CN102279053A - Uncooled infrared focal plane array imaging system containing time modulation device - Google Patents

Abstract

The invention provides an uncooled infrared focal plane array imaging system including a time modulation device, including infrared modulation imaging optical paths 1, 2 and 3, illumination optical paths 4 and 5, optical readout optical path 6, and image acquisition and processing system 7. 1 focuses on the external target and is imaged at 3 and 3 after 2 time modulation; the light emitted by 4 is collimated by 5 and then directed to 3, and is modulated by 3 and then focused and imaged at 7 and 7 by 6 to output infrared heat image. The core of the present invention is that a time modulation device 2 is set in the optical path of the uncooled infrared focal plane array imaging system, so that 7 alternately receives infrared image signals and background and system noise signals; 7 uses background noise signals to correct the infrared image signals, thereby Eliminate the effects of vibration, environmental illumination changes, infrared focal plane array device deformation, light source changes, optical-mechanical structure deformation, and CCD noise on system imaging quality, and improve system stability, reliability and sensitivity.

Description

An Uncooled Infrared Focal Plane Array Imaging System with Time Modulation Device

technical field

The invention relates to an uncooled infrared focal plane array imaging system including a time modulation device, in particular to a high-performance uncooled infrared focal plane array imaging system in the form of infrared modulation imaging and optical readout.

Background technique

Infrared thermal imaging technology has a very wide range of applications in both military and civilian fields, and has received more and more attention from all walks of life. However, the traditional infrared thermal imaging system has not been widely used on a large scale due to problems such as its technology, cost, volume, weight, and power consumption.

In recent years, the optical readout micro-cantilever focal plane array (focal planearray, FPA) thermal imaging system based on MOEMS technology uses the focal plane array device FPA as the infrared image sensor, which greatly reduces the volume and weight of the infrared system, and provides a large-scale , The widespread use of infrared imaging systems provides strong conditions. The focal plane array device is a micro-cantilever beam structure. The micro-cantilever beam is composed of two materials with a large difference in thermal expansion coefficient. When the micro-cantilever beam absorbs infrared radiation, the temperature of the beam rises, and the two-material layer will quickly reach Heat balance, after heat balance, due to the large difference in thermal expansion coefficients of the two materials, the stress between them will cause the beam to bend, and the amount of bending is proportional to the heat absorbed by the micro-cantilever beam. Therefore, the external temperature field will cause the corresponding deformation of the micro-cantilever array. If the deformation of each micro-cantilever in the micro-cantilever array can be accurately detected, the external temperature field distribution can be obtained. In other words, it can be obtained infrared image.

There are two main ways to detect the deformation of the micro-cantilever: electrical readout and optical readout. The former obtains the deformation of the cantilever by detecting changes in electrical parameters such as capacitance or resistance at the bend of the micro-cantilever. The peripheral equipment of this method is relatively simple, but an additional complex circuit needs to be constructed on the FPA, which increases the difficulty of manufacturing the FPA, and the heat of the circuit itself will affect the quality of the infrared image to a certain extent. The other is called optical readout, which is the process of realizing infrared light-thermomechanical deformation-the change of reflected light intensity when irradiated with visible light-reverting the image. On each micro-cantilever beam, there is a small mirror. When the micro-cantilever array is irradiated with visible light, the mirrors of the micro-cantilever array will reflect the visible light. When the deformation of each micro-cantilever is different, the reflective effect of the mirrors carried by each micro-cantilever on the irradiated visible light will also be different. Different, the deformation of the cantilever beam can be obtained by detecting the change of reflected light, and then restored to an infrared image. This method needs to configure more complex peripheral devices than electrical readout, but it does not need to construct a readout circuit on the FPA, which avoids the influence of the heat generated by the readout circuit on the imaging quality.

