The design and fabrication of the ultra-miniature microlens array homogenizer using two-photon polymerization is presented in this paper. The flat-top laser beam shaper includes refractive type, diffuser type and microlens array homogenizer. The drawback of the refractive and diffuser type is that the uniformity on the homogenization plane is associated with the laser Gaussian beam profile. However, the microlens array homogenizer is independent of laser beam profiles. Therefore, the microlens array is employed for the laser beam shaper in this study. In the simulation, the incident Gaussian elliptical laser beam is successfully transformed into a homogenized rectangular distribution by the microlens array homogenizer. Because the flat-top beam distribution is in the range of micrometer (μm) level in this study, the pitch of the microlens array is reduced to tens of microns, which is not suitable for general machining. Therefore, 3D printing using two-photon polymerization fabrication without tool interference issues is utilized. Finally, the microlens array homogenizer is successfully fabricated. The ultra-miniature flat-top laser beam shaper can accomplish a uniform rectangular distribution of 220 μm X 300 μm, which can be applied for high precision applications such as laser processing, laser medical, and laser display.
KEYWORDS: Confocal microscopy, Imaging systems, Tomography, Tissues, Image resolution, Data storage, Super resolution, 3D imaging standards, 3D image processing, Luminescence
Confocal microscopy has been a standard tool to acquire 3D fluorescence biological images at sub-micron resolution. The scattering effects in turbid tissue and the specifications of high N.A. objective lens limit the image dimensions, so the confocal microscopy frequently provides images for micro-anatomy. However, the high quality large volume tomography is still desired to provide correlative images between micro- and macro-anatomy. In this presentation, we extend the dimensions of micro-image at single-cell resolution from tens micrometer levels to multi-millimeter levels by integrating steps of tissue clearing, vibratome sample sectioning, stepper image stitching, and confocal imaging techniques, and we named this system as Serial Tiled-Z axial (STZ) tomography. Mapping the whole-body connectome, a wiring diagram of the entire nervous system is the first application of STZ tomography and provides the whole body neural circuits for governing internal body functions and external behaviors. STZ tomography generates high-resolution in situ datasets for accurate registration of structural and functional data collected from different individuals into a common three-dimensional space for big data storage, search, sharing, analysis, and visualization. Inserting a super resolution module, STZ tomography opens the door to super resolution imaging of routine systematic neuroanatomy of large tissues, such as the whole mouse and human brain. The second application is to map tumor tissue samples which are free from distortion problem from dehydration in the H&E protocol.
The design of the ultra miniaturized camera using 3D-printing technology directly printed on to the complementary metal-oxide semiconductor (CMOS) imaging sensor is presented in this paper. The 3D printed micro-optics is manufactured using the femtosecond two-photon direct laser writing, and the figure error which could achieve submicron accuracy is suitable for the optical system. Because the size of the micro-level camera is approximately several hundreds of micrometers, the resolution is reduced much and highly limited by the Nyquist frequency of the pixel pitch. For improving the reduced resolution, one single-lens can be replaced by multiple-aperture lenses with dissimilar field of view (FOV), and then stitching sub-images with different FOV can achieve a high resolution within the central region of the image. The reason is that the angular resolution of the lens with smaller FOV is higher than that with larger FOV, and then the angular resolution of the central area can be several times than that of the outer area after stitching. For the same image circle, the image quality of the central area of the multi-lens system is significantly superior to that of a single-lens. The foveated image using stitching FOV breaks the limitation of the resolution for the ultra miniaturized imaging system, and then it can be applied such as biomedical endoscopy, optical sensing, and machine vision, et al. In this study, the ultra miniaturized camera with multi-aperture optics is designed and simulated for the optimum optical performance.
Laser interference lithography (LIL) is a maskless lithography technique with many advantages such as simple optical design, low cost, maskless, infinite depth of focus, and large area patterning with single exposure. Compare to the tradition optical lithography, LIL is very suitable for applications which need periodic nanostructure, such as grating, light-emitting diode (LED), photonic crystals, etc. However, due to the principle of LIL, the exposure result is very sensitive to the light source and the environment vibration. Defects which perpendicular or parallel to the grating occurs when the LIL system is effect by the environment vibration. The reason that cause this defect is Moiré fringe. When the periodic structure is fabricated in an environment with vibration source, the grating structure will have a small angle rotational vibration and the Moiré fringe defect is formed. In order to eliminate the Moiré fringe defect, this paper developed a new LIL system with chopper and accelerometer. The accelerometer can measure the vibration frequency. And by setting the chopper frequency equal to the vibration frequency, the Moiré fringe defects can be eliminate. In this paper, we use a piezo stage to generate a stable vibration source with tunable frequency. In this way, we can produce a repeatable Moiré fringe defect. By setting the chopper frequency equal to the stage vibration frequency, the Moiré fringe defect can be eliminate. And we successfully fabricated large area periodic structure without any vibration defects. The periodic structure is 360nm pitch and the area is 2x3 cm2 .
