CN104266766A - Infrared thermal imaging system - Google Patents

Abstract

The embodiment of the present invention discloses an infrared thermal imaging system, including: an infrared detector; an impedance conversion circuit for buffering the output signal of the infrared detector and changing the impedance characteristics of the output signal; a single-ended to differential circuit for converting the output signal from a single end to a differential and conditioning the differential signal so that the differential signal adapts to the dynamic range of the analog-to-digital conversion circuit; an analog-to-digital conversion circuit for converting the differential signal into a digital signal; a timing control and data processing circuit for controlling the timing of the analog-to-digital conversion circuit and performing signal processing on the digital signal. The infrared thermal imaging system provided by the embodiment of the present invention has good low noise and low power consumption performance.

Description

An infrared thermal imaging system

the

technical field

The invention relates to the technical field of infrared imaging, in particular to an infrared thermal imaging system.

the

Background technique

Infrared thermography is a technology that "sees" or "measures" the radiant heat energy of an object by using an infrared imaging measuring instrument. Infrared rays are too long to be perceived by the human eye. However, in the infrared world, as long as the temperature of the object is above absolute zero, it will radiate heat outward. Therefore, we can image it by detecting its heat.

Infrared thermal imaging technology has strong environmental adaptability and works well at night and in bad weather; it has good concealment and strong anti-interference ability; it can identify camouflaged targets that cannot be identified by visible light; the infrared imaging system is small in size, light in weight and low in power consumption , high reliability, and can be applied to precision-guided weapons. It is an important supporting technology for building a national defense security system, and has great application prospects in both military and civilian fields. The core device in the infrared imaging system is the infrared detector. From the perspective of electronic design, in order to improve the imaging quality of the entire infrared imaging system, in addition to selecting high-performance detectors, design low-noise and high-quality infrared detector signals Processing circuitry is very critical.

the

Contents of the invention

One of the objects of the present invention is to provide an infrared thermal imaging system with low noise and low power consumption.

The technical solutions disclosed in the present invention include:

An infrared thermal imaging system is provided, which is characterized in that it includes: an infrared detector; an impedance transformation circuit, the impedance transformation circuit is connected to the infrared detector, and is used to buffer the output signal of the infrared detector and change the The impedance characteristics of the output signal; a single-ended to differential circuit, the single-ended to differential circuit is connected to the impedance conversion circuit for performing single-ended to differential conversion of the output signal, generating a differential signal, and conditioning the differential signal, making the differential signal adapt to the dynamic range of the analog-to-digital conversion circuit; the analog-to-digital conversion circuit, the analog-to-digital conversion circuit is connected to the differential amplifier circuit, and is used to convert the differential signal into a digital signal; timing control and A data processing circuit, the timing control and data processing circuit is connected to the analog-to-digital conversion circuit for controlling the timing of the analog-to-digital conversion circuit and performing signal processing on the digital signal.

In one embodiment of the present invention, the impedance conversion circuit includes an RC filter circuit and a voltage follower, and the RC filter circuit is connected to a non-inverting input terminal of the voltage follower.

In an embodiment of the present invention, the single-ended-to-differential conversion circuit is realized by a fully differential operational amplifier.

In one embodiment of the present invention, the analog-to-digital conversion circuit includes a differential-input analog-to-digital converter.

In an embodiment of the present invention, the signal processing includes: blind pixel compensation, one-point correction and/or grayscale stretching.

The infrared thermal imaging system provided by the embodiments of the present invention has good performance of low noise and low power consumption.

the

Description of drawings

Fig. 1 is a schematic structural block diagram of an infrared thermal imaging system according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of an impedance transformation circuit according to an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a single-ended-to-differential conversion circuit and an analog-to-digital conversion circuit according to an embodiment of the present invention.

the

Detailed ways

The specific structure of the infrared thermal imaging system of the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic structural block diagram of an infrared thermal imaging system according to an embodiment of the present invention.

In one embodiment of the present invention, an infrared thermal imaging system includes an infrared detector (not shown in FIG. 1 ). The infrared detector can detect the thermal radiation of the imaging target and generate an output signal Vo.

As shown in FIG. 1 , in an embodiment of the present invention, the infrared thermal imaging system further includes an impedance transformation circuit 10 , a single-ended to differential conversion circuit 12 , an analog-to-digital conversion circuit 14 and a timing control and data processing circuit 16 .

The impedance conversion circuit 10 is connected to the infrared detector, and is used for buffering the output signal Vo of the infrared detector and changing the impedance characteristic of the output signal Vo so as to facilitate the processing of the output signal by subsequent circuits. In FIG. 1 , the signal processed by the impedance transformation circuit 10 is denoted as V1.

In one embodiment of the present invention, the structure of the impedance transformation circuit 10 is shown in FIG. 2 , which includes an RC filter circuit 102 and a voltage follower 100 . The RC filter circuit 102 is connected to the non-inverting input terminal of the voltage follower 100 .