Theoretically speaking, optical readout has lower background noise and higher sensitivity than electrical readout microcantilever FPA system, but according to the current domestic and foreign technical data, optical readout is far from the expected imaging effect, Even lower than the electrical readout method. Studying the imaging principle of the optical path of the optical readout FPA infrared imaging system, it can be seen that there are many factors that affect the stability, reliability, and sensitivity of the system. There are two reasons for this. system design level. It is an important research direction to further improve the performance of the optical readout uncooled infrared focal plane array imaging system.

Contents of the invention

The purpose of the present invention is to improve the working stability, reliability and sensitivity of the optical readout uncooled infrared focal plane array imaging system, and to provide a time-modulated infrared imaging system that can effectively eliminate environmental vibration, environmental temperature and illuminance changes, and infrared The effects of focal plane array device deformation, light source power supply ripple, light source aging, optical-mechanical structure deformation, and CCD noise on system imaging quality, and technology to improve system stability, reliability and sensitivity.

The purpose of the present invention is achieved by the following technical solutions:

① The new high-performance uncooled infrared focal plane array imaging system of the present invention includes an infrared modulation imaging optical path, an illumination optical path, an optical readout optical path, and an image acquisition and processing device. The infrared modulation imaging optical path includes an infrared imaging lens, a light modulator and an infrared focal plane array sensor, which provide the imaging system with spatial modulation signals of infrared images, background and noise signals in time division according to a certain time frequency; the illumination optical path includes a light source, a collimator lens group, which provides visible illumination imaging beams for the imaging system; the optical readout optical path includes several imaging lens groups and filters, which are used to filter and focus imaging on the visible illumination imaging beams spatially modulated by the infrared modulation imaging optical path, and image imaging is performed on the CCD On the target surface; the image acquisition and processing device outputs an infrared image after processing the signal.

② The imaging characteristics of this system are: the infrared imaging lens focuses and images the external target, and the light modulator located in the focusing imaging optical path time-modulates the infrared imaging light and shoots it to the infrared focal plane array device, and the infrared focal plane array device receives the The infrared imaging light after time modulation, and its array pixels produce corresponding changes; the light emitted from the light source, after being expanded and collimated, shoots into the infrared modulation imaging optical path and enters the optical readout optical path after being spatially modulated, imaging on the surface of the CCD. Since the spatial modulation signal provided by the infrared modulation imaging optical path has time division, part of the time is the infrared image signal, and the other part of the time is the background and system noise signal, so the image signal received by the CCD is also an infrared image signal, background and system noise signal alternately at a certain frequency. System noise signal, and these two signals have the characteristics of the same optical path, and they are basically synchronized in time.

③ During the image processing process, the system uses the background and system noise signals to continuously correct the infrared image signal, so as to eliminate environmental vibration, environmental temperature and illumination changes, infrared focal plane array device deformation, light source power supply ripple, and light source aging , The impact of optical-mechanical structure deformation and CCD noise on the imaging quality of the system, and the purpose of improving the stability, reliability and sensitivity of the system.

Beneficial effect

The invention can realize the correction of the infrared image, and deduct the effects of environmental vibration, ambient temperature and illuminance changes, infrared focal plane array device deformation, light source power supply ripple, light source aging, optical-mechanical structure deformation, and CCD noise on the imaging quality of the system. Improve system stability, reliability and sensitivity. Compared with the previous uncooled infrared focal plane imaging system, under the same conditions, its imaging performance is improved, and the requirements for the use environment and system components are correspondingly reduced.

Description of drawings

FIG. 1 is a schematic diagram of an existing optical readout uncooled infrared focal plane imaging system;

Fig. 2 is the schematic diagram of novel high-performance uncooled infrared focal plane imaging system of the present invention;

Wherein, the reference signs are explained as follows: 1. Infrared imaging lens group; 2. Optical modulator; 3. Infrared focal plane array; 4. Light source; 5. Collimating lens group; 6. Optical readout optical path; 7. Image acquisition and processing device.

Detailed ways

Specific embodiments of the present invention will be described in detail below.