This paper has developed the multi-beam laser interference lithography (LIL) system for nano/micro pattern sapphire substrate process (PSS/NPSS). However, the multi-beam LIL system is very sensitive to the light source and the vibration. When there is a vibration source in the exposure environment, the standing wave distribution on the substrate will be affected by the vibration and move in a certain angle. As a result, Moiré fringe defects occur on the exposure result. In order to eliminate the effect of the vibration, we use the software ANSYS to analyze the resonant frequencies of our multi-beam LIL system. Therefore, we need to design new multi-beam LIL system to raise the value of resonant frequencies. The new design of the multi-beam LIL system has higher resonant frequencies and successfully eliminates the bending and rotating effect of the resonant frequencies. As a result, the new multi-beam LIL system can fabricate large area and defects free period structures.
Laser interference lithography (LIL) is a great way to produce micro and nano scale periodic structures. The principle of LIL is that two or more coherent laser beams overlap with each other and form a standing wave in the space which can be recorded by the photoresist. However, due to the principle of LIL, exposure result is very sensitive to the light source, especially in large area exposure. Regular defects occurs in large area exposure result when the laser source has multiple longitudinal mode or mode hopping. Therefore, this paper design and build up an advanced achromatic interference lithography system to solve this problem. Due to the principle of achromatic interference lithography, the exposure result is no longer relative to the wavelength of the laser source, and the pitch of the periodic structures is half of the grating pitch. As a result, achromatic interference lithography is able to eliminate the regular defects caused by the unstable laser source. But traditional achromatic interference lithography system is not very efficient due to transmission lost and only first order light is used. This paper build up an advanced achromatic interference lithography system with two reflective blazed gratings. Because of the principle of the reflective blazed grating, we can improve the efficiency of our achromatic interference lithography system. In this paper, 20 mm2 of large area periodic structures with 420nm pitch and 130 nm linewidth have been successfully fabricated without any defects.
Wire-grid polarizers (WGPs) are composed of 1-D nanoscale periodic structures and are widely used in liquid crystal display devices to enhance the brightness and improve the utilization rate of the backlight source. This paper proposes the design and application of a WGP device for an microelectromechanical system physical force sensor derived through an optical measurement method. Infrared (IR) light was served as the signal source, with the initial angle set incident to the WGP, which was fabricated on microstructures such as cantilever beam, thin-film or bridge structures. According to the operation principle, when a physical force affects the microstructures, the incident angle of the signal light changes, which easily produces different transmission signal values for detection by an IR photodetector. Therefore, the proposed system can be used for optical contactless sensing in physical force sensing modules. Furthermore, the WGP structure introduced in this paper was defined using laser interference lithography and deposited with Al by E-beam evaporation.
Laser interference lithography (LIL) is a maskless lithography technique with many advantages such as simple optical design, inexpensive, infinite depth of focus, and large area patterning with single exposure. However, the intensity of normal laser beam is Gaussian distribution. In order to obtain large area uniform structure, we have to expand the laser beam much bigger than the wafer and use only the center part of the beam. Resulting in wasting lots of energy and the production capacity decrease. In this study, we designed a beam shaping device which consists of two parallel fused silicon optical window with different coating on both side. Two optical window form an air thin film. When the expanded laser beam pass through the device, the beam will experience many refraction and reflection between two optical window and interference with each other. The transmittance of laser beam will depend on the incident angle. The output intensity distribution will change from Gaussian distribution to a flat top distribution. In our experiment, we combined the beam shaping device with a Lloyd’s mirror LIL system. Experiment results indicated that the LIL system with beam shaping device can obtain large area uniform pattern. And compare with the traditional Lloyd’s mirror LIL system, the exposure time is shorten up to 4.5 times. In conclusion, this study design a beam flattening device for LIL system. The flat top beam can improve the large area uniformity and the production capacity of LIL. Making LIL more suitable for industry application.
In this presentation, we show our preliminary results which is related to neurons activation in vivo by laser. A laser
scanning system was adopted to guide laser beam to an assigned fly and an assigned position. A 473-nm laser can be a
heat punishment source to restrain a wild-type fly’s moving area. Furthermore, neurons in optogenetics transgene flies
can be triggered by the blue laser in this system.
The major efficiency loss in current liquid crystal displays(LCD) are the absorption in polarizers and
color filter, and both can be resolved with decent backlight design which takes light polarization and color
separation into consideration. Those improvement schemes on the backlight normally will not trade off
the image quality readily achieved in the commercial LCD. Both polarization and color separation
schemes for the backlight are reviewed with categorization on the basic concept, followed by the proposal
of possible combinations for both direct lit and edge lit configuration with the consideration on the
availability of associated components. Two total solutions, including polarization conversion module for
LED and pixelized backlight with RGB LED for direct lit and edge lit respectively, are given with
demonstration of preliminary result achieved so far as the efficiency improvement schemes for LCD
backlight.
In this paper we investigated the actuation behavior of the antagonistically driven Dielectric Elastomer Actuators (DEAs).
The motivation is to improve the viscoelastic creeping behavior that intrinsically exists within most DEAs, since
creeping behavior may cause some unwanted effects to the performance of DEAs, especially when we apply the DEAs
to some mechanical devices which need to operate stably for a long time. Our experimental results showed that the
actuator can generate very stable displacement, make the pattern of actuator's movement more regular and take
advantage of mechanical energy in a more efficient way by coating two dielectric elastomers with different area ratios
and applying DC voltage to both of them at the same time.
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