Optomechanical Instrument Register

Detector, Single Photon, Infrared

noreply@blogger.com (JD52) — Thu, 12 Oct 2006 01:21:00 +0000

Industrial Products

The id201. is a complete photon counting system based on a cooled InGaAs/InP avalanche photodiode (APD). The operation temperature is set to -50°C to optimise the signalto-noise performance. A temperature variation of less than 0.1°C is achieved through a thermoelectric cooler controlled by a PID regulator. The APD is operated in the so-called gated mode.

The id201 offers advanced functionalities, including:

A trigger unit providing the timing signal for the gate generation. The user can choose from external or internal trigger sources:
• The external trigger source can have NIM, TTL and a Var input types. The Var input type lets the user select three parameters: level, slope, load. The id201 accepts external trigger frequencies up to 4 MHz. Larger frequencies can be used, but the id201 will automatically limit the trigger frequency to 4 Mhz.
• An internal trigger source is also available. Trigger frequencies of 1kHz, 10 kHz, 100 kHz and 1 MHz can be selected. The trigger signal is also available on a front panel connector for the synchronization of other devices (e.g. pulsed laser source, such as the id300).

A delay function providing a delay between the trigger and the gate signals. This allows the user to scan the gate and synchronize the gate and the optical signals. Coarse synchronization should be done using cables and optical fibers, while fine adjustment can be obtained with the internal adjustable delay line. The delay can be adjusted from 0 to 25ns in 100ps increments.

A generator unit and a pulser unit produce a gate with the appropriate duration and amplitude. A variable deadtime can be selected to suppress afterpulse occurences. The following parameters can be selected using an intuitive graphical user interface:

Dead Time. At high trigger frequencies, afterpulsing may significantly deteriorate the performance. To suppress detrimental afterpulsing effects, the id201 allows one to set a dead time after a detection. The dead time duration can be chosen between 1μs, 2μs, 5μs or 10μs. When this mode is enabled, the module will ignore trigger signals during a time equal to the deadtime after each registered avalanche event. The unit displays the actual trigger rate.

Gate Width. Five different values of the gate can be set: 2.5ns, 5ns, 20ns, 50ns or 100ns. A user-defined gate duration can also be entered. Gate widths of 2.5ns and 5ns result in an effective gate of typically 500ps and 1.5ns. These short gates provide a very low noise level for applications where the arrival time of the photon is known with high accuracy.

Photon detection probability at 1550nm that can be chosen between 10%, 15%, 20% and 25%, independently of the gate width and trigger frequency. A user-defined detection probability can also be entered. Large detection probability levels allow one to obtain oustanding timing resolution.

An internal counter whose result is displayed on the front panel to monitor the detection and the trigger signals. For each detection, the module also produces electronic pulses (NIM and TTL) available on front panel connectors. These pulses can, for example, be registered by an external counter or sent to a processing unit, such as a time-to-amplitude converter.

An auxiliary counter, which offers the possibility to count external signals. The result of the counter can then be displayed on the LCD screen.

The electronic circuit of the id201 has been designed to reach outstanding timing resolution of less than 300 ps at25% detection probability.

All the user-adjustable parameters can be easily entered from the front panel or when this option is selected from a computer connected to the RS232 port. The graphical user interface offers several display modes: 1) display the internal and auxiliary counters as frequencies, 2) display the number of counts of the internal and auxiliary counters, 3) display the trigger rate and the internal counter as frequencies, 4) display the ratio of the internal counter over the trigger counter as well as the auxiliary counter frequency, and 5) display all the important detector parameters.

