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RETROREFLECTORS
Retroreflectors are used with reflex type sensors. Two types of retroreflector target materials are available: corner cube and embedded glass bead reflectors. Corner Cube Retroreflectors This type provides the highest signal return to the sensor. Cube style reflectors exhibit 2000 to 3000 times the reflexivity of white paper. Three adjoining sides are arranged at right angles to each other. When a ray of light strikes one of these sides (A), it is reflected to the second (B), then the third (C), and then back to the source in a direction parallel to its original course. Thousands of these cube shapes are molded into a rugged plastic reflector or vinyl material. Glass Bead Retroreflectors Glass bead retroreflectors are available in tape form with an adhesive back. The bead style surface is typically rated at 200 to 900 times the reflectivity of white paper ? much lower than corner cube reflectors. Glass bead retroreflectors can not be used with polarized reflex sensors. Retroreflector Size The size of the retroreflective target has a major effect on the excess gain and range of a reflex sensor. At a point where the sensor's beam size is larger than 3 inches, a 3-inch diameter retroreflector will return about 36 times more light than a 1/2-inch diameter retroreflector. Several retroreflectors can be grouped together to provide a larger reflective area. Larger retroreflectors can also simplify sensor alignment by providing a larger target to aim the sensor at. Using Retroreflectors with Polarized Reflex Sensors Only corner cube retroreflectors can be used with polarized reflex sensors. When polarized light from the sensor's light source strikes a corner cube retroreflector, it is returned to the sensor in a depolarized state. This allows some of the light to pass through the detector's polarizer, which is positioned at 90? to the source polarizer, to allow the sensor to operate. Glass bead retroreflectors do not depolarize light and will not work with polarized reflex sensors. Although corner cube tape works with polarized reflex sensors, we recommend testing sensor and tape prior to installation. |
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