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This paper proposes both symmetrical and asymmetric Y-junctions with arc-bend branch structures for auxiliary indoor-illumination applications. These arc-bend branch structures can be used as a concave-mirror-like light guide, to change the direction of beam propagation and also to converge the beam spread angle. Optical simulation results show that the proposed arc-bend Y-junctions can achieve an inner coupling efficiency, not including plastic/air interfaces, above 90% in both usages: beam combiner and splitter. Particularly, when the applied branch opening angle becomes large, this high optical efficiency becomes more significant than those of linear straight Y-junctions. Moreover, it is also confirmed that the coupling efficiency of the symmetric arc-bend junction can be as high as 90.0%, and the asymmetric coupling efficiency is 93.4%, even if the branch opening angle is quite large.

The objective of this study is to develop a measurement system for blue light blocking lens. The main features of the system are using a light pulse modulator and filtering circuit technology to prevent ambient light interference, no any expensive optical filters are needed. Our system is composed of a transmitter circuit, a receiver circuit and a signal processing circuit. The transceiver driving circuit including the modulated LED of 10 kHz and measured the light signals from unwanted noise and unmodulated all light by a photodiode, and then converted by the transimpedance amplifer. The transmitter circuit uses Darlington drive circuit to optimize the LED operating current. The percentage error of the transmittance data is nearly 6%, compared with that of the OCEAN USB 2000 spectrometer's, so proved that this device is feasibility. This experiment has also shown that the chromaticity coordinates will be changed when using blue light lens. Based on the experiment, the brightness of the blue light blocking lenses cannot be too low which will cause color deviation problems. From the analysis result in table 4, the color deviation is nearly 17% at green blocking blue light lenses and 21% at yellow blocking blue light lenses on y coordinates. Therefore, these two blocking blue light lenses are not suitable for use as blue light blocking lenses. The color deviation of coated blue film and brown 20% blocking blue light lens have nearly 3% on x-y coordinates. But, those of 8% in 30% brown and 17% in green lenses are also not suitable for blue light blocking lens using. Thus the most suitable for blue light blocking lenses using is 20% brown blocking lens. In the future, this proposed device may be used as a powerful measurement tool on the eyeglasses test line.

Relay lens is the lens used for transfer an object to the intermediate image plane or directly to enlarge or reduce the object with some magnifications. The design addressed in the study is to reduce an 1mm2 object to 0.5mm image spot size. A Gaussian image theory helps to investigate the initial configuration and potential solutions. The final design reaches high image performance.

Alvarez lens is one of the free form lens designs. After optimized, the focusing distance curve of Alvarez lens keeps smoothly when Δd increased. We also found the effects of the affective factors, and the good performances of geometric image and illumination surface analysis.

Seidel aberration has been used successfully in finding starting points for a lens system, especially in designing a relay lens, which may have the symmetric condition with aperture stop, and the benefit of zero Seidel aberrations of com, distortion, and transverse chromatic aberration. In this paper, a relay lens has been designed based on the principle of zero Seidel aberrations. The MTF of the design is near diffraction limited, which has an excellent image performance of high resolution.

A fisheye lens, which contains eight glass materials and 180-degree field-of-view, has been designed. The values of MTF have over 40c/mm@216c/mm for all fields. Eight lens glasses can be divided into two groups, which are four aspheric lenses and four spherical lenses.

An 110-degree field of view objective for endoscope has been designed. It contains 4 lenses and has 0.9 relative illuminations. The axial MTF value reaches 0.4 @ 200 c/mm and the relative distortion is less than 29%.

An enlarging lens, composed of a charge-coupled-device (CCD) lens and an f-Θ lens, has been designed for real time laser lithography visual inspection purposes. The object of this design is to enlarge the image of the working specimens in real time, which used to be done by an independent magnifying system after the lithography process. F-Θ lens has both roles in this design, being a laser lithography lens and a specimen imaging lens. A beam splitter has been inserted between the f-Θ lens and the CCD lens, which divides the UV laser beam and the visible beam to form a coaxial system. This design also reaches the image requirements in both wavelength bands, that the value of MTF is nearly diffraction-limit in UV wavelength and greater than 0.45 at 40 c/mm in visible wavelength.

When UV-curable material is used with a spherical glass lens, it is classified as a hybrid lens and can provide a new degree of freedom in designing a lens system. This method is used to explore the optical limitation of an ultrawide-angle imaging system of a folded structure, which is utilized to achieve a compact volume. The f-number and field of view of the system are 2.0 and 190°, respectively. Diffraction-limited performance is achieved within a field of view of 80° with Strehl ratios greater than approximately 80%. Even at the maximum field of view of 190°, the Strehl ratio is nearly 75%. The lens configuration is NNPNN, where N and P denote negative and positive optical power, respectively; this configuration uses only two aspherical hybrid lens surfaces. Comparisons of different optimizations are also provided.

