CN102661800B - Reflective optic reading method based on MEMS infrared imaging systems - Google Patents

Abstract

The present invention is a kind of reflective optic reading method based on MEMS uncooled infrared imaging systems.When there is no infrared object in background environment, FPA micro-cantilevers do not bend, by concave mirror Fourier transformation occurs for the light being at this moment reflected back by FPA, the frequency spectrum of formation passes through the filtering of reflective filter, it is imaged on again by the inverse Fourier transform of another concave mirror on CCD, using this as being used as reference image.When there is infrared object in environment, micro-cantilever heated bending in focal plane arrays (FPA), the light that FPA is reflected back changes, and certain displacement occurs by the frequency spectrum after concave mirror, again by the filtering and the inverse Fourier transform of concave mirror of reflective filter, it is imaged on CCD.Diagram picture and reference image make the picture that difference operation can be obtained by infrared radiating object.This method is folded light path, reduces the size of optical pickup system, and has reached the purpose for improving image quality, improving detectivity.

Description

Reflective optic reading method based on MEMS infrared imaging systems

■ technical fields

The present invention is a kind of optical reading method based on FPA uncooled infrared imaging systems.The reading method is directed to mesh Preceding read-out system structure is excessively huge and the problem of low sensitivity, invents a kind of new optical reading method.This method Original lens imaging is instead of using speculum, and instead of using reflective filter traditional wave filter so that system Compacter, light, design freedom is bigger, and adds the sensitivity of system detection to a certain extent.

■ background technologies

Either domestic or external, the novel optical reading FPA thermal imagings based on MEMS are increasingly by weight Depending on.Light reading uncooled infrared imaging system is compared with traditional electrical readout mode, and summary gets up to have following several respects advantage：

1. the core Sensitive Apparatus of the uncooled infrared imaging system based on micro-cantilever can work at room temperature, and not Need refrigeration plant.

2. due to using optical read-out mode, turn the phenomenon of heat energy in the absence of electric energy, so read-out system will not be Additional heat energy is produced on detector.

3. cross wire and electron scanning beam need not be carried out between pixel, easily increase the quantity of pixel on detector, Manufacture difficulty and cost are not introduced, the complexity and production cost of making is reduced.

4. enter row metal connection between not needing probe unit in leg, so as to be realized between probe unit and substrate Good is thermally isolated, so that each being thermally isolated for pixel can reach radiation limit.

5. micro-cantilever array uses micro fabrication that can be compatible with Si manufacture crafts now, therefore largely Reduce exploitation and cost of manufacture.

According to several advantages described above, now both at home and abroad all to novel optical reading uncooled infrared imaging system Performance and integrated carried out extensive probe into.

At present, uncooled infrared imaging system is used for the most base of optical reading method for reading FPA micro-cantilever deflection angles In the 4f systems of transmission-type, and use the filtering mode of the edge of a knife, aperture, slit, square hole etc..By taking pin-hole filter-ing method as an example：It is small Hole filtering read-out system is to be focused on infrared ray on FPA by Infrared Lens, and FPA is in vacuum chamber, and light source is visible ray LED.Turn into directional light after the collimated element of light that LED is sent, the directional light is radiated on FPA and reflected through FPA.It is anti-from FPA The light beam penetrated turns into converging light by first imaging len, and is focused near the aperture on focal plane.Because each reflecting small The deflection angle of unit is different, converged position of these light on aperture plate can be made different, only when converged position and aperture During position suitable, these light can pass through aperture and second imaging len.When these light are saturating by second imaging After mirror, directional light can be turned into and be imaged on CCD.When there is no infrared emanation object in environment, each cantilever beam junior unit Deflection angle it is identical, therefore collimation after directional light reflected through FPA after have identical direction, pass through first imaging len Post-concentration is burnt together, and the position of focus is all overlapping, the reflected light process of the upper each junior units of the FPA for receiving CCD Light intensity after aperture is identical, therefore the gray value of each position of output image is identical.When there is hot object in environment, due to each Individual junior unit is heated different and deflects different angles, causes the direction through the FPA light beams reflected different so that the light beam passes through Focus is misaligned after first imaging len is focused on, therefore is changed by the light intensity of aperture, ultimately results in and is received on CCD Light intensity change, obtain gray value it is different image output.The detectivity of this method is not only black with detection target The temperature of body is relevant, also relevant with LED luminous intensity and CCD sensitivity.This method easily realizes that array is surveyed without vibration isolation Amount.But the spatial resolution of this method and detectivity can not be improved simultaneously, spatial resolution not enough and fogging image Deng.Summary is got up, and the optical reading method of transmission-type has the defect of following several respects：

1. system architecture size is larger, it is unfavorable for miniaturization and portable.