For more information regarding this product please contact:

id Quantique SA
de la Marbrerie 3
1227 Carouge
Switzerland
Tel: +41(0)22 301 83 71
Fax: +41(0)22 301 83 79
Email: mailto:sales@idquantique.com

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Detector, Single Photon, Visible

noreply@blogger.com (JD52) — Thu, 05 Oct 2006 00:42:00 +0000

Industrial Products

Single Photon Detectors in Visible Range by id Quantique SA

id Quantique’s id100 consists of compact and affordable single-photon counting modules with best-in-class timing resolution. Based on a reliable silicon avalanche photodiode sensitive in the visible spectral range, these modules are able to detect weak optical signals down to the single photon level. The includes:

- two free-space versions, the id100-20 and id100-50 with a 20um, respectively a 50um diameter photosensitive area.
-a fiber-coupled version, the id100-MMF50, coming with a standard FC/PC optical Input

The free-space and fiber-coupled modules are easy-to-use, self-contained and can be integrated in every optical setup. With a timing resolution as low as 40ps and a remarkably short dead time of 45ns, these modules outperform existing commercial detectors in all applications requiring single-photon detection with high timing accuracy. Besides an extremely fast IRF (Instrument Response Function), the modules have an excellent timing stability up to count rates of at least 20MHz

The id100 consists of an avalanche photodiode (APD) and an active quenching circuit integrated on the same silicon chip. The chip is mounted on a thermo-electric cooler and packaged in a standard TO5 header with a transparent window cap. A thermistor is used to measure temperature. The APD is operated in Geiger mode, i.e. biased above breakdown voltage. A high voltage supply used to bias the diode is provided by a DC/DC converter . The quenching circuit is supplied with +5V. The module output pulse reflects the arrival of a photon with high timing resolution. The pulse is shaped using a hold-off time circuit and sent to a 50ohm output driver. All internal settings are preset for optimal operation at room temperature. No user adjustment is necessary. In the fiber-coupled version, the TO5 header and the optical fiber are included in the housing. The optical input consists of a FC/PC connector on the front side of the module.

For more information regarding this product please contact:

id Quantique SA
de la Marbrerie 3
1227 Carouge
Switzerland
Tel: +41(0)22 301 83 71
Fax: +41(0)22 301 83 79
Website: http://www.idquantique.com
Email: mailto:msales@idquantique.com

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Viewer, 3D, Stereoscopic

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 01:01:00 +0000

A Stereoscope 3-D Viewer has been designed and developed for television sets and computers. It can be viewed without headgear or special glasses. The Viewer uses a camera to track the viewer’s eyes, allowing the Viewer to change position and still maintain 3D imaging.

The Viewer consists of folded focusing optics, two liquid crystal display video projectors mounted behind a partially silvered screen and a reflective screen. The left image and the right image fields of a stereoscopic image are projected and reflected off a pair of 45° retroreflective mirrors at the bottom of the cabinet. The silvered mirror suspended at 45° is in front of a 50-inch rear projection screen. This provides for the passage of 50 percent of the reflected light.

A small TV camera is positioned under the cabinet and tracks the viewers eyes to ensure correct image focus in both eyes. The tracking is updated 25 times per second. This information is used to adjust the position of the projected images automatically keeping the images aligned for 3D viewing.

The two images are spaced at 32 mm, half an eye spacing, to prevent image spillover. The eye tracking system allows both vertical and lateral viewer motion. The internal mirror optics is controlled by a logic servomechanism from information signals analyzed from the TV camera inputs. The projectors move horizontally for viewer lateral movement and the silvered mirrors tilt for viewer vertical movement.

Source: Laser Focus World, 1996
Reference: Xenotech , Perth West, Australia

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Vibrometer, Torsional, Laser

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:59:00 +0000

A Laser Torsional Vibrometer has been designed and developed that can measure the fluctuating rotational speed of a component. Measurements are made by pointing two low-power laser light beams at the test sample.

The Vibrometer is insensitive to solid body vibrations of the rotating component by the use of parallel Laser light beams. The Vibrometer can operate on any cross section of a shaft by allowing gears of irregular shape to be a moving target.