An internally focusing design is developed for a compact endoscopic lens to have optical performance close to the diffraction limit. When changing the working distance from infinity to a predetermined short distance, the overall system length and the field of view remain constant. It is numerically demonstrated that the diffraction-limit-like performance is maintained over a wide range of working distances, showing a novel capability of adjustable focuses. The design concept is numerically proven to be feasible and can enable very high-resolution examination for doctors checking the positions of biological entities through the immediate capture of clear images at different working distances. The corresponding lens configuration, PNN, is shown to be useful in achieving the high-resolution performance once the number of lens elements is four, where P and N are used to denote positive and negative optical power, respectively, for the lens groups. A corresponding tolerance analysis is also presented.

A duplex Y-branch coupler for plastic optical fibers is studied in this paper. Two high efficient structures with different spirals are constructed, and achieve coupling efficiency both in forward and reverse directions greater than 93%.

The wide-angle lenses, which apply four pieces of glass lenses with the angle of view 100 degree, the distortion controlled within 40%, and MTF in the angle of view above 40lp/mm

A lens design method based on prescribed candela distribution is presented. By using this method, an LED lens of arbitrary beam angle can be obtained with uniformity greater than 0.8 and optical efficiency above 90%.

In many photovoltaic (PV) or sunlight-illumination systems, solar trackers are always essential to obtain high energy/flux concentration efficiency, and that would lead to increase cost and extra power consumption due to the complex structure and heavy weight of the trackers. To decrease the cost while without sacrificing efficiency, a Fresnellens concentrator incorporated with a simple and cheap shutter, which consists of high reflective mirrors instead of conventional trackers, is proposed in this paper to provide solar tracking during the daytime. Thus, the time-variant and slant-incident sunlight rays can be redirected to vertically incident upon the surface of the Fresnel lens by appropriately arranging mirrors and swinging them to the proper slant angles with respect to the orientation of sunlight. The computer simulation results show that power concentration efficiency over 90%, as compared with the efficiency of directly normal incident sunlight, can be achieved with the mirror reflectance of 0.97 and for any solar incident angle within ±75 degrees to the normal of the Fresnel lens. To verify the feasibility and performance of the concentrator with the proposed shutter, a sunlight illumination system based on this novel structure is demonstrated. Both computer simulation and practical measurement results for the prototype of the sunlight illumination system are also given to compare with. The results prove the simple and high efficient shutter applicable to general PV or sunlight-illumination systems for solar tracking.

An LED panel lamp is presented for general indoor illumination. This lamp consists of arrayed LED light sources with each LED united with an evening lens so that the Lambertian distribution of LED light is altered, and the illuminance on a target plane can be uniform. The computer simulation result shows that the illuminance uniformity is 0.737, and the maximum illuminance is 140 lx on a detecting screen at 1.5 m away.

This paper presents a free-form lens design for indoor illumination. The lens consists of a TIR (total internal reflection) surface on the sidewall, a refractive surface on the front side, and a concave surface on the rear side. The TIR surface is decorated with a free-form profile that light rays emitted from the LED with a larger spread angle to the axis will experience a total internal refection and output from the front refractive surface. While the central part of the front refractive surface has a convex surface that makes light rays closing to the optical axis more evenly distributed. The purpose of the rear concave surface is to let light rays emitted from the LED enter the lens straightforwardly. With this lens light rays from a Lambertian-type LED light source can be redistributed so that a uniform illumination can be achieved. The optical simulation results show that the measured optical efficiency is 75% while the uniformity is 80% on a target plane of 6-m diameter and at 2.5-m away.

A simple approach is presented to design an LED lighting module to provide a uniform illumination. The reflector of the module is designed using a prescribed candle-power distribution to achieve a uniform illumination on a target surface. Both the design methodology and the construction of the reflector are stated in detail. The optical efficiency and uniformity of the module are calculated according to a ray-tracing result. In addition, the effects of the reflector's aperture and the LED chip size on the optical efficiency and uniformity are also investigated that the result can provide a reference to LED-luminaire designers and manufacturers.

A novel design of direct LED backlight is presented. The module is composed of white light LEDs, parabolic reflectors and novel lens caps. The predicted uniformity is up to 92%.

A novel vehicle headlamp structure is presented. It delivers light rays from plural LEDs via a fiber to the headlamp to form a legal low-beam pattern with a predicted optical efficiency of 45%.

A freeform lens design method based on energy mapping and complementary optimization approaches is proposed to achieve uniform illumination with extended light-emitting diode (LED) sources. This method is primarily derived from a simple source–a target energy mapping approach, while a complementary illuminance on the target plane is introduced to optimize the primary axisymmetric lens so that the profile of the lens can be reformed to produce uniform illumination when applying an extended LED source. By using this optimization method, the illuminance uniformity and optical efficiency of the lens can be improved, respectively, from 0.56 to 0.85 and from 92.4% to 94.3% for an LED light source with chip diameter of 8.9 mm, while the aspect ratio of the lens clear aperture to the source diameter is only 3.8.

