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In this study, a texture mask (TM) machine learning method for predicting metal surface roughness produced by different machining methods is proposed. The problems caused by angle deviation in the image acquisition process can be effectively improved, and the training time of the model can be reduced. The surface roughness, with a roughness average (Ra) below 1 um, produced by two similar processing methods, flat lapping and grinding, is examined for prediction and verification. The performances of TM and other feature extraction methods, under different irradiation system conditions and different angle deviations, are also evaluated and compared. The results show that the proposed TM method is more accurate than other methods when the problem of angle deviation occurs. We also compare TM with the convolutional neural network (CNN) method. The accuracy of both methods exceeds 91%, but the training time for TM is significantly less than that of the CNN method. The results show the texture mask method to be an accurate and efficient texture extraction method suitable for use in an automatic system.

Current metalenses with large numerical apertures suffer from low efficiency. In this paper, we demonstrate a refractive-meta hybrid system consisting of a ball lens mainly providing the ray bending ability, and a meta-corrector to eliminate aberration of the optical system. Spatial frequency requirement of the meta-device is significantly reduced since system ray bending ability is mainly provided by refractive element. As a result, a large pixel liquid crystal spatial light modulator is sufficient to demonstrate the concept of meta-corrector for the refractive-meta hybrid system with a numerical aperture of 0.52. It is shown that the focal spot size can be significantly reduced from 322.07 μm to 0.636 μm for ray-tracing simulation, and 101.6 μm to 7.7 μm for measurement, as an appropriate phase distribution of the meta-corrector is added. We believe this pilot experiment can be applied to ball lenses and other optical lens-sets like cookie triplets as well.

In this paper, we demonstrate a design for a laser picoprojector with a high rate of reduction in the speckle contrast value. The method utilizes a holographic diffuser, deformable mirror, and fast electrically tunable (FET) lens. Then we compare the reduction rate of the speckle contrast value for holographic diffusers with different divergence angles and an FET lens with different optical power ranges combined with a deformable mirror. The increase in reduction rate of speckle contrast value means that the minimum value of the speckle can be reached faster. There reduction rate increases from 4.76 to 5.74 for the 5 × 5 holographic diffuser, 3.45 to 5.66 for the 10 × 10 holographic diffuser, and 1.52 to 4.58 for the 30 × 30 holographic diffuser.

We demonstrate a circularly polarized optical microscope (POM) by incorporating a hole-patterned electrode (HPE) liquid crystal (LC) lens fabricated by photoalignment. The focal plane is controlled by voltages on the HPE LC lens with a tuning range of 2.2 mm without any mechanical movement. The diopter can be controlled from 0 to − 5.0 D , and the wavefront optical path difference is less than 0.25 λ for our proposed HPE LC lens. Such a low aberration is obtained, because the LC directors are well aligned along with the axially symmetrical electrical field, and there is no observed twist deformation of the LC directors. Finally, we applied our circularly polarized POM to inspect the reflectance properties of several beetles, and we find that the “Chrysochroa toulgoeti” beetle exhibits right circularly polarized reflectance from some small areas on its wings.

In this paper, an achromatic total internal reflection (TIR) prism set, consisting of two stacked prisms, is designed to reduce the lateral color aberration of a mini projector with light-emitting-diode (LED) light sources. Two different types of the prism set are proposed. Type 1 prism set is the first prism with a small Abbe number material stacked with the second prism with a large Abbe number material. By analyzing the optical properties of the proposed ATIR prism sets, we are able to choose an appropriate optical material combination of the prism set. For type 1 prism set, the corresponding lateral color aberration is 0. 65 μ m and the size is 2306 mm3. Nevertheless, the type 1 suffers from efficiency loss of 15.5%. For type 2 prism set, the corresponding lateral color aberration is 0. 61 μ m and the compact prism size is 3000 mm3. Although the size of type 2 prism set is larger than that of type 1, the efficiency loss can be as low as 1 %.

The capsule endoscope is an important tool for the intestinal examination. But the main disadvantage of the traditional capsule endoscope is the limited field of view. In order to solve this proble...