The Vibrometer tracks the change in light beam frequency produced by the Doppler effect of scattered light from a moving target. A Laser light beam (HeNe , 2 mW) is divided into two equal parallel beams. The Doppler shifted Laser light back scattered from one point is mixed with Laser light from another point on the receiver photodetector. The photodetector output current is modulated at the difference frequency or beat frequency. This frequency is insensitive to whole body, radial or axial, shaft or Vibrometer movement.

Source: Dr.Neil Halliwell, Institute of Sound and Vibration Research, University of Southampton, UK
Reference:
Bruel and Kjaer, A/S Naerum, Denmark
Loughborough University of Technology

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Vibrometer

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:57:00 +0000

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Velocimeter, Doppler, Flow

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:55:00 +0000

A Flow Doppler Velocimeter has been designed and developed using the Doppler principle for non-intrusive flow measurement of an incompressible fluid in a narrow tube.

The Velocimeter consists of a three-section optical head and a separate electronics module. Laser Diode wavelength (780 nm) stability is temperature control by a thermoelectric cooler. An optical flat splits the output light beam from the Laser Diode into two light beams, which are focused by a lens.

The middle section of the Velocimeter contains a flow tube, which has a quartz window for access to the flowing medium. The focused light beams intersect at the desired measuring position in the flowing medium.

The rear section contains the receiver system. This receiver contains a photodetector, a controllable iris aperture and a preamplifier.

Source: None Available
Reference: Gregory Getzer, Ophir Corporation, for the Marshall Space Flight Center, Alabama

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Thermometer, Fiber Optic, Probes

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:53:00 +0000

A Fiber Optic Thermometer has been designed and developed capable of measuring temperatures of minute test samples without disturbing or heat sinking the test sample. The small photodetector mass of the thermometer allows rapid response and high sensitivity transient sensing levels. The probes are nonmetallic, electrically nonconducting, and unaffected by EMI.

The Thermometer uses a temperature sensitive phosphor fixed to the end of quartz Fiber Optic. The Fiber Optic is connected back to the Thermometer. Blue-violet light pulses are sent down the Fiber Optic, causing the phosphor to glow. Decay of the fluorescence after each pulse varies precisely with temperature. This variation provides the basis for temperature measurement at the photodetector with an absolute accuracy of ±0.1 °C. The temperature range is -200 °C to 450 °C. The fluorescent decay time is measured by multipoint digital integration of the decay curve. The Fiber Optic transmits the excitation pulses and returns the fluorescent signal.

A four photodetector array is used for thermal mapping. The array is made from non-fragile 250 μm plastic Fiber Optic in a Teflon sheath. The total outside diameter is less than 0.9 mm and can fit into a specially designed 19 gauge catheter needle.

There are two Thermometer configurations for surface measurement; 1) Phosphor coating on the test sample surface for non contact measurement and 2) Elastometer tipped probe for contact measurement, where the elastometer is clear and can operate as a lens.

Source: None Available
Reference: D. R. Wickersheim, Luxtron, Mountain View, CA;

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Telescope, Star Tracker, Hard Mounted

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:51:00 +0000

A Hard Mounted Star Tracker telescope has been designed and developed using a large, two-dimensional focal plane array to image an extended field of view without requiring a scanning system. The Star Tracker is capability being rigidly mounted (strapped down / hard mounted) to the super structure. The accuracy of the Star Tracker is limited by (1) the focal plane array (CCD), (2) the dark current, (3) pixel response non-uniformity’s, (4) pixel surface structure, and (5) lens aberrations.

To achieve the required accuracy over the entire field of view, the CCD surface plane must lie within 5 μm of the desired image plane. The CCD surface plane is accurately measured relative to the heat sink, and the focal plane mounting shim ring is machined to fit. The shim ring is of a low thermal conductivity enabling the Star Tracker to operate with its lenses near room temperature. The laboratory measurements are interpolated to yield data that is applicable to the space flight orbital environment. By proper calibration for operational temperature, allowance for thermal expansion is not necessary. In flight and during calibration, the CCD’s are operated at a temperature of -40 ^oC ±5 ^oC by passively cooling the focal plane assembly to 0 °C with copper conductors to an external radiant radiator. Active cooling is achieved by applying power to a Peltier cooler.

