric signal from the light sensor into a digital signal, and a digital camera that outputs video data from the TV camera.
A / D converter for converting the data into
The above digital for each area divided into a grid on the screen of
Divide the data and take in the digital data
Each range obtained by dividing the selection signal for determining the contrast according to the surrounding brightness in combination with the digital signal
An arithmetic unit for outputting for each, from and a storage device for converting the contrast determination data by the selection signal, it is possible to determine the contrast by digital processing, therefore the contrast determination is performed at a high speed, further main object
If you don't know where on the screen
The screen is divided into grids, and an appropriate contrast determination output for each divided screen can be output simultaneously with video data, real-time processing of video data becomes possible, and data conversion is stored in a storage device. By using the determined contrast determination data and digitizing the entire circuit, it is possible to use a CMOS with low current consumption, and as a result, there is an effect that the system design becomes easy.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a screen division according to the embodiment.

FIG. 3 is a flowchart for explaining the operation of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Operation part 2 ROM 3 Comparator 4 Light amount sensor 5 A / D converter 6 D / A converter

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-47790 (JP, A) JP-A-62-226772 (JP, A) JP-A-2-170779 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H04N 7/18

Claims (1)

(57) [Claims] 1. A television intercom for photographing a visitor with a television camera and projecting the visitor on a monitor television,
A light-amount sensor that senses ambient brightness and outputs an electric signal at a level corresponding to the brightness, a comparator that converts an electric signal from the light-amount sensor into a digital signal, and video data from the television camera. Digital day
A / D converter for converting to a monitor, and the monitor TV screen
The above digital data is divided into each area divided into a grid
Divide and import the digital data and digital
A calculation unit that outputs a selection signal for determining the contrast according to the surrounding brightness in combination with the signals for each of the divided ranges, and a storage device that converts the selection signal into contrast determination data based on the selection signal. A contrast determining circuit for a TV door phone.