MXPA00003630A - Compact moisture sensor with efficient, high obliquity optics - Google Patents

Abstract

Compact moisture sensor (10) mounted on inner surface (30) of windshield (18) to detect moisture on outer surface (32) and control windshield wipers (20). Includes coupler (24) having collimator (37) and focuser (42) and housing (28) detachable covering coupler. Planar circuit board (26) disposed within housing (28) includes emitters (56) and detectors (58) mounted such that the axes of emission and detection are perpendicular to windshield (18) when housing (28) is secured to coupler (24). Collimator (37) and focuser (42) are disposed adjacent emitter (56) and detector (58) such that the optical axes of collimator (37) and focuser (42) form oblique angles with respect to emission and detection axes. Two emitters and two detectors are used to form four optical paths of equal length and optical efficiency. In operation, a light beam from emitter (56) enters windshield (18) at a forty-five degree angle and is reflected back form outer surface (32) of windshield (18) to detector (59), which generates a control signal based on the amount of light reflected from the outer surface.

Description

COMPACT SENSOR OF MOISTURE, WITH EFFICIENT OPTICAL OF HIGH OBLIGUITY BACKGROUND OF THE INVENTION The present invention relates generally to an optical moisture sensor, which is mounted on the inner surface of a windshield and, more particularly, to an optical, compact moisture sensor, having optical emitters. , detectors and optical components mounted on a flat circuit board, which is placed parallel to the interior surface. A coupler, which has collimating and focusing lenses, is used to refract the light beams, as they travel from the emitters, and are reflected from the outer surface of the windshield, from the new detectors. Motor vehicles have long been equipped with engine-driven windshield wipers to wipe moisture from the outer surface of this windshield, at least within the driver's field of vision and generally over a larger area, so that increase vision through the windshield. In the vehicles Currently, the windshield wiper system includes multi-position or variable speed switches, which allow the driver to select a wide range, if not infinitely variable, of speeds to suit the conditions. The wiper controls are manually operated and typically include a delay characteristic, whereby the wipers operate intermittently at selected time delay intervals. The cleaning control systems have been recently developed, which include a humidity sensor, mounted on the windshield, to automatically activate the engine, when moisture is deposited on the surface of the windshield or other window of the vehicle, in which a cleaner can be used, such as the rear window. When detecting rain or other moisture on the glass surface, the cleaners can be controlled accordingly. Such cleaning control systems relieve the driver of the inconvenience of frequently adjusting the speed of the cleaner as the driving conditions change. The control systems of cleaners with optical moisture sensors,. It has been incorporated into the production of • years. passenger car models. In order to increase commercial use and consumer acceptance of cleaner control systems, there is a need for a more compact and less expensive optical moisture sensor. The wiper control systems have employed a number of different technologies to detect the moisture conditions encountered by the vehicle, which include conductive, capacitive, piezo-electric and optical sensors. Optical sensors operate with the principle that a beam-of-light is diffused or deflected from its normal path by the presence of moisture on the outer surface of the windshield. Systems employing optical sensors have the singular advantage that the resource for detecting alterations in an optical path is directly related to the phenomena observed by the driver (i.e., disturbances in the optical path that provides the driver's vision). Noak (U.S. Patent No. 4,355,271) describes an optical moisture sensor, which has components optics mounted in a box type housing, attached to the interior surface of the windshield. Moisture sensing devices for controlling the windshield wipers of a vehicle, as described by McCumber et al., And Tender (U.S. Patent Nos. 5,059,877 and 5,239,244) also disclose a box-like housing, surface mounted inside the windshield, to enclose the optical and electronic parts. In optical moisture sensors, light from an emitter is directed * to the windshield at an angle of approximately forty-five degrees, with respect to the windshield. The light is then reflected by the outer surface of the windshield at approximately a forty-five degree angle and is directed to the detector. The presence of moisture on the surface of the windshield affects the reflection of light at the air and glass interface, on the outer surface of the windshield, and this change in the reflected light is electronically processed and used as the signal to activate the windshield wipers. McCumber et al (U.S. Patent No. 4,620,141) describes an automatic control circuit for initiating a sweeping the windshield blades, in response to the presence of water droplets on the outer surface of a windshield. When the angle of entry of the light beam on the windshield is greater than fifty degrees, a loss of the signal frequency occurs. When the entry angle is less than forty degrees, a loss of sensitivity occurs and the sensor is not able to properly detect the moisture in the windshield. Consequently, it is essential that the angle of entry of the light beam from the emitter enters the windshield at approximately forty-five degrees. The desired angle of forty-five degrees can be achieved by mounting the optoelectronic devices (emitters and detectors) at forty-five degree angles or by diverting light, as it travels between the devices and the glass windshield. Stanton (U.S. Patent No. 5,414,257) discloses an optical sensor having optoelectronic devices mounted on a circuit board at an appropriate angle, with respect to the surface of the glass, such that its optical axis extends at the appropriate angle of forty. and five degrees or can be diverted to do it. Stanton teaches the molding of flexible epoxy resin devices and • bends the device guides at an angle to facilitate angled mounting. The problem with the folding of the electronic device guides is that the automatic component insertion equipment can not insert components with bent guides, which increases the cost of assembling the circuit boards. In addition, bent guide devices are less reliable from a performance standpoint. The assembly of the optoelectronic devices in the circuit boards without bending the guides is described by Zettler (U.S. Patent No. 5,560,245). The emitters and detectors are mounted on smaller satellite circuit boards, which are angled with respect to the main circuit board. These satellite circuit boards are angled to align the emitters and detectors at the appropriate forty-five degree angle with the windshield. Although this assembly configuration does not require the formation of guides, the use of small circuit boards creates other problems. The Small circuit boards used to mount the optoelectronic devices can not accommodate the system of circuits that process the signal, which must be located on a separate circuit board. The use of multi-circuit boards and the orientation of these boards of circuits in the sensor housing increase the cost of the sensor. Conventional optoelectronic devices, which include the new surface mount technology (SMT), are usually designated so that the optical axis is perpendicular to the circuit board on which they are mounted. Teder (U.S. Patent No. 5661303) discloses the use of a simple circuit board mounted coplana with the windshield surface, resulting in a low and compact cost sensor recint. However, this design requires optical components that have an optical ej, which are approximately parallel to the optical ex of the optoelectronic devices. It is convenient to reduce the size and cost of the optical components to further reduce the size and cost of the humidity sensor.

Another way to reduce the size and cost of the optical sensor includes reducing the number of optoelectronic components. Noak reveals the use of a single detector to simultaneously detect two or more emitters. Muller (U.S. Patent No. 5015931) discloses that several beams can be derived from a single non-directional emitter. Such configurations provide the desired area of detection with a smaller number of detectors. McCumber et al. (U.S. Patent No. 4,620,141) teaches that a balanced configuration tends to reject the effect of ambient light. The issuers, however, typically vary by about 2: 1 in signal strength. This has limited the ability of optical moisture sensor systems to achieve a good balance of the signal. The optical path shown by Muller in the patent 5015931 is unequal length ole. Thus, the trajectories would be of differing optical efficiency and can not be used to make a well-balanced system. Teder (U.S. Patent No. 5661303) uses four emitters and two detectors to achieve four optical paths of equal length, however.