Source: None Available
Reference: None Available

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Spectrometer, Raman, Basic

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:49:00 +0000

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Stabilizer, Image, Prism

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:48:00 +0000

An Image Stabilizer has been designed and developed containing a system to neutralize optomechanical instrument shakes (lenses, binoculars, and camcorders).

The Image Stabilizer system consists of a vari-angle Prism optical system and contains two transparent plates coupled by a flexible film. It is a sealed unit filled with a high-refractive-index fluid. Horizontal and vertical photodetector signals are fed to a microprocessor. The detected hand movement or other vibration inputs are sent from the microprocessor as input signals to tiny motors. The correcting signals provide the motors with instant and continuous adjustments to shape the Prism optical system.

There is also a non-prism Image Stabilizer, which uses tiny gyros controlled by a built-in microprocessor. This Image Stabilizer senses unwanted camera movement that triggers signals to a magnetic coil surrounding a special group of lens elements. The coil moves the lens group horizontally or vertically to counteract shake for maintaining a steady, centered image.

Source: None Available
Reference: Ph: 1-800-OK-CANON; web site http://www.usa.canon.com.

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Spectrometer, Saturation, Laser

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:47:00 +0000

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Spectrometer, Raman, Polarizer

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:46:00 +0000

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Spectrometer, Monolithic, Silicon

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:45:00 +0000

The Monolithic Silicon Spectrometer (wavelengths > 1.1 μm) has been design and developed consisting of three optical components made from two blocks of Silicon joined into a single piece. The resulting Spectrometer is a compact, lightweight unit that would remain permanently aligned, even when exposed to shock and vibration.

The three optical components consist of a collimating Fresnel lens, a focusing Fresnel lens, and a diffraction grating. These components would be fabricated by machining the required mating alignment features and optical surfaces.. On one Silicon block, the diffraction grating would be micromachined or diamond turned into one face, and the focusing Fresnel lens would be micromachined or diamond-turned into the opposite face. The collimating Fresnel lens would be micromachined or diamond-turned into one face of the other Silicon block. The diffraction grating would be coated with a metal deposition for use in a reflective mode.

After fabrication, the two Silicon blocks would be subjected to a process that is reminiscent of both electroplating and diffusion welding and would work only for Silicon. The Silicon blocks would be placed in contact with alignment fixtures, mated, heated in an oven while a small electric potential was applied between the Silicon blocks. This process would bond the two Silicon blocks.

Source: None Available
Reference: Paul K. Henry and Gregory H. Bearman, Caltech, Pasadena, CA for NASA’s Jet Propulsion Laboratory

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Spectrometer, Infrared, Miniature

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:41:00 +0000

A Miniature Infrared Spectrometer has been designed and developed where light beam enters the Spectrometer through a rectangular hole in a baffle and strikes an off-axis parabolic mirror. The mirror images the field of view onto an entrance slit. The slit is followed in an optical train by four side-by-side concave Laser-ruled holographic diffraction gratings. Each grating is independently adjustable and optimized for a 2,000-A portion of the overall-A wavelength range. Each grating is corrected for aberrations and acts as a dispensing, focusing, and field-flattening optical element combined into one.

The portion of the spectrum from each grating is focused onto one of four strips on a 40-mm-diameter photocathode mounted on the faceplate of an image intensifier. Half the faceplate is coated with S1 photocathode material (sensitive primarily in the near infrared); the other half is coated with S20 photocathode material (sensitive primarily in the visible). The output of the image intensifier is coupled and minified by a Fiber Optic taper onto an 11.4-by-8.8-mm CCD array. Peltier devices cool the photocathode and the CCD.

The optical system of the spectrometer is moderately fast, aperture about 1/6 of the focal length. The instrument has a dynamic range of 10.5. The Spectrometer is 37 cm by 37 cm by 48 cm.

