Optical Position Sensors for Measuring Position and Motion
The key to understanding optical position sensing systems is to understand the sensors which form the heart of such systems. These fall into two basic categories: Segmented and continuous.
Segmented sensors consist of two or more distinct photosensitive elements separated by a small gap. These highly-sensitive devices are best used as nulling and centering devices. Their useful range is limited by the illumination spot size. This category includes Quadrant and BiCell type sensors.
Continuous sensors consist of a single photodiode, without any gaps. These devices are best for measuring a light spot’s movement over a wide range (greater than the spot size). This category includes duo-lateral, tetra-lateral, and superlinear types.
Continuous Position Sensors
Continuous sensors are distinguished by the number of axes (one, two, or four), sensor shape (circular or rectangular) and sensor size.
- Model 1232 Tetralateral Sensor, (20 mm)2
- Model 1233 Tetralateral Sensor, (1 cm)2
- Model 1237 Tetralateral Sensor, 44 mm diameter
- Model 1241 Tetralateral Sensor, (2.5 cm)2
- Model 1238 Single-axis Lateral sensor (11.5 mm); 35mm Lens Adapter
- Model 1239 Single-axis Lateral sensor (300 mm); 35mm Lens Adapter
- Model 1248 Duo-Lateral Sensor, (1 cm)2
- Model 1250 Duo-Lateral Sensor, (20 mm)2
- Model 1252 Superlinear Sensor, 76 mm
Segmented Position Sensors
Segmented sensors are distinguished by the number of axes (two or four), sensor shape (circular or rectangular), sensor size, and the size of the gap between segments.
- Model 1240 Quadrant Sensor, 10 mm diameter, 0.127 mm gap
- Model 1242 Quadrant Sensor, (1.3 mm)2, 0.127 mm gap
- Model 1245 Quadrant Sensor, (10 mm)2, 0.127 mm gap
- Model 1262/9DMI Quadrant Sensor, 10 mm diameter, 0.013 mm gap
- Model 1243 BiCell Sensor, 1.3 mm x 2.5 mm, 0.127 mm gap
Position Sensing Amplifiers and Position Sensing Indicators
A position-sensing amplifier (PSA) processes the signal produced by a position sensor and produces an output signal correlated with position.
- UDT Instruments Model 301-DIV Position Sensing Amplifier: The Model 301-DIV amplifier links position-sensing photodetectors with your indicators or controls. This versatile system works with bi-cell detectors for nulling and centering operations, or with single-axis lateral-effect detectors for continuous position measurement. It also can normalize the differential output of two discrete detectors.
- UDT Instruments Model 501 Dual-Channel Position Sensing Amplifier: The Model 501 dual channel position sensing amplifier was designed with a 1.5 MHz frequency bandwidth with auto polarity, auto range selection and an external control port. Maximum output voltage range is 10 volts. The range indicators are four range LED illuminated for HI-LO sum levels and the current model uses quadrant or tetralateral position sensing detectors.
A position-sensing indicator (PSI) combines a position-sensing amplifier and display module in a single instrument, in order to provide a direct positional readout.
- UDT Instruments Model 431 X-Y Optical Position Indicator: The Model 431 uses a network of analog amplifiers and dividers. The first amplifier stages operate in the transimpedance mode, boosting the photodetector current and converting it to a voltage. The secondary stages add and subtract the signals from each of the front-end amplifiers. A divider network divides the difference by the sum. And a final buffer amplifier drives the digital display and analog output.
- UDT Instruments Model 531 X-Y Optical Position Indicator: When interfaced with continuous or segmented position sensing detectors, the Model 531 determines the location of the centroid of an incident light spot, and displays its X-Y position both digitally and graphically. This position information may then be transferred by computer over a built-in IEEE-488 interface.