It is convenient to reduce the size and cost of the humidity sensor, using even fewer components. The optical humidity sensor must be securely coupled to the windshield and the optics contained therein must be optically coupled to the windshield to effectively eliminate the interface between the light emitters-detectors and the glass surface from the optical point of view. Purvis (U.S. Patent No. 5,262,640) describes an intermediate adhesive inner layer for fixing the sensor housing and the optics contained therein to the windshield. The sensor housing is fixed directly to the surface of the windshield or other window of the vehicle, by means of an intermediate inner layer, disposed between the sensor housing and the inner surface of the windshield. Vehicle manufacturers want a sensor that is already installed by the windshield manufacturer, or a sensor that is very easy to install on the production line of the vehicle. The windshield manufacturer sends these windshields nested together, so there is very little space to mount a sensor.

Schofield (U.S. Patent No. 4,930,743) discloses the use of a bra, such as a mirror holder for posterior vision, to mount the optical moisture sensor. This approach requires an additional support structure or the addition of silicone parts, to optically attach the moisture sensor to the windshield. A bra mounting system results in additional parts and increased costs. Bendix (U.S. Patent No. 5,278,425) and Stanton (U.S. Patent 257) teach that a lens can be permanently affixed to the windshield, so that a sensor housing can be removably mounted on the lens. This lens can impart focal power to the beam, as shown in Bendix. Alternatively, the lens can couple the beams to the windshield through flat surfaces normal to the direction of the beam, as revealed by Stanton. However, both Bendix and Stanton require a lens that is approximately as thick as the windshield. When windshields are stacked for transport from the glass manufacturer to the vehicle assembly line, the additional space needed for the lens adds additional handling costs to the cost of the windshield. It is convenient to have a sensor which attaches to the windshield and is thin enough so as not to interfere with the nesting of the windscreens during transport. Modern solar control windshields, such as windshields sold under the trademark "EZ-KOOL", commercially available from Libbey-Owens-Ford Co., absorb the infrared rays used by many optical moisture sensors. Sensors without the coupling or optics that collect light will probably be too inefficient for use with these windshields. In German Patent No. DE 3314770 to Kohler, et cl., The lenses in a coupler increase the detected area and efficiency of a humidity sensor. Watanabe (US Patent No. 4,701,613) discloses a series of V-grooves, which couple the spokes in and out of a windshield with an efficiency-enhanced nail, however, the devices are mounted at an angle of forty-five degrees with respect to the surface of the glass, because the slots do not gather the deviated rays of light and focus them-over-focus detecforY It is convenient to mount the optoelectronic components on a simple flat circuit board, while improving the efficiency of the optical sensor. humidity, for use in modern solar control windshields.

COMPENDIUM OF THE INVENTION The present invention relates to a humidity sensor, for mounting on a first surface of a glass sheet, for detecting moisture in a detection area on a second surface of the glass sheet. The humidity sensor includes a coupler to be mounted on the first surface of the glass sheet, to couple the light rays in and out of the glass and a removable housing, secured to a coupler. A flat circuit board is secured in the housing and has a device surface which is disposed generally parallel to the first surface of the glass sheet. An emitter, to emit rays of light around an emission axis, is mounted on the surface of the device. The emission axis extends from the emitter, approximately perpendicular to the surface of the device of the circuit board. A collimator, to collimate the light guides coming from the emitter inside a beam of light collimated, has an opening, with a physical center and an optical center, spaced from the physical center. An optical axis extends through the optical center. The emitter and the collimator are arranged so that the optical axis forms a first oblique angle with respect to the axis of emission. - - - A detector, having a detection surface and a detection axis, extending from the detection surface, is mounted on the surface of the flat circuit board device, so that the detection axis is approximately perpendicular to the surface of the device, the detector detects the light that hits the detection surface and generates signals in response to the detected light. The coupler also includes a focusing means, to focus the beam of collimated light on the detection surface. This focusing means has an opening with a physical center and an optical center spaced from the physical center. An optical axis extends through the optical center. The focusing means and the detector are arranged so that the optical axis forms a second oblique angle with respect to the detection axis. _ _ The sensor is provided with multiple optical emitter-detector systems, to provide an array of detected areas. A pair of emitters is used in conjunction with a pair of detectors to achieve four separate optical paths of equal length and four detection areas on the glass surface. The emitters and detectors form a balanced electrical system, which is electrically connected to the control circuitry of the windshield wiper, to control the operation of the wiper system. An efficient and cost-effective resource for mounting moisture sensors on the windshield of a vehicle is supplied. In the present invention, the coupler will be mounted generally on the inner surface of the windshield by the glass manufacturer, before transporting the windshields to the manufacturing floor of the vehicles. The vehicle manufacturer conveniently assembles the sensor housing, which includes the circuit board. on the coupler, as the vehicle is assembled. Because the coupler is small, thin and relatively cheap, this coupler can be mounted e " all windshields that are transported from the glass manufacturer to a specific assembly line in the automobile plant, without changing the conventional packing materials used by the glass manufacturer. As the windshields are installed in a vehicle, the sensor assembly can be completed by conveniently attaching the sensor housing to the coupler. The cost of manufacturing the sensor is reduced by assembling all the optoelectric components and the process circuits of the signal on a simple, flat circuit board. Surface mounted technology and on-board chip technology, combined with automatic assembly techniques for circuit board production, provide improved efficiency and cost reductions in sensor fabrication. The configuration of the present invention eliminates the use of multiple circuit boards and the formation of guides on optical devices. A substantial portion of the light rays emanating from each emitter are coupled to each of the detectors, providing high optical efficiency.

Additionally, a pair of emitters and a pair of detectors are used to form four optical paths of equal length, to provide a balanced optical system having four detection areas. The numbers of the optoelectronic components is reduced, which lowers the cost of the sensor, without reducing the effectiveness and efficiency of the humidity sensor.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing, like other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment, when considered in light of the accompanying drawings, in which: Figure 1 is a fragmentary perspective view, showing an optical sensor of. humidity, mounted on the windshield of a car; Figure 2 is an enlarged perspective view, showing the mounting of the humidity sensor of the present invention, on the inner surface of the windshield; "~ Figure 3 is an enlarged perspective view, showing the relationship of the assembly between the housing and the coupler of the present invention; Figure 4 is a cross-sectional view, showing the collimator mounted adjacent to the emitter in the present invention; Figure 5 is a side view, taken along line 5-5, showing the opening of the collimating lens; Figure 6 is a perspective view, showing the collimator, extending from the coupler of the present invention; Figure T is a side view, taken along line 7-7, showing the opening of the lens of collimation; Figure 8 is a plan view of an alternative embodiment of the present invention, illustrating the four optical paths; Figure 9 is a schematic diagram illustrating the optoelectronic components of the alternative embodiment of the present invention; Y Figure 10 is a cross-sectional view of a second alternative embodiment of the present invention, illustrating the lens of collimation using a semented lens.