1. System composition

The novel high-performance uncooled infrared focal plane imaging system of the present invention is composed of an infrared modulation imaging optical path, an illumination optical path, an optical readout optical path, and an image acquisition and processing device, as shown in Figure 2:

The infrared modulation imaging optical path is composed of an infrared imaging lens group 1, an optical modulator 2 and an infrared focal plane array 3. The infrared lens focuses the thermal image of an external target, and the optical modulator located in the imaging optical path performs time modulation on the infrared imaging beam. The modulated light is imaged on 7, and the pixel array of 7 produces regular changes;

The illumination optical path includes a light source 4 and a light source collimator lens group 5, and the illumination optical path provides visible, non-interfering, parallel illumination and imaging beams for the entire system;

The optical readout optical path 6 includes a number of imaging lenses and filters, which are used to focus and image the visible illumination imaging light beam spatially modulated by the infrared modulation lens group on the CCD surface in the image acquisition and processing device;

The image acquisition and processing device 7 processes the signal output by the optical readout path according to certain rules, and outputs an infrared thermal image.

2. Imaging Process

The novel high-performance dual-beam optical readout uncooled infrared focal plane imaging system of the present invention has an imaging process as shown in Figure 2:

The infrared thermal image of the external target enters the novel high-performance dual-beam optical readout uncooled infrared focal plane imaging system (shown by arrow I) of the present invention through the infrared lens 1, and is time-modulated by the light modulator 2 located in the imaging optical path , and then imaged on the focal plane array 3 (shown by arrow II), the focal plane array 3 absorbs heat, and the reflector of the pixel array will deflect under the drive of the cantilever beam.

The divergent light emitted by the light source 4, after being expanded and collimated by the collimating lens group 5, enters the infrared modulation imaging optical path (shown by arrow III), and the illuminating imaging beam modulated by the focal plane array 3 enters the optical readout optical path 6 (shown by arrow IV), the optical readout optical path images it on the CCD target surface of the information collection and processing device. Since the spatial modulation signal provided by the infrared modulation imaging optical path has time division, part of the time is the infrared image signal, and the other part of the time is the background and system noise signal, so the image signal received by the CCD is also an infrared image signal, background and system noise signal alternately at a certain frequency. System noise signal.

3. Correction of infrared images with background and system noise signals

The novel high-performance uncooled infrared focal plane imaging system of the present invention corrects the infrared image with the background and system noise signals as follows:

(1) Acquisition of infrared images

The infrared image acquisition process of the optical readout uncooled infrared focal plane imaging system shown in accompanying drawing 1 is: first, the reference object is imaged by the system, and at this time the default is that the external environment focal plane array 3 has no imaging, then the image acquisition and processing device 7 Each pixel obtains an energy EO; then the system images the external infrared object, and the external image is imaged on the focal plane array 3 through the infrared lens group 1, so that the pixels of the focal plane array 3 produce a corresponding angular deflection, resulting in image acquisition and The difference between the energy Ei obtained by each pixel of the processing device 7 and the EO production process, the difference between the two is the infrared thermal image, namely:

Infrared thermal image Ei ₀ ＝E ₀ -Ei ……………………(1)

Among them: E ₀ =E·η ₁ ·η ₂ ·η ₀ …………………(2)

Ei=E · η ₁ · η ₂ · η ……………………(3)

E is the luminous intensity of the light source 4, η ₁ is the light transfer efficiency of the light source collimating lens group 5, η ₂ is the light transfer efficiency of the readout optical path 6, η ₀ is the light transfer efficiency of the focal plane array 3, and η is the system pair The light transfer efficiency of the focal plane array 3 after imaging the infrared object;

In essence, E, η ₁ , η ₂ , η ₀ , and η in formula (2) and formula (3) will fluctuate with time: E will change with the aging of the light source and the ripple of the light source power supply; η ₁ , η ₂ will change due to changes in the external environment and structural deformation; η ₀ will change greatly due to external vibrations, which will lead to distortion of the calculation results of formula (1). Especially when the system needs to work for a long time, the infrared image output by the system will be distorted and become more and more blurred, gradually losing the imaging ability.

