CN202057893U - Infrared DLP (digital light processing) telecentric projection system - Google Patents

Abstract

The utility model discloses an infrared DLP (digital light processing) telecentric projection system, which is mainly used for research on an infrared scene simulator and provides a telecentric light path structure without a TIR (total internal reflection) prism. The infrared DLP telecentric projection system comprises an infrared light source, an ellipsoidal reflective bowl, a hollow square rod, a group of lighting relay lenses, a DMD (digital mirror device) chip, a plane mirror and a group of projection objective lenses. The design of a DLP telecentric projection light path at the infrared wave band can be implemented through the system. The infrared DLP telecentric projection system has the advantages of adaptability to the infrared wave band, telecentric projection, simple manufacturing, high reliability, convenience in optimization and lower cost.

Description

A kind of infrared DLP heart optical projection system far away

Technical field:

This patent relates to a kind of optical system, and is special, relates to the heart optical projection system infrared far away that a kind of digital light is handled (DLP), and this system is used for Infrared Scene emulation field.

Background technology:

Infrared dynamic scene simulation technology is a support with new and high technologies such as computing machine, information processing, microelectronics, a large amount of infrared simulation tests and limited field trial are combined, not only can optimization system design, improve system performance, and can in time diagnose and get rid of hidden danger and fault, can improve development quality effectively; In addition, can also significantly reduce the outfield experiments number of times, thereby play the purpose of shortening lead time, saving research fund, raising system performance by using emulation technology.

The infrared image emulator comprises infrared target and background generation systems and optical system, function is the infrared image that the digital picture that computing machine generates is converted to corresponding spectral coverage, and project the entrance pupil place of infrared imaging system and be full of entrance pupil, make the big or small consistent of infrared scene image patch on detector, the space distribution unanimity of emittance with real goal and background.Require the only time space of its projection incoherent, unpolarized.

In the modern shadow casting technique, TFT-LCD, LCOS and DLP are the advanced projection display techniques of comparison main flow.LCD and LCOS all are not suitable for infrared band, and DLP is owing to being the reflected light modulation, with the projected light Wavelength-independent, so go for infrared band.Compare active illuminating shadow casting techniques such as resistance bridge, the optical system of using DLP shadow casting technique to finish the infrared image emulator has characteristics such as high resolving power, high frame frequency, no dead pixel and good uniformity.

In the DLP shadow casting technique, optical system is used the digital micromirror device (DMD) of Texas Instrument Co company research and development.DMD is that (Micro Electromechanical System MEMS), also is a kind of semiconductor spatial light modulator (SLM) to a kind of microelectromechanical systems.DMD is called MEMS to be formed because it is built in by thousands of turnover tiny mirror (micro mirror of different model DMD varies in size) above the hinge arrangement of static RAM (SRAM) top.On the other hand, because these micro-reflectors come light modulated with the high speed reflection way, be a kind of reflective SLM so DMD may also be referred to as.The micro-reflector of DMD has three kinds of states, is respectively open and close, level state.Concrete principle of work is exactly, and to DMD, and circuit is controlled the state of each sheet DMD to the illumination light of incident with certain angular illumination.If " opening " state, the illumination incident light will enter follow-up projection optical system by the DMD reflection, if " pass " state, the illumination incident light does not enter optical projection system.Like this, in an integration period of detector, control DMD is in the time of " opening " " pass " state, has just controlled the luminous energy that enters optical projection system.So, just can produce the gray level image that also projection needs by the different dmd array of these reflected energies of control.

The residing whole optical system of DLP comprises the illumination optical system projection optical system of unifying, and the former is a nonimaging optics, and the latter is an image optics.In the DLP optical projection system, the quality of illumination is most important for the performance impact of total system.

DLP light path reference " the Single-Panel DLP that provides in official of Texas Instrument Co company ^TMProjection System Optics " provided two kinds of typical single-chip formula DLP projection optical system frameworks: core structure far away and non-core structure far away.

The optical system of core structure far away, the illumination section system adopts telecentric beam path in image space, and it all is parallel making the chief ray that shines on the DMD plane.Because core structure far away, the emergent pupil of illuminator and the entrance pupil of optical projection system be all in the infinite distance, so this structural design is got up than being easier to, optical projection system and illuminator can be divided the design simultaneously of coming.Generally speaking, in this structure, optical projection system and illuminator separate with a TIR (total-internal-reflectance) prism, so projection section and illumination section do not have parameter influence mutually.Under this framework, DMD need not biasing, and illumination uniformity also can be accomplished fine.

Non-telecentric beam path, be exactly illumination path be non-telecentric beam path, the last reception of DMD is not the irradiation of parallel light cone.Owing to be not telecentric beam path, consider efficiency of light energy utilization problem, design should be with the entrance pupil of the emergent pupil of illuminator and optical projection system to being complementary.So non-telecentric system, illumination and optical projection system can not separately design.Non-telecentric beam path is compared telecentric beam path, because illuminating bundle is not parallel, generally comes separately illuminator and optical projection system without the TIR prism.Adopt the DMD biasing, and big illumination incident angle, even complicated free-form surface mirror could separate enough angles with illuminator and optical projection system.Its advantage is that the illumination incident angle is bigger, and the contrast of DLP drop shadow effect is higher, and structure can design compactly, is fit to miniaturization Design.But because the illuminating bundle of non-telecentric beam path is not parallel, so the even angle of its illuminating bundle is not so good as core structure far away.