We present a freeform lens for application to LED uniform illumination. This lens, which is designed with a method of simple source-target luminous intensity mapping, can produce irradiance uniformity of greater than 0.8 and optical efficiency above 90% with an arbitrary half-beam angle greater than 45 deg. Typically, as compared with a conventional source-target energy mapping method, this design method can achieve better optical performance of lenses for general LED lighting. When a non-Lambertian-type light source is employed, for example, the chip on board LED, the use of the method can result in a compact LED lens without losing the optical performances of high irradiance uniformity and high optical efficiency as yielded by lenses for Lambertian-type LED light sources.

Sample tracking with a high spatial sensitivity is highly desired in force measurement with optical tweezers. However, the trick that sample tracking via forward scattering pattern detection would provide a higher sensitivity than that via regular image detection has never been investigated. In this paper, we systematically study the influences of the position and the numerical aperture of the condenser on sample tracking via forward scattering pattern detection. In our experiment, a 60X condenser is used to form the forward scattering pattern of a sample bead upon a CCD camera. As the bead is transversely shifted at a step size of 30nm by a PZT XYZ stage, we measure the magnitude of the corresponding shift of the forward scattering pattern when the 60X condenser of different angular apertures is placed at various locations along the optical axis. Our result shows that the most sensitive forward scattering pattern occurs when the condenser collimates the forward scattering light from the sample bead. We also find that the larger the numerical aperture is, the higher the sensitivity of forward scattering pattern detection will be.

Optically compensated refractive zoom lenses use lens groups which are mechanically coupled at a fixed separation, moving between another set of fixed separation lens groups. Such systems exhibit an image position which oscillates about a mean focal plane as the lens is zoomed. These systems are simple to implement mechanically, but they have the disadvantage that they are bulky compared with equivalent mechanically compensated zoom lens types. In a catadioptric optical system we can exploit the same sort of mechanism by moving lens groups placed between (catadioptric) mirrors, and in this case the overall system can be compact. The simplest form of system of this type consists of one lens and one mirror and this has similarities to a three-lens optically compensated refractive zoom system. In this paper the first order analysis of optically compensated catadioptric systems is given and the design of some simple representative systems are developed.

A tunable single-pair hollow-beam-converter (TSHBC) dark-field microscopy is proposed and fabricated. The TSHBC is composed of one pair of parallel reflective mirrors of complementary cone shape. By simply adjusting the longitudinal separation between the two mirrors of TSHBC, a dark-field image with more high contrast and high energy efficiency can be obtained for a given objective lens. Furthermore, the selection criteria of the condenser lens and objective lens are provided for the structure of an optimal dark-field microscopy with TSHBC.

Reflective optical surfaces offer lower aberrations than the equivalent refractive optical components and they are also free of chromatic aberrations; so the use of reflective surfaces in zoom systems should lead to better performance than the equivalent refractive systems. This is clearly a naive view because it ignores the problem of central obstruction and also the very low level of complexity of a reflective zooming group (at least notionally a single surface). On this bases we have exploited the additional complexity that Mangin or back-reflective mirrors offer, showing how a high degree of correction over a modest zoom range may be achieved with remarkably compact constructions.

The two-group zoom lens is the simplest arrangement which is capable of achieving a modest useful zoom range and adequate aberration correction for practical implementation. The first order layout of these systems is straight-forward and the real battle that has to be fought is to balance the effects of vignetting and aberration stability. This paper reviews the `+-' type, the `-+' type and shows how the quality of the overall performance evolves with the redistribution of aberration correction between the two groups of the zoom system, finishing with the analysis of a practical system which uses a relatively complex construction to achieve high performance.

We present a simple freeform lens design method for an application to LED collimating illumination. The method is derived from a basic geometric-optics analysis and construction approach. By using this method, a highly collimating lens with LED chip size of 1.0 mm × 1.0 mm and optical simulation efficiency of 86.5% under a view angle of ± 5 deg is constructed. To verify the practical performance of the lens, a prototype of the collimator lens is also made, and an optical efficiency of 90.3% with a beam angle of 4.75 deg is measured.

A fiber-and-LED-based vehicle headlamp is presented in which light rays emitted from multiple high-power LEDs are gathered using a light collector and then guided into a projector lamp via an optical fiber. This proposed headlamp is intended to reduce the lamp size and the heat-dissipation problem simultaneously. Detailed geometric analysis of the headlamp is given, and the optical efficiency for each component part is also calculated using a TracePro program. The computer simulation results show that the headlamp can produce a legal Economic Commission for Europe low-beam pattern with a total optical efficiency up to 49.4%, and only eight 5-W LEDs (120 lm each) are required.