JPH0548406B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an infrared imaging device that has a multi-element detector and displays a video signal obtained by photoelectrically converting infrared rays emitted from a target object, and particularly relates to an infrared imaging device that has a multi-element detector and displays a video signal obtained by photoelectrically converting infrared rays emitted from a target object. This invention relates to an infrared imaging device that has been improved to suppress DC level fluctuations and maintain a constant display brightness level.

An infrared imaging device captures infrared rays emitted from a target object by scanning the imaging unit, photoelectrically converts the captured infrared rays using an infrared detector to convert them into video signals, and processes and displays this video signal as an image. Displays the target object as an infrared image pattern using a cathode ray tube or LED.

In an infrared imaging device, a multi-element detector is used to photoelectrically convert infrared rays from the scanning position of a target object, and the video signals converted by each detection element are combined and displayed as a video pattern. If there is variation in the DC level of the output video signal of each detection element, uneven brightness will occur in the video pattern displayed on the display section, and a clear display of the pattern image will not be obtained. Therefore, in order to prevent unevenness in the brightness of the video pattern, a clamp circuit is provided at the output end of each sensing element to clamp the DC level of the output video signal of each sensing element at a predetermined level, thereby aligning the video signal above a certain level. This prevents uneven brightness due to variations in the DC level.

However, due to the temperature of the environment in which the infrared imaging device is installed, changes in the gain of the device's amplifier circuit, changes in the polarity of the video signal, and inverted display may cause DC level fluctuations in the video signal, resulting in changes in brightness. occurs. Conventionally, in order to eliminate this change in brightness, the operator has to adjust the set voltage of the clamp circuit each time, which requires considerable effort. Therefore, there has been a demand for an infrared imaging device that does not require such manual adjustment, automatically keeps the DC level of the output video signal of each element constant, and always provides an optimal brightness video pattern.

[Conventional technology]

FIG. 3 is a block diagram of an infrared imaging device using a conventional multi-element detector. In the figure, an imaging unit 2 captures infrared rays emitted from positions 11 to 1n of a target object 1, condenses the infrared rays, and makes the infrared rays enter each detection element of a multi-element detector disposed at a focal point. In other words,
The infrared rays at position 11 enter the sensing element 31, the infrared rays at position 1n enter the sensing element 3n, and so on, which are arranged in correspondence with the imaging positions. Once the infrared rays at the vertical position shown in the figure are captured, the infrared rays from one side of the target object are sequentially captured as the imaging unit 2 scans horizontally. The infrared rays at each vertical position incident on the elements 11 to 1n are photoelectrically converted into a video signal by a detection element corresponding to the position. The converted video signals are input to preamplifiers 41 to 4n, amplified, and clamped to clamp circuits 51 to 5, respectively.
input to n. The clamp circuits 51 to 5n clamp the DC component of the video signal using the DC voltage V set by the level setting circuit 8, and align the video signal above a certain level. The output video signal of the clamp circuit is input to the display unit 7 via the amplifier circuits 61 to 6na. The display unit 7 performs image processing on the input video signal and displays the temperature pattern of the target object on a cathode ray tube or LED.

[Problem that the invention seeks to solve]

In the case of the above-mentioned conventional infrared imaging device, the DC level of the video signal may be changed depending on the temperature of the installation environment of the infrared imaging device, etc. by changing the gain of the device's amplifier circuit or switching the polarity of the video signal to display inverted display. This causes a change in brightness due to a change in the DC level. Therefore, in the past, operators had to adjust the DC setting voltage of the level setting circuit each time to eliminate changes in brightness.
It required effort.

[Means for solving problems]

The present invention provides an infrared imaging device that solves the above problems, and includes a plurality of sensing elements that scan a target object and capture infrared rays at the scanned position, and an output signal of each of the sensing elements. In an infrared imaging device comprising a clamp circuit that regulates a DC level to a predetermined level, and in which the brightness level of an image is set by each of the clamp circuits, the output signals of the respective clamp circuits are added together to determine the DC level of the added signal. A detection means for detecting, a comparison circuit for comparing an output DC level of the detection means with a predetermined level, and a circuit for superimposing a brightness adjustment based on the output of the comparison circuit on the specified level of the clamp circuit. This is done by an attached infrared imaging device.