In this paper, we present a rotational symmetry for an ultrashort throw (UST) lens with offset field. The UST lens has a throw ratio of 0.23 and a total track of 195 mm. The optical elements of the...

In this paper, an anamorphic digital light processing illumination system design with a freeform surface lens is described. A lens with a freeform surface lens is combined with the achromatic total internal reflection prism set for application in a relay lens system. In order to achieve a high contrast ratio without sacrificing illumination system efficiency, the novel, to the best of our knowledge, design uses an x - y polynomial surface for the freeform surface lens to reduce the overlap angle of the anamorphic angular distribution in angular space. Moreover, there is no need to use a baffle at the aperture stop in this novel design. We can reach a half-cone angle of 17.49° in the y direction of the angular distribution in angular space. The overlap angle is only 0.98°. Finally, with this novel design, we can achieve a high contrast ratio of 9128:1 and an illumination system efficiency is 66.4%. The four-corner average spot size at the active area of the digital micromirror device chip is controlled at about 240 µm, and the optical distortion is less than 1%. The corresponding lateral color aberration is 3.61 µm.

In this paper, we design a three-stage Fresnel lens concentrator with a low f number. The proposed concentrator consists of a primary optical element (POE) and a second optical element (SOE). The nine-sector three-stage Fresnel lens is composed of three types of triangular prisms: the refractive triangular prism, single total internal reflection triangular prism, and double total internal reflection triangular prism. In order to increase the uniformity and acceptance angle of the POE coupled to the SOE, the SOE is also divided into nine sectors. Finally, it is found that this nine-sector three-stage Fresnel lens concentrator can achieve a concentration ratio of 1000×; the uniformity is 25.8, optical efficiency is 81.8%, f number is 0.46, and acceptance angle is ±0.73°.

In this paper, we designed a three-zone multifocus hybrid Fresnel lens concentrator without a homogenizer. This concentrator uses three types of prisms: a refractive prism, a single total internal reflection (STIR) prism, and a double TIR (DTIR) prism. In order to achieve a uniform irradiance distribution, the Fresnel lens is cut into four quadrants and reconnected. Moreover, by decreasing the angle of the edge ray, the hot spot effects caused by the STIR and DTIR prisms can be reduced. Finally, the three-zone multifocus hybrid Fresnel lens concentrator can achieve a geometric concentration ratio of 2121X, f-number of 0.441, optical efficiency of 76.570%, acceptance angle of ± 0.268 ∘ , uniformity of 57.002%, and hot spot criteria of 1.369.

The efficiency balance phenomenon for see-through head-mounted displays with different microstructure conditions can be found both theoretically and using optical simulation software. A simple mathematical calculation is used to determine the relationship between the real image (see-through function) energy and the virtual image energy. The simulation is based on factors taken from previous research studies. It is found that the balance value of the optical efficiency remains almost constant (66.63% to 67.38%) under different microstructure conditions. In addition, suitable conditions for the microstructures in see-through head-mounted displays for daily applications can be predicted.

In this study, we design a Cassegrain-based concentrator with tailored mirrors. The proposed concentrator comprises a primary optical element (POE) and a secondary optical element (SOE). The POE is a parabolic concave mirror and the SOE is a hyperbolic convex mirror. In order to achieve uniform irradiance distribution without a homogenizer, the POE is tailored and tilted to generate a uniform distribution by overlapping the energy well. The Cassegrain-based concentrator with tailored mirrors can achieve a geometric concentration ratio of 1236 × , a concentration ratio of 1034 × , an optical efficiency of 83.66%, an acceptance angle of ± 0.38 ∘ , a uniformity of 7.87, and an aspect ratio of 0.254.

A low-aberration hole-patterned-electrodes (HPE) liquid crystal (LC) lens with positive and negative focal lengths is demonstrated in this Letter by using four hybrid-aligned nematic LC layers filled with dual-frequency LC materials. The diopter can be controlled from the positive lens ( 0 D ∼ 1.1 D ) to the negative lens ( 0 D ∼ − 1.25 D ). The aberration is analyzed using the Zernike polynomial, and the wavefront optical path difference is improved from 2 λ for the conventional one-layer HPE LC lens to less than 0.25 λ for our proposed LC lens. The proposed LC lens does not require the use of a polarizer, increasing the optical efficiency two times compared with the conventional LC lens.