DESCRIPTION OF THE PREFERRED MODE Referring now to Figure 1, there is generally shown a humidity sensor 10, according to the present invention, and a portion of a car, including a hood 12, side posts 14 and a roof 16, which they define an opening into which a windshield 18 is mounted. The windshield wiper blades 20, shown in their rest position, along the lower edges of the windshield, are operable in a conventional manner to oscillate in arcs 22 and sweep. the moisture accumulated from the surface of the windshield 18. The humidity sensor 10 is secured to the windshield within the area swept by the wiper blades 20. As shown in Figure 2, the humidity sensor 10 includes a coupler 24, a circuit board 26, for mounting the electronic components 27, and a housing or 28 of the sensor, which can be attached to the coupler 24 to enclose the circuit board 26. The coupler 24 includes a mounting surface 29, which is secured to the inner surface 30 of the windshield 18 for optical detection of moisture on the outer surface 32 of the windshield. This humidity sensor 10 is typically mounted adjacent to the rear view mirror (not shown) on the inner surface 30, so as to minimize any obstruction of vision of passengers in the automobile, although the sensor can be mounted on any other part on the windshield. The windshield 18 is, in general, relatively flat in the area where the sensor 10 is to be mounted, so that the mounting surface 2_9 of the coupler 24 can be flat. However, it is considered that the mounting surface 29 of the coupler 24 may be correspondingly contoured to match the curved surface of the windshield, when appropriate. The sensor 10 can also be mounted on other advantages, which include the rear window. An inner layer 34 double sided adhesive is used to secure the mounting surface 29 of the coupler to the windshield 18 or another window. The inner layer 34 is made of silicone or other transparent, flexible, similar plastic material. This coupler 24 can be secured to the windshield 18 by the glass manufacturer, before transporting this windshield 18 to the automobile assembly line. A rectangular sleeve 36 extends from the coupler 24 opposite the mounting surface 29 and retaining tabs 37 extend outwardly from the ends of the sleeve to secure the coupler to the housing 28, as described below. The coupler 24 also has a collimator 37, which includes a collimation body 38, which extends from the coupler and a collimating lens 40, disposed adjacent to the collimation body. The collimating lens 40 has an optical axis 41, which extends through the collimating body 38 at an angle of forty-five degrees, with respect to the inner surface of the windshield 30. This coupler 24 further includes a focusing means 42, having a focusing body 43, extending from the coupler, and a focusing lens 44, disposed adjacent to the focusing body. The focusing lens 44 has an axis optical 45, which extends through the focusing body 43 at an angle of forty-five degrees with respect to the inner surface of the windshield 30. The coupler 24, the collimation body 38, the lens 40 of collimation, the body 43 of focus and focus lens 44 are preferably formed integrally from a single piece of material. The collimating lens 40 is formed by shaping the surface of the collimation body 38 and the focusing lens 44 is formed by shaping the surface of the focusing body 43, in the manner described below. Alternatively, a separate collimation lens 40 may be disposed adjacent the collimation body 38 and a separate focusing lens 4-4 may be disposed adjacent the focusing body 43. The coupler is formed of a refractor material, such as polycarbonate, or a polyester resin, although any suitable material can be used which can withstand a wide range of temperatures, to which a car can be subjected. The coupler 24 optically couples light rays in and out of the windshield 18, so that the light hours - are not diverted in accordance they pass from the collimating body 38 to the windshield and from the windshield to the focusing body 43. In addition, the coupler 24 supplies a secure base for mounting the collimating lens 40, the focusing lens 44 and the housing 28 to the windshield. 18. The thickness of the coupler 24 is an important consideration from a packaging point of view when transporting the windshield from the glass manufacturer to the automotive assembly line Special shelves and packaging material are designed to pack the windshields Individuals as close as possible to transport efficiency while protecting the windshields during transport to prevent scratching or other damage to the windshields Automobile windshields typically include a mounting button (not shown) on the windshield to mount the windshield. mirror of the rear view, so that the transport shelves can accommodate such mounting button The coupler 24 of the present in Vention is less than 5mm thick, thinner than the mounting button of a typical mirror. As a result, the thin coupler 24 allows the glass manufacturer to mount the Coupler 24 on the windshield production line, without having to change the handling processes of the packaging and material, used to deliver the windshield to the automotive assembly line. The ability to mount the coupler in windshield production operations, without changing packaging and material handling characteristics, is an important consideration in gaining increased use of the moisture sensor and cleaning control system by automobile companies. . Referring now to Figures 2 and 3, the sensor housing 28 is made of a hard plastic material or other rigid material, and is opaque to block the indexed light. For clarity, Figure 3 shows the coupler 24 without displaying the collimator or focuser devices. The housing 28 includes a base 46 and four side walls 48, which extend from the base, preferably forming a box-shaped enclosure. The housing 28 has a dimension to fit over the sleeve 36 of the coupler 24, after this coupler has been secured to the windshield 18. The slots 50 are formed inside the walls 48 of the housing for receiving the tabs 37. of the coupler and detachably retain the housing 28 to the coupler 24. The side walls 48 of the housing 28, like the sleeve 36 of the coupler 24, are each made in a slightly deformable form to facilitate pressure fitting of the housing in place on the coupler, so that the tabs 37 of the coupler enter the slots 50. Optionally, the notches can be cut into the sleeve 36 of the coupler 24 to increase the deformation. - - Once the housing 28 is pressed into place on the sleeve 36 of the coupler, any lateral forces applied to the coupler 24 were transferred through the walls 48 of the housing to the sleeve 36. The walls 48 of the housing and the coupling sleeve 36 have a large surface area and will have no tendency to concentrate forces leading to rupture. Furthermore, the non-circular configuration of the coupling sleeve 36 absorbs the torsional forces applied to the housing 28. The present humidity sensor will thus tend to remain firmly fixed to the windshield in the event of a collision or if it is handled awkwardly by a curious passenger. A notch 51 in the side wall 48 of housing 28 facilitates its removal with a coin or screwdriver. Preferably, the coupler 24 is autoclaved on the windshield with the aid of a very high adhesion silicone, although any suitable material can be used. The shallowness of the coupling method of the coupler allows this installation to be made by the windshield manufacturer, without impacting the windshield package density, as described above. Vehicle manufacturers are averse to any process that uses adhesives or other chemicals and prefer to have the moisture sensor coupler fixed to the windshield. "~ - ~ In addition to making the moisture sensor resistant to impact, the perimeter design secured to the perimeter is simple to install. In contrast to the methods of attaching the humidity sensor, which are characterized by separate fasteners or other joining characteristics, the present humidity sensor housing can be press-fitted onto the coupler in a one-handed operation. This reduces the time it takes for the vehicle manufacturer to install the humidity sensor, reducing the cost of the system.

