KEYWORDS: Sensors, Distortion, Modulation transfer functions, Spatial frequencies, Imaging systems, Optical transfer functions, Point spread functions, Optical engineering, Signal to noise ratio, Prototyping
A novel sensor for use in displacement metrology is proposed. It is based on grating imaging, which conventionally uses two amplitude gratings to generate a sinusoidal image. In the conventional method, the poor signal-to-noise ratio of the displacement output is one of the barriers to precise measurement, because 75% of the illumination light is trapped by the two amplitude gratings. In the proposed sensor a cylindrical lens array and a sine phase grating are used as the first and the second grating, respectively. Therefore, the illumination light is intercepted by neither, so that four times higher displacement signal amplitude than that of the conventional sensor can be expected. Consequently, four times higher signal-to-noise ratio can be obtained. Furthermore, the proposed sensor generates a sinusoidal output with little distortion by using the sine phase grating with optimized conditions, so that accurate measurement can be expected. In our prototype, a cylindrical lens array with a 200-µm period and a reflective sine phase grating with a 100-µm period were used.
An ultra-miniaturized sensor head for absolute measurement which has a size of less than 5 mm cube is realized. The sensor works by means of the optical triangulation. To achieve the optical function, the sensor consists of a three layer polymer waveguide patterned by X-ray lithography, an incoupling fiber and two detection fibers and micro cylindrical lenses which are also fabricated by X-ray lithography. The fibers and the cylindrical lenses are placed into the waveguide without any active alignment by using waveguide walls as guiding and fixing structures. The ratio of intensity detected in the two detection fibers is a measure for the distance between the object and the sensor. The detection range of the sensor is 1 to 6 mm between the sensor and an object with diffusively reflecting surface.
This paper presents a new fingerprint sensor for automated fingerprint identification systems. This fingerprint sensor consists of alight source, a charge coupled device and fiber optic faceplates. Because of the fiber optic faceplates, this fingerprint sensor does not have the space for image formation that a lens has and thus can be miniaturized. The size of the prototype fingerprint sensor, which has a 12 mm by 18 mm fingerprint input face, is 48 mm by 72 mm by 44 mm. The verification performance is evaluated by using this prototype.
Semiconductor position sensitive devices (PSD) enable to measure the position of a light spot using simple construction. A circular PSD, which has a circular photosensitive region, can be used for angular measurement. This paper presents a new type of circular PSD called Multi Electrode Circular PSD (ME-CPSD) and demonstrates its application for angular measurement. This device, constructed on Si substrate, has a photosensitive region, a resistor line and 16 output electrodes. The photosensitive region has the shape of a ring which is formed by a radial arrangement of long and narrow photodiodes. The outer end of the photodiodes are connected to the continuous resistor line. Photoexcited carriers which are generated in the photodiode by the incident light flow to the resistor line and are extracted by the multioutput electrode which divides the resistor into 16 equal parts. To measure the position of the light spot, a pair of electrodes is selected by switches connected to every electrode and the position of the light spot is calculated from the output current of the selected electrodes. Compared to conventional circular PSDs, the reliability of the angular measurement is improved, because the ME-CPSD does not have an undetectable region caused by the unavoidable discontinuity in the structure of conventional circular PSDs. This device can change its measuring range by selecting the pair of electrodes, making it not only capable of measuring any absolute angular position, but allows also a more precise angular measurement by selecting narrower electrode intervals. This device has the capability to realize a high precision noncontact angular measurement system with simple construction.
The laser-addressed ferroelectric liquid crystal light valve (FLCLV) consists of metal-insulator-semiconductor (MIS) photoconductive sensor and ferroelectric liquid crystal (FLC). It has a high resolving power of 50 1p/mm for laser pulse recording and 130 1p/mm for 2-dimensional image recording. The multibeam laser scanning method is applied in this display system, which achieves high writing speed (0.5 s/frame) and high resolution (1500 X 1600 pixels--higher than that of HDTV.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.