Cold rollings for Al5182 aluminum alloy strips are carried out to evaluate the optical parameters with the applications of two lubricants and various operating conditions. In order to obtain these optical parameters, the fractal parameters which includes periodic lengths ( L x , L y ) and fractal dimensions ( D x , D y ) in the modified three-dimensional formula for the fractal surface morphology have been solved first for the rolled surfaces. This three-dimensional formula can provide an effective way to correlate these fractal parameters with the optical parameters using TracePro software, which can help to define rolling conditions efficiently for the specific demand of optical properties. The deterministic results for fractal surface simulations using MATLAB in series and 20° incident angle simulation in TracePro software explain that an increase in D x and D y will yield dense profiles which elevates the maximum illuminance and lower down the minimum illuminance. While an increment in L x and L y would increase the characteristic distance between two predominant asperities and increase minimum illuminance and decrease maximum illuminance. Finite element analyses prove that different friction coefficients in the upper and lower rolls potentially induce surface deflection and thus affect the optical properties. A high illuminance uniformity can be achieved by making a compromise among the fractal parameters ( D x , D y , L x and L y ) such that a small difference in the maximum and minimum illuminances is available.

A relay lens system design for a mini-projector with telecentric illumination is described. The reverse total internal reflection (RTIR) prism for angular magnification and lateral magnification is discussed in detail, and magnifications under different digital micromirror devices (DMD) are compared. The tilt-and-roll pixel (TRP) DMD chip (tilt angle is ± 17 ∘ ) is the latest spatial light modulator, and the f-number of the illumination system is 1.71. Using the TRP DMD, the lateral magnification and the angular magnification for the RTIR prism can be increased by 3.77% and 8.73% over that obtainable using the conventional DMD chip (tilt angle is ± 12 ∘ ). In order to solve for the angular magnification of an RTIR prism, the baffle is set at the aperture stop of the relay lens system. There is a trade-off between the efficiency and the contrast ratio with the baffle. When B (the position of the baffle) is at 0.11, the contrast ratio of the illumination system is 7590:1 and the efficiency is 57%. The spot size at the edge and corner of the DMD active area is controlled to be less than 250 µm, and the optical distortion is less than 1%.

An optical design for an immersive head-mounted display (HMD) with a liquid lens is described. This design combines the liquid lens with an immersive HMD system to improve the image quality for myopic and hyperopic users. A penta-prism is also incorporated and used to change the direction of the optical path to improve any optical aberration caused by the gravity effect. This immersive head-mounted display has a field of view of 14.9 degrees, focal length of 47.78 mm, and f-number of 5.97 with an exit pupil diameter of 8 mm, eye relief of 15 mm. The value of the MTF is above 0.9 at 3.3 lp/mm.

We proposed a speckle reduction system in the laser pico-projector. The holographic diffusers and the fast electrically tunable lens (FET lens) were adopted in the method of the speckle reduction. This research focuses on speckle reduction by the different divergence angle of the holographic diffusers. Moreover, the speckle contrast value can be further reduced by the fast electrically tunable lens. Different divergence angle of the holographic diffuser provides the different angular diversity to compare the speckle reduction ability. We propose three experimental methods to explore speckle reduction. In experiment 1, we use a holographic diffuser and the FET lens. The speckle contrast value can be reduced to 0.08353. In experiment 2, the speckle contrast value can be reduced to 0.06403 under the balance between power consumption and speckle reduction. In experiment 3, we adjust different waveforms to get lower speckle contrast value. Finally, the speckle contrast value is 0.048 at 400Hz. That is lower than 0.05 successfully. That caused the speckle phenomenon is undetectable by human eye.

In this paper, a novel light separator with contrast ratio enhancement but maintaining the optical efficiency of the DLP projection system is proposed. The main capability of the novel light separator is to direct the uncontrolled light away from the image system. The working theorem for the novel light separator is derived as well. Uncontrolled light is kept away from the image system by a total internal reflection surface, thereby effectively improving the image quality. Compared with previous work, the FO:FO contrast ratio can be improved from 46347:1 to 48250:1, the ANSI can be improved from 295:1 to 306:1, while the image system efficiency remains at 76.2%.