A single, flat 26 circuit board is held in the housing by the tabs 52, which extend inwardly to the interior "from the inner surface of the housing walls 26. The circuit board 26 includes a device surface 54- wherein the electronic components 27 are mounted. the circuit board 26 is mounted in the housing 28, so that the surface of the device 54 is approximately parallel to the inner surface 30 of the windshield 18 when the housing 28 is secured to the coupler 24 and This coupler is secured to the windshield The electronic components 27 are mounted on the surface 54 of the device of the circuit board 26, so that the top surfaces of the electronic components are approximately parallel to the surface 54 of the device. Conventional surface mounting can be used to assemble the components on the circuit board 26. The electronic components 27 include a transmitter 56, a detector 58 and a signal processing circuit system 59. Although a single emitter 56 and detector 58 are shown, multiple emitters and detectors may be used, as shown in FIG. describe below. The emitter 56 is preferably a light emitting infrared diode, although any suitable emitter can be used, and the detector 58 is preferably a photodiode, although any suitable detector can be used. The emitter 56 and the detector 58 are surface mounted devices, such as the SFH-421 and BP-34FAS part numbers from Siemens, respectively. The emitter 56 and the detector 58 can also be carried out using a silicon die directly attached to the circuit board 26 in a chip approach on the board. The signal processing circuit system includes conventional components 59 mounted on circuit board 26. In addition, the light slots 61 can be mounted on the circuit board to exclude ambient light from the detector 58 and to prevent inappropriate optical communication or interference between the emitter 56 and the detector 58 in the housing 58. This emitter 56 and detector 58 are electrically connected to the signal process. Additional details regarding the operation of the signal processing circuit system and the interface to the controller and the cleaner control system are they can be obtained from US Patents: Nos. 4,620,141, 5,059,877, 5,239,244 and 5,568,027. To the extent that these details may be necessary to complete the descriptions and accounts necessary for the purposes of the present application, they are considered to be incorporated herein by reference. As shown in Figure 4, the emitter 56 is typically composed of a housing or plastic case 60, an infrared emitter die 62, mounted within a depression in the box, and a region 64 filled with clear epoxy. The emitter 56 radiates light rays 65, typically of a specific wavelength, such as the infrared energy of 880 nM, although other wavelengths may be used. The light rays 65 are emitted as a divergent beam of rays, which is symmetrical about an emission axis 66, which extends from the emitter primarily in a direction perpendicular to the surface 54 of the device of the circuit board 26. The light rays 65 emanate from the emitter 56 on a display of angles, with each ray traveling at an angle? E with respect to the axis of emission 66. The intensity of each of the 65 rays, which diverge from the emitter 56, it is approximately the cosine of? e. Thus, the rays 65 from the emitter 56 are stronger along the axis 66 of emission. In the near field, where the invention operates, the rays at an angle? E of the emitter greater than about fifty degrees, are shaded by the emitter case 60, and thus are less intense. As shown in Figure 2, the detector 58 includes a detection surface 67, which extends approximately parallel to the surface 54 of the device. A major sensitivity detection axis 68 extends from the detection surface 67 in a direction that is primarily perpendicular to the detection surface 67 and the surface 54 of the circuit board device 26. The detector 58 also has an acceptance angle (not shown) that extends symmetrically about the detection axis 68, so that the light beams striking the detector within the acceptance angle will cause the detector 58 to generate a signal of control. The specific emitter 56 and the detector 58 that will be used are selected so that the detector is sensitive to the wavelength of the light emitted by the emitter.

When the housing 28 is secured to the coupler 24, as shown in Figure 2, the collimator body 38 and the collimator lens 40 extend toward the emitter 56 and the focusing body 43 and focusing lens 44 extend toward the detector . A portion of the light rays 65 emanating from the emitter 56 collide with the collimating lens 40 and collimate in a beam 72 traveling through the collimation body 38 along the optical axis 41 of the collimation lens. The light rays striking the collimating lens 40 preferably range from about 10 to about fifty degrees with respect to the emission axis 66, although the lens can be configured to accept light rays of smaller or larger angles. The collimating lens 40 is disposed relative to the emitter 56 so that the optical axis 41 forms an oblique angle 69 with respect to the emission axis 66. The oblique angle 69 is preferably between 39 and 51 degrees, although it may be smaller or larger. The surface of the collimation lens 40 should be configured, as described below, to form a collimated beam of sufficient intensity that the detector 58 can produce a signal that can be used.