Source: NASA Tech Briefs
Reference: Marsha R. Torr, NASA, Marshall Space Center, Houston, Texas

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Spectrometer, Infrared, Fiberoptic

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:39:00 +0000

A Fiber Optic Infrared Spectrometer has been designed and developed based on a double-pass version of the Schmidt optical system. The optical system is contained in a piece of solid glass (two pieces cemented together), which is mechanically and thermally stable.

A light beam is fed from Fiber Optics into the Spectrometer through a flat entrance surface. The Fiber Optic cable is co-planar with a PbS photodetector array with a blocking filter and displaced a small distance out of the page displacement.

A diffraction grating disperses the light beam angularly according to wavelength and reflects it back through the optical system to the array of PbS photodetectors. The optical system, operating as a camera on the return pass, focuses the light beam wavelength spectrum on the photodetector array. The wavelength display on the photodetector arry is an indication as the function of light beam position.

The diverging light beams are partially collimated by the primary mirror. A narrow stripe at the center of the mirror is left uncoated to prevent reflection of the light beam directly back onto the photodetectors array. The collimated rays are folded 90 degrees by total internal reflection. The light beam then passes out of the optical system, through a corrector surface fully collimating the light beam.

Source: None Available
Reference: N. Page and Mary White, Caltech, Pasadena, CA for NASA’s Jet Propulsion Laboratory

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Spectrometer, Grating, Rotation

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:37:00 +0000

A Rotating Grating Spectrometer has been designed and developed, which can be mounted on top of the rotor of a turbo molecular pump with a maximum rotating speed of 43,200 rpm. The pumps rotor is magnetically supported resulting in minimal mechanical vibrations.

The Grating and the pump rotating blades are machined from a solid aluminum block, which is mounted to the top of the shaft. The shaft diameter is 235 mm and the shaft height is 331 mm. The diameter of the Grating is 134 mm and the total number of grooves is 2000 with a blaze angle of 45°. The material of the vacuum window for both the incident and diffracted beams is Teflon or crystal quartz. The window thickness is 3 mm and a 40 mm diameter.

It takes about three minutes for the Spectrometer to reach steady state revolutions. The laser light beam is chopped at the exit of the Laser and the reference light beam is blocked from the photodetector. This configuration provides an output AC voltage of the photodetector, which is nearly proportional to the input light beam power. A comparison is made between the output voltages from the light beam diffracted from the grating in the stationary position, with the voltage due to a light beam reflected from a flat mirror replacing the grating.

Source: , “Frequency shift of 1.45 MHz for 337-m HCN laser beam with a super rotating grating” by T. Maekawa, T. Minami, K. Makino, S. Tanaka, S. Kubo, and M. Iguchi; Rev. Sci. Instrum. 62(2), February 1991; Maekawa, Minami, Makino, Tanaka, Department of Physics, Kyoto University, Kyoto 606, Japan; Kubo, National Institute for Fusion Science, Nagoya 464-01, Japan; Iguchi, Hachiohji Factory, Osaka Vacuum, Ltd., Hachiohji 193, Japan
Reference: None Available

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Spectrometer, Grating, Fiber Optic

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:35:00 +0000

A Grating Fiber Optic Spectrometer has been designed and developed with a light and dark diffraction pattern embossed directly on the Fiber Optic by a laser. The Laser has an output wavelength corresponding to an absorption band of the Fiber Optic (germanium-doped).

The diffraction pattern modifies the Fiber Optic core by changing the index of refraction in the dark bands. The spacing between the light lines and the dark lines is the Grating period. The embossing procedure requires the removal of the Fiber Optic coating, exposing the core to a high-energy laser, and then recoating the Fiber Optic. Recoating does not restore the original mechanical intensity of the Fiber Optic. The Laser embossed grating of the Fiber Optic results in an optical filter with a wavelength range of 400 nm to 2000 nm and a bandwidth of 0.1 nm at 1300 nm.

