Throw Ratio Research Articles

Design and manufacturing technology of ultrashort-throw projectors with freeform mirrors

Ultrashort-throw projectors allow large screens in very limited space and without concerns about shadows that obstruct the image, which is the development trend of the projector industry. However, the technical problems of image distortion and uneven illumination restrict its industrialization development. The freeform mirror is the core component of the ultrashort-throw projection system, and the high-performance design method and corresponding manufacturing technology are the key factors of ultrashort-throw projectors to achieve rapid development. In this paper, the initial shape of the freeform mirror is designed by geometric construction with energy mapping. The ultrashort-throw projection imaging system model is established. After optimization, the throw ratio is 0.2, the projection screen is 80 inches, the total length of the projection lens is 155 mm, the field of view is 152 deg, and the edge illumination of the system is 97% of the center illumination. The assembly and adjustment method of the lens and the processing and coating method of the mirror are studied, and the experimental prototype is assembled and tested. This paper aims to establish the theory of freeform surface design and provide theoretical and technical support for the construction and system design of off-axis complex freeform surface.

基于自由曲面反射镜的低投射比超短焦投影物镜的光学设计

基于自由曲面反射镜的低投射比超短焦投影物镜的光学设计

Development of a parameterization image stitching algorithm for ultrashort throw laser MEMS projectors

AbstractWe present a novel design of a parameterization image stitching algorithm for ultrashort throw laser MEMS projectors. The resultant method allows the use of projectors with short or even long throw ratios to achieve ultrashort throw projection through a parameterized algorithm to stitch multiple images into one single frame, alleviating the trade‐off between the resolution and frame rate in conventional laser MEMS displays. To evaluate the effectiveness, we construct a test system that consists of three off‐the‐shelf projectors with a throw ratio of 1.3 and three planar reflective mirrors. Using our method, the integrated system yields an ultrashort throw ratio of 0.26, greatly reducing the projection distance from 12 to 2.6 ft for the 120‐in. screen in diagonal. Moreover, our algorithm can be fine‐tuned to correct for image distortion, intensity variation, and edge mismatch induced by two‐axis light beam steering, thereby further improving the image quality.

Design and engineering verification of an ultrashort throw ratio projection system with a freeform mirror.

A refractive-reflective combined ultrashort throw ratio projection optical system is designed. We use a freeform mirror to shorten the projection distance and correct distortion, and a plane mirror to turn back the optical path and reduce system volume. The projection system design method combines refractive lens group design and freeform surface mirror design with integrated optimization. The system's throw ratio is 0.11 with a projection distance of 320mm and a 130in. (1 in.=25.4 mm) screen size, which illustrates the advantages of the low throw ratio. The system's maximum distortion is 0.07%. To demonstrate the proposed system's performance, a prototype is developed. Experimental results confirm that the system performs excellently while meeting the design requirements. The system's advantages include low throw ratio, excellent imaging quality, miniaturization, and engineering feasibility.

Zoom projection lens design for small throw ratio and large field of view

In order to meet the requirements of large screen projection displays, we propose an ultra-thin zoom projection lens with a small throw ratio (TR), ultra-short throw distance and large field-of-view (FOV) using a digital micromirror device as a spatial modulator. A refractive–reflective system is developed to correct the distortion and shorten the projection distance. The image size (diagonal, 16:9 aspect ratio) of the projector is 80–120 in. (2.032–3.048 m) with a TR of 0.22, TV distortion < 0.6%, root mean square (RMS) spot size < 1.1 mm, relative illumination > 85% and modulation transfer function > 0.4 at 0.55 lp/mm for all fields and zoom conditions. When the tolerance error is considered, the RMS value is less than 1.3 mm for all fields and zoom conditions. Finally, the projection lens is fabricated and tested according to the designed model.