Similarly, the focusing lens 44 is disposed relative to the detector 58 in such a manner that the optical axis 45 of the focusing lens 44 forms an oblique angle 71 c to the detection axis 68. The oblique angle 71 is preferably between 39 and 51. The surface of the focus lens 44 is configured, as described below, to focus the collimated beam 72 on the detection surface of the detector.The collimated beam 72 focuses on a range of converging rays having sufficient intensity in the detection surface 67 that the detector can produce a signal that can be used.The range of light rays converging on the detection surface preferably varies from about 10 to about fifty degrees with respect to the detection axis, although the range of rays it can form smaller or larger angles with respect to the detection axis The light travels from the emitter 56 to the detector 58 along an optical path 73. The light rays from the emitter which are collimated in the collimated beam 72, travels along the optical path in the windshield 18 at an angle of forty-five degrees with respect to the inner surface 30. The collimated light beam 72 collides with the outer surface 32 in the detection region 74 and is reflected along the optical path 73 again through the windshield and in the focusing body 43, at an angle of forty-five degrees with respect to the inner surface 30. The optical axis 45 of the focusing lens 44 is translated from the optical axis 41 of the collimating lens 40 on the surface of the coupler 24 by the distance T. No simple ray of light travel laterally along this translation; rather, it is an artifice that indicates that the optical center of the system travels on the surface of the coupler 24. The distance T is selected so that the focusing lens 44 meets the full width of the beam 72. The surface 40 of collimation is a truncated rotational surface, symmetric about the optical axis 41. The translation T of the optical axis 41 to the optical axis 45 comes around due to the asymmetry nature of the collimating and focusing openings. The external surface of the glass acts as a mirror of bending. Due to the effects of this bending mirror, the rays near the emission axis collide with the detector at an angle away from the detection axis. Thus, a beam passing through the optical center of the collimator will not pass through the optical center of the focusing lens, which moves away from the detection axis. Referring now to Figures 5 and 6, the collimation lens 40 has an aperture 82 that receives light, defined by the perimeter 80. The perimeter 80 may be of the physical edges of the collimating lens 40 or this perimeter 80 may define the area of the lens surface that receives the light emitted directly from the emitter 56 and which collimates such light, as described above. The light rays striking the lens surface outside the aperture 82 are not collimated and are not effectively transmitted to the detector 58. The aperture 82 that receives the light has a width, as shown, measured in the direction of line 5-5 of reference. The aperture 82 receiving the light has a physical center 84 positioned at the center of the perimeter 80. The optical center of the lens is defined as the point at which an optical axis intercepts the surface of the lens. Likewise, by definition, a ray of light that travels at Along the optical axis, which enters the lens opening, through the optical center goes straight, while all other rays entering the lens opening are deflected by the lens along a path parallel to the optical axis . The collimation lens 40 has an optical center 86 displaced, which is separated from the physical center 84 and, therefore, is an optical axis 41 displaced from the center. Preferably, the optical center 86 is displaced from the physical center 84 by approximately 22% of the width W, although any suitable displacement can be used. The surface of the collimation body 38 of the coupler 24 can optionally be covered with an opaque material to exclude the rays that do not collide in the opening 82, or such rays can be allowed to pass through the coupler without obstruction. Additionally, the surface of the collimation lens outside the perimeter 80, defining the aperture 82, can optionally be covered with an opaque material, to exclude the rays that do not collide in the aperture 82, or such rays can be allowed to pass through the coupling without obstruction. Only those rays of the emitter which pass through the opening 82 are useful in detecting rain. Referring now to Figure 7, the focusing lens 44 has an aperture 90 that transmits light, defined by the perimeter 88. This perimeter 88 may be of the physical edges of the focusing lens 44 or the perimeter 8B may define the area of the surface of the lens that transmits the beam 72 of collimated light in a beam focused to the detection surface 67 of the detector 5 ~ 8. The light rays "emerging from the focusing lens to the exterior of the aperture 90 do not focus on the detector 58. The aperture has a width W, as shown.The focusing lens 44 has a physical center 92 placed in the center of the perimeter 88. This optical center 94 of the lens 44 is off center, i.e. spaced from the physical center 92 and, therefore, the optical axis 45 of the focusing lens is also off center. Preferably, the optical center 94 is displaced from the physical center 92 by about 22% of the width, although any suitable displacement can be used.The surface of the focusing body 43 of the coupler 24 can optionally be covered with an opaque material, for Exclude the beams that do not collide in the opening 90, or such handles may be allowed to pass through the coupler without obstruction. Additionally, the surface of the focusing lens 44 to the outside of the perimeter 88 which defines the aperture 90, may optionally be covered with an opaque material, to exclude the rays that do not collide in the aperture 90, or such rays may be allowed to pass through the aperture. coupling without obstruction. - _ __ When the humidity sensor is in operation, the controller (not shown) indicates the emitter 56 that causes the light rays 65 to be emitted symmetrically around the emission axis. The light beams 65 that collide in the aperture 82 of the collimation lens, are collimated in a beam 72 traveling along the optical path 73 which is parallel with the optical axis 41 of the collimation lens. The light beam 72 is optically coupled in the inner layer 24 and then in the windshield 18., along the optical path 73. The light beam 72 travels through the windshield 18, continuing at an angle of about forty and five degrees and is reflected by the outer surface 32 of the windshield 18 in the detection region 74. The reflected beam it passes again through the windshield 18 along the optical path 73 at an angle of forty and five degrees with respect to the surface of the windshield. The collimated light beam 72 travels through the body 43 to focus the focus lens 44. The focusing lens focuses the collimated one on the surface of the detector 58. If moisture has accumulated on the windscreen in the detecting region 74d, not all the collimated light beam will be reflected back to the focusing body 43 and the detector 58 will produce a signal representing the amount of light that is detected. Although the detector generally has the highest sensitivity when the light beams are perpendicular to the circuit board 26, any light beam 72 within the acceptance angle of the detector 58 will be detected. The circuit system 59 of the signal process receives the signal from the detector and interprets the change in the signal as the presence of humidity and controls the cleaners accordingly. For proper operation, the collimating lens 40 d must be positioned with respect to the emitter 56 so that a sufficient amount of light rays 65 colliding with the aperture 82 of the lens will be collimated. Referring again to Figure 4, the angle of a line intercepting the surface - of the collimating lens 40 with respect to the windshield is shown by? X. The values of? X vary on the surface of the collimation lens. As mentioned before, it is preferable that the rays of the collimated light beam 72 travel within the windshield 18 at a TQ angle of forty-five degrees, with spectrum to the surface 30 of the windshield. In order for the collimation lens to refract the emitter's rays at the required forty-five degree angle, it can be shown manipulating Snell's law ? x = aratg [(sin (? E) -n - (sin (? G)) / cos (? E) - n - cos (? G))] Where n is the refractive index of the coupler 24. This coupler 24 is preferably molded of polycarbonate, having a refractive index of n = 1.57 to 880 nM. Alternatively, the