The Spectrometer requires a broadband light source coupled to the Fiber Optic. The Grating reflects or filters out the wavelength determined by the Grating spacing. The Grating spacing is changed when used as a strain gauge, resulting in different wavelengths being reflected.

Source: “Measuring with Light” (in four parts) by Peter L. Fuhr, Sensors Magazine, April-July 2000; Peter L. Fuhr, San Jose State University, San Jose, CA
Reference: “Fundamental of fiber optic sensing: technique, applications and more applications”, by Peter L. Fuhr, Sensor Expo Conference Program, Anaheim, CA, May 2000

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Spectrometer, Grating, Convex

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:33:00 +0000

A Convex Grating Spectrometer has been designed and developed with a 1:1 magnification Offner relay mirror system, which is modified by replacing the single concave spherical primary mirror with two concave spherical mirrors. The two mirrors of the same or different radii are positioned at particular distances from a concentric convex spherical diffraction grating (which has replaced the convex secondary mirror of the Offner optical system). The spherical diffraction grating has its grooves parallel to the entrance slit of the spectrometer configuration.

By adjusting the mirror distance locations and the mirror reflection angular orientation, all aberrations are corrected without the need to increase the size of the spectrometer for a given entrance slit size used to correct astigmatism. This situation allows the imaging spectrometer volume to be less for any given application than would be possible with a conventional imaging spectrometer while providing excellent spatial and spectral imaging of the slit image spectra over the focal plane.

The light beam from the image field passes through an entrance slit and is diffracted by the diffraction grating with the grooves (lines) parallel to the slit. The image on the focal plane can be displayed or recorded using the output signal from a variety of photodetectors.

The Spectrometer consisted of a large spherical mirror facing a concentric convex diffraction grating. The center of curvature of both the mirror and the grating are at the same point on a plane that contains the object (slit) on one side of the convex diffraction grating and an image detector array on the other side of the convex diffraction grating (opposite the slit). The diffraction grating has its groove lines parallel to the slit.

Tilt of the diffraction grating does affect the symmetry of the optical system and does introduce coma into the image. The all reflection configuration can perform in the spectral range from the ultraviolet to the far infrared. The flatness of the focal plane image allows for the use of pixel array photodetectors.

Source: “Design of grating spectrometer from a 1:1 Offner mirror system” by Deborah Kwo, George Lawrence and Michael P. Chrisp; SPIE Procedures, Vol.818, 1987, pages 275-279
Reference:
1) United States Patent Number 5,880,834, inventor Michael P. Chrisp
Patent Counsel, NASA, JPL, Resident Office; Reference Number NPO-19293

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Spectrometer, Filter, Wedge

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:30:00 +0000

The Filter Wedge Spectrometer has been designed and developed with a rotating interference Filter Wedge wheel in the shape of an annulus split along a diagonal. One semicircular half continuously covers 1.2 to 2.4 microns wavelength, and the other half covers 3.2 to 6.4 microns wavelength. The Spectrometer used a lead selenide photodetector, which is cooled by thermal radiation to 165 K. The field of view is 2.6° with a resolving power (λ/δλ) of 100. The weight of the Spectrometer is 13 pounds and a power load of 9 Watts.

Photodetector are used to detect the start of a scan, 90° and 180° rotation of the Filter Wedge wheel. This Filter wheel position data is used to control the calibration circuit. The calibration circuit counts the number of Filter wheel scans and commands the Spectrometer into a calibration cycle after 47 scans.

During the calibration cycle, the preamplifier input is switched from the photodetector to the output of the calibration circuit. Four step voltages modulated at the 300 Hz chopper frequency and in phase with the chopper reference voltage are gated into the preamplifier during the first quarter cycle. Four step voltages chopped at the 300 Hz rate and out of phase with the chopper reference voltage are gated into the preamplifier during the next quarter cycle. During the last half cycle, a signal causes a calibration target to cover the optical port is generated and preamplifier input is switched back to the photodetector output. The calibration target temperature is at least 10 K cooler than the reference target and is presented during the 3.2 to 6.4 micron wavelength filter scan.

