Optoelectronic sensor for detecting moisture on a windshield with means to compensate for a metallic layer in the windshield

• US 5,498,866 A
• Filed: 02/10/1994
• Issued: 03/12/1996
• Est. Priority Date: 06/01/1993
• Status: Expired due to Fees

• Current Assignee: Leopold Kostal GmbH & Company KG
• Original Assignee: Leopold Kostal GmbH & Company KG
• Inventors: Bartling, Ralf, Bendicks, Norbert
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): NICHOLS, STEVEN
• Application Number:
  US08/194,254
• Time in Patent Office: 761 Days
• Field of Search: 250/227.25, 318/483, 318/444, 318/DIG. 2, 340/602
• US Class Current: 250/227.25
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0837 with a particular arrangement of the optical elements
• CPC Class Codes: G01N 21/43 by measuring critical angle
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A sensor device for detecting the degree of wetting of a multi-layer transparent pane, made in particular of glass, by an, in particular, drop-shaped precipitation. The sensor device is provided with a beam guide element which comprises two beam windows and cooperates with a beam transmitter and a beam receiver. In order to prevent spurious beams caused by an extremely thin intermediate layer located in the pane from having a noticeable influence on the signal used to control the windscreen wiper system, the beam guide element comprises a further beam exit window in the central region of its rear surface facing away from the pane. The region is located between the two beam windows. The further beam exit window is allocated to the measuring path and cooperates with an additional beam detector. Only those irrelevant beams reflected at the extremely thin metallic intermediate layer located in the pane exit therefrom. The signal resulting from the existing irrelevant beams which is detected by the additional beam detector is used to correct the signal supplied by the actual beam detector. Alternatively; signal correction can be achieved by an electrical circuit.

Claims

1. An optoelectronic sensor device for detecting the degree of wetting of a multi-layer transparent pane by drop-shaped precipitation, the sensor device comprising:

a beam guide element having a front surface connected to an inner surface of the pane not exposed to the precipitation in a region of a wiping area covered by a motor driven windscreen wiper device, the beam guide element having at least one measuring path with a beam entry window and first and second beam exit windows;

a beam transmitter associated with the beam entry window;

a first beam detector associated with the first beam exit window in such a manner that beams emitted by the beam transmitter are reflected in dependence upon the precipitation present on the pane and directed to the first beam detector, which provides a first signal dependent upon the associated quantity of precipitation;

a second beam detector associated with the second beam exit window in such a manner that only spurious beams reflected at a partially transparent metallic intermediate layer located in the pane are detected by the second beam detector, which provides a second signal representative of a quantity of the spurious beams; and

compensating means for correcting the first signal supplied by the first beam detector and representative of a quantity of mixed beams including useful beams and spurious beams, the correction being dependent upon the second signal supplied by the second beam detector.

2. The sensor device of claim 1, wherein the second beam exit window is disposed in a plane which lies parallel to the plane of the first beam exit window.

3. The sensor device of claim 2, wherein the second beam exit window is directly adjacent to the first beam exit window.

4. The sensor device of claim 1, wherein all beam windows have an associated beam lens.

5. The sensor device of claim 1, wherein the second beam exit window has a width corresponding to the width extension of the beams in the measuring path, and a height dependent upon the spacing of the metallic intermediate layer relative to the inner surface of the pane, a beam lens being allocated thereto and designed as a corresponding portion of an aspherical lens topography.

6. The sensor device of claim 5, further comprising two measuring paths extending in parallel adjacent to each other, a correspondingly designed portion of a fresnel-lens-type lens configuration being provided for both measuring paths together.

7. The sensor device of claim 1, wherein the compensating means comprises a plurality of electrical components which produce an electrical correction signal, the correction signal being phase-shifted and supplied to a current summation point located electrically behind the first beam detector.

8. The sensor device of claim 7, wherein the electrical components include a pulse-preparation stage and a phase-shifting stage as well as a correcting stage disposed electrically downstream thereof, the phase-shifting stage lying at the current summation point with its output over a capacitor provided for the purpose of suppressing a direct current portion, the pulse-preparation stage and phase-shifting stage being connected with the phase shifting stage input at the output of the pulse stage;

the input of the pulse stage being connected to the output of a final stage associated with the first beam detector.

