JP2000050247A - Video interphone device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a video image with constant brightness by suppressing flickers of a fluorescent lamp, even when a level of a video signal is changed by the fluorescent lamp in the video interphone system. SOLUTION: A monitor master set M1 has 3 stages of integration circuits SKA, SKB, SKC that measure a video signal S1 from a slave set CAK1, a comparator CMP1 that compares an output voltage from the integration circuit with a reference voltage VREF1 to output a voltage depending on the difference, and a drive circuit DRV1 that changes the luminance of a backlight BL1 of a liquid crystal display device LCD1, depending on an output voltage of the comparator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television intercom apparatus, and more particularly to a television intercom apparatus that suppresses flicker of a video signal from a camera slave unit due to a fluorescent lamp and displays an optimal image on a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, there has been proposed a television intercom apparatus of this kind. The television intercom apparatus shown in FIG. 3 includes a camera slave unit CAK11 and a monitor master unit M11, and the camera slave unit CAK11 and the monitor master unit M11 are connected to the trunk line LN11.

The camera slave unit CAK11 includes a lens LZ1.
1, solid-state imaging device CCD11, timing generator TG1
1. A signal processing circuit SS11 is provided. The monitor master unit M11 includes a synchronization separation circuit SP11 and a camera slave unit CAK.
LCD device LCD11 for displaying a video signal from LCD11
And a backlight BL11 which is illumination of a liquid crystal display device
And a drive circuit DRV11 for changing the brightness of the backlight
Is provided.

[0004] In the television intercom apparatus configured as described above, the camera slave unit CAK11 is connected to the solid-state imaging device CC.
A subject (not shown) is imaged at D11, and a video signal S11 to which a synchronization signal or the like is added is output at a signal processing circuit SS11. Timing generator TG11 is camera slave unit CAK
All 11 timing signals are generated and shutter control is performed based on the brightness of the subject.

The video signal S1 sent to the monitor master unit M11
1 is input to the liquid crystal display device LCD11, and the synchronization signal separated by the synchronization separation circuit SP11 is
The image of the subject is input to 11 and is displayed. The backlight BL11, which is the illumination of the liquid crystal display device LCD11, has a constant brightness set by the drive circuit DRV11.

[0006]

In this television intercom apparatus, when a subject is illuminated with a fluorescent lamp (not shown) and imaged, flicker occurs due to the fluorescent lamp.
That is, FIG. 2 shows a state in which the solid-state imaging device CCD 11 takes an image every 1/60 s, and the fluorescent lamp emits light at 1/50 s. Since the period of the shutter of the solid-state imaging device CCD 11 and the period of the fluorescent lamp are different, the brightness of the video signal differs in each field, and the image flickers. For this reason, in order to obtain an image with a constant brightness, the shutter speed has to be fixed at 1/100 s.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a television intercom apparatus which suppresses flicker by controlling a backlight of a liquid crystal display device on a monitor base unit. And

[0008]

In order to achieve the above object, a television intercom apparatus according to the present invention comprises an integrating means for integrating a video signal for each field within a flicker cycle, and an integrated output for each field. The liquid crystal display includes a comparison unit that compares the voltage with a reference voltage that is set in common, and a control unit that changes brightness of illumination of a backlight of the liquid crystal display device according to a comparison result of the comparison unit.

[0009] In the television intercom apparatus configured as described above, the integrating means has an integrating means corresponding to the flicker cycle, and thus integrates the video signal independently for each field within the flicker cycle. Receiving the integrated output for each field, the comparing means compares each integrated output with a common integrated output. Then, the control means controls the brightness of the backlight according to the comparison result. As a result, flickering of the image can be reduced.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a television intercom apparatus according to the present invention. As shown in FIG.
The camera slave unit CAK1 and the monitor master unit M1 are each composed of a main unit LN1.
Is connected to

The camera slave CAK1 includes a lens LZ1 for picking up an image of a subject (not shown), a solid-state image sensor CCD1,
A timing generator TG2 that generates all the timing signals of the camera slave unit CAK1 and controls the shutter based on the brightness of the subject, and a synchronizing signal and the like by the timing generator TG2 to the video signal S1 captured by the solid-state imaging device CCD1. Is provided. The subject is illuminated by a fluorescent lamp (not shown) and
It is assumed that the image is captured by the solid-state imaging device CCD1 via Z1.

The monitor master unit M1 is provided with a synchronization separation circuit S for separating a synchronization signal of the video signal S1 from the camera slave unit CAK1.
P1, a timing generator TG1 for generating each timing signal from the separated synchronization signal, a liquid crystal display LCD1 for monitoring the video signal S1, a backlight BL1 for illuminating the liquid crystal display LCD1, and a timing generator TG
A resistor R which integrates the video signal S1 for each field within the flicker cycle of the fluorescent lamp according to the timing signal from
Capacitors CA, CB, CC (integrating circuits SKA, SK
B, SKC), that is, three systems of integrator circuits SK corresponding to three kinds of level fluctuations of the video signal different for each field.
Which capacitors CA, CB, CC of A, SKB, SKC
SWA1 and SW2 to select whether to store electric charges
WB1, SWC1, SWA2, SWB2, SWB3,
Capacitors CA, CB, CC (integrating circuits SKA, SK
B, SKC), and a comparator CMP1 for comparing the electric charge accumulated in each field with an integrated output for each field and a reference voltage VREF1 commonly set, and illumination of the backlight BL1 of the liquid crystal display device LCD1 with the voltage of the comparison result. Is provided with a drive control circuit DRV1 for changing the brightness of the image.

