Compact single-panel LCD projector with high uniformity.

In this study, we introduce a single-panel LCD projector that employs a direct-lit LED array as its illumination system. Each LED in the array is coupled to a Fresnel lens to ensure light collimation. To create a uniform light distribution on the LCD panel, the LED array is arranged in a hexagonal pattern. To eliminate the hotspot effects caused by individual LED units, the optical distance between each unit and the LCD panel is extended to allow sufficient light mixing. Köhler illumination is adopted to generate adequate and homogeneous illumination on the screen. With these design enhancements, we managed to shrink the system by 29% of the traditional designs and increase uniformity to 90.1%.

Prediction of surface roughness in different machining methods using a texture mask feature extraction method: publisher's note.

This publisher's note corrects errors in Appl. Opt.61, 10637 (2022)APOPAI0003-693510.1364/AO.475290.

Prediction of surface roughness in different machining methods using a texture mask feature extraction method.

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.

High-contrast ratio and high-efficiency anamorphic DLP illumination system design with a freeform surface lens.

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.

Circularly polarized optical microscope using a low aberration liquid crystal lens.

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 -5.0D, and the wavefront optical path difference is less than 0.25λ 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.

Three-zone multifocus hybrid Fresnel lens concentrator.

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.

High speckle reduction rate in a laser projection system.

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.

Cassegrain-based concentrator with tailored mirrors.

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.

Low-aberration liquid crystal lens with positive and negative focal length.

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 (0D∼1.1D) to the negative lens (0D∼-1.25D). The aberration is analyzed using the Zernike polynomial, and the wavefront optical path difference is improved from 2λ for the conventional one-layer HPE LC lens to less than 0.25λ 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.

Designing an anamorphic illumination system with an RTIR prism for a tilt-and-roll-pixel-type projector.

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 ${\pm 17}^\circ $±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 ${\pm 12}^\circ $±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%.

Nine-sector three-stage Fresnel lens concentrator: publisher's note.

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

Nine-sector three-stage Fresnel lens concentrator.

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°.

High-efficiency directional backlight design for an automotive display.

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.

Speckle reduction using deformable mirrors with diffusers in a laser pico-projector.

We propose a design for speckle reduction in a laser pico-projector adopting diffusers and deformable mirrors. This research focuses on speckle noise suppression by changing the angle of divergence of the diffuser. Moreover, the speckle contrast value can be further reduced by the addition of a deformable mirror. The speckle reduction ability obtained using diffusers with different divergence angles is compared. Three types of diffuser designs are compared in the experiments. For Type 1 which uses a circular symmetric diffuser the speckle contrast value can be decreased to 0.0264. For Type 2, the speckle contrast value can be reduced to 0.0267 because of the inclusion of an elliptical distribution diffuser. With Type 3 which includes a combination of the circular distribution diffuser and elliptical distribution diffuser, the speckle contrast value can be reduced to 0.0236. For all three types, the speckle contrast value is lower than 0.05. Under this speckle value, the speckle phenomenon is invisible to the human eye.

Non-telecentric projection lens design for an LED projector.

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.

Optical design for a see-through head-mounted display with high visibility.

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.

Simulation of autofocus lens design for a cell phone camera with object distance from infinity to 9.754 mm.

This paper presents the simulation of an autofocus lens design with large depth of field for a cell phone camera. The object distance of the lens is from infinity to 9.754 mm. When the object distance is from infinity to 550 mm, the value of the modulation transfer function (MTF) is greater than 0.6 for the spatial frequency of 114 lp/mm, the optical distortion is less than 1.5%, and the relative illumination is greater than 67%. When the object distance is from 325 to 9.754 mm, the MTF values is greater than 0.4 for close-up shooting. The optical distortion is less than 1.454%, and the relative illumination is greater than 68.8%.

Dual-view angle backlight module design.

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.

Dual view capsule endoscopic lens design.

A dual view capsule endoscopic (DVCE) lens is proposed with front view and back view functions. This is a hybrid lens with a catadioptric mirror and an aspherical surface to support both view functions. The field of view (FOV) for the front view function is 90 degrees. The FOV for the back view function is 260 to 290 degrees. The TV distortion for the front view and back view function is under 30% and 25%. The corner relative illuminations for the two view functions are above 0.53. The Modulation Transfer Function (MTF) performance at the Nyquist Frequency for the two view functions can be kept above 0.35, even under tolerance they can remain above 0.2. Moreover, the telecentric conditions at the image plane of the DVCE system can support constant magnification through focusing. This condition can reduce the measurement error by slightly defocusing of the lens. Thus, the two view functions can offer physicians a wide viewing angle to deal with lesions over the fold.

Simulation design of a wearable see-through retinal projector.

This study proposes a new simulation design for a wearable see-through retinal projector combined with a compact camera. The see-through retinal projector is composed of an illumination system and eyepiece system. In this eyeglass-mounted design, all the information is projected directly into the user's eyes using a see-through retinal projector. The retinal projector forms a 20 in. (50.8 cm) upright virtual image located 2 m in front of the human eye, and the illumination system provides uniform illumination for liquid crystal on silicon (LCoS) panels. Moreover, an RGB LED array is used as the light source to generate color images with color sequences. The compact camera has a lens with an aperture of F/2.8, a half field-of-view (FOV) of 30°, and 2 million pixels. This optical system design with the combination of a see-through retinal projector and a compact camera has a volume of about 5.83 cm(3) and a weight of 6.02 g.