[Effect]

The above-mentioned infrared imaging device adds the output video signals of each detection element of the external element detector using an adder circuit, and converts the DC voltage of the output added signal of the adder circuit into a direct current (DC).
The level detection circuit detects the detected DC voltage and
A comparator circuit compares a predetermined DC setting voltage and detects the difference, and the polarity of the detected DC voltage is inverted by an inverting circuit and superimposed on the clamp voltage of the DC level detection circuit to detect the difference between each detection element. Corrects fluctuations in the DC voltage of the video signal. In other words, when the DC level of the video signal increases, it is suppressed, and when it decreases, it is expanded, and the brightness of the display section is always constant.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an infrared imaging device using a multi-element detector according to an embodiment of the present invention, FIG. 2 is a block diagram of essential parts of an infrared imaging device according to an embodiment of the present invention, and FIG. The same parts are indicated by the same symbols.

The infrared imaging device of the present invention, as shown in the block diagram of FIG. An addition circuit 91 and a DC level detection circuit 92 as detection means for detecting the level, and a DC level detection circuit 92
A comparison circuit 93 that compares the detected DC voltage with a set DC voltage of a predetermined value and outputs the difference voltage.
and an inverting circuit 94 which functions to invert the polarity of the output differential voltage of the comparator circuit 93 and superimpose it on the DC setting voltage of the level setting circuit 8.

In its operation, output video signals representing the temperature at the vertical position of the target object outputted from the amplifier circuits 61 to 6n are inputted to the addition circuit 91. Adder circuit 91 adds each input video signal and outputs the result to DC level detection circuit 92 . The DC level detection circuit 92 detects the DC voltage component of the added video signal and outputs it to the comparison circuit 93. The comparator circuit 93 compares the detected DC voltage inputted with reference to the set voltage V1 built into the comparator circuit, and if the detected DC voltage is larger than the set voltage V1, it increases the +DC voltage corresponding to the magnitude, and if the opposite, the detected DC voltage is - Outputs the difference voltage between DC voltages. Set voltage V1 built into the comparison circuit 93
is set to a value that provides the optimum brightness for the display unit. The output DC difference voltage of the comparator circuit 93 is transferred to the inverter circuit 9.
4, the polarity is inverted, amplified by a predetermined amount by an amplifier 95, and superimposed on the clamp DC voltage of the clamp setting circuit 8 to be applied to each clamp circuit 51 to 5.
Output to n.

As a result, the DC level of the video signal forms a negative feedback loop, and the deviation between the DC level of the video signal and the set level is 1/1 of the loop gain.
Therefore, the brightness for optimum display can always be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, by forming and adding a negative feedback loop to the infrared imaging device, fluctuations in the DC level of the video signal are suppressed, and the display brightness level is kept constant at the optimum value. This has the effect of eliminating the need to frequently manually adjust the brightness level.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an infrared imaging device using a multi-element detector according to an embodiment of the present invention, FIG. 2 is a block diagram of essential parts of an infrared imaging device according to an embodiment of the present invention, and FIG. 3 is a conventional infrared imaging device. 1 is a block diagram of an infrared imaging device using a multi-element detector. In the figure, 1 is the target object, 11 to 1n are the positions of the target object, 2 is the imaging unit, 3 is the multi-element detector, 3
1 to 3n are detection elements, 41 to 4n are preamplifiers,
51 to 5n are clamp circuits, 61 to 6n, 95 are amplifiers, 7 is a display section, 8 is a level setting circuit, 91
Reference numeral 92 indicates an adder circuit, 92 a DC level detection circuit, 93 a comparison circuit, and 94 an inversion circuit.

Claims (1)

[Claims] 1. It is equipped with a plurality of detection elements that scan a target object and capture infrared rays at the scanning position, and a clamp circuit that regulates the DC level of the output signal of each of the detection elements to a predetermined level. In an infrared imaging device that sets the brightness level of the clamp circuit, the detection means adds the output signals of the respective clamp circuits and detects the DC level of the added signal, and the comparison circuit compares the output DC level of the detection means with a predetermined level. and a circuit for superimposing and applying a brightness adjustment voltage based on the output of the comparison circuit to the specified level of the clamp circuit.