Method and apparatus for detecting impurities on plate surface

• US 5,808,734 A
• Filed: 08/26/1996
• Issued: 09/15/1998
• Est. Priority Date: 03/09/1994
• Status: Expired due to Fees

• Current Assignee: Matti Kolari
• Original Assignee: Matti Kolari
• Inventors: Kolari, Matti
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Smith, Zandra V.
• Application Number:
  US08/619,665
• Time in Patent Office: 750 Days
• Field of Search: 356/237, 318/443, 318/444, 318/480, 318/DIG. 2, 250/341.8
• US Class Current: 356/237.2
• 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 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

The present invention relates to a method and apparatus for selective measurement of liquid and solid particles deposited on plate surfaces. The method is based on the transmission of radiation, which originates from total reflection from the interface between liquid droplets at the surface of the plate and surrounding gas, e.g., air. This radiation is transferred inside the plate as radiation undergoing total internal reflection between the surfaces of the plate. Such measuring radiation reaches a detector protected from background radiation, whereby intensity increase can be measured and used for the control, e.g., windshield wipers and washer equipment.

Claims

1. A method of detecting liquid and/or solid dirt on the surface of a transparent plate (1), in which method radiation emitted from a source (10, 11) of electromagnetic radiation and is received by at least one detector means (14) sensitive to said electromagnetic radiation, whereby the presence of liquid and/or dirt on the surface (2, 3) of said transparent plate (1) is detected in the form of an intensity change of the radiation received by said detector means (14), comprising

(a) placing said source (10, 11) of radiation relative to the surface (2) of said plate (1) so that the radiation emitted by the source is incident via a gas-phase medium on the measured area of the surface of the plate (1), whereby the radiation is transmitted through the plate (1) to air without reflection when the plate is dry and/or clean, but a fraction of the radiation

(i) undergoes refraction from liquid droplets deposited on the plate on the same side (2) as said source of radiation, or

(ii) undergoes total reflection from liquid droplets (4) deposited on the surface (3) of the plate on the opposite side from said source of radiation, or

(iii) is scattered by droplets of radiation-transparent medium containing solid particles deposited on the surface of the plate,

so as to make said fraction(s) of the radiation enter the inside of the plate (1),

(b) transferring said fraction(s) of radiation due to presence of liquid and/or solid particles, in the inside of the plate (1) by total internal reflection to the detector means (14), and

(c) detecting said fraction of radiation as an increase in the intensity of the radiation.

2. A method as defined in any of claim 1, wherein the detector means (14) comprises a transducer piece (12) which is made of a transparent material and has a detector element (14) attached to it, and which detector means is mounted at a suitable point either on the surface (2) of the plate or so as to be partially or entirely embedded inside the plate (1), whereby a fraction of the radiation travelling by total internal reflection in the inside of the plate (1) can exit from the plate (1) into the transducer piece (12) and further pass through the piece to the detector element (14).

3. A method as defined in claim 2, wherein a nontransparent interface between the transducer piece (12) and the plate surface (2) is provided with a transparent window (13) and the detector element (14) is aligned with respect to the window (13) of the transducer piece (12) so that only the radiation travelling by total internal reflection in the inside of the plate (1) can reach the detector (14).

4. A method as defined in claim 2, wherein the radiation from the source of radiation to the point of measurement and/or the radiation from the transducer piece (12) to the detector element (14) are transmitted via an optical fiber (20, 21).

5. A method as defined in claim 4, wherein the measurement is performed using a branched optical fiber (21) so that the radiation used for detecting the presence of solid dirt is transmitted to the point of measurement via the same optical fiber as is used for taking the measuring radiation from the transducer piece (12) to the detector element (14).

6. A method of detecting liquid and/or solid dirt on the surface of a transparent plate (1), in which method radiation emitted by at least one source (10, 11) of electromagnetic radiation is transmitted to propagate in the form of radiation undergoing total internal reflection in the inside of said plate (1) and is received by at least one detector means (14) sensitive to said electromagnetic radiation, whereby the presence of liquid and/or dirt on the surface (2, 3) of said transparent plate (1) is detected in the form of an intensity change of the radiation received by said detector means (14),

wherein said source (10, 11) of radiation is placed relative to the surface (2) of said plate (1) so that the radiation emitted by the source is incident via a gas-phase medium on the measured area of the surface of the plate (1), whereby the radiation is transmitted through the plate (1) without reflection when the plate is dry and/or clean while a fraction of the radiation undergoes refraction from liquid droplets deposited on the surface (2) of the plate and/or undergoes total reflection from liquid droplets (4) deposited on the surface (3) of the plate and/or is scattered by droplets of radiation-transparent medium containing solid particles deposited on the surface of the plate, so as to make said fraction(s) of the radiation enter the inside of the plate (1), and

said fraction(s) of radiation is/are transferred in the inside of the plate (1) by total internal reflection at the surfaces (2, 3) of the plate to the detector means (14),

said fraction of radiation is detected from the intensity increase of the radiation, and wherein

