Introduction

Optec manufactures several different filter wheel models with different feature sets. All models offer the same core features including computer control, automatic wheel ID recognition and easily changeable wheels.

The IFW wheel is 6 inches in diameter and is rotated on the center axis by a small stepper motor. The wheel has a precision bearing in the middle and uses a Neoprene O-ring for the drive. Each filter position uses tabs and spaces to hold the different types of filters. Supported filters are 2” (50mm) for 5 position wheels, 1” (25mm) for 8 and 1.5” (36mm) for 9 position wheels.

The shaft of the stepper motor makes friction contact with a Neoprene O-ring that is secured to the circumference of the wheel. It takes approximately 2000 steps of the stepper motor to complete one rotation of the wheel. For the original IFW it takes approximately 16 seconds for one complete wheel rotation. The new High Speed models can complete a rotation in around 2 seconds. One filter position change takes approximately 3.2 seconds for a low speed and around 1 second for a high speed.

Small magnets are inserted into each wheel opposite the filters, which indicate to the electronics the current wheel ID and filter position. Hall effect sensors detect the magnets and are read by the micro controller. The the filter numbers are marked near the corresponding filter.

Another set of holes, only one of which contains a magnet, are used to identify the wheel and are referred to as the wheel ID. These holes are marked with the letters A, B, C, D, and E for the 5-position wheels, F, G and H for the 8-position wheels and I, J and K for the 9-position wheels. As the wheel rotates during the HOME procedure, the lettered ID hole with the magnet will pass over a second Hall effect sensor initiating a control pulse. The number of steps from this control pulse to the next signal pulse by the position magnet (filter position number 1) determines the wheel ID and position number 1. After the home is complete the wheel will stop at filter 1 and wait for further commands.

A lightweight, 6061 aluminum alloy is used for all machined parts. All parts are machined from solid aluminum blocks for optimum strength. In addition, all aluminum parts are bright dip and black anodized for maximum corrosion protection.