設(shè)計(jì)lightools v7軟件視頻教程軟件教程lt2014年lighttools backlight

1、Copyright 2005 UCLModelling New Backlight TechnologiesDavid R. Selviah, Kai Wang and Xia MoDepartment of Electronic & Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.Lighting and Backlighting“ Seminar, Bletchley Park, UK, 2nd Nov. 2005 2Copyright 2005 UCLInt

2、roductionNovel experimental backlight designs can be assessed most economically by modelling rather than fabrication of prototypes.The design can be optimised by modelling to meet a required specification as prototypes cannot be so easily changed.The model must correctly include all relevant optical

3、 elements and phenomena.Refractive and reflective optical elements, diffractive optical elements, DOE, and graded refractive index elements. Optical refraction, reflection, diffraction, scattering, absorption, polarization, and Gaussian beam propagation. 3Copyright 2005 UCLModelling technique choice

4、Beam Propagation Modelling, BPM, is more suited to waveguide devices of small width having few modes 50 m), very good for illumination system design, does not need complicated mathematical equations explicitly as these are integrated in the program.Rays are traced from the optical source to the opti

5、cal detector monitoring it as it passes individual optical elements.However, Ray tracing cannot accept a multimode light source input unless multiple sources are superimposed but this increases the modelling computation time.5Copyright 2005 UCLRay trace modelling programsASAP, Advanced System Analys

6、is Program, Breault, Tucson rectangular gratings, multi-microlenses combinationZEMAX, Optima Research, circular grating apertures, a few microlenses stackedLight Tools and Code V, Optical Research Associates, USATracePro, Lambda Research, lighting systemsSPEOS, Optis, France OptTaliX, Optenso, Germa

7、nyOptics Lab, Science Lab softwareSPIR, Oxalis Laser6Copyright 2005 UCLNon-sequential ray tracingRay tracing which requires the user to specify the order of the optical surfaces. It es inefficient when the system is complicated. Non-sequential ray tracing automatically determines which surface a ray

8、 will strike next. Optics may be located anywhere. Rays can follow any path and can encounter the same surface many times. Rays can be traced forwards, backwards, continuously, or in stepsRay splitting occurs automatically.Total internal reflection is treated properly. Non-sequential ray tracing can

9、 simulate illumination systems.It also allows the simulation of diffraction and interference effects in micro-optical array systems.7Copyright 2005 UCLConventional backlight designCCFL extended light sourceGlass or polymer wedge lightguideScattering dots on bottom or top of lightguideMicroprism or p

10、ainted dot scatterer- Bezier dot arrangementDiffuser to even out uniformity of light sourceTwo orthogonally crossed microprismatic film, BEF, to collimate lightDBEF or BEF-RP to polarise and recycle polarisationPolarisers before and after display to give good contrast.Red, Green, Blue, gelatine colo

11、ur filters inside display.8Copyright 2005 UCLConventional LCD BacklightPolyimidePassivationITO Lightguide TFT, GlassLiquid crystalCollimating BEFsPolarizer Colour filter, GlassDiffuser Polarizer Screen Spacers CCFL Scattering dot 9Copyright 2005 UCLBACKLIGHT ELEMENTSLIGHT TRANSMISSIONLightguide40%Di

12、ffusers 95%Addressed Cell Assembly, ACA Rear Polarizer45%2.6%TFT40%Colour filters17%Analyzer 85%Total1.0%Transmission efficiency of each element10Copyright 2005 UCLNovel UCL backlight designLED Light source instead of CCFLLED may be red, green, blue or whiteArray of Discrete Slit Gratings instead of

13、 dot scatterersHas the advantage that it separates colours by diffractionMicrolens array to collimate light normal to the displayTIR lightguideNo wedge in lightguide at presentOutput diffuser after the displayIBM* reported a similar design after we designed it but their design has a continuous grati

14、ng rather than slit gratings.*Yoichi Taira, et al, “Making a Color LCD without Color Filters”, Information Display, 4 & 5 /03, pp. 40-42 (2003)11Copyright 2005 UCLNovel LCD BacklightLEDs Lightguide TFT, GlassLiquid crystalPolarizer Pixels, GlassDiffractive slit grating PolyimidePassivationITO Polari

