This paper presents a novel SU-8 polymer-based grating light modulator fabricated using conventional process
technology which requires no expensive equipments and materials. A set of fifty 2.5μm-thick SU-8 micro beams of
20μmwidth x 100μm-length is patterned by photolithography on the aluminum sacrificial layer to form a grating. The
micro beams are arranged in parallel with an inter-beam gap of 20μm. The wide inter-beam gap tolerates low patterning
precision. Narrow air gaps of 0.5μm beneath the micro beams are formed by combination of wet-etching of the
aluminum sacrificial layer and freeze drying method, where cyclohexane is chose as sublimation liquid because of the
high freezing point and the ease of sublimation. When a voltage is applied across the upper and lower electrodes to
attract the micro beams to the substrate, neighboring micro beams are actuated to deflect in phase and the optical path
length between the upper electrode/mirror on the micro beam and the lower mirror on the substrate decreases by quarter
wavelength, the 0th and 1st order diffracted light intensities vary from maximum and minimum, respectively, or vice
versa. The voltage to obtain maximum modulation for HeNe laser beam of 632.8nm wavelength is 70V. The rise and fall
response times of the light modulation are 3.08 microsecond and 4.63 microsecond, respectively.
We have developed an improved version of a high-definition real-time depth-mapping Axi-Vision Camera that enhances the speed of the depth detection, reduces external light interference, and is more compact. The new depth-detection method uses a high-resolution, fast-frame-rate CMOS sensor with a rolling shutter. The depth is calculated from four near-infrared light (NIR) images in successive video frames to cancel the effects of external light interference. Therefore, the external light interference immunity is improved so that the depth information can be detected accurately under external light at an intensity up to 30% of that of NIR light illumination. Furthermore, the compact-imaging optical system is achieved by using a specially designed HDTV camera lens, which internally separates only NIR light and provides NIR images on an image intensifier coupled with a CMOS sensor. Further compact sizing of the camera system is achieved by arranging specially developed small, high-power reflection-type LED arrays for the NIR illumination around the camera lens. As a result of this compact sizing, the volume is 1/5 that of the prototype system. We also demonstrated a method to obtain 3-D information from image data captured by this Axi-Vision Camera.
Versatile three-dimensional (3D) image data as in the form of I(X,Y,Z) defined in the camera coordinate system are
acquired from sets of color image and depth image, which are simultaneously captured at a video frame rate by a 3D
camera named Axi-Vision camera. The X and Y coordinates are calculated from the image coordinates (x, y) on the
image plane of CCD based on the perspective projection theory. The Z coordinate can be obtained for each pixel of the
color image directly from the depth image without any complex processing. Thus, the 3D image data of objects, I(X,Y,Z),
is obtained from the relation between the camera coordinate and the image coordinate systems. A stereoscopic video
image display is demonstrated using the 3D image data using an integral photography (IP) system, which combines a 4-
inch VGA liquid crystal color display panel and a pinhole array. Aliasing, an issue from mismatch of image qualities
between the 3D image data and the IP system, is effectively suppressed by pre-processing the color Axi-Vision image
data using a two-dimensional lowpass filter, which is designed based on analyses of the maximum spatial frequency of
the 3D image transformed appropriate for the LCD size and the Nyquist spatial frequency of the IP system.
We present a device model for a lateral p-n junction quantum-well edge-emitting laser-transistor with an extra gate contact. Such a contact provides an opportunity to control the confinement conditions of the electrons injected into the active region and, as a consequence, the threshold current and output optical power by the
gate voltage. Using the proposed model, we calculate the laser dc characteristics and estimate its modulation performance. We show that the application of negative gate voltages can lead to a substantial decrease in the threshold current. The estimated cutoff modulation frequency associated with the gate recharging can be much higher than those associated with the photon and electron lifetimes.
This paper proposes and demonstrates a scheme for generating pseudo-random wavelength
hopping sequences in semiconductor lasers by using chaotic dynamics. The system consists of a
wavelength tunable light source, a nonlinear wavelength element, and a delayed opto-electric feedback.
By feeding back the filter output signal to the light source to control the lasing wavelength, it is
possible to achieve periodic or chaotic wavelength variation patterns with a wide variation range
covering several longitudinal modes. In experiments, wavelength hopping among up to 10 modes was
observed with the hopping frequency about 100 MHz. Synchronization of the wavelength hopping in
two separate lasers is performed by coupling part of the feedback signal of one laser into the feedback
of a second laser. Synchronization was observed between the on-off intensity modulation patterns of
each pair of corresponding longitudinal laser modes.
A novel 3D camera named Axi-vision camera was developed. IT can acquire both color and distance information of objects. An intensity-modulated light illuminates objects and the camera with an ultra-fast shutter captures the light reflected from the scene. The distance information is obtained from two images of the same scene taken under linearly increasing and decreasing illuminations. The camera does not require scanning, multiple camera units, or complicated computations. It is possible to acquire distance information for each pixel of a TV image at real time. The operational features and technical specifications of the camera were investigated. The application to TV program production, such as replacing the image of an object at a particular distance by another, was demonstrated. A new 3D display system is also proposed, developed and demonstrated.
The polymer-dispersed liquid crystal (PDLC) films of the optically addressed light valves in the high-definition television (HDTV) projection display described here can modulate unpolarized light with high spatial resolution as well as with a high optical efficiency based on the light scattering effect. A PDLC film suitable for use in HDTV projection display was developed by evaluating the microscopic spatial light modulation and polymer-network morphological properties of test films prepared using various curing conditions for photopolymerization-induced phase separation. Films produced under optimum curing conditions have a fine polymer-network structure appropriate for films used in the light valves of a HDTV projection display. Our prototype full-color HDTV projection display using three PDLC light valves provides a resolution of 850 TV lines, a brightness greater than 1800 ANSI lumens, and a maximum contrast ratio of 100:1.