Core structure far away is simple, but the TIR prism is to the branch light action of light beam, even in theory, also have only 25% energy to throw away at most, and TIR prism glueing material is bigger for infrared absorption, causes the energy loss of this structure too big, is not suitable for infrared optical system.But not heart framework far away, maximum problem is that design and manufacturing cost are bigger, may also need to use the free form surface reflecting surface and come separately illuminator and optical projection system.The design more complicated of free form surface, research and development and processing cost are very big.

Summary of the invention:

This patent proposes a kind of infrared DLP optical system, overcomes the restriction and the shortcoming of core structure far away and non-core structure far away, makes it to have to make simply the characteristics that reliability height, cost are cheap relatively.This patent is applied to the manufacturing of Infrared Scene emulator.

This patent proposes a kind of infrared DLP projecting light path of telecentric light.Heart projection structure far away has the illumination uniformity height, characteristics such as projection accuracy height.The telecentric system of this patent does not need to use the TIR prism, and it is very favorable improving for the infrared system capacity usage ratio.Simultaneously do not need the dmd chip of setovering yet, thereby can erect light path easily.The design of illuminator, what mainly consider is illumination uniformity and capacity usage ratio.Utilize the structure of this patent, can obtain uniform illuminating effect and high energy utilization rate.

This patent DLP light engine is suitable for infrared band fully.Infrared optical system, lens materials costs an arm and a leg, and this patent is simple in structure, and size is less, helps controlling the manufacturing cost of Infrared Scene generator.In this patent, illuminator and optical projection system all can adopt more common infrared optical material preparation.It must be noted that the spectral transmission problem of the optical window of DMD micro mirror array.Common dmd array is packaged, on the optical window material can not see through infrared light, in order to be applicable to infrared band, therefore in this patent, must use the DMD that changed the optical window material.

This patent is achieved through the following technical solutions, and specifically comprises: infrared light supply, spheroid shape reflector, hollow square rod, illumination relay lens, dmd chip, plane mirror, projection objective.Infrared light supply can be selected blackbody radiation source or Elema for use, and infrared light supply places on the focus of ellipsoid reflector, and its light beam converges on another focus of spheroid shape reflector.On another focus that converges, place hollow square rod inlet.Hollow square rod inside will plate the reflectance coating of infrared medium-wave band reflectivity more than 90%.After light enters square rod, after in square rod, repeatedly reflecting, play the effect of a light integrators, obtain uniform light distribution in the square rod exit.Behind hollow square rod, place the illumination relay lens group.These group lens are a kind of critical illumination designs, make the equally distributed light intensity in square rod exit be imaged onto DMD micro mirror array place.Because the heart framework far away that adopts is so this lens combination emergent pupil should be at infinity.The illuminating lens group there is no high requirement to aberration, eliminates spherical aberration as far as possible and gets final product.24 ° of inclinations of the optical axis of dmd chip and illumination path are placed on the image planes of illuminating lens.Lay a plane mirror directly over dmd chip, catoptron is used to change optical axis direction, makes illumination relay lens group and projection objective separately, and is unlikely to influence each other.A part of illuminating bundle is blocked in the almost unavoidable meeting of plane mirror.Theoretical and experiment can draw, if plane mirror enters the mouth to the conjugation of illumination relay lens group at hollow square rod, the light beam that this part is blocked can influence the homogeneity of DMD illumination hardly.Plane mirror and projecting light path's optical axis included angle are 50 °, can separate the locus of optical projection system and dmd chip so naturally.The reflected light of modulating through the DMD micro mirror array (Infrared Scene) projects through heart projection objective far away.Owing to be heart framework far away, the entrance pupil of lens objectives should be in negative infinite distant place.

In order to improve capacity usage ratio, optical projection system and illuminator should have equal work F number.And determining of optical projection system F number generally determined by the resolution and the diffraction limit of total system.

Description of drawings:

Fig. 1 is the infrared DLP light engine structural representation of this patent.

Fig. 2 is the structural representation of illuminator in the infrared DLP light engine of this patent.

Fig. 3 is the synoptic diagram of optical projection system in the infrared DLP light engine of this patent.

Fig. 4 is in this patent, illuminator and reflector position explanation synoptic diagram.

Embodiment:

As shown in Figure 1, this patent comprises: infrared light supply 1, spheroid shape reflector 2, hollow square rod 3, illumination relay lens 4, DMD micro mirror array 5, plane mirror 6, projection objective 7.Infrared light supply 1 places on the focus of ellipsoid reflector 2, and according to the geometric properties of ellipse, its light beam will converge on another focus of spheroid shape reflector.Reflectance coating will be plated in reflector inside, and at infrared band reflectivity more than 90% is arranged.Reflector 2 the rim of a bowl sizes should be by the numerical aperture decision of follow-up illuminating lens system 4.