coupler can be made of glass, acrylic or some clear material. From this equation, it can be shown by the example, that stopping an angle TE of the emitter of 10 degrees, a surface angle of the lens of 76 degree coll ation is required. At such an excessive angle, about half the intensity of the beam from the emitter is reflected off the surface of the lens of collimation, and thus does not enter the windshield 18. The reflection increases dramatically at even smaller emitter angles. Therefore, this ratio- between the angle of the emitter and the angle of the collimating lens surface establishes a lower limit on the distance between the first 40 of the collimator and the axis 66 of emission. Similarly the same lower limit is placed in the distance between the focusing lens 44 and the detection axis 68. The light rays passing through the focusing lens 44 closer to about 10 degrees to the detection axis 68, reflecting internally away from the inner surface of the focus lens 44 d and will reduce the beam intensity; focused that reached detection surface 67. _ _ _ _ Other effects establish an upper limit in the distance between the axis 66 of emission and the lens d collimation 40. As TE increases, the obliquity reduces the strength of the emitting beam which varies according to the eos T as described below. Likewise, at TE values of approximately fifty degrees, the rays of the emitted light are shaded by the emitter box 50. Thus the range of angles that can be usefully coupled in the windshield 18 is confined to the emitter angles between about 10 and fifty degrees. Again, at lower angles, a too large fraction of the beam is reflected off the lens surface of the collimator. At larger angles, the obliquity reduces the force of the emitted light and the light is shadowed by the emitter box. Within this range of emitter angles, the effects of reflection and obliquity are canceled approximately. Thus the rays of light emitted are reasonably uniform within the prescribed range of emitter angles. This restriction of the emitting beam leads to an advantage - more in that it allows the design to fit within the 5 mm height requirement of the coupler. A wider range of emitter beams requires a workshop coupler. Similarly, light guides traveling in excess of about fifty degrees from the detection axis 68 will be received poorly by the detector 58 due to the high obliquity. As with the collimator 37, restricting the angles of the rays received from the focusing lens 44 by the detector. 58 allows a shallow coupler design 24. The surface of the collimating lens 40 is configured to allow the collimation lens to collimate a large portion of the light rays traveling from the emitter, when the emitting axis 66 forms an oblique angle with respect to the optical axis 41. Preferably, The surface of the collimation axis is a convex, continuous refractive surface, although the surface can be segmented as described below. Proper configuration of the lens surface can be determined using an optically designed software system, such as the Zemax system by Focus Software, of Tucson, AZ. The resulting surface configuration is best represented by a polynomial sphere (imperfect sphere). The surface is given by the sinking function, which generates the distance z between the surface and the radius from the optical axis. That surface can be, for illustration purposes: z = (cr2) / (1 + A / 1 - (1 -k) c2r2) + c ^ r2 + c ^ r4 + 0C3I-6 + a4r8 + Where : This method of describing an aspheric lens is familiar to those skilled in the art of optical system design. Alternatively, a spherical lens of 3.163 mm radius can be substituted, however, the aberration is induced, which can reduce the intensity of the light transmitted by the lens. The given values will allow a slight divergence of the collimated beam. facilitating the requirements of tolerance of the placement of the issuer. Although only an optical path is required to obtain a function of the moisture sensor, a simple optical path can provide a surface sensor area not suitable for the uniform operation of the cleaners. Referring now to Figure 8, an alternative embodiment of the present invention is provided, with a different arrangement of optical components that provide multiple optical paths. The alternative mode sensor 100 includes a first and second emitter 156a and 156b, and a first and second detectors 158a and 158b, mounted to a surface of the circuit board device (not shown) in a manner similar to that described above. The first emitter 156a is located on the circuit board (not shown) at a first corner 102a of a square 104 and a second emitter 156b is located "on the circuit board at a second corner 102b opposite the first corner 102a. first and second emitters 156a and 156b include emission axes (not shown), similar to the emission axis 69 of the emitter 56 shown in Figure 4. The first detector 158a is located on the circuit board at a third corner 102c of the square 104 and the second detector 158b is located on the circuit board in a fourth corner 102d opposite the third corner 102c. The first and second detectors, 158a and 158b, include detection axes (not shown) similar to the detection axis 68. detector 56 shown in Figure 4. The circuit board is mounted in a housing 28, shown in Figure 3, in a manner similar to the circuit board 26 described above. The sensor 100 includes a coupler 106 having a mounting surface (not shown) that is mounted to the windshield, in a manner similar to the coupler 25, described above. The housing 28 is attached to the coupler 106 in a similar manner as the coupler 24 described above. The coupler 106 includes a first collimator -108a located adjacent the first emitter 156a at the first corner 102a, when the housing 28 joins the coupler 106. The coupler 106 also includes a second collimator 108b located adjacent the second emitter 156b at the second corner. 102b, wherein the housing is attached to the coupler 106. Each collimator 108a and 108b includes two collimation bodies 109 and two collimation lenses 110. The two collimation lenses 110 abut each other so that their optical axes 111 form an angle "of approximately ninety degrees, when viewed as shown in Figure 8. The collimating lenses 110 are preferably formed integrally with the bodies. of collimation 109, although lenses separate ones may be arranged adjacent to each collimation body, as described above. Each collimation lens 110 is similar to the collimating lens 40 described above and to avoid a repetition will not be described in such detail. Each collimating lens 110 has a physical center, an optical center and an optical axis, similar to the physical center 84, optical center 86 and optical axis 41 of the collimating lens 40, as shown in Figures 4, 5 and 6, Collimating lenses 110 of the first collimator 108a are disposed adjacent the first emitter 156a so that each optical axis forms an oblique angle with respect to the emitter axis described above. The collimating lenses 110 of the second collimator 108b are disposed adjacent the second emitter 156b so that each optical axis forms an oblique angle with respect to the axis of the emitter, described above. The surface of the collimating lenses 110 are similarly formed to the collimating lens 40 described above, such that the optical center is displaced from the physical center for the reasons described above. The coupler 106 also includes a first focuser 114a located adjacent the first detector 158a in the third corner 102c, when the housing 28 is attached to the coupler 106. This coupler 106 further includes a second focuser 114b, located adjacent the second detector 158b at the fourth corner 102d, when the housing 28 is attached to the coupler 106. Each focuser 114a and 114b includes two focusing bodies 115 and two focusing lenses 116. The two focusing lenses 116 abut each other so that their optical axes form an angle of approximately ninety degrees, when viewed as shown in Figure 8. Focusing lenses 116 are preferably formed integrally with the focusing bodies 115, although separate lenses may be arranged adjacent to each focusing body, as described above. A corner of each collimating lens 110 and focusing lens 116 is removed to allow juxtaposition, but the performance of the lenses is not adversely affected. Each focusing lens 116 is similar to the focusing lens 44 described above and will not be described in detail to avoid repetition. Each focusing lens 116 has a physical center, an optical center, and an optical axis similar to the physical center 92, optical center 94 and axis 45 of the focus lens 44, as shown in Figures 2 and 7. The focusing lenses 116 of