A see-through head-mounted display (HMD) with a compact size is designed, with a light guide plate system adopted to decrease the volume of the system. The key design feature of this invention is the see-through HMD which is based on a light guide plate with a trapezoidal microstructure. The proposed design is extremely compact compared to the conventional HMD system. The HMD serves as a near-eye viewing optical system that magnifies an image which is displayed through a microdisplay. Based on a 0.61 in. microdisplay, the HMD system has a diagonal field of view (FOV) of 30 degree and an ${\rm f}/\#$ of 3.66, with an exit pupil diameter of 8 mm and eye relief of 15 mm.

This study investigated the complex dielectric permittivity of freestanding multiwalled carbon nanotube buckypaper (MWCNT-BP) and a synthesized hybrid alumina-filled buckypaper (Al2O3-BP) composite with different alumina loadings (5–30 wt%). The non-destructive microwave transmission technique for complex permittivity determination involving cavity perturbation was employed to characterize a set of Al2O3-BP sheets. This was done by filling a rectangular cavity resonator with a standard dielectric Teflon sample and then performing permittivity measurements for the buckypaper (BP) samples in the X-band frequency range (7–12 GHz). Field-emission scanning electron microscopy (FESEM) was used to analyze the morphology of the MWCNT-BP and the alumina-loaded BP composites. DC electrical resistivity measurements clearly demonstrated conductor–insulator transition. The effect of alumina loadings on the dielectric properties of the synthesized hybrid Al2O3-BP sheet is discussed.

An optical design for a see-through head-mounted display with high visibility is described. This design, which is based on a light guide plate with triangular microstructures, can overcome the limitations of the balance in optical efficiency. The optical efficiency of the virtual image can be larger than the optical efficiency of the real image, which ensures high visibility. The visibility can be increased to 22 with this design, much higher than the visibility possible with previous designs for a see-through head-mounted display, making this suitable for daily application.

A newly designed non-telecentric projection zoom lens is proposed for a mini-projector with LED light sources. The projection lens consists of six spherical lenses. The zoom ratio of the projection lens is 1.1. At the wide condition, the working F/# can maintain at 2.4 and the throw ratio can operate at 1.23. The root mean square (RMS) spot sizes of all fields are smaller than 15 μm for all zoom ranges. The optical distortion and the TV distortion were suppressed to be smaller than 1.5% and 1%, respectively. For the image quality issue, the modulation transfer function (MTF) value for all fields is above 0.4 at 46 lp/mm for all zoom conditions. Even when the tolerance error was considered, the MTF value for all fields is still above 0.3 for all zoom conditions. Using this non-telecentric projection zoom lens, a very sharp image could be achieved with low cost. This low cost projection lens is very suitable for business applications.

A see-through head mounted display (HMD) with a compact size is designed, with a light guide plate system adopted to decrease the volume of the system. The key design feature of this invention is the see-through HMD which is based on a light guide plate with a trapezoidal microstructure. The proposed design is extremely compact compared to the conventional HMD system. The HMD serves as a near-eye viewing optical system that magnifies an image which is displayed through a microdisplay. Based on a 0.61 in. microdisplay, the HMD system has a diagonal field of view (FOV) of 30 degree and an f/# of 3.66, with an exit pupil diameter of 8 mm and eye relief of 15mm.

In this paper, we present a novel light separator with the ability to enhance the contrast ratio and maintain the optical efficiency in a digital light processing (DLP) projection system. The working theorem for the novel light separator is derived as well. In this novel light separator design, the ghost ray is directed away from the projection lens by a total internal reflection surface. Since the ghost ray does not even enter the projection lens, the contrast ratio enhancement is more effective than that achieved by an asymmetrical stop. Compared with the conventional method, the full-on/full-off (FO:FO) contrast ratio is increased from 921:1 to 46347:1 and the American National Standards Institute (ANSI) contrast ratio is increased from 177:1 to 295:1. The imaging system efficiency can maintain at 79.8% under the contrast ratio enhancement process.