Resistor R, integrating circuits SKA, SKB, SK
C capacitors CA, CB, CC, switch SWA1,
SWB1, SWC1, SWA2, SWB2, and SWB3 constitute a photometric circuit SK1 controlled by a timing signal from a timing generator TG1. The operation of the TV door phone apparatus thus configured will be described with reference to FIGS. 1 and 2 by taking a combination of a shutter cycle of 1/60 s and a fluorescent light emitting at 1/100 s as an example.

The camera slave unit CAK1 has a solid-state image sensor CC.
A subject is imaged at D1, and a signal processing circuit SS1 outputs a video signal S1 to which a synchronization signal and the like are added. The timing generator TG2 generates all the timing signals of the camera slave unit CAK1 and controls the shutter based on the brightness of the subject. The video signal S1 sent to the monitor master unit M1 is input to the liquid crystal display device LCD1, and the synchronization signal separated by the synchronization separation circuit SP1 is applied to the liquid crystal display device LCD1.
1 and an image of the subject is displayed. The level of the video signal differs for each field due to the difference between the cycle of the shutter of the solid-state imaging device CCD1 and the cycle of the fluorescent lamp.
The image flickers. In this combination, as shown in FIG. 2, there are three types of level fluctuations, which are repeated in three cycles. For this reason, the photometry circuit SK1 includes three systems of integrating circuits SKA, SKB, and SKC corresponding to three types of levels, that is, the capacitors CA, CB, and CC are switches SWA1 and SWA.
2, switching is performed for each field by SWB1, SWB2, SWC1, SWC2. For example, the photometric voltage for the exposure period A is always obtained from the integrating circuit SKA, the photometric voltage for the exposure period B is always obtained from the integrating circuit SKB, and the photometric voltage for the exposure period C is always obtained from the integrating circuit SKC. These photometric voltages are supplied to a comparator CMP1. In the comparator CMP1, the three types of photometric voltages are independently compared with the reference voltage VREF1. In this example, when the photometric voltage is higher than the reference voltage VREF in the comparator CMP1, the voltage is low, and when the photometric voltage is lower than the reference voltage VREF, the voltage is high. The output of the comparator CMP1 is input to the backlight luminance adjustment driver DRV1, and the backlight has low luminance when the voltage is low and high luminance when the voltage is high. For this reason, when the level of the video signal is low, the backlight of the liquid crystal display device has high brightness, and when the level of the video signal is high, the backlight of the liquid crystal display device is controlled so as to have low brightness. Can be smaller.

As described above, according to the television intercom apparatus of the present invention, it is possible to reduce the flicker of an image without fixing the shutter speed and monitor the optimal image on the liquid crystal display device against flicker caused by fluorescent light. It becomes possible. In the above embodiment, the shutter cycle is described as 1/60 s. However, the same effect can be obtained with 1/30 s in the television door phone apparatus of the present invention.

[0016]

As is apparent from the above description, according to the television doorphone apparatus of the present invention, the flicker caused by the fluorescent lamp is suppressed, the flicker of the image is reduced, and the optimum image is displayed at a constant brightness on the liquid crystal display. It can be projected on the device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a television door phone apparatus according to the present invention.

FIG. 2 is a diagram showing an operation example in the TV door phone device according to the present invention.

FIG. 3 is a block diagram showing a conventional TV door phone apparatus.

[Explanation of symbols]

 CAK1 Camera slave unit CCD1 Solid-state image sensor S1 Video signal M1 Monitor base unit BL1 Backlight LCD1 Liquid crystal Display device SP1 Separating circuit TG1 Timing generator SKA, SKB, SKC ... Integrating circuit (integrating means) (CA, CB, CC ... Capacitor) VREF1 ····· Reference voltage CMP1 ····· Comparator (comparison means) DRV1 ····· Drive control circuit (control means)

Claims (1)

[Claims] 1. A video signal (S1) obtained by imaging an object illuminated by a fluorescent lamp with an image pickup device (CCD1) of a camera slave unit (CAK1) and a backlight (BL1) of a monitor master unit (M1). Illuminated by a liquid crystal display (LCD)
A television intercom apparatus for monitoring in 1), wherein the main monitor unit separates a synchronization signal of the video signal from the camera slave unit, and generates a timing signal from the separated synchronization signal. A timing generator (TG1), and integrating means (SKA, SKA) for integrating the video signal for each field within the flicker cycle of the fluorescent lamp according to a timing signal from the timing generator.
KB, SKC), comparison means (CMP1) for comparing the integrated output for each field with a reference voltage (VREF1) commonly set, and illumination of the backlight according to the comparison result of the comparison means. And a control means (DRV1) for changing the brightness of the television intercom.