2. spatial resolution and detectivity cannot be improved simultaneously, spatial resolution is not enough and image is not clear enough.

3. wave filter is mostly using the edge of a knife, aperture or slit etc., system defect is (at the beginning of such as FPA manufacturing defect, junior unit Aberration that the form of beginning is inconsistent and optics is produced etc.) influence to imaging is larger.

4. a mutually complementary wave filter is difficult to realize and is easily influenceed by air agitation.

Different from the optical reading method of transmission-type, reflective optical reading method is the optical element using reflection, And using and conventional filter position mutually complementation reflective filter.With wave filter (such as aperture, slit of traditional 4f systems Deng) compare, reflective filter is the form complementary with conventional filter, that is, the method put with round dot or side.Use transmission The 4f systems of formula are difficult to realize to use round dot, side's point to be used as wave filter, it is more difficult to realizes the form of narrow band filter, and is also easy to Influenceed by air agitation.In addition, the mode of traditional pin-hole filter-ing is not easily found optimum filtering position.

The ■ content of the invention：

The purpose of the present invention is to utilize reflective 4f system imagings performance, using reflective filter, by micro-cantilever array Heated corner be converted into light intensity signal.

The purpose of the present invention is realized by following technical scheme：Reflective wave filter is to be scribed on level crossing necessarily Position beyond the round dot of radius, round dot position not reflected light, round dot can be used as the filter of reflective 4f systems diffraction spectra with reflective Ripple device.Assuming that the optical reflection face of each micro-cantilever unit can be reduced to the rectangular slab of rule and parallel to each other, this Sample one by one rectangular slab line up be formed two dimension optical grating construction.When using visible illumination, each rectangle element In spectrum plane formation identical diffraction spectra, but be due to each rectangular slab be heated post deflection angle it is different, each unit spreads out The displacement for penetrating spectrum is also just different.The corner of some micro-cantilevers is bigger than normal, causes the diffraction spectra of light largely to move into retroreflective regions, leads to The luminous energy increase crossed；The corner of some micro-cantilevers is less than normal, and the diffraction spectra of light is most of still in non-reflective region, passes through The increased degree of luminous energy is smaller (vice versa).During original state, when there is no infrared radiating object in environment, focal plane arrays (FPA) The initial angle of the reflector of FPA each junior unit is the same, after directional light is incident at an angle, FPA rectangular slab list Member is by reflection 4f systems, in spectrum plane formation identical diffraction spectra, after the filtering of reflective filter and concave mirror, imaging On CCD, and using this as being used as benchmark.When there is infrared radiating object in environment, object is imaged on FPA by Infrared Lens On, corresponding different deflection occurs for the junior unit on FPA, after directional light is incided on FPA, is reflected through FPA reflectors Corresponding deflection also occurs for light, at this moment, and the diffraction spectra of light produces certain displacement with the deflection of junior unit.Again pass by reflection After the filtering of wave filter and concave mirror imaging, it is imaged on CCD, the luminance difference being imaged twice can be obtained by infra-red radiation thing The thermal-induced imagery of body.

■ beneficial effects

Traditional lens imaging can be replaced using the present invention, will using reflecting element concave mirror and reflective filter The heated corner of micro-cantilever array is converted into light intensity signal.Compared with traditional method, the design freedom of reflective filter Larger, this method can not only reduce the size of whole system, can also improve detection sensitivity, improve to a certain extent The efficiency of light energy utilization, and influence of the system defect to imaging is smaller than using traditional 4f optical pickup systems.

