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Optical Chopper Accessories

A number of accessories and replacement parts are available for rotating disk choppers.

Synchronizer

The 300Synch synchronizes any 300, 320, or 350 as "slave" with any other chopper or an arbitrary clock as "master". Relative phase can be adjusted.

Blades (Disks)

Blades come in four basic types: standard 102mm blades for the 300 systems, special 200mm blades for the modified 300 systems, dual frequency disks for the 320 systems, and miniature 30mm blades for the 350 and 360 systems. All the blades standard have a 1:1 mark:space (duty cycle) ratio. Ratios with greater periods of non-transmittance can be obtained by mounting two disks of the same type at the same time, with slight differences in alignment. Disks can be gold-plated for an additional cost. Special order blade configurations can be manufactured, though the cost is for a minimum batch and runs approximately $1,000.

  • The 300-series blades come in 2, 5, 10, 30, 200, and 445-slot variants. The 300C and 300CD systems are shipped with the 2, 5, 10, 30, and 200-slot disks included.
  • The 200mm blades are available as 2-slot and 4-slot disks.
  • The 320-series dual-frequency blades have two series of slots, one concentric to the other. They come in 3/30, 4/7, 8/60, and 53/60-slot configurations. The listings show their inner, then outer, slot numbers. The 320 system includes all 4 blade.
  • The 350/360-series blades are available with 2, 4, and 40 slots. The 350 systems come with the 2 and 4 slot blades.  The 360 OEM systems come with one of the three blades (specified by customer at time of order).

Blade Protectors

Blade protectors are available for the 300 and 320 systems. The blade protector protects the blade from damage, but does limit the positions where light beams can be aimed.

The 350C and 350CD chopper heads come encased in a protective box and thus no additional protector is available.

High Frequency Accessories

Because of the narrow slots on the 300-200 and 300-445 blades, only a small aperture can be chopped. The 300HF high frequency accessories use the Moiré fringe effect to enable light beams of larger size to be chopped. For the 300HF-20K, beams of up to 25mm diameter can be chopped; for the 300HF-44K, beams of up to 10mm diameter can be chopped. The 300HF consists of a fixed blade on a mounting plate which bolts onto the standard 300H chopping head. A second blade (200 or 445 slot, as appropriate) is provided and this is mounted onto the motor boss in the usual way. When the moving blade and the fixed blade are in phase, a maximum of 50% of the incident light is transmitted. When the two blades are out of phase, almost the entire beam is blocked. As alignment and manufacture of the two blades is not 100%, the actual amount of transmitted light will vary from approximately 5% to 45%.

Heads and Motors

The standard head, 300H, is used on the 300C/CD and 320C/CD systems, and is available separately as a unit including the cable. The head can be bench mounted or mounted on an optical stalk (bench rod).

A specialized head, the 300H-200mm, is used in conjunction with the 300C/CD system and the special 200mm disk when larger aperture is required.

The 360C system, a miniature OEM chopper, uses the 360H head.

Reduction gearing greatly extends the lower range of chopping frequencies. The motor runs at its normal speed, and the reduction gearing slows the turning off the boss on which the disk is mounted. Gearing is available in the following ratios - 7.2:1, 20:1, 32:1, 64:1, 131:1, 199:1, and 325:1. It is appropriate for use with the 2, 5, 10, and 30-slot disks (102mm).

Replacement motors are available: the 300M12 for 300C and 300CD choppers with serial numbers > 636, the 300M24 for 300C and 300CD choppers with serial numbers <= to 636, and the 350M for 350C and 350CD choppers.

Bosses for the 300M motors (and 300H head, which includes this boss) are available. The 300-series disks are mounted on this boss.

Other Parts

All rotating blade choppers, including the miniature systems, use the 300S optoswitch. This is included as an item in the head and is also available separately.

Cables connecting the head to the control board/unit come in three standard types. The 300I-A has 2 cylindrical DIN connectors, and is found on older 300C and 300CD systems. The 300I-B replaces the 300I-A on newer 300C and 300CD systems, and has 1 'D' and 1 cylindrical DIN connector. Both are three meters long. The 360C unit uses the one-meter 360I cable. Cables can be ordered in longer lengths at additional cost, although there is a limit on length based on signal loss.

Questions? Comments? Suggestions? Send email to the Webmaster at Boston Electronics.