This publisher's note amends the author listing in Appl. Opt.58, 122 (2019)APOPAI0003-693510.1364/AO.58.000122.

We proposed a novel backlight system, which consisted of a hybrid light guide plate (LGP) and one diffuser sheet. The hybrid LGP contains a flat plate without any microstructures and one layer of optically patterned film (OPF). Comparing with the conventional edge-lit backlight system, the on-axis luminance could be improved to 6.1 × by using the novel backlight system and the half-luminance angle decreased from 21 deg to 10 deg in vertical direction, and decreased from 21 deg to 6 deg in horizontal direction. At the same time, this design also achieved a uniformity of illumination of 89%. The design can predigest the fabrication and reduce the number of components. Moreover, since the microstructures arrangement was periodical, user could use light-emitting diodes (LEDs) on the both sides. When user turned on both side LEDs, the on-axis luminance were improved 1.7 × comparing with turning on single side LEDs.

The design of the LEDs lighting in general household illumination was proposed and compared with the fluorescent lighting in this study. Using the LED as a light source would promote energy saving lighting for household illumination purposes. We used the LightTools and DIALux software to design and simulate different standards of illuminance, different correlated color temperatures and different color rendering indices for household environments. The power consumption and efficiency of traditional illuminated light sources and an LED light source with the same standard of illuminance for lighting the household environment were analyzed and compared with each other. Finally, our results show the advantages of using white-light LEDs for lighting and household illumination.

We introduce a viewing angle switchable backlight module, which consists of a hybrid light guide plate and dual-light sources on the same layer. Comparing with the conventional backlight module, the on-axis luminance of the narrow viewing angle improved 4.9-times and the half-luminance angle decreased 11 degrees in the horizontal direction. When using the wide viewing angle mode, the on-axis luminance improved 2-times and the half-luminance angle improved 56 degrees in the horizontal direction.

This study employed roller imprint lithography and dry etching to fabricate patterned sapphire substrates (PSSs) of convex-shape with features of various heights. A soft polymer, polydimethylsiloxane (PDMS), was used as a mold to duplicate the pattern of a hard silicon template. The imprinted material was spin deposited onto a PDMS mold and transferred to the sapphire substrate using roller imprinting equipment. Inductive coupled plasma (ICP) etching was then used to fabricate the PSS. After epitaxial growth and chip processing, the current-voltage characteristics and light output of various LEDs were measured. The results demonstrate that the PSS process did not detract from the electrical properties of the LEDs; in fact, the output power of the proposed PSS LEDs was 25-30% greater than that of conventional LEDs. Simulation results show that PSS LEDs with structures of various heights would enhance optical efficiency in a manner similar to that demonstrated in these experiments.

This paper presents a periscope type 3X zoom lenses design for a five megapixel cellphone camera. The configuration of optical system uses the right angle prism in front of the zoom lenses to change the optical path rotated by a 90° angle resulting in the zoom lenses length of 6 mm. The zoom lenses can be embedded in mobile phone with a thickness of 6 mm. The zoom lenses have three groups with six elements. The half field of view is varied from 30° to 10.89°, the effective focal length is adjusted from 3.142 mm to 9.426 mm, and the F-number is changed from 2.8 to 5.13.

Generally, mobile phone use one camera to catch the image, and it is hard to get stereo image pair. Adding a biprism array can help that get the image pair easily. So users can use their mobile phone to catch the stereo image anywhere by adding a biprism array, and if they want to get a normal image just remove it. Using biprism arrays will induce chromatic aberration. Therefore, we design a double biprism arrays to reduce chromatic aberration.

The design of subretinal prosthetic devices including a self-powered implantable chip and an extraocular optical goggle is presented. Various optoelectronic and biological technologies are adopted in the device design to enhance both performance and biocompatibility. Experimental results and initial animal test results are described. Future development are also discussed.

In this paper, we design a single concentrator to homogenize and concentrate the solar energy. The proposed concentrator only consisted of an array of refraction prisms. In order to homogenize the irradiance, all pitches of the Fresnel concentrator focus on the different position of the receiver. Finally, the Fresnel lens that achieves the uniformity of U is 14.6. An acceptance angle of 0.305° is achieved without using additional secondary optics. Full Width at Half Maximum (FWHM) of illumination distribution is 1.4 mm.