the first focuser 114a are disposed adjacent the first detector 158a, so that each optical axis forms an oblique angle with respect to the axis of the emitter described above: The focusing lenses 116 of the second focuser 114b are disposed adjacent the second detector 158b so that each optical axis forms an oblique angle with respect to the axis of the emitter described above.The surfaces 116 of the focusing lenses are formed similarly to the focusing lens 44 described above, so that the optical center is displaced from the physical center for the reasons described above Four optical paths 173a, 173b, 173c and 173d are provided The first optical path 173a extends from the first emitter 156a through a collimating lens 110 and collimation body 109 of the first collimator 108a, in the windshield at an angle of forty-five degrees with respect The interior surface of a first sensor area 174a, again through the windshield at an angle of forty-five degrees, with respect to the inner surface of the windshield, through a body 115 of focusing and focusing lens 116 of the first focuser 114a to a first detector 158a. The second optical path 173b extends from the second emitter 156b through a collimator lens 110 and collimator body 109 of the second collimator 108b, in the windshield at an angle of forty-five degrees with respect to the internal surface to a second detection area 174b, again through the windshield at an angle of forty-five degrees with respect to the inner surface of the windshield, through the focusing body 115 and focusing lens 116 of the first focuser 114a to the first detector 158a. The third optical path 173a extends from the first emitter 156a through a lens 110 of the collimator and the body 109 of the collimator, of the first collimator 108a, into the windshield at an angle of forty-five degrees with respect to the internal surface a a second detection area 175c, again through the windshield at an angle of forty-five degrees with respect to the inner surface of the windshield, through the focusing body 115 and the focusing lens 116 of the second focuser 114b to the second detector 158b. The fourth optical path 173b extends from the second emitter 156b through the lens 110 of the collimator and the body 109 of the collimator of the second collimator 108b within the windshield at an angle of forty-five degrees with respect to the inner surface to a fourth detection area 174d, again through the windshield at a forty-five degree angle, with respect to the inner surface of the windshield, through the focusing body 115 and focusing lens 116 of the second focuser 114b to the second detector 158b. During operation, the emitter 156a and 156b emit light rays that diverge in a hemisphere, so that each of the adjacent collimator lenses 110 receives an equal amount of light. The two collimation bodies 109 and lenses 110 in the first collimator 108a produce first and second collimated light beams, 172a and 172b, similar to the collimated beam 72 described above. The first and second collimated light beams, 172a and 172b, extend at right angles to each other, when viewed as shown in Figure 8, and each light beam travels along the first and third optical paths, 173a and 173c, respectively. The two collimation bodies 108 and lenses 110 in the second collimator 108b, produce a third and fourth collimated light beams, 172c and 172d, similar to the collimation beam 72 described above. The third and fourth collimated light beams 72a and 72d extend at right angles to each other, and each light beam travels along the second and fourth optical paths 173b and 173d, respectively. The first beam 172 of collimated light is reflected by the outer surface of the windshield in the first detection area 174a, again through the focusing body 115 and the focusing lens 116 to the first detector 158a. If moisture is present in the first detection area on the outer surface of the windshield, some of the collimated light beam will be reflected back into the focuser 114 and the first detector 158a will emit a signal corresponding to the change in detected light. The signal will be processed by the signal processing circuit system (not shown) similar to the circuit system 59 of the signal processing shown in Figure 2 and the cleaners will be controlled accordingly. Similarly, the second, third and fourth beam of collimated light will be reflected outside the corresponding detection areas, and the first or second detectors will detect any change in the light received. By using four detection areas, the humidity sensor 100 can provide improved cleaner control and increased visibility. The arrangement of the optical components in the sensor 100 of humidity of the alternative mode, provides a balanced optical system, because the four optical paths 102 are of equal length and equal optical efficiency. This arrangement will compensate for differences in efficiency between issuers 56, which can vary considerably. Both detectors 58 will receive an equal amount of light from a particular emitter, and the sum of the light received from both emitters will be the same for each detector. __ Referring to Figure 9, a balanced electrical system 190 is shown for use in conjunction with the balanced optical system, described above, to provide a balanced moisture sensor system. Pulse emitters of the pulsed current source, 156a and 156b, are preferably connected in series by line 191. A light beam (represented by the lines in dashes 172a, 172b, 172c, 172d) traveling along an optical path, couples each emitter 156a, 156b, to each detector 158a, 158b. Each optical path has an equal length and a similar optical efficiency. The detectors 158a, 158b operate in the current mode and are connected together in a common summation mode 192. The signal processing and control circuitry_, connected to the node 192, detects the presence of rain. For a humidity sensor system, perfectly balanced, no current will flow from node 192 to signal processing and control circuit systems, in the absence of rain. A balanced moisture sensing system is convenient because it "requires less dynamic range of the circuitry of the signal process and increases the ability for the system to reject ambient light." Modern solar control windshields, such as windshields sold with the trademark "EZ-KOOL", commercially available from Libby Owens Ford, Co., reduce the passage of infrared light through the windshield.The optical moisture sensors, used in such windshields, they must have high efficiency, since the windshield reduces the transmittance of the infrared beam from the emitter to the detector. The humidity sensor 100, described above, provides an efficient sensor capable of being used with these solar control windshields. The moisture sensors, described above, have been tested 'on the EZ-KOOL brand-name solar control windshields, which use couplers composed of a molded polyester resin, which produces 17 microamps per ampere of the emitter's current, which is sufficient for a typical circuit system of signal processing. The humidity sensor provides a combined detection area of 57 square millimeters, using only two emitters and two detectors, and the production versions will probably have even larger detection areas. t_ - Referring now to Figure 10, an alternative embodiment of the collimator lens is shown, which uses a selenized lens or Fresnel lens 202, rather than the continuous convex lens 40, discussed above. The Fresnel lens 202 can also be used as the focus lens e instead of the convex focusing lens 44, continued V discussed above. Due to the similarity between the lens Collimating and focusing lens, as discussed before, only a Fresnel lens collimator is discussed. A similar Fresnel lens can be used for the focuser, which realizes similarity to the continuous convex lens focuser 40, described above. The Fresnel 202 collimator lens has the advantage that the lens region and thus the "moisture" sensor as a whole, can be made thinner.The resulting thinner coupler 24 comes at the expense of some optical efficiency, and a somewhat more mold complex, necessary to form the coupler and the lenses 202. Such a lens can be constructed by projecting the surface of the collimator lens of Figures 4 and 6 onto the inner surface of the coupler 24, allowed to extend to a depth D in a module operation. results in the collimator lens 202 comprised of a number of refractive segments 204. Note that in contrast to the common construction of a Fresnel lens, the plane of projection of the light rays is not orthogonal to the optical axis, but rather angled to provide reflection of the external surface of the glass, as described above.