An ultrashort throw ratio projection lens design based on a catadioptric structure

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 UST lens are comprised of two parts. First, a catadioptric projection lens where the catadioptric function permits reaching an ultrashort throw ratio, short total track, while at the same time requiring fewer lens elements. The second part is a collimating lens which takes advantage of the telecentric condition to generate uniform total internal reflection (TIR) in the TIR prism. With this design, an effective focal length of -1.96 mm and a f-number of 2.4 can be obtained. The root mean square spot size and lateral colour of all fields are smaller than one pixel in size. The maximum optical distortion of −0.97% and TV distortion of 0.2% are acceptable. In terms of image quality, the modulation transfer function (MTF) values for all fields are above 0.65 at 0.245 line pairs/mm. Even when the tolerance error is considered, the MTF values for all fields are still above 0.3. The suitability of the novel UST lens design for projection applications is discussed.

Optical design of ultrashort throw liquid crystal on silicon projection system

An ultrashort throw liquid crystal on silicon (LCoS) projector for home cinema, virtual reality, and automobile heads-up display has been designed and fabricated. To achieve the best performance and highest-quality image, this study aimed to design wide-angle projection optics and optimize the illumination for LCoS. Based on the telecentric lens projection system and optimized Koehler illumination, the optical parameters were calculated. The projector’s optical system consisted of a conic aspheric mirror and image optics using either symmetric double Gauss or a large-angle eyepiece to achieve a full projection angle larger than 155 deg. By applying Koehler illumination, image resolution was enhanced and the modulation transfer function of the image in high spatial frequency was increased to form a high-quality illuminated image. The partial coherence analysis verified that the design was capable of 2.5 lps/mm within a 2 m×1.5 m projected image. The throw ratio was less than 0.25 in HD format.

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.

Multifield direct design method for ultrashort throw ratio projection optics with two tailored mirrors.

In this work, we present a multifield direct design method for ultrashort throw ratio projection optics. The multifield design method allows us to directly calculate two freeform mirror profiles, which are fitted by odd polynomials and imported into an optical design program as an excellent starting point. Afterward, these two mirrors are represented by XY polynomial freeform surfaces for further optimization. The final configuration consists of an off-the-shelf projection lens and two XY polynomial freeform mirrors to greatly shorten the regular projection distance from 2 m to 48 cm for a 78.3 inch diagonal screen. The values of the modulation transfer function for the optimized freeform mirror system are improved to over 0.6 at 0.5 lp/mm, in comparison with its rotationally symmetric counterpart's 0.43, and the final distortion is less than 1.5%, showing a very good and well-tailored imaging performance over the entire field of view.

Flat-Concave Dual-Mirror Configuration Design for Upright Projection-Type Ultrashort Throw Ratio Projectors

An off-axis flat-concave dual-mirror (FCDM) configuration for an ultrashort focal length projection lens based on the digital light processor (DLP) upright projection-type projector is proposed in this paper. This projection lens is composed of two lens groups: the FCDM system and the relay optical system. The flat mirror and the contour of the concave mirror are determined according to the relationship between the chief ray from the exit pupil of each field of view (FOV) and the corresponding assigned position on the screen. A curved image is formed between exit pupil and concave mirror, aiming to correct field curvature. The second lens group consists of a set of conventional refractive lenses which convert a curved object onto the image panel. Based on this method, a projection lens with an ultrashort throw ratio (TR) of 0.34, including a full FOV 139.8 $^{\circ}$ and distortion of less than 1%, is designed. Additionally, the colorimetric performance, uniformity, optical efficiency and size of the designed projector are analyzed. Results show that the proposed projector system with high optical performance is compact and suitable for household or educational applications.

Method to design two aspheric surfaces for a wide field of view imaging system with low distortion.

This paper presents a distortion correction method for designing a wide field of view (FOV) lens for an imaging system. The lens is composed of two aspheric surfaces and several spheres. In the preliminary design, profiles of the aspheric surfaces can be obtained according to aplanatism, refraction law, and polynomial fitting methods, where the numeric computation, the differential geometry computation, and the polynomial fitting algorithm are stated in detail. Then the lens is optimized by the damped least squares method. Theoretically, this method cannot eliminate aberrations absolutely but can balance some kinds of aberrations to the image well. Furthermore, a projector lens with a wide FOV, low distortion, and low throw ratio [TR = (projection distance)/(image diagonal size)] is designed successfully by this method.