We introduce a novel backlight module, which consists of a hybrid light guide plate (HLGP) and a brightness enhancement film (BEF). The HLGP comprises the functions of conventional light guide plate, reflector, and a BEF. The HLGP allows one-dimensional light to be collimated. We add an additional BEF above the HLGP, and let the crossed-dimension light to be collimated. Comparing with the conventional edge-lit backlight module, the total flux can improve 1.5 times and the on-axis luminance can improve 4.0 times by using the novel backlight module.

In this study, we demonstrated a simple method that can be used to simultaneously modulate the far field pattern and enhance the light extraction of GaN-based light-emitting diodes (LEDs). In this method, microstructures were imprinted on a reliable spin-on-glass surface on top of a transparent conductive layer. The far-field pattern was modulated using microoptical structures, and at the same time, the light extraction was enhanced owing to the small refractive index difference and surface roughness. There was no decrease in the electrical performance of these devices. The peak intensity shifted from 0 to 22° in one-dimensional (1D) asymmetrically blazed periodic structures, and a flattened distribution with a uniform intensity within a span of 110° was observed in two-dimensional (2D) symmetrically periodic structures. This method achieved 13 and 40% light enhancements for 1D and 2D structures, respectively.

We propose a high-efficiency directional backlight module (DBM) for automotive display applications. The DBM is composed of light sources, a light guide plate (LGP), and an optically patterned plate (OPP). The LGP has a collimator on the input surface that serves to control the angle of the light emitted to be in the horizontal direction. The OPP has an inverse prism to adjust the light emission angle in the vertical direction. The DBM has a simple structure and high optical efficiency. Compared with conventional backlight systems, the DBM has higher optical efficiency and a suitable viewing angle. This is an improvement in normalized on-axis luminous intensity of 2.6 times and a twofold improvement in optical efficiency. The viewing angles are 100° in the horizontal direction and 35° in the vertical direction. The angle of the half-luminous intensity is 72° in the horizontal direction and 20° in the vertical direction. The uniformity of the illuminance reaches 82%. The DBM is suitable for use in the center information displays of automobiles.

Light emitting diodes (LEDs) have numerous advantages as light sources in projectors. LEDs are more compact, exhibit a larger color gamut, have a longer lifetime, and need a lower supply voltage. However, there is still one important disadvantage: the optical power per unit of etendue (luminance) of an LED is significantly low. As a result of the etendue limitations of LEDs, the projected flux on the screen will not be high. Despite this shortcoming, LED’s are still of great interest for low power applications because of their other superior properties. Thus we collect the available light flux optimally and combine multiple high luminance LEDs within the system. In this study we discuss three collection systems designed to collect the LED flux with high optical efficiency while retaining small device size. The best collection efficiency attained with our collection systems is 96%. The fabrication tolerance and cost of our collection systems are also analyzed.

We propose a bilayer light guide plate (BLGP) with specially designed microstructures and two light source modules to achieve an adjustable viewing angle backlight for ecofriendly displays. The dual viewing angle backlight module has a thin, simple structure and a high optical efficiency. Comparison with the conventional edge-lit backlight module shows an improvement in the on-axis luminance of the narrow viewing angle mode of 4.3 times and a decrease in the half-luminance angle of 7° in the horizontal direction. When using the wide viewing angle mode, there is an improvement in the on-axis luminance of 1.8 times and an improvement in the half-luminance angle of 54° in the horizontal direction. The uniformity of illuminance can reach 80% in each mode. The backlight optical sheet number is reduced from 5 to 1.

In this paper, a novel light separator with contrast ratio enhancement but maintaining the optical efficiency of the DLP projection system is proposed. The main capability of the novel light separator is to direct the uncontrolled light away from the image system. The working theorem for the novel light separator is derived as well. Uncontrolled light is kept away from the image system by a total internal reflection surface, thereby effectively improving the image quality. Compared with the conventional contrast ratio enhancement method, the FO:FO contrast ratio can be improved from 839∶1 to 48250∶1, while the image system efficiency remains at 76.2%