■ is illustrated

Fig. 1 is the reflective 4f optical read-out sides with the uncooled ir thermal imaging system based on MEMS based on the present invention The principle schematic of method

Wherein：1- spot lights, 2- colimated light systems, 3- focal plane arrays (FPA)s, 4- concave mirrors, 5- speculums, 6- reflective filters, 7- concave mirrors, 8- photelectric receivers

Fig. 2 is the reflective filter used in reflective optic reading method

Wherein：9- plane mirrors, the light tight round dots of 10-

■ embodiments

The present invention is described further below in conjunction with the accompanying drawings：

As shown in figure 1, when the external world does not have infrared radiating object, the junior unit of focal plane arrays (FPA) is at same shape State.At this moment, the light that spot light 1 is launched passes through the modulation of colimated light system 2, is changed into directional light injection.It is burnt flat that directional light is irradiated to 3 On the array FPA of face, the reflector in focal plane arrays (FPA) FPA junior units reflects directional light.It is reflected back through focal plane arrays (FPA) FPA Light pass through by concave mirror 4, form diffraction spot on the focal plane of concave mirror, that is, object frequency spectrum, the frequency spectrum of formation passes through Reflective filter 6 is filtered, and filtered frequency spectrum passes through the process of an inverse Fourier transform of concave mirror 7 again, and focusing is flat Face array FPA is imaged.The image on the basis of this picture.Wherein plane mirror 5 serves folding light path, reduces system dimension Effect.When the external world placed infrared object, the light that infrared object is sent is imaged on 3 focal plane arrays (FPA)s after Infrared Lens On FPA, the cantilever beam of corresponding junior unit deflects on 3 focal plane arrays (FPA) FPA.Now, it is parallel after collimation lens 2 Illumination is mapped on FPA, can also be deflected certain angle after the corresponding junior unit deflected is irradiated in directional light, be passed through again Cross by concave mirror 4, plane mirror 5, reflective filter 6, now, the diffraction spectra of light largely moves into retroreflective regions, passes through Luminous energy increase, then be imaged by concave mirror 7, the piece image for must to be one have infrared object information that CCD is collected, by the diagram As carrying out making the difference the thermal imagery that can be obtained by infrared object with original image.

Wave filter for reflective playback mode as shown in Figure 2.Be scribed on plane mirror 9 one it is non-reflective Round dot 10, for being filtered to diffraction spectra.When not having infrared object to be in environment, the diffraction spectra of micro-cantilever is most of by not Reflective circular hole is sponged, and the fraction of diffraction spectra is by the reflective surface outside circular hole.When the external world placed infrared object When, part micro-cantilever deflects different angles respectively according to the heat of absorption, and respective diffraction spectra occurs corresponding skew, had The corner of cantilever beam slightly is bigger than normal, causes the diffraction spectra of light largely to move into retroreflective regions, and the luminous energy increase degree passed through is larger； The corner of some micro-cantilevers is less than normal, and the diffraction spectra of light deviates from that retroreflective regions are less, the increased degree of the luminous energy passed through also compared with It is small.So CCD can just capture the change of different brightness, increase the sensitivity of infrared imaging system.In addition, reflective Wave filter can also be as needed by lighttight round dot 10, and the side's of being designed as point, arrowband or arbitrary shape are to meet the need of system Ask.

Claims (3)

1. a kind of reflective optic reading method based on MEMS infrared imaging systems, it is characterised in that：This method is red in MEMS Realized in outer imaging system, system is by illumination path, focal plane arrays (FPA) micro-cantilever FPA, Infrared Lens, concave mirror, anti- Wave filter, photodetector and display composition are penetrated, Infrared Lens are by infrared emanation target conjugate imaging surface after FPA On, FPA junior units is occurred temperature distortion deflection, the directional light of illumination path outgoing reaches concave surface after FPA front surface reflections Speculum, concave mirror carries out Fourier transformation to FPA temperature distortions deflection light field, and Fourier spectrum is filtered by reflective filter Ripple, then be imaged on by the inverse Fourier transform of another concave mirror on photodetector, display shows that FPA is heated inclined Field information after turning.

2. the reflective optic reading method as claimed in claim 1 based on MEMS infrared imaging systems, it is characterised in that：Instead The reflective filter for penetrating the use of formula optical reading method has only blocked the low frequency portion of most of junior unit frequency spectrum in the position of frequency spectrum Point.

3. the reflective optic reading method as claimed in claim 1 based on MEMS infrared imaging systems, it is characterised in that：According to There is certain angle between the directional light and FPA of the outgoing of Mingguang City road, the off-axis angle of concave mirror and FPA outgoing in the reading method The angle of light is identical, so that it may so that infrared object into picture it is identical with original ratio, will not deform.