超短投影距的投影物镜设计

超短投影距的投影物镜设计

Field curvature correction method for ultrashort throw ratio projection optics design using an odd polynomial mirror surface.

This paper presents a field curvature correction method of designing an ultrashort throw ratio (TR) projection lens for an imaging system. The projection lens is composed of several refractive optical elements and an odd polynomial mirror surface. A curved image is formed in a direction away from the odd polynomial mirror surface by the refractive optical elements from the image formed on the digital micromirror device (DMD) panel, and the curved image formed is its virtual image. Then the odd polynomial mirror surface enlarges the curved image and a plane image is formed on the screen. Based on the relationship between the chief ray from the exit pupil of each field of view (FOV) and the corresponding predescribed position on the screen, the initial profile of the freeform mirror surface is calculated by using segments of the hyperbolic according to the laws of reflection. For further optimization, the value of the high-order odd polynomial surface is used to express the freeform mirror surface through a least-squares fitting method. As an example, an ultrashort TR projection lens that realizes projection onto a large 50 in. screen at a distance of only 510 mm is presented. The optical performance for the designed projection lens is analyzed by ray tracing method. Results show that an ultrashort TR projection lens modulation transfer function of over 60% at 0.5 cycles/mm for all optimization fields is achievable with f-number of 2.0, 126° full FOV, <1% distortion, and 0.46 TR. Moreover, in comparing the proposed projection lens' optical specifications to that of traditional projection lenses, aspheric mirror projection lenses, and conventional short TR projection lenses, results indicate that this projection lens has the advantages of ultrashort TR, low f-number, wide full FOV, and small distortion.

Adsorption of Methylene Orange on Embedding Carbon Nanotubes Sodium Alginate /Chitosan Gel Beads

This study focused on the carboxylation method on multiwalled carbon nanotube (MWCNT) structure and property. The applicability of a novel adsorbent, the SA/MWCNT-CTS composite were obtained by controlling the reaction conditions. The SA/MWCNT-CTS composite was applied to the absorption of methyl orange (MO) from simulated dye wastewater .Adsorption dynamics and thermodynamics of SA/MWCNT-CTS microspheres were examined by UV-visible spectroscopy, and the associated adsorption mechanism was preliminarily investigated. Changes in the absorbance, throw ratio, conductivity, and the pH value of MO solution of MO solution during adsorption by SA/MWCNT-CTS microspheres were also studied. Results showed that the prepared SA/MWCNT-CTS microspheres retained excellent inherent chemical stability and had strong MO adsorption capacity. CS contains many hydroxyl groups, which are involved in the adsorption of organic dye. The adsorption process had a negative value of free energy change (∆G0); therefore, the process was a spontaneous reaction. At lower MO equilibrium concentrations, the SA/MWCNT-CTS microspheres had a greater capacity for adsorption.

Adsorptive removal of methyl orange from aqueous solution with crosslinking chitosan microspheres

Chitosan (CS) microspheres were successfully prepared via emulsion polymerization using biodegradable chitosan as raw material and glutaraldehyde as crosslinking agent. Micron-scale monodisperse CS microspheres were then obtained by controlling the reaction conditions. Simulated dye wastewater, containing methyl orange (MO), was examined for the adsorption dynamics and thermodynamics of CS microspheres by UV–vis spectroscopy, and the associated adsorption mechanism was preliminarily investigated. Changes in the absorbance, throw ratio, conductivity, and dissolved oxygen content of MO solution during adsorption by CS microspheres were studied, and the chemical structures of CS microspheres before and after MO adsorption were characterized by Fourier transform-infrared spectroscopy. Results showed that the prepared CS microspheres retained excellent inherent chemical stability and had strong MO adsorption capacity. CS contains many hydroxyl groups, which are involved in the adsorption of organic dye. The adsorption process had a negative value of free energy change (ΔG°); therefore, the process was a spontaneous reaction. At lower MO equilibrium concentrations, the CS microspheres had a greater capacity for adsorption.

