An efficient and uniform illumination system with a freeform mirror for a color-sequential LCOS pico projector based on LED is proposed in this paper. The novel homogenizer is composed of a micro lens array and a freeform mirror. A freeform mirror with XY polynomial profile is adopted for the reshaping of light pattern, the correction of keystone distortion and the folding mirror for the reduction of volume. Typically, the design of micro lens array, the aspect ratio of the lenslet is corresponding with that of the panel. However, the crosstalk phenomenon occurs due to each lenslet with different collecting angle in horizontal and vertical direction, especially when the aspect ratio of the panel in our study is 16:9. The crosstalk phenomenon not only reduces efficiency but also generates stray light on the panel. Therefore, we use a micro lens array with square lenslet to eliminate it. Subsequently, the square light pattern on the panel needs to be reshaped to fit the aspect ratio of the panel. A cylindrical mirror with a fixed power is used to compress the light pattern first. However, for the requirement of different focal distances from the cylindrical mirror to the panel on entire surface, it generates severe keystone distortion. A freeform mirror with progressive power variation is employed for the correction of keystone distortion with high overfilled efficiency and the reshaping of the light pattern fitting the ratio of the panel. In the results of optical simulation, JBMA uniformity on the panel is 98 % and the coupling efficiency from LED to the plane of the panel is 85 %. Furthermore, the alignment tolerance of the freeform mirror has also been discussed. Finally, the freeform mirror is fabricated by ultra-precision diamond milling process. The form accuracy and surface roughness of the freeform mirror are less than 0.5 um and 5 nm, respectively.
In this research, ultra-precision slow tool servo (STS) diamond turning technique has been adopted to generate a
freeform surface. In the previous studied, we have developed a model of three-dimensional (3-D) tool shape
compensation for generating 3-D tool path in STS diamond turning of asymmetrically freeform surface. However, the
form error is not acceptable when the surface sagitta or tangential slope variation too large. Therefore, the surface form
error compensation method has been developed in this studied. The surface form error has been compensated from 3μm
to less than 1μm by the compensation method.
This research develops a precise hybrid optical micro-component (PHOMC) that includes polymer and glass materials.
Although glass offers better anti-thermal, anti-environmental, anti-scraped, anti-corrosive, and optical properties than
polymer materials do, glass materials are difficult to fabricate for microstructures. This research describes the fabrication
of a PHOMC, which retains the advantages of glass materials; in addition, the cost of microstructure polymers is lower
than for glass. In this study, polymers with micro sine waves can change the spot light intensity from a Gaussian
distribution to a line with uniform distribution. The glass base can protect the PHOMC to avoid damage from the
environment. First, the sine wave was designed using optical design software to change the light profile. A precise
diamond-turning technique was used to fabricate a mold with a sine-wave profile. A glass plate was used for the base of
the PHOMC. During the heating process, a thermosetting polymer was formed to match the sine-wave profile, and
covered the glass base. The PHOMC is 10 mm in diameter, and a sine wave with 100 μm in amplitude and 6.283 in
angular frequency was obtained. The surface profile of the PHOMC was evaluated using an ultra-precise laser confocal
microscope. Processing parameters, such as the forming temperature, are discussed in this paper. The PHOMC with the
sine wave that was developed in this study can generate a reference straight line for use in alignment, machine vision
systems, construction, and process control.
As the demand for precision optical components with sub-millimeter feature size steadily increasing, numerous efforts have been made in developing new techniques and in improving the existing approaches to efficiently and economically produce those components. Glass molding process (GMP) is one of these methods to enable mass production of precision glass optical components in recent years. One of the key issues in GMP is precision mold insert fabrication. Since the mould are normally made of hard and brittle materials such as tungsten carbide (WC) and silicon carbide (SiC), precision diamond grinding is by far the principal choice used to machine the GMP mould. As the feature size of optical component gets smaller, the size of mould and grinding wheel used to fabricate the mould gets smaller too. This makes the grinding process a very time consuming and expensive task. This research aimed to improve the small mold fabrication processes by developing an effective way of producing small diamond wheels and in-process monitoring wheel profile. Diamond wheels of around 0.2mm to 0.5mm in diameter after truing and WC aspheric mold insert of form accuracy around 0.47μm were successfully produced in this research.
The applications of AMLA (aspheric micro lens array) have been frequently required in opto-electro industries, such as optical communication, contact image sensor (CIS) module of scanner, wafer level optics, etc. In addition to the typical requirements of aspheric lens, for instance form accuracy and surface roughness, the pitch error of each micro lens has been highly required. Three ultra-precision freeform machining methods have been widely applied for the manufacturing of AMLA, namely fast tool servo, slow tool servo and diamond milling. UPDM (Ultra-precision diamond milling) have the advantage with no tool interference problem in comparison with tool servo machining techniques. In this paper, the tool setting error compensation method and the tool path of UPDM has been developed for the fabrication of a 5 by 5 AMLA model. The form accuracy and surface roughness of each lenses of the AMLA was less than 0.2μm and 5nm, respectively. And the pitch error of each micro lens was less than 2μm in 25 micro lenses.
The concept of the remote phosphor is proven to be one of the effective solutions for improving luminous efficacy of pc-WLEDs by solving the problem of phosphor thermal and scattering loss. However, most of them need to use larger packaging design to enhance their performance. Such development is adverse to market trends, which also resulted in higher manufacturing costs and the difficulties in luminaire design. In this paper, we present the analysis of pc-WLEDs as the function of the packaging size and figure out its limitation, so that we can apply to reduce the device size but keep the luminous efficacy as high as possible.
In this research, we propose a high performance non-image illumination module of pico-projector which includes light source, collimator and liquid crystal on silicon (LCoS) panel. The light source is RGB LED. The collimator consists of two glass collimator lenses and two double sides micro lens array (MLA) for light homogenizer. MLAs play a critical role in the LED illumination module. Dual double-side MLAs have been adopted for the homogenizer to satisfy the numerical aperture in the optical design. The good uniformity and high accuracy MLA structure was generated by ultra precision diamond shaping method and the MLA plate is subsequently fabricated by injection molding. Finally, a non-image illumination module with power efficiency 30.87 lm/w and uniformity of 56% on LCoS panel in a very compact size, less than 1.6 cm3 in volume, has been developed.
Three ultra-precision machining processes namely fast tool servo, slow tool servo and diamond milling, are frequently
used to produce optical freeform surface. Slow tool servo machining has the advantages of no extra attachment and fast
setting-up, however the three dimensional tool shape compensation and tool-path generation must be conducted carefully
for getting high form accuracy and fine surface finish. This research aimed to develop a model of three dimensional tool
shape compensation for generating 3D tool path in slow tool servo diamond turning of asymmetrically toric surface for
astigmatic contact lens. The form accuracy of freeform surface was measured by ultra-high accuracy 3D profilometer
(UA3P) with user define function. After correction, the form error is less than 0.5μm both in X- and Y-direction and the
surface roughness is less than 5nm.
The high filling factor double side micro lens array (MLA) for laser beam shaping has been widely applied in optoelectrical
applications. In this paper, we demonstrated the double side MLA for the laser beam shaping process. The
point laser source has been successfully transformed into a two dimension uniformity light imaging. The ultra-precision
slow tool servo (STS) diamond shaping and plastic injection method for MLA fabrication had been studied. The
complexity micro structure of high filling factor MLA via the planning of cutting tool path is used in this research. The
high alignment accuracy of both sides MLA is obtained by artful fixture design. The form accuracy and surface
roughness are less than 0.1μm and 10nm, respectively. The alignment error of both sides MLA is less than 10μm.
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