Abstract:
Photoelectric cell with means of configuring the operating mode. The cell has several optosensitive zones  11, 12,  D capable of outputting magnitudes that are activated or processed in different manners, by configuration and/or processing means  7, 19.  The cell may thus be used in reflex mode, proximity mode or proximity with background elimination mode. Amplifying parts  16   a,    16   b  are provided at the side of the optosensitive zones to amplify electrical magnitudes before routing them to the microcontroller  19  in the processing circuit  6.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a photoelectric cell designed for detection of an object, comprising an optical component equipped with a photosensitive area that generates an electrical reception signal on a conductor as a function of the incidence of an optical beam, and an amplification and processing circuit generating an output signal that depends on the electrical signal. 
     2. Discussion of the Background 
     A photoelectric cell is well known. When they operate by detection of a light flow originating from infinity without any proximity effect, they form par of a first family of cells called reflex, polarized reflex or barrage cells. When they operate by detection of light rays at high incidence, they form part of a second family of cells operating either by measurement of energy in a “proximity” subfamily, or by triangulation, comparing two channels of a PSD type component in a “proximity with background elimination” subfamily. Detection modes for these two families will be referred to as “reflex model” and “proximity mode” in the rest of this document, for simplicity. Cells in the first family are used particularly to detect the presence of an object, whereas cells in the second family are used particularly to detect the distance or brightness of an object. 
     The optical components necessary to make these two families are different. Their surface area is small, typically of the order of 0.6×0.6 mm for reflex cells, but larger and typically with an apparent size 1.6×1.6 mm for proximity cells or 1×2 mm for proximity with background elimination cells. The result is that several types of components need to be procured and stored (typically at least three different components) in order to manage these two product families. 
     Furthermore, magnetic compatibility constraints affecting photoelectric cells are increasing, whereas the optical components that use them at the present time have the disadvantage that they offer low intrinsic amplification in the case of phototransistors, and even zero amplification in the case of photodiodes. 
     SUMMARY OF THE INVENTION 
     The purpose of this invention is to overcome these disadvantages by using simple arrangements that can be taken particularly on the optosensitive component or the processing circuit, so that it becomes easier to make a photoelectric cell insensitive to parasites and capable of operating in different operating modes in order to offer different detection possibilities. 
     According to a first aspect of the invention, the photoelectric cell comprises configuration means capable of acting on the photosensitive area or the processing circuit in response to a means of selecting a reflex operating mode or a proximity operating mode for the cell. 
     According to a second aspect of the invention, the photosensitive area is separated by separation into at least two adjacent partial areas isolated from each other, each of these partial areas being capable of supplying electric magnitudes to one of the two channels connected to the amplification and processing circuit, and configuration means are provided to select the operating mode specified for the cell; these configuration means are preferably capable of activating and/or processing electrical magnitudes output from the partial areas, for example by means of switches and/or a microcontroller, as a function of the selected operating mode. 
     Preferably, and when it is required to configure the cell in reflex mode and in proximity mode the adjacent partial areas are capable of outputting electrical magnitudes to a first conductor and a second conductor connected to the channel and configuration means are provided to activate the first conductor in reflex mode and the second conductor in proximity mode; the photosensitive area used in proximity mode may itself be separated by a demarcation transverse to separation, into isolated adjacent areas that are connected to the respective channels and the surface area of which varies continuously along the main direction of the component, this direction being the direction of displacement of the optical spot of the incident beam on the photoreceptive area in proximity mode. 
     Preferably, and when it is required to configure the cell in proximity mode or in proximity with background elimination mode, the photosensitive area used may be separated by demarcation transverse to the main direction, into isolated adjacent zones; the surface area of which varies continuously along the main direction of the component, which is an integrated component preferably comprising two amplifying parts of the amplification and processing circuit at the side of the photosensitive area, that amplify the signal originating form the partial areas or photosensitive zones and which are connected through the respective channels to a remaining part of the amplification and processing circuit that controls the configuration described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more detailed description will now be made of a non-restrictive embodiment of the invention, with reference to the attached drawings. 
     FIG. 1 diagrammatically shows a photoelectric cell. 
     FIG. 2 shows the composition of an optoreceptive component of a photoelectric cell according to the invention. 
     FIGS. 3 and 4 show the optoreceptive component configured in reflex mode and in proximity mode. 
     FIG. 5 shows a variant of the component according to the invention. 
     FIG. 6 shows another variant. 
     FIG. 7 shows one form of construction of the configuration means; 
     FIG. 8 shows an example of processing applied to voltage signals output by the component. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The photoelectric cell illustrated in FIG. 1 comprises an electronic circuit  1  that generates electrical emission pulses and an emission diode  2  that emits a light beam collimated by a lens  3 . The, cell emission assembly does not form part of the invention and will not be described further. The cell also comprises firstly a reception assembly provided with a lens  4  that focuses the received light beam as a function of the presence of an object, an optosensitive device  5  that transforms the received light flux into an electrical magnitude, and an electronic reception circuit  6  that amplifies and processes this magnitude to generate an output signal S that depends on whether or not an object is present. The cell is connected through a link with two or three wires to an energy source E and a load L. 
     As will be described later, the cell is capable of operating either in reflex mode or in proximity mode as defined above, under the control of configuration means  7 . 