Source: “Meteorological infrared instruments for satellites” by I. L. Goldberg, NASA Goddard Space Flight Center, SPIE Proceedings, Volume 1 (1969), 13th Annual Technical Symposium

Reference: None Available

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Spectrometer, Cancer, Breast

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:29:00 +0000

A multichannel Spectrometer for Breast Cancer detection has been designed and developed utilizing a unique holographic transmission grating. The grating contains a photosensitive gel material with periodic index of refraction. Reduced light scattering results because of the gel material, fewer edges are exposed. This type of holographic grating provides refraction throughout the gel material volume with more light reaching the photodetector. Spectral efficiency of 80 percent and a spectral wavelength range from 500nm to 1100nm has been achieved.

Light illumination passes through the breast over a few centimeters and measurements are taken at several locations. The light beam leaving the breast is collimated and imaged onto the grating. A CCD camera collects spectral signals from the grating’s refracted light beam. This configuration allows the imaging of several light beams channel simultaneously in real time.

Source: Photonics Spectra, April 2003

Reference: Lothar Lilge, Ontario Cancer Institute, Prince Margaret Hospital, Toronto, Canada; Ph: 416-946-4501, Ext. 5743; Olga Pawluczuk, P&P Optica Inc., Kitchener, Ontario, Canada,

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Scatterometer, Intensity, No Filter

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:28:00 +0000

An Intensity Scatterometer was designed and developed with a configuration that measures both reflected and scattered light intensities without the use of neutral density filters.

A helium neon Laser (λ = 0.6328 μm) is mounted to one arm of a stage positioner. The incident beam is chopped at 40 Hz. A photodetector with an active area of 1 mm² is mounted to the other rotating arm. The test sample and test sample holder are mounted to a vertical translation stage, which is mounted to a rotating stage. The Laser is calibrated by moving the test sample vertically allowing the light beam to proceed straight to the photodetector. The modulation frequency of the illuminating light beam keeps ambient stray light interference to a minimum. The reflected light beam is incident on a large photodetector without a neutral density filter. The photodetector signal is determined by the power of the reflected light and the responsivity of the photodetector. With the neutral density filter in place the photodetector signal would then include the transmittance of the filter. The large photodetector is replaced by a small photodiode.

With the three photodetector signals from the three setups, it is possible to determine: 1) transmittance of the neutral density filter and 2) ratio of the large photodetector to the small photodetector responsivity.

Source: None Available

Reference: H. Wang and O. N. Stavroudis, Centro de Investigaciones en Optica, Leon, GTO, Mexico

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Scanner, Pen Shape, Fiber Optic

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:24:00 +0000

A Pen Shape Scanner has been designed and developed consist of a housing structure, an array of Fiber Optics, a linear imaging photodetector (fabricated on a transparent substrate), a light source, a roller, and a rotary encoder. A double deck structure configuration of two printed circuit boards is the electronics package.

An imaging photodetector is formed on a glass substrate and coupled to an array of Fiber Optics. The light source is placed over the imaging photodetector. The ends of the Fiber Optics are in contact with the document. Each photodetector has multiple apertures coupled to multiple Fiber Optics. The Fiber Optics is coupled partially to the apertures and partially to the photodetectors. The illumination light is transmitted through the glass substrate and then through apertures. The light passes through the Fiber Optics and to the document to be scanned. The reflected scattered light returns on the same Fiber Optics and is detected by the photodetectors. The opaque electrode of the photodetectors blocks direct illumination by the light source. Light absorption material is used at the Fiber Optics boundaries so that optical crosstalk inside the Fiber Optic array is kept to a minimum providing maximum image resolution.

