Retroreflective photoelectric sensor
a photoelectric sensor and retroreflective technology, applied in the direction of optical radiation measurement, instruments, polarising elements, etc., can solve the problems of light leakage, the quantity of received light in the presence of light-reflecting target objects cannot be made sufficiently smaller than that in its absence, and achieve reliable detection capability and production cheap
Inactive Publication Date: 2006-08-10
OMRON CORP
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Benefits of technology
[0008] It is therefore an object of this invention in view of the problem described above to provide a retroreflective photoelectric sensor which can be produced inexpensively and still has a reliable detection capability.
Problems solved by technology
With a sensor of this structure with both the first and second polarizers placed behind the lens, however, there was a problem of light leakage even if the two polarizers are set in the mutually perpendicular relationship (or the cross-nicol relationship, forming so-called crossed nicols) such that the quantity of received light in the presence of a light-reflecting target object could not be made sufficiently smaller than that in its absence.
Method used
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Embodiment Construction
[0024] The invention is described next by way of an example with reference to drawings but this example is merely one of many that embody the invention and hence is not intended to limit the scope of the invention.
[0025]FIGS. 1A and 1B are schematic drawings for explaining the principle of a retroreflective photoelectric sensor 100 of a biaxial type respectively when there is not and there is an object in the target area of detection. In FIGS. 1A and 1B, symbol 200 indicates a reflector having a reflecting surface 200a, symbol 300 indicates a light-reflecting target object of detection with a reflecting surface 300a, symbol L1 indicates light emitted from the sensor 100, symbol L2 indicates reflected light from the reflector 200 and symbol L3 indicates reflected light from the target object 300.
[0026] As can be clearly understood from FIGS. 1A and 1B, the retroreflective sensor 100 is placed opposite the reflector 200 so as to sandwich therewith a target area of detection where th...
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A retroreflective photoelectric sensor has a light-emitting optical system having a light-emitting element and a first polarizer and serving to transmit light from the light-emitting element through the first polarizer, a light-receiving optical system having a second polarizer and a light-receiving element and serving to convert light received through the second polarizer into an electrical signal by the light-receiving element, the first and second polarizers having mutually perpendicular polarizer axes, a single lens for both emitting light from the light-emitting element and receiving light to the light-receiving element therethrough, a beam splitter serving to direct light received from the light-emitting optical system to the single lens and light received from the single lens to the light-receiving optical system, and a phase shifter inserted between the light-emitting optical system and the single lens.
Description
[0001] This is a divisional of application Ser. No. 10 / 731,526 filed Dec. 8, 2003, currently pending.BACKGROUND OF THE INVENTION [0002] This invention relates to a retroreflective photoelectric sensor which may be used with a reflector to together sandwich a target detection area for detecting a light-reflecting target object in the detection area. [0003] A retroreflective photoelectric sensor is used generally with a reflector to together sandwich a target detection area therebetween and detects the presence or absence of a target object of detection based on the difference in the character of reflected light from the reflector and that from the target object of detection for light emitted from the sensor. In the case of a retroreflective photoelectric sensor for a target object, a reflector with a reflection characteristic that affects the polarization mode of the light emitted from the sensor is used, and the presence or absence of a target object of detection is determined on th...
Claims
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IPC IPC(8): H01J40/14G01J1/02G01V8/14H01H35/00
CPCG01V8/14
InventorMAJIMA, YOSHIKAZUKURUMADO, YUKINORINAKAMURA, ARATA
OwnerOMRON CORP