JPS598492A - Color television camera - Google Patents

Abstract

PURPOSE:To obtain a picture with good S/N, by forming the titled camera into a black-and-white TV camera removed with an infrared ray cut filter at a low illuminance, for improving the sensitivity of the TV camera using a solid-state image pickup element as a photodetector at the low illuminance. CONSTITUTION:A switch 10 is set so as to remove the infrared ray cut-off filter 4 from the optical system and an analog switch 9 is turned off, when an object is a low illuminance. All beams of light including infrared rays are made incident to the solid-state image pickup element via lenses 2 and 3 in this case. Then, the spectral characteristic of a silicon photodiode of a photoelectric conversion section of the solid-state image pickup element is used effectively and the sensitivity of the TV camera is improved remarkably. Since the chrominance signal is interrupted by turning off the switch 9, a black-and-white TV signal is outputted to an output terminal 8 and the camera acts like a black-and-white TV camera. Thus, the sensitivity at the low illuminance is improved and the picture having good S/N is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television camera, and particularly to one using a solid-state image sensor as a light receiving element.

FIG. 1 shows the general configuration of a television camera using a conventional solid-state image sensor. In the figure, (1) is a solid-state image sensor, +21 and +31 are lenses that form a subject image on the solid-state image sensor (4), and (4) is an infrared cut filter inserted in these optical systems. FIG. 2 shows typical spectral characteristics of a silicon photodiode used in the photoelectric conversion section of the solid-state image sensor (1). FIG. 3 shows typical spectral characteristics of an infrared cut filter.

The operation of a television camera using the conventional solid-state image sensor shown in FIG. 1 as a light receiving element will be described. lens +21
The optical image formed on the solid-state image sensor (1) by the light that has passed through the +31 and the infrared cut filter (4) is converted into an electrical signal by the solid-state image sensor, a preamplifier 15).
The amplified line color matrix circuit (6) separates the signals into, for example, luminance σ), red (R), and blue FB) signals, and the signal processing circuit (71) outputs them to an output terminal (81) as a standard color television signal.

The infrared cut filter (4) inserted into the optical system of a conventional television camera that uses a solid-state image sensor as a light receiving element is necessary to balance the color of the television camera, as shown in Figure 3. Due to such spectral characteristics, the sensitivity on the long wavelength side of the spectral characteristics of the solid-state image sensor shown in Figure 2 cannot be used effectively, and the sensitivity is lower than that of conventional television cameras, etc., which use Sachicon tubes as photodetectors. Images taken in low light conditions were noisy, especially in color, and the minimum practical illuminance was also high.

This invention was made to eliminate the drawbacks of the above-mentioned conventional ones, and improves the SA ratio of captured images at low illuminance.
The aim is to realize a television camera that can significantly reduce the minimum practical illuminance.

FIG. 4 is a diagram showing the configuration of a television camera according to the present invention. In the figure, 01 is a mechanical switch attached to the camera housing, and this switch G (J is a switch for infrared cut filters (4 is for the optical system). At the same time as the infrared cut filter (4) is inserted and removed, the analog switch (9) is turned on and off. Fig. 5 shows an embodiment of the mechanism in which the infrared cut filter (4) is inserted into and removed from the optical system by the switch αa.

In the television camera according to the present invention, when the subject has sufficient illuminance, the switch Gα is set so that the infrared cut filter (4) is inserted into the optical system, and the analog switch +91 is set to the ON state. In this case, the configuration is exactly the same as that of a television camera using a conventional solid-state image sensor as a light receiving element as shown in FIG. 1, and a standard color television signal is outputted to the output terminal (8).

When the subject is in low illuminance, the switch O old infrared degree filter (4) is removed from the optical system, and the analog switch (9) is turned OFF.

In this case, the integrated image sensor (1) has a lens +2+ (:°
All light including infrared light enters through 3), and the spectral characteristics of the silicon photodiode in the photoelectric conversion section of the solid-state image sensor shown in Figure 2 are effectively utilized, which improves the sensitivity of the television camera. Or improve to the middle school. In this case, if the brightness Crt of the output of the color matrix circuit (6) and the balance of red (R) and blue (Bl change, the color) can be balanced, the color signal is cut off by turning off the analog switch (91). Therefore, a black-and-white television signal is output to the output terminal (8), and there is almost no problem in practical use as a black-and-white television camera.

In the above explanation, we have explained the case where switch 001 is manually switched depending on the illuminance of the subject, but it is also possible to electrically detect the illuminance of the subject and use this signal to automatically operate switch 4. Needless to say.

As described above, according to the present invention, in a color television camera that uses a silicon photodiode in the photoelectric conversion section and captures an image through an infrared cut filter, when the amount of light incident on the photoelectric conversion section is less than a predetermined value, the infrared cutoff is performed. A switch having a mechanism for switching so as to guide light that does not pass through a filter to a photoelectric conversion unit, and a circuit for switching in response to this mechanism so that the output signal from the photoelectric conversion unit is only a luminance signal component that does not include a color signal component. By removing the infrared cut filter and using a black-and-white TV camera in low-light conditions, the sensitivity in low-light conditions is the same as above, and a good image can be obtained. It has a very low effect.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a television camera that uses a conventional solid-state image sensor as a light receiving element, Figure 2 is a typical spectral characteristic of a silicon photodiode used in the photoelectric conversion section of a solid-state image sensor, and Figure 3 is an infrared ray. FIG. 4 is a typical spectral characteristic diagram of a cut filter, and FIG. 5 is a configuration diagram of a television camera according to the present invention.
The figure is a perspective view showing a mechanism section for inserting and removing an infrared hot filter, which is a component of an embodiment of the present invention, into an optical system. In the figure (11 is a solid-state image sensor, (2) and 0 (:3+
is a lens, (4) is an infrared cut filter, (51 is a Prianos, (61 is a chroma) IJ circuit, (7) is a signal processing circuit, (8) is an output terminal, [91 is an analog switch, and QOI is The switch, (40) is the holder for the infrared cut filter (4), (41) is the control rod, and (42) is the spring. In addition, the same reference numerals in the drawings indicate the same or equivalent parts. Agent Kuzu Nobuo - Figure 1 Figure 2 Figure 4 (-+- Figure 3 Figure 4 (S1 Figure 5, 40

Claims (1)

[Claims] In a color television camera that uses a silicon photodiode as a photoelectric conversion section and captures an image through an infrared cut filter, when the amount of light incident on the photoelectric conversion section is less than a predetermined value, the light that does not pass through the infrared cut filter is transferred to the photoelectric conversion section. A color television equipped with a switching mechanism that has a switching mechanism that switches the signal to the photoelectric conversion section and a circuit that responds to this mechanism and switches the output signal from the photoelectric conversion section so that the output signal is only a luminance signal component that does not include a color signal component. camera.