(2) Correct the infrared image with the background and noise signal

The new high-performance uncooled infrared focal plane imaging system shown in Fig. 2 adds a light modulator 2 on the basis of Fig. 1 to time-modulate the infrared imaging light. The image acquisition and processing device receives the infrared image Es and the background and noise image Eo in 7 time divisions, and these two types of signals appear alternately according to a certain time frequency, that is, appear at time t, then Es appears at time t+1, and appears at time t+2 Eo...Because the interval Δt between t and t+1 is very small, the changes of E, η ₁ , η ₂ , η ₀ , and η will be very small, even negligible, so if according to:

E _(t+1) ＝Eo _t -Es _(t+1) …………………(4)

If the calculated result outputs an infrared image, it can largely overcome the difficulty of image distortion or even loss of imaging ability caused by E, η ₁ , η ₂ , η ₀ , and η changing with time. That is to say, the imaging system can be compared Good deduction of environmental vibration, ambient temperature and illuminance changes, infrared focal plane array device deformation, light source power supply ripple, light source aging, optical mechanical structure deformation, CCD noise on the system imaging quality, improve system stability, reliability and sensitivity.

Claims (7)

1. un-cooled infrared focal plane array imaging system that contains the time modulating device, comprise the infrared modulation imaging optical path, illumination path, optical read goes out light path, image acquisition and treating apparatus, it is characterized in that adopting the photomodulator in the infrared modulation imaging optical path that imaging infrared light is carried out the time modulation: under the different modulating state, the corresponding unlike signal of the image that image acquisition and treating apparatus collect source, has different meanings, when Flame Image Process, utilize unlike signal that infrared image is revised, thereby elimination ambient vibration, environment temperature and illumination change, the infrared focal plane array device distortion, the light source power ripple, light source ages, the mechanical-optical setup distortion, the CCD noise improves system works stability to the influence of system imaging quality, reliability and sensitivity.

2. the un-cooled infrared focal plane array imaging system that contains the time modulating device according to claim 1, it is characterized in that the infrared modulation imaging optical path comprises infrared imaging camera lens, optical modulation assembly, infrared focal plane array, illumination path comprises light source, collimating mirror group, and optical read goes out light path and comprises imaging lens group and wave filter.

3. the un-cooled infrared focal plane array imaging system that contains the time modulating device according to claim 1, it is characterized in that the described infrared imaging light beam that enters in the infrared modulation imaging optical path, carried out the time modulation by the optical modulation assembly, make the output of infrared modulation imaging optical path have timesharing, portion of time is an infrared image, and another part time is the detection system ambient noise signal.

4. a kind of un-cooled infrared focal plane array imaging system that contains the time modulating device according to claim 1, the diverging light that it is characterized in that sending from light source enters the infrared modulation imaging optical path after the collimating mirror group expands bundle, collimation.

5. novel high-performance non-refrigerating infrared focal plane imaging system according to claim 4 is characterized in that surveying the light path of infrared image, and in full accord with the light path of detection system ground unrest, imaging pixel is also in full accord.

6. novel high-performance non-refrigerating infrared focal plane imaging system according to claim 5 is characterized in that image acquisition and treating apparatus acquisition time infrared image signal and ambient noise signal, and the timesharing frequency is by decision modulation period of photomodulator.

7. novel high-performance non-refrigerating infrared focal plane imaging system according to claim 6, it is characterized in that image acquisition and treating apparatus utilize ambient noise signal, infrared image signal is revised, be out of shape with illumination change, infrared focal plane array device distortion, light source power ripple, light source ages, mechanical-optical setup to eliminate ambient vibration, environment temperature, the CCD noise is to the influence of system imaging quality, raising system works stability, reliability and sensitivity.

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