9. The sensor device of claim 8, wherein the output of the first beam detector is placed over a resistance to earth;

a capacitor, provided for suppressing the direct current portion, being connected at one side to the electrical connection between the first beam detector and the associated resistance, said capacitor being connected at the other side to the current summation point which is associated with a current-voltage conversion stage as part of evaluation circuitry; and

a phase-selective rectification stage being connected to the current-voltage conversion stage.

10. An optoelectronic sensor device for detecting the degree of wetting a multi-layer transparent pane by drop-shaped precipitation, the sensor device comprising:

a beam guide element having a front surface connected to an inner surface of the pane not exposed to the precipitation in a region of a wiping area covered by a motor driven windscreen wiper device, the beam guide element having at least one measuring path with a beam entry window and a first beam exit window spatially separate therefrom and aligned at an angle of approximately 90°

thereto;

a beam transmitter associated with the beam entry window;

a first beam detector associated with the first beam exit window in such a manner that beams emitted by the beam transmitter are reflected in dependence upon the precipitation present on the pane and directed to the first beam detector, which in each case provides a first signal dependent upon the associated quantity of precipitation; and

compensating means for correcting the first signal supplied by the first beam detector and resulting from a quantity of mixed beams, the correction being dependent upon a quantity of spurious beams reflected at a partially transparent metallic intermediate layer located in the pane;

the beam guide element further comprising a second beam exit window, which is allocated to the measuring path and cooperates with a second beam detector, the second beam exit window being situated in a central region of a rear surface of the beam guide element facing away from the pane, said region being located between the two beam windows so that only those spurious beams reflected at the metallic intermediate layer in the pane exit from the second beam exit window and are detected by the second beam detector, which provides a second signal resulting from a quantity of the exiting spurious beams for use in correcting the first signal supplied by the first beam detector, the first signal resulting from a quantity of mixed beams composed of beams exiting the first beam exit window, and beams from a useful beam portion and a spurious beam portion, said quantity of mixed beams having a quasi clear geometrical relationship to the quantity exiting from the second beam exit window;

wherein the second beam exit window has a width corresponding to the width extension of the beams in the measuring path, and a height dependent upon the spacing of the metallic intermediate layer relative to the inner surface the pane, a beam lens being allocated thereto and designed as a corresponding portion of an aspherical lens topography.

11. The sensor device of claim 10 further comprising two measuring paths extending in parallel adjacent to each other, a correspondingly designed portion of a fresnel-lens-type lens configuration being provided for both measuring paths together.

12. An optoelectronic sensor device for detecting the degree of wetting a multi-layer transparent pane by drop-shaped precipitation, the sensor device comprising:

a beam guide element having a front surface connected to an inner surface of the pane not exposed to the precipitation in a region of a wiping area covered by a motor driven windscreen wiper device, the beam guide element having at least one measuring path with a beam entry window and a beam exit window spatially separate therefrom and aligned at an angle of approximately 90°

thereto;

a beam transmitter associated with the beam entry window;

a beam detector associated with the beam exit window in such a manner that beams emitted by the beam transmitter are reflected in dependence upon the precipitation present on the pane and directed to the beam detector, which in each case provides a signal dependent upon the associated quantity of precipitation; and

compensating means for correcting the signal supplied by the beam detector and resulting from a quantity of mixed beams, the correction being dependent upon a quantity of spurious beams reflected at a partially transparent metallic intermediate layer located in the pane, the compensating means comprising a plurality of electrical components which produce an electrical correction signal, the correction signal, in contrast to the signal supplied by the beam detector, being phase-shifted and supplied to a current summation point located electrically behind the beam detector, the electrical components including a pulse-preparation stage and a phase-shifting stage as well as a correcting stage disposed electrically downstream thereof, the phase-shifting stage lying at the current summation point with its output over a capacitor provided for the purpose of suppressing a direct current portion, the pulse-preparation stage and phase-shifting stage being connected with the phase shifting stage input at the output of the pulse stage;

the input of the pulse stage being connected to the output of a final stage associated with the beam detector.

13. The sensor device of claim 12 wherein the output of the beam detector is placed over a resistance to earth;

a capacitor, provided for suppressing the direct current portion, being connected at one side to the electrical connection between the beam detector and the associated resistance, said capacitor being connected at the other side to the current summation point which is associated with a current-voltage conversion stage as part of evaluation circuitry; and

a phase-selective rectification stage being connected to the current-voltage conversion stage.