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| | | 3. Diffuse mode sensor | | |
| | | Object in sampling range | | |
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| | | The structure of the diffuse mode sensor is based on the same principle as a retrorefective sensor. It does not have a reflector, however. Instead, the light reflected from the recorded object is evaluated by the receiver. | | |
| | | Bright background | | |
| | | Near element receives more light object is detected | | |
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| | | Scanning range | | |
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| | | Due to the diffuse reflection (re-emission) through the object, the detection range of the light sensor is reduced in comparison to the retroreflective sensor. This is referred to as the detection range. The detection range means the maximum distance from the professional transmitter at which an object can still be reliably detected. | | |
| | | Far element receives more light object is ignored | | Object in the background | | |
| | | Scanning range | | |
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| | | Characteristics: • A nearly constant detection range on diffusely reflecting materials with sharply differing re-emission levels. • Dark objects in front of a bright background are reliably recorded. • Not sensitive to interfering reflections of objects outside the adjusted detection range. • High stability control. • Inexpensive installation since the sensor consists of only one unit and no reflector is required. The principle of foreground suppression is similar to background suppression. Diffuse mode sensor of this type ignore all objects that are located closer to the sensor than a previously adjusted minimum detection range. Convergent mode sensor (HGU) A convergent beam sensor is a more efficient type of diffuse mode sensing. The emitter professional lens is focused to an exact point in front of the sensor and the receiver lens is focused to the same point. The range for a convergent beam sensor is fixed and defined as this focus point. The sensor is able to detect an object at the focus point, plus or minus some distance. Because all the emitted energy is focused to a single point, a high amount of excess gain is available. This excess gain enables the sensor to easily detect narrow or low reflectivity targets. | | |
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| | | -Sensitivity adjuster Background suppression sensor Diffuse mode sensor with background suppression were developed to achieve a defined detection range with any objects - independent of its brightness, color or other properties such as the brightness of the background. The following illustration shows the functional principle of a diffuse mode sensor with background suppression. The light emitted by the transmitter falls on the object, focused by the optics. If the object is located within the detection area, a part of the reflected light, focused by the receiver's lens, forms an image on the near element of the receiver (N); the professional scanner emits the signal "on". As the distance from the object increases, this light spot moves in the direction of the far element (F). At the edge of the detection zone, half of the light spot lies on the near element, half on the far element, and the scanner emits an "off" signal. If the object recedes further, the light spot only falls on the far element, and the scanner continues to emit "off". | | |
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| | | Subject to reasonable modifications due to technical advances. | | Copyright Pepperl+Fuchs, Printed in Germany | | |
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| | | Pepperl+Fuchs Group • Tel.: Germany +49 621 776-0 • USA +1 330 4253555 • Singapore +65 67799091 • Internet http://www.pepperl-fuchs.com | | |
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