15、zer Spacers Microlenses arrayFront diffuser 12Copyright 2005 UCLOne pixel of novel backlightLCD pixelsMicrolensGratingLightguideReflected 0thorder1storderLCD pixelsMicrolensGratingLightguideReflected 0thorder1storder13Copyright 2005 UCLModelling and optimisation of UCL backlightA ray tracing model i

16、s constructed to optimize the overall power efficiency and uniformity of illumination. Modelling using ASAP and ZEMAX. The trade off between output efficiency and the uniformity of the light guide under different thickness of the light guide, the best value for the grating pitch and the trade off be

17、tween output efficiency and the uniformity of the light guide under different diffractive efficiency is investigated by non-sequential ray tracing. 14Copyright 2005 UCLLEDRay Tracing ModellingModel of chip LEDs15Copyright 2005 UCL16Copyright 2005 UCLModelled chip LEDCxxxMB290-Sxx00 white LED provide

18、d by CREE Optoelectronics. It combines a highly efficient InGaN material with G-SiC substrate which gives a high intensity LED. It is suitable for use in LCD backlight units 17Copyright 2005 UCLTwo methods to simulate an LEDPut a Lambertian diffuser in front of an array of point sources. It can be c

19、onsidered as an LED junction since the output from the diffuser follows the Lambertian distribution. A rectangle emitter instead of an array of point sources which is much easier and even more accurate than the first method.18Copyright 2005 UCLFundamentals of using emitterEmitted rays in a cosine di

20、stribution of the form The output obeys Lambertian distribution if Cn set to 1.The light comes out from the emitter is totally random, which works more close to reality.An electrode was included in the simulation. The emitting rays can not be set as white in ZEMAXThe combination of 3 primary colours

21、, i.e. red, green and blue, was used to simulate white LEDs. 19Copyright 2005 UCLThe model of the chip LED in ZEMAX ElectrodeSubstrateEmitting area Used the combination of 3 colours, red, green and blue, to simulate white LEDs 20Copyright 2005 UCLThe space intensity distribution of the LEDWith elect

22、rodeWithout electrodeYXZWith electrode the output power is lower the output distribution is almost the same 21Copyright 2005 UCLRadian intensity along the Y coordinateintercept the value of radiant intensity along the Y coordinate The Y coordinate units are degrees non-sufficient number of input ray

23、s cause zigzag curves. Using a certain number of rays (1 m), it is hard to get a perfectly smooth curve. With electrodeWithout electrodePeak Intensity: 0.29 Watts/SteradianTotal Power: 0.83 WattsPeak Intensity: 0.33 Watts/SteradianTotal Power: 1.00 Watts22Copyright 2005 UCLRadian intensity along the

24、 Y coordinateWith electrodeWithout electrode Need to use sufficient number of rays (30 M) to generate a smooth curve The simulation time increased more than 30 times compared to previous onePeak Intensity: 7.91 Watts/SteradianTotal Power: 24.88 WattsPeak Intensity: 9.70 Watts/SteradianTotal Power: 3

25、0.00 Watts23Copyright 2005 UCLOutput characteristic of the model LED junctionWith electrodeWithout electrodeThe output characteristic obeys the Lambertian distribution The performance was affected by the electrode. The output power is lower, The output space distribution is not changed as much as th

26、e power output. 24Copyright 2005 UCLThe layout of an LED array for LCD illuminationThis array consists of 83 CxxxMB290-Sxx00 LED chips and is used as the light sources for 25 mm 35 mm backlight system 25Copyright 2005 UCLOutput space intensity of the LED arrayPeak Radiance: 25.873 Watts/cm2/Steradia

27、nTotal Power: 66.636 WattsSize of Detector: 40 mm 10 mm40 mm10 mmModelling of light guide26Copyright 2005 UCL27Copyright 2005 UCLNovel LCD BacklightLEDs Lightguide TFT, GlassLiquid crystalPolarizer Pixels, GlassDiffractive slit grating PolyimidePassivationITO Polarizer Spacers Microlenses arrayFront