Optical design, such as the Zemax, mentioned above, can be used to generate the required surface directly, using appropriate tilt commands to achieve the desired plane of projection. As a further method of surface generation, the formula derived from the previous Snell's law can be used to generate the required angles. The disadvantage of the semented approach is that it creates regions of occlusion, as shown in 206. These regions of occlusion occur when light rays strike a non-useful return segment, 208. Such segments are necessary to maintain the geometry of the lens within the depth D. However, the occlusion regions 206 are not capable of directing light-in. desired direction and degrade the optical efficiency of the system. The multiple trajectory configuration of the invention, as shown in Figure 8, is not modified. Similarly, the joining method is not changed. The Fresnel approach can be manufactured with many segments, as shown, or with as few as two. Likewise, while it is preferred that the projection be on the plane of the inner wall of the coupler, the projection plane may be somewhat inclined towards the optical devices. Such a form of embodiment requires smaller regions of occlusion. In addition to the front windshield of a motor vehicle, the humidity sensor of the present invention can also be used on other glass surfaces, for the detection of moisture.

Claims (20)

1. CLAIMS 1. A humidity sensor, which is mounted on a first surface of a glass sheet *, to detect moisture in an area detected on a second surface of the glass sheet, this humidity sensor comprises: a) a coupler, for mounting on the first surface of the glass sheet, for optically coupling the light rays in and out of the glass, b) a housing, secured to the coupling, c) a flat circuit board, secured in the housing and having a device surface which is arranged generally parallel to the first surface of the glass sheet; ~ - d) an emitter, mounted on the surface of the device, to emit rays of light around an axis of emission , which extends from the emitter approximately perpendicular to the surface of the device, e) a collimator, optically coupled to the "coupler, to collimate the light rays -from the emitter into a beam of collimated light, this collimator has an aperture that receives light with a physical center and an optical center, so that an optical axis extends through the optical center and this optical center is spaced from the physical center, the collimator is arranged so that the optical axis form a first oblique angle with respect to the emission axis; f) a detector, which. has a detection surface and a detection axis, which extends from the detection surface, to detect the light hitting the detection surface around the detection axis and to generate signals in response to the detected light, this detector is mounts on the surface of the device of a flat circuit board, so that the detection axis is approximately perpendicular to the surface of the device; and g) a focusing device, optically coupled to the coupler, to focus the collimated beam of light on a converging array of rays on the detection surface, this focusing device has a light transmission aperture with a physical center and an optical center, so that an optical axis extends through the optical center and this optical center is spaced from the physical center, the focusing device is arranged so that the optical axis forms a second oblique angle with respect to the detection axis.
2. 2. The humidity sensor of claim 1, wherein the collimator includes a collimation lens and the focusing device includes a focusing lens. "
3. 3. The humidity sensor of claim 2, wherein the coupler, the collimator, the collimating lens, the focusing device and the focusing lens are formed integrally from a single piece of material.
4. 4. The humidity sensor of claim 1, further including a signal processing circuit, mounted on the circuit board and connected to the emitter and detector, to control the light emitted by the emitter and to process the signals from the detector. "
5. 5. The humidity sensor of claim 1, wherein the first oblique angle is between thirty and nine and fifty-one degrees, and the second oblique angle is between thirty-nine and fifty-one degrees too.
6. 6. The humidity sensor of claim 1, wherein the optical center of the aperture receiving light from the collimator, moves at least 20% of the width of the aperture that receives light from the physical center of the aperture receiving the light
7. 7. The humidity sensor of claim 1, wherein the optical center of the aperture transmitting the focuser light, is displaced by at least 20% "" of the "width" of the light transmitting aperture from the physical center of the aperture. the opening that transmits the light.
8. 8. The humidity sensor of claim 1, wherein the collimator is arranged to collimate the light rays -emitted from the emitter, where the range of the light rays is about ten to fifty degrees with respect to the emission axis.
9. 9. The humidity sensor of claim 1, wherein the focusing device is arranged to focus a collimated beam of light on a converging array of rays on the Detection surface, where the range of light rays varies from approximately ten to fifty degrees with respect to the detection axis.
10. 10. The humidity sensor of claim 2, wherein the collimation lens and the focusing lens are continuous convex lenses.
11. 11. The moisture sensor of claim 1, wherein the collimator includes a collimated semented lens and the focusing device includes a semented focusing lens.
12. 12. The humidity sensor of claim 2, wherein the collimator includes a second collimation lens and the focusing device includes a second focusing lens, and the humidity sensor further includes a second emitter and a second detector, mounted on the surface. of the device, a second collimator, optically coupled to the coupler and including a third and fourth "collimation" lenses, and a second focusing device, optically coupled to the coupler and including a third and fourth focusing lenses, where the light rays of both emitters they are collimated in the light beams and the light beams are focused on both detectors.
13. 13. A humidity sensor, for mounting on a first surface of a glass sheet, for detecting moisture in a plurality of detection areas on a second surface of the glass sheet, this humidity sensor comprises: a) a housing; b) a first and second emitters, arranged in the housing to emit light rays; c) a first detector, arranged in the housing, for detecting rays of light traveling along a first optical path, extending from the first emitter to the second surface _ of the glass, in one of the detection areas and back to the first detector and to detect "the light guides traveling along a second optical path, which extends from the second emitter to the second surface of the glass in one of the detection areas and back to the first detector , where the length of the second optical path is approximately equal to the length of the first optical path; and d) a second detector, arranged in the housing, for detecting rays of light traveling along a third optical path, extending from the first emitter to the second surface of the glass in one of the detection and detection areas. new to the second detector and to detect the light guides traveling along a fourth optical path extending from the second emitter to the second surface of the glass in one of the detection areas and back to the second detector, where the lengths of the third and fourth optical paths are approximately equal to the length of the first optical path.
14. 14. The humidity sensor of claim 13, further including a coupler, having collimators, for collimaging a portion of the light rays emitted from the emitters around the emission axes, extending perpendicularly with respect to the first surface of the glass sheet, in collimated, traveling light beams _a along the optical paths, and focusing devices, to focus the collimated beams into convergent rays on the detectors, having detection axes extending perpendicularly with respect to the first surface of the glass sheet.
15. 15. The humidity sensor of claim 14, wherein the collimators include an aperture that receives light, with a physical center and an optical center, such that an optical axis extends through the optical center and this optical center is spaced from the physical center, the collimators are arranged so that the optical axes from the first oblique angles with respect to the emission axes and where the focusing devices include an aperture that transmits light, with a physical center and an optical center, so that a The optical axis extends through the optical center and this optical center is spaced from the physical center, and the focusing devices are arranged so that the optical axes form oblique second angles, with respect to the detection axes. ~~
16. 16. A humidity sensor, for mounting on a first surface of a glass sheet, for detecting moisture in a plurality of detection areas on a second surface of the glass sheet, this humidity sensor comprises: a) a first emitter, to emit rays of light arranged in a first corner of a square; b) a second issuer; to emit irayos of light arranged in a second corner of a square, opposite the first corner; c) a first collimator, arranged adjacent to the first emitter, to collimate the rays of light emitted from the first emitter in a first and second collimated light beams; . "d) a second collimator, arranged adjacent to the second emitter, to collimate the rays of light emitted from the second emitter, in a third and fourth collimated light beams; e) a first detector, arranged in a third corner of a square, to detect the first beam of collimated light, traveling along a first optical path between the first emitter and the first detector, and the third beam of collimated light, traveling along a second optical path, between the second emitter and the first detector, this second optical path has a length approximately equal to the first optical path, and to generate signals in response to the detected light beams; and f) a second detector, arranged in a fourth corner of a square, opposite the third corner, for detecting the second beam of collimated light, traveling along a third optical path, between the first emitter and the second detector, and the fourth beam of collimated light, traveling along a fourth optical path, between the second emitter and the second detector, these third and fourth optical paths each having a length approximately equal to the first optical path and for generating signals in response to the detected light beams.
17. 17. A humidity sensor, for mounting on a first surface of a glass sheet, to detect the humidity in a detection area on a second surface of the glass sheet, this humidity sensor comprises: a) a coupler, having a mounting surface for mounting on the first surface of the glass sheet, for coupling the light rays in and out of the glass; b) a sleeve, arranged around the perimeter of the coupler and extending from this coupler opposite the mounting surface; c) tabs, which extend outwardly from the sleeve; d) a housing, for mounting on the sleeve, having a base and side walls, extending from the base, these side walls - have inner surfaces with grooves formed therein, this housing is removably mounted on the sleeve , so that the tabs extend into the slots, to secure the housing to the coupler; e) a flat circuit board, secured in the housing and having a device surface for receiving electronic components; f) an emitter, mounted on the surface of the devices, to emit rays of light symmetrically around an axis of emission; and g) a detector, mounted on the surface of the device, having a detection surface for detecting the light emitted by the emitter and for generating control signals, in response to the detected light.
18. 18. The humidity sensor of claim 17, further including a collimator, extending from the surface of the coupler, opposite the mounting surface, to collimate the light rays emitted from the emitter within a beam of collimation light, and a focusing device, which extends from the surface of the coupler opposite the mounting surface to focus the beam of collimated light into a converging array of light rays on the detection surface.
19. 19. The humidity sensor of claim 18, wherein the emitter includes an emission axis, extending from the emitter approximately perpendicular to the surface of the device, and the detector includes a detection axis, extending from the detection surface. approximately perpendicular to the surface of the device.
20. 20. The humidity sensor of claim 19, wherein the collimator includes an aperture that receives light, with a physical center and an optical center, such that an optical axis extends through the optical center and the physical center is spaced from the physical center, the collimator is arranged so that the optical axis forms a first oblique angle with respect to the emission axis, and the focusing device includes an aperture that transmits light, with a physical center and an optical center, so that an axis optical is extended through the optical center and this optical center is spaced from the physical center, the focusing device and the detector are arranged so that the optical axis forms a second oblique angle with respect to the detection axis.