Specifications of the Pen Scanner are as follows: 1) Pen Size: width 13 mm, length 110 mm.; 2) Imaging Photodetector: Thin film technology; 3) Fiber Optic array: thickness 2 mm, 0.9 numerical aperture; 4) Color Light Source: An array of three color LED’s.

Source: "Development of a pen shaped scanner and its applications" by Ichiro Fujieda, Hiroshi Haga, Fujio Okumura, Yasuyoshi Matsumoto, Hiroshi Kohashi, Hiroshi Matsuo and Shigeki Miura, 216, Japan, Optical Engineering 38(12), December 1999

Reference: None Available

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Retinoscope, Retina, Illumination

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:22:00 +0000

A Retinoscope Illuminates the Retina of the eye and locates the image of the Retina in space. The Retinoscope consists of a light source and a viewing aperture. The position of the retina image is at a ‘far point’ and its positional value in dioptric units is equal to the ocular refractive error. The ‘far point’ can be located and its distance measurement provides information for calculating the ocular refractive error.

The Retinoscope operator places a variety of lenses in front of the eye in order to bring the ‘far point’ to focus at the aperture peephole. The ocular refractive error is equal to the lens power required for focus, less the working distance of the lenses.

The sleeve of the Retinoscope can be moved to bring the light source closer or farther away from the condensing lens. As the sleeve is moved, a narrower or wider interception of light is produced, illuminating a larger or smaller area of the retina. The smaller the Retina’s image, the less the Retinoscope fills the pupil. If the plane of the ‘far point’ is too far from the pupil, the sleeve sliding will not bring the retina into focus.

Source: Various Publications
Reference: None Available

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Retina, Projector, Direct

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:21:00 +0000

A Direct Retina Projector has been designed and developed that can project imagery directly onto the human eye retina. There are no intermediate screens or externally projected images. The Projectors operating principle is to scan a light beam of ultra low energy, 400-nanowatt red Laser Diode directly onto the retina in a controlled raster pattern.

The Projector provides 40-degree horizontal field of view and 30-degree vertical field of view. The range-of-motion is a 2-inch cube. The exit pupil of the image light beam is 1.5 mm for a monochrome system and 7 mm for a color system. The laser light beam is digitally modulated to accurately recreate each individual pixel intensity. As many as three lasers can be combined and synchronized for a partial color or a full-color system. The light beam can be routed through a single Fiber Optic for displaying.

Synchronized high-speed scanning mirrors are used for the horizontal scan and the vertical scan for each pixel position. The Projector re-scans a 640 pixel X 480 pixel image 60 times a second. The light beam reflects off a small reflecting surface before entering the eye for final imaging on the retina.
Source: Aviation Week, July 1996
Reference: Micro Vision Inc., Seattle, WA

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Retina, Diagnostic, Laser

noreply@blogger.com (JD52) — Thu, 21 Sep 2006 00:19:00 +0000

A Retina Diagnostic Laser System has been designed and developed that enables diagnosis of abnormal blood vessel growth beneath the retina.

The Laser System consists of a Vertical Cavity Surface-Emitting Laser with a photodetector array, providing improved performance over the scanning laser Ophthalmoscope. The prototype instrument contains an Infrared Laser Diode to provide a 3 dimensional map of the eye's sub-retinal layers. These layers are where improper retina blood vessel growth and can interfere with the light-gathering cells. The Laser System photodetector array provides visualization of the deeper layers of the fundus (back of the eye) in the infrared wavelength region.

The Laser System provides higher-quality images at a safe and comfortable laser energy level and causes no retina damage. The Laser System has an axial image resolution of 250 mm at half height. This resolution level provides the presence of an abnormal structure beneath the retina. This observation can allow real-time retina diagnosis. There is also no requirement for injecting contrast enhancing agents (dyes).

Source: None Available
Reference:
(1) Dr. Ann Elsner, Schepens Eye Research Institute, Boston, MA; Ph 1-617-912-0100
(2) Jack Jewell, Cielo Communication, Broomfield, CO

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