Hollow square rod 3 absorbs the light of infrared light supplies and reflector reflection, carries out the light integration, goes out the uniform beam distribution of interruption-forming space distribution at hollow square rod 3.Illumination relay lens 4 exports the surface that is imaged onto DMD micro mirror array 5 with hollow square rod 3, forms illumination uniformly.Because DMD micro mirror flip angle is 12 °, TI company recommends incident light to become 24 ° of angle incidents with DMD plane normal direction, and at this moment projected image has the highest contrast and brightness, and the efficiency of light energy utilization is the highest.The DMD micro mirror array with the illuminating bundle spatial modulation after, light modulated reflexes in the projection objective 7 through plane mirror 6.

As shown in Figure 2, be the illuminator synoptic diagram in this patent.In this patent, hollow square rod 3 exits are uniform light distribution, so illuminator adopts critical illumination, hollow square rod outlet is a pair of image conjugate relation with the position of DMD micro mirror array.In this patent, illumination relay lens group 4 (is eliminated aberration optimization except satisfying hollow square rod 3 outlets with the image relation of DMD micro mirror array 5, the general spherical aberration of eliminating gets final product), also should satisfy the image conjugate relation (satisfying Gaussian optics image relation gets final product) of hollow square rod 3 inlets and plane mirror 6 positions.And illumination relay lens 4 need satisfy the coupling of the optical extend between light source/square rod and the demonstration/projection objective, the capacity usage ratio of raising total system.According to the requirement of Infrared Scene generator resolution and the diffraction limit of infrared band, determine the work F number and the numerical aperture of illuminator.For guaranteeing is telecentric beam path, and the emergent pupil of illumination relay lens 4 should be at infinity.

As shown in Figure 3, be projection objective synoptic diagram in this patent.Adopt the object space telecentric beam path, must optimize and eliminate all kinds of primary aberrations, dot chart is controlled in the diffraction limit.Must be noted that in the Infrared Scene analogue system parameter of projection objective system should cooperate the follow-up optical parametric of examining system for the treatment of to determine, the emergent pupil of optical projection system needs and treats the entrance pupil coupling of examining system, and field angle should be in system testing scope to be measured.During the projection optics camera lens, must reserve the distance of enough DMD to the first eyeglass, in the design this patent to make things convenient for mounting plane catoptron 6.

Analyze critical illumination system in this patent by the Fourier optics angle now as shown in Figure 4.In projecting light path, owing to have only 24 ° angle between illuminating bundle and the folded light beam, so consider factors such as lens barrel is installed, illuminating lens very likely contacts on the space with projection objective.For fear of interacting, before dmd chip, place plane mirror 6.As can be seen, plane mirror 6 has blocked the partial illumination light beam.The illuminating ray of all directions enters hollow square rod 3 inside, because the reflection of different number of times takes place in square rod the angle difference that enters.After the light reflection, form a virtual light source, repeatedly after the reflection, just form a virtual two-dimension light source array 8.This two-dimension light source array should form conjugate relation with the position of placing plane mirror 6 in the porch of hollow square rod 3.From the angle of Fourier optics, two-dimension light source array 8 is light sources, and the outlet of hollow square rod 3 is object planes, and the position of plane mirror 6 is frequency plane (being with normal phase factor), and the position of DMD micro mirror array 5 is image planes.Concrete theoretical analysis and derive with reference to Su Xianyu " information optics " chapter 2 of Li Jitao.According to the method for spatial filtering, on frequency plane, shelter from decentering point spectrum distribution far away, will filter the high-frequency information of object space.Filter the part high-frequency information and can't influence the homogeneity of imaging.Even cover half light, can realize even illumination.Plane mirror and projecting light path's optical axis included angle are 50 °, can separate the locus of optical projection system and dmd chip so naturally.

Claims (2)

1. one kind infrared DLP optical projection system, comprise: infrared light supply (1), spheroid shape reflector (2), hollow square rod (3), illumination relay lens (4), DMD micro mirror array (5), plane mirror (6) and projection objective (7), it is characterized in that: infrared light supply (1) places on the focus of ellipsoid reflector, and its light beam converges on another focus of spheroid shape reflector; On another focus that converges, place hollow square rod (3) inlet, after light enters square rod, after in square rod, repeatedly reflecting, play the effect of a light integrators, obtain uniform light distribution in the square rod exit; Place illumination relay lens group (4) in hollow square rod (3) back, make the equally distributed light intensity in square rod exit be imaged onto DMD micro mirror array place; DMD micro mirror array (5) is placed on the image planes of illumination relay lens with 24 ° of inclinations of optical axis of illumination path, plane mirror (6) is placed on directly over micro mirror array (5), become 50 ° with DMD micro mirror array (5) normal direction, the light modulated that plane mirror (6) reflects DMD is introduced projection objective (7) and is formed infrared target.

2. a kind of infrared DLP optical projection system according to claim 1 is characterized in that: the position of the entry position of described hollow square rod (3) and plane mirror (6) is in the object-image conjugate relation in the system of illumination relay lens (4).

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