JPS60242777A - Television camera with automatic liquid crystal dimmer - Google Patents

Abstract

PURPOSE:To offer a television camera with automatic dimmer small in size and low in power consumption by inputting the output of a video signal circuit to a level detecting circuit to drive a liquid crystal dimmer panel. CONSTITUTION:A light passing through a lens 1 is attenuated by the liquid crystal dimmer panel 12, and the image is formed on an image pickup element 2. The image pickup element 2 converts an optical image into an electric signal and outputs the result to a video signal circuit 3. The video signal circuit 3 amplifies the said electric signal, mixes a synchronizing signal from a synchronizing signal generating circuit 4 and outputs the video signal. The automatic dimmer circuit 5 uses a level detection circuit 6 so as to detect the amplitude of the video signal, a comparator circuit 7 compares the result with a set reference voltage so as to attain proper luminous amount, a voltage proportional to the difference is outputted to drive the liquid crystal dimmer panel 12.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an automatic light control device for a television camera.

[Prior art]

Conventional automatic light control devices for television cameras use a method that uses a motor to move the diaphragm. The light control device is a device that adjusts the amount of light that reaches an image sensor. FIG. 1 is a block diagram of a conventional television camera having an automatic light control device, in which 1.1 is a lens, 2 is an image sensor, 8 is a video signal circuit, 4 is a synchronization signal generation circuit,
6 is an automatic light control circuit, 6 is a level detection circuit, 7 is a comparison circuit, 8 is a drive circuit, 9 is a motor, and 10 is an iris diaphragm.

To briefly explain the function of each part, first, an optical image is formed by the lens 1 on the imaging surface of the image sensor 2.

The image sensor 2 converts the optical image into an electrical signal and outputs it to the video signal circuit 8. The video signal circuit 8 amplifies the output electrical signal of the image sensor 2, mixes the synchronization signal from the synchronization signal generation circuit 4, and outputs a video signal. The automatic dimming circuit 5 female detects the magnitude of the video signal with the level detection circuit 6, compares it with a reference voltage set to provide an appropriate amount of light in the comparison circuit 7, outputs the difference, and outputs the difference, and then outputs the difference. 8, a signal is issued to drive the motor 9 by an amount corresponding to the output of the comparison circuit 70. As the motor 9 rotates, the aperture area for the chromatic diaphragm changes, thereby optimizing the amount of light that reaches the image sensor 2.

The conventional automatic light control device requires (1) a large drive current to drive the motor 9, the automatic light control circuit 5 is large in size, and consumes a lot of power.

(2) Since the motor 9 and the diaphragm 10 are used, there is a problem that the volume is large.

〔the purpose〕

The present invention is intended to solve these problems, and its purpose is to provide a television camera with an automatic light control device that is small in size and consumes low power.

〔overview〕

The television camera with an automatic liquid crystal light control device of the present invention is a television camera equipped with a lens, an image sensor, a liquid crystal light control panel disposed between them, a video signal circuit, and a synchronization signal generation circuit.
The present invention is characterized in that the output of the video signal circuit is input to a level detection circuit, the output of the level detection circuit is input to a comparison circuit, and the output of the comparison circuit is used to drive the panel.

〔Example〕 Hereinafter, the present invention will be described in detail based on examples.

FIG. 2 shows a configuration diagram of an embodiment of a television camera with an automatic liquid crystal dimmer according to the present invention. In FIG. 2, the same numbers as in FIG. 1 indicate the same parts, and 12 is a liquid crystal light control panel.

The liquid crystal light control panel 12 changes the amount of transmitted light depending on the driving voltage. The liquid crystal used in digital watches and the like is sandwiched between two glass plates, making it thin and compact.

The light that has passed through the lens 1 is attenuated by the liquid crystal light control panel 12 and then focused on the image sensor 2 . The image sensor 2 converts the optical image into an electrical signal and outputs it to the video signal circuit 8. The video signal circuit 8 amplifies the electric signal, mixes the synchronization signal from the synchronization signal generation circuit 4, and outputs a video signal. The automatic light control circuit 5 detects the magnitude of the video signal using a level detection circuit 6.
The comparison circuit 7 compares it with a reference voltage set to provide an appropriate amount of light, and outputs a voltage proportional to the difference to drive the liquid crystal light control panel 12.

The liquid crystal light control panel 12 attenuates the amount of light reaching the image sensor 2 to an appropriate amount depending on the drive voltage of the automatic light control circuit 5.