In the embodiment of FIG. 2 , the RC filter circuit 102 is a first-order RC filter circuit.

In an embodiment of the present invention, the single-ended-to-differential circuit can be realized by a fully differential operational amplifier.

As shown in FIG. 1 , the single-ended to differential circuit 12 is connected to the impedance transformation circuit 10, and is used to convert the output signal (that is, V1) processed by the impedance transformation circuit 10 from single-ended to differential to generate a differential signal (in FIG. 1 CH+ and CH-), and condition the differential signal to make the differential signal CH+ and CH- adapt to the dynamic range of the subsequent analog-to-digital conversion circuit 14 . The voltage value of the common-mode signal output by the fully differential operational amplifier is determined by the V _CM voltage, and the V _CM pin is connected to the reference voltage center point VCM of the analog-to-digital converter.

The analog-to-digital conversion circuit 14 is connected to the single-ended-to-differential conversion circuit 12 for converting the differential signal into a digital signal. the

In an embodiment of the present invention, the analog-to-digital conversion circuit 14 may include a differential-input analog-to-digital converter, that is, be implemented by a differential-input analog-to-digital converter.

In one embodiment of the present invention, the structures of the single-ended-to-differential conversion circuit 12 and the analog-to-digital conversion circuit 14 are shown in FIG. 3 . In this embodiment, the single-ended-to-differential conversion circuit 12 adopts the ADA4940-1 operational amplifier with low noise, low distortion and ultra-low power consumption. The analog-to-digital converter is AD9649-20, the maximum sampling rate of this chip is 20MHz, which meets the requirement of the detector outputting the highest frequency of 5MHz, and the input voltage range is 0-2V. The input voltage range of the positive terminal of the differential op amp is 0.5V to 3.2V, and the input voltage of the negative terminal is 2.5V. For this differential op amp, the differential input V _pp =2.7V. Since the gain of the operational amplifier is 0.5, the differential output V _pp =1.35V, the output common-mode voltage is 1V equal to that of the back-end ADC, and the differential output range is (1-1.35/2)V～(1+1.35/2 ) V, that is, 0.325V ~ 1.675V, in line with the 0V ~ 2V differential input voltage range of AD9649.

As shown in FIG. 1 , a timing control and data processing circuit 16 is connected to the analog-to-digital conversion circuit 14 . The timing control and data processing circuit 16 generates the timing control signal of the analog-to-digital conversion circuit 14, which is used to control the timing of the analog-to-digital conversion circuit. In addition, the timing control and data processing circuit 16 also performs signal processing on digital signals, for example, performs Blind element compensation, one-point correction and/or grayscale stretching of digital signals.

In the embodiment of the present invention, the timing control and data processing circuit 16 can be realized by FPGA or other suitable logic devices.

The infrared thermal imaging system provided by the embodiments of the present invention has good performance of low noise and low power consumption.

The present invention has been described above through specific examples, but the present invention is not limited to these specific examples. Those skilled in the art should understand that various modifications, equivalent replacements, changes, etc. can also be made to the present invention. As long as these changes do not deviate from the spirit of the present invention, they should all be within the protection scope of the present invention. In addition, "one embodiment" described in many places above represents different embodiments, and of course all or part of them may be combined in one embodiment.

Claims (5)

1. an infra-red thermal imaging system, is characterized in that, comprising:

Infrared eye;

Impedance inverter circuit, described impedance inverter circuit is connected to described infrared eye, for cushioning the output signal of described infrared eye and changing the impedance operator of described output signal;

Single-ended transfer difference circuit, described single-ended transfer difference circuit is connected to described impedance inverter circuit, for carrying out single-ended transfer difference to described output signal, generates differential signal, and nurse one's health described differential signal, make described differential signal adapt to the dynamic range of analog to digital conversion circuit;

Analog to digital conversion circuit, analog-digital conversion circuit as described is connected to described single-ended transfer difference circuit, for converting described differential signal to digital signal;

Sequential control and data processing circuit, described sequential control and data processing circuit are connected to analog-digital conversion circuit as described, for controlling the sequential of analog-digital conversion circuit as described and performing signal transacting to described digital signal.

2. the system as claimed in claim 1, is characterized in that: described impedance inverter circuit comprises RC filtering circuit and voltage follower, and described RC filtering circuit is connected to the in-phase input end of described voltage follower.

3. system as described in claim 1 or 2, is characterized in that: described single-ended transfer difference circuit is realized by Full differential operational amplifier.

4. as the system in claims 1 to 3 as described in any one, it is characterized in that: analog-digital conversion circuit as described comprises the analog to digital converter of Differential Input.

5. the system as claimed in claim 1, is characterized in that, described signal transacting comprises: blind element compensation, a point calibration and/or gray scale stretch.