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There are 464 photodiode elements with 464 ouput channels in the array (We guarantee less than 3% defective channels). The fiber-optic array is a perfect hexagonal pattern of 469 elements. It uses 0.75 mm fiber-optics to couple individual photodiodes to a hexagonal aperture of 20 mm. At the image plane the fibers are tightly packed and fill 92.6 percent of the active area. This is significantly higher than that of monolithic arrays (50 %). The design is discrete which allowed flexibility in the choice of photo-diodes. This increases the signal- to-noise ratio in experiments with low light levels where the dark current of the photodetector becomes a major source of noise.

Dynamic Range
The array uses optical grade polymethyl acrylic fiber optics. This fiber consists of an inner acrylic core and a thin fluorinated cladding. This gives a high Core/Clad ratio for a large active area of the array aperture. The following are the properties of the fibers:

Core: Polymethyl Methacrylate
Cladding: Fluorinated Polymer
Fiber diameter: 0.030 (0.75 mm)
Optical properties:
Spectral Range: 400-800 nm
Attenuation: :<200 db/km @@ 650 nm
Refraction Index: Core: 1.492
Clad: 1.417
Numerical Aperture: 0.47
Accepting Angle: 56o

The optical attenuation of the fiber is negligible (the distance between aperture and the diodes is less than 15 cm). An optimum optical coupling has been achieved by polishing both ends of the optical fibers and coupling the silicon surface of the diode and the fiber with a thin layer of optical epoxy.

Electrical Properties
The photodiodes are near perfect photo-electrical silicon devices. They have a high quantum efficiency (> 0.9), low dark noise, and very low 1/f noise. Tests have showed that they contribute no noise to the input end of the I/V converter cards. The electrical properties of the photodiode are: Sensitivity: 0.5 A/W @ 650 nm Shunt resistance: 20 to 50 G ohms Dark current: > 5 pA Capacitance: 30 pf

Mechanical Construction
The diode array and all the amplifiers are housed in a metal case made of 1/4" and 1/8" aluminum, providing a strong mechanical protection and an excellent electro-magnetic shielding. The module is 11" x 8" x 13" and weighs 25 lbs. The mother-board in the housing is designed to directly interface with the preamplifier cards. The housing comes with a C-mount but adapters for other mounts can be installed by the customer.

Coupling the H-469III diode array to the microscope:
With a proper adaptor, the diode array can be mounted on C-mount port, TV port or any other port with a real image of a microscope. However, it is recommend that it be mounted on a "simple" port for a maximum light throughput. Most research microscopes provide this kind of high throughput port. The rule of thumb is that the fewer lenses between objective and the fiber optics, the higher the throughput. On the housing outside the optical aperture there are four mounting holes tapped with 10-32 threads for mounting adapters other than C- mounts. These holes can accept 10-32 screws up to one inch long. Longer screws may break the seals inside the housing. The array unit is a heavy load for the microscope and support only via the image port is not recommended. Additional mechanical support can be constructed using two threaded 1/4-20 holes on the back of the housing. Newport optical bench parts can be attached to the holes.


PROTECT THE FIBER OPTICS APERTURE. DO NOT TOUCH IT. NEVER USE ALCOHOL OR ORGANIC SOLVENTS TO CLEAN THE APERTURE. The fibers on the aperture are acrylic plastics. They are softer than glass and can be scratched by sand, metal and other hard objects. These fibers are also very sensitive to alcohol and organic solvents. If they must be cleaned, use lens paper to wipe, and if necessary, use distilled water and mild detergent. AVOID EXPOSING THE FIBER OPTICS APERTURE TO UV LIGHT. UV may shorten the life of the fiber optics. In ordinary fluorescence microscopes, UV can never reach image ports, unless unusual modifications were made. If your microscope has been modified and you use light source with UV light, make sure the array aperture is not exposed to the UV light. USE STRONG MECHANICAL SUPPORTING HARDWARE TO SECURE THE ARRAY AND MICROSCOPE. THE ARRAY IS A HEAVY INSTRUMENT WITH CABLES RUNNING FROM IT. DO NOT SUPPORT THE ARRAY ONLY BY THE MICROSCOPE. If array is mounted on top of the microscope, be sure to secure the microscope on the table. The array needs to have an extra support in addition to the image port. Two 1/4-20 threaded holes on the back of the housing can be used to mount Newport standard optical bench parts for mechanical support.

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