28、 diffuser 28Copyright 2005 UCLA edge-lit light guide with the LEDs illumination This light guide is made from a transparent polymer with a refractive index equal to 1.5, Its dimensions are 25 mm35 mm with a thickness of 0.99 mm. It can illuminate a 75105 pixels LCD The size of one pixel is 331 m 331

29、 m 29Copyright 2005 UCLFresnel Reflection and TransmissionIn ray tracing simulations, every element of the optical mode is normally assigned a refractive index. When the ray arrives at the surface of an element, calculations are carried out using the Fresnel Formulae It based on its angle of inciden

30、ce and the refractive indices of the media on both side of the interface boundary.The energy of rays: 30Copyright 2005 UCLTotal Internal ReflectionThe TIR light guide is fabricated without cladding, from a transparent polymer with a refractive index of 1.50 giving a critical angle by the formula, Th

31、e light generated from LEDs enters the lightguide, the angular distribution of rays is bound within .The refractive angle of the ray at the internal surface of the lightguide is , which is larger than . According to Snells Law, all rays incident on the entrance of the lightguide at angles less than

32、will strike the interior wall at angles greater than and so will be totally internally reflected and will travel along the lightguide.This means that all beams incident on the input face of the guide are guided. 990mRequirement Model n=1.5 n=1.5 Air Air 31Copyright 2005 UCLTotal internal reflections

33、 inside the light guide32Copyright 2005 UCLOne pixel of novel backlightLCD pixelsMicrolensGratingLightguideReflected 0thorder1storderLCD pixelsMicrolensGratingLightguideReflected 0thorder1storder33Copyright 2005 UCLThe grating equationDiffracted BeamReflected Beam-10+1Incident Beam d is the groove s

34、pacing of the grating. The groove spacing in nanometres is obtained by taking the reciprocal of the groove frequency, and multiplying by 106. is the angle of incidence. m is the angle of diffraction. m denotes the order number of the diffracted beam. 34Copyright 2005 UCLModelling of the operation of

35、 a diffraction grating in ZEMAX0th order-1st order+1st order Consider only 3 diffractive orders, -1st, 0th and +1st since most power is distributed in these three orders. The incident white (other 2 colours are overlaid by red one) light is divided into 3 orders, The grating can separate input rays

36、at +1st order.35Copyright 2005 UCLSeparating the light into three colours0th order+1st orderWhen rays are incident on the grating at an angle of less than 90 degree and is greater than the critical angle of total internal reflection, the1st order was emerged from light guide the 0th order was totall

37、y reflected the 1st order was not be encountered at all36Copyright 2005 UCLColour separation at a diffraction gratingPlaced a detector far from the light guide (1 m away)Detector+4.86 to +26.76-22.88 to +4.18-10.5 to +13.4237Copyright 2005 UCL3D model of colour separating backlightStrip detectors pl

38、aced above each gratings38Copyright 2005 UCLCircular grating arrays on the upper surface of the light guideZEMAX cannot easily: model rectangular gratings change the pitch of the gratings. 39Copyright 2005 UCLModelling of colour separating backlight (ZEMAX)40Copyright 2005 UCLSpace intensity distrib

39、ution of the output of the backlight modelPeak Irradiance: 13.86 Watts/cm2Total Power: 5.49 Watts41Copyright 2005 UCLModelling of colour separating backlight (ASAP)LED42Copyright 2005 UCLVaried thickness of the light guideThickness of a light guideArray of LEDsVaried thickness from 0.3 mm to 3 mm 43

40、Copyright 2005 UCLTrade-off between efficiency and uniformity (normalized intensity) The output efficiency is reduced as the thickness is increased while the uniformity of the output rays is improved. Consider the crossed point to be the optimum thickness.UniformityEfficiency0.7544Copyright 2005 UCL

41、Trade-off between efficiency and uniformity under different diffractive efficiencyEfficiencyUniformity when the diffractive efficiency is equal to 0.5, the 0th order is eliminated, no rays is reflected by the gratings. more rays transmit through the gratings. When the diffractive efficiency is equal to 0. no rays can come out from the light guide all the rays were guided inside the lig