FIG. 8 is a characteristic diagram showing the relationship between the driving voltage of the liquid crystal light control panel 12 and the light transmittance. The light transmittance is high while the drive voltage is low, and the transmittance decreases as the drive voltage increases.

FIG. 4 shows a more specific embodiment of the automatic filJJ optical circuit 5. In FIG. In Fig. 4, 14 is a power supply terminal, 15 is a video signal input terminal, 16 is a rectangular wave input terminal, 17 is a liquid crystal dimming panel drive terminal, 18 is a liquid crystal dimming panel, and 19 is a Pg
p-type transistor, 21) is npn-type transistor 21
, 22, 23 are capacitors, s is a variable resistor, and 5°26.27.28 is a resistor.

The operation shown in FIG. 4 will be explained in detail with reference to the voltage waveform diagram of each part shown in FIG. In FIG. 5, the left half is for a dark screen, and the right half is for a bright screen. 2α is the video signal input terminal waveform, and the amplitude is small for a dark screen and large for a bright screen. The video signal is AC-coupled by a capacitor 21, divided by a variable resistor and then by a resistor 5, and applied to the base of a pnp transistor 19. Fig. 5b Id p n The base waveform of the p-type transistor 19 of"'f'-type transistor 19 allows 'l current to flow through the collector for the first time when the base potential drops by 0.7V or more from the power supply voltage V. So,
As shown in the collector waveform of a Cepnp transistor in FIG. 5, a low voltage is generated when the screen is dark, and a high voltage is generated when the screen is bright. On the other hand, a rectangular wave is input to the rectangular wave input terminal 16 as shown in the rectangular wave input terminal waveform shown in FIG. 5d. The square wave is divided by resistor A, 27, added to the base of the npn type transistor, and
A rectangular wave with the amplitude of the voltage generated at the collector of the k pnp transistor 19 is taken out from the collector of the n-type transistor 2), and the rectangular wave is coupled with AC by the capacitor n and output to the liquid crystal dimming panel drive terminal 17. . FIG. 5e shows the waveform of the LCD light control panel drive terminal, and
It is AC driven. For dark screens, the driving voltage is small, and for bright screens, the line driving voltage is large, so the bright screen t
First, the light transmittance of the liquid crystal light control panel 18 is low. In order to adjust the amount of light that reaches the image sensor 2 to an appropriate amount, the variable resistor 24 that divides the video signal and inputs it to the base of the pnp transistor 19 is adjusted.

〔effect〕

As described above, the present invention has the following effects.

(1) Since the driving current of the liquid crystal dimming panel is small, it is possible to use small automatic light circuit elements, and the configuration is extremely simple, so the automatic light control circuit is small and has low power consumption. , we have realized miniaturization and lower power consumption of TV cameras.

(2) Since a thin and small liquid crystal light control panel is used, a small TV camera has been realized.

(8) Since the automatic liquid crystal light control device uses a low-cost liquid crystal panel and a simple automatic light control circuit, it has realized a low-cost television camera.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a television camera including a conventional automatic light control device. FIG. 2 is a configuration diagram of a television camera with an automatic light control device according to the present invention. Figure 8 is a characteristic diagram of the liquid crystal light control panel. Figure 4 shows a specific example of an automatic light control circuit. FIG. 5(a) to (e) are voltage waveform diagrams of each part of Fi. 1...Fist lens 2...Imaging collector 8...Video signal circuit 4...Synchronization signal generation circuit 5...Automatic light control circuit 6...Level detection circuit 7.e.Comparison circuit 8. -Drive circuit 9...Motor lO...Color aperture 12...LCD light control panel 14...Power terminal 15...Video signal input terminal 16...Square wave input terminal 17... LCD dimming panel drive terminal 18...Liquid crystal dimming panel 19@・11 PNP type transistor addition @@? Lp74 type transistor 21, 2
2, Z3... Capacitor... Medium variable resistor 25, 26, 27, 28... Resistance device Applicant: Suwa Seikosha Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) In a television camera equipped with a lens, an image sensor, a liquid crystal dimming panel arranged between them, a video signal circuit, and a synchronization signal generation circuit, the output of the video signal circuit is input to the level detection circuit, and the output of the level detection circuit is is input into the comparison circuit,
A television camera with an automatic liquid crystal light control device, characterized in that the liquid crystal light control panel is driven by the output of a comparison circuit.