티타늄합금 코팅된 자동차 부품의 마모특성 향상에 관한 연구

본 논문에서는 박막코팅기술의 공정은 고경도 박막과 질화층의 접합력을 높이기 위하여 적용하였다. 이 박막코팅기술은 프레스 금형에 사용되는 경도와 인성을 얻을 수 있는 복합 박막을 형성했다. 이러한 박막 코팅 생산 기술은 물리증착방법을 이용하여 진공 챔버의 진공도를 증가하고, 건파워의 투사율을 향상시켰다. 티타늄합금 타겟은 각종 정밀가공 부품에 복합박막코팅기술 개발을 통하여 성능과 표면재질을 개선하였다. In this paper, The process of thin-film coating technology was applied to improve adhesion of the hardness thin film and nitride layer. This thin-film coating technology have formed composite thin-film to gain hardness and toughness used in press mold. The thin-film coating manufacturing technology increased vacuum present in the vacuum chamber and improved the throw ratio of the gun power using physical vapor deposition coating technology. Ti alloys target improved performance and surface material through the development of a composite film coating technology for various precision machining parts.

Fast-Response Blue-Phase Liquid Crystal for Color-Sequential Projection Displays

Color sequential projection display using a vertical field switching (VFS) polymer-stabilized blue phase liquid crystal (BPLC) is proposed. The VFS-BPLC exhibits submillisecond response time which is useful for suppressing color breakup. The proposed projector also has a small throw ratio. With phase compensation, the distortion from oblique LC panel could be corrected.

High‐efficiency optical system for ultra‐short‐throw‐distance projector based on multi‐laser light source

Abstract— A novel laser‐light‐source projector having the three outstanding features of high brightness, ultra‐short throw distance, and high color reproduction has been developed.These features have recently come to be required in the high‐end projector market. The technologies for the laser‐light‐source projectors fully utilize the advantages of lasers, such as high luminance, small étendue, and high color purity. By integrating a triple‐rod illumination system with a multi‐laser light source and an ultra‐wide‐angle projection system, the developed high‐efficiency optical system has achieved a brightness of 7000 lm and a throw ratio of 0.28 with an image size of 100–150 in. Another new technology, laser color processing (LCP), has offered vivid color reproduction which has a color gamut that is up to 180% wider than the BT.709 standard without appearing unnaturally colored. Furthermore, a speckle suppression effect produced by the multi‐laser light source has been demonstrated. In this paper, an overview of these newly developed technologies that are used in the novel laser‐light‐source projector is presented, and solutions to the issues of speckle noise and safety are presented.

65.3: Distinguished Paper: High Efficiency Optical System for Ultra‐Short Throw Distance Projector Based on Multi‐laser Light Source

AbstractWe have developed a high‐efficiency optical system that uses multiple lasers as a light source. This optical system enables us to produce a novel laser projector with a high brightness and an ultra‐short throw distance. By utilizing the advantages of a laser, we have achieved a brightness of 7,000 lm and a throw ratio of 0.28 with an image size of 100–150 inches.

Combustion, fire, and explosion in nature - some biomimetic possibilities

In the current paper, three areas involving fire and/or explosions in nature are explored: (a) the knobcone pine, (b) the scotch broom seed, and (c) the combustion chamber of the bombardier beetle. Each is described and some possible biomimetic applications of each of these are discussed. The knobcone pine has a high temperature controlled unique gas emission insulating system. The Scottish broom has a mechanical, humidity controlled propulsion device for dispersing its seed, and the bombardier beetle has a mass ejection system which enables the propulsion of a liquid/gas mixture to a throw ratio of 200 times its own characteristic length. The biomimetic applications in each of these examples lie in the area of fireproofing (knobcone pine), propulsion (scotch broom), and mass ejection devices such as in reigniters for gas turbines (bombardier beetle).