     In the photoelectric cell shown (see FIG.  2 ), the optosensitive device  5  forms part of an integrated type unit component C that also comprises an amplifying part of the electronic reception circuit. The integrated component C is provided with a photoreceptive area  10  that extends along an X direction corresponding to the direction of displacement of the optical spot during movement of an object to be detected in proximity mode. The photoreceptive area  10  is formed on the surface of an appropriate optosensitive material; it currently operates in photodiode, but it could also operate differently and is separated into two areas  11 ,  12  isolated from each other and adjacent in the X direction. The areas  11 ,  12  are isolated along a separation line  14  perpendicular to the X direction. 
     The partial areas  11 ,  12  are separated by a demarcation  15  located in skew, for example diagonal, into zones of adjacent isolated trapezoidal or triangular photodiodes D 1   a,  D 1   b  and D 2   a,  D 2   b  respectively, the surface area of which varies approximately continuously along the X direction. This variation may be linear or non-linear. The integrated component C comprises lateral amplifying areas  16   a,    16   b  adjacent to the photosensitive area  10 , that are located on the two opposite sides of the component and that at least partly (as we will see later) perform the amplification function for circuit  6 . Two connecting channels A, B connect zones  16   a  and  16   b  to the rest of circuit  6 . The photodiode zones D 1   a,  D 2   a  of areas  11 ,  12  are connected in parallel to channel A through conductors  11   a,    12   a,  whereas the photodiode zones D 1   b,  D 2   b  of areas  11 ,  12  are connected in parallel to channel B through conductors  11   b,    12   b;  conductors  12   a,    12   b  are fitted with electronic switches  13   a,    13   b  respectively, acted upon by configuration means  7  to control whether or not these zones are activated. 
     Currents Ia, Ib transported by conductors  11   a,    12   a,  and  11   b,    12   b  are conducted to amplifying circuits and appropriate ambient light suppressers  17   a,    17   b  located in zones  16   a,    16   b,  and voltages Va, Vb are created on channels A, B which are analyzed in an appropriate part of the electronic reception circuit  6 . Consequently (see FIG.  8 ), circuit  6  comprises for example a sampler-blocker  18  and a microcontroller  19  with an integrated digital-analog converter  20 , the reference input  20   a  of this converter being connected to a programmable voltage regulator  21  that forms part of the configuration means  7 . The voltage regulator  21  outputs different voltage levels in reflex and in proximity mode, in response to a reflex/proximity operation signal transmitted by the microcontroller through a line  19   a  following a configuration order Sc output by a switch or a connection wire. 
     Apart from programmable voltage regulator  21 , the configuration means  7  may comprise (see FIG. 7) a comparator  22 , a fixed voltage V 0  being applied to one of the inputs of this comparator and a voltage Vcc output by the programmable voltage regulator  21  being applied to the other input. The configuration may be switched through any usual electronic or mechanical means. 
     As shown in FIG. 5, the photosensitive areas  11 ,  12  may each be separated into more than two zones by several separations  15 . Area  11  (zones D 1   a,  D 1   b ) may be located as shown at the center of the component along the X direction, whereas the area  12  (zones D 2   a,  D 2   b ) and another zone  12 ′ (zones D′ 2   a,  D′ 2   b ) are located on opposite sides of zone  11  along the X direction. 
     The photosensitive zones D may be inter-digitate as shown in FIG. 6 to adapt the cell to a light spot smaller than the width of the photosensitive area  10 . In this case the area  10  is separated into several rectangles  23  each composed of two triangles  23   a,    23   b  or other zones with surface areas gradually increasing or decreasing along the X direction and with appropriate geometry; triangles  23   a  being connected to channel A and triangles  23   b  being connected to channel B. 
     Depending on the case, the photoelectric cell described may operate in reflex mode or in proximity mode with the same receiving lens  4 , or with different lenses. 
     The photoelectric cell described operates as follows. 
     In order to operate in reflex mode, the signal Sc with a specific logic level is transmitted to the microcontroller  19 , and the microcontroller switches the programmable voltage regulator  21  through line  19   a;  the regulator  21  outputs its first voltage level and switches  13   a,    13   b  are open (FIG.  3 ). Only photodiodes D 1   a,  D 1   b  output a current when the photosensitive surface  10  receives the light flux. The voltages Va, Vb resulting from the amplification in amplifiers  17   a,    17   b  are summated by the processing circuit  6 , and the output signal switches as a function of the value of this sum. 
     In order to operate in proximity mode, the signal Sc with the inverse logical level is transmitted to the microcontroller  19  and the microcontroller switches the programmable voltage regulator through line  19   a;  the regulator  21  outputs its second voltage level and switches  13   a,    13   b  are closed (FIG.  4 ), All photodiodes D 1   a,  D 1   b  and D 2   a,  D 2   b  output current and voltages Va, Vb are either summated by the microcontroller  19  in the processing circuit  6  (operation in proximity), or are compared with each other by the microcontroller  19  (operation in proximity with background elimination) and the output signal switches as a function of the value of this sum or the result of the comparison. 
     When it is required to make the cell operate in proximity and proximity with background elimination modes only, line  19   a  may be omitted and the configuration is made using signal Sc by the microcontroller  19  that decides to summate the voltage signals originating from the various photosensitive zones, or to compare the signals on channels A and B, depending on the required mode.