(a) the measuring radiation is emitted by two different sources of which one source (10) of radiation employed for detecting the liquid component is so aligned that the angle β

1 of the measuring ray to the plate surface (2) toward the detector means (14) is in the range 90°

-180°

, while the other source (11) of radiation employed for detecting the presence of solid particles is so aligned that corresponding angle β

2 is in the range 0°

-90°

, or, alternatively,

(b) the radiation employed for detecting the presence of solids is transmitted to the inside of the plate with the help of a transducer piece so as to make the rays propagate inside of the plate at the measured area by total internal reflection at the plate surfaces (2,

     3), or

(c) the detector means (14) is mounted with respect to said transparent plate (1) so as to receive the radiation propagating by total internal reflection inside of the plate (1) via the surface of the plate at the edge of the plate (1), or

(d) the measuring ray is emitted in pulses from two different sources (10,

     11) of radiation at different instants of time and is received by a single detector element (14) and the magnitude of the radiation received by the detector element (14) is measured during the pulse or thereafter, whereby selective measurement of both the liquid and solid dirt is accomplished using a single detector element.

7. A method as defined in claim 6, wherein the detector means (14) comprises a transducer piece (12) which is made of a transparent material and has a detector element (14) attached to it, and which detector means is mounted at a suitable point either on the surface (2) of the plate or so as to be partially or entirely embedded inside the plate (1), whereby a fraction of the radiation traveling by total internal reflection in the inside of the plate (1) can exit from the plate (1) into the transducer piece (12) and further pass through the piece to the detector element (14).

8. An apparatus for detecting liquid and/or solid dirt on the surface of a transparent plate (1), in which apparatus radiation emitted by from a source of electromagnetic radiation is detected from an intensity change of reflected radiation, wherein

said apparatus has at least one radiation-emitting element (10, 11) placed relative to the surface (2) of the plate (1) so that the radiation emitted by said element is incident via a gas-phase medium on the measurement area of the surface of the plate (1) and the radiation emitted by said element is transmitted through the plate (1) to air without reflection when the plate is dry and/or clean, but a fraction of the radiation

(i) undergoes refraction from liquid droplets deposited on the surface (2) of the plate the same side as said radiation emitting element or

(ii) undergoes total internal reflection from liquid droplets (4) deposited on the surface (3) of the plate on the opposite side from said radiation element, or

(iii) is scattered by droplets of radiation-transparent medium containing solid particles deposited on the surface of the plate,

so as to make said fraction(s) of the radiation enter the inside of the plate (1) and become transferred inside of the plate (1) by total internal reflection at its surfaces (2, 3), and

said apparatus further has a radiation receiving detector means (14) adapted to receive the radiation travelling inside of the plate (1) by total internal reflection and to detect the fraction of radiation as an intensity increase of the received radiation.

9. An apparatus as defined in claim 8, wherein said radiation receiving means comprise a transducer piece (12), which is made of a material transparent to the measuring radiation and incorporates a detector element (14) attached to it either directly or via a radiation transmitting element (20, 21) and/or a radiation collecting optical system (23), whereby the radiation travelling by total internal reflection in the inside of the plate (1) can exit from the plate (1) into the transducer piece (12) and further pass through the piece to the detector element (14).

10. An apparatus as defined in claim 9, wherein the outer surface of the transducer piece (12) is provided with a nontransparent and from inside nonreflecting layer and that the nontransparent interface between the transducer piece (12) and the plate surface (2) is provided with a transparent window (13) and the detector element (14) is aligned with respect to the window (13) of the transducer piece (12) so that only the radiation travelling by total internal reflection in the inside of the plate (1) can reach the detector (14), whereby the outer surface of the transducer piece (12) as well as the interface between the plate surface (2) and the transducer piece (12) are nontransparent with the exception of the window (13) over such an area that a line drawn from the edge (D) of the window (13) closer to the detector (14) to the top edge of the detector (14) forms with the surface of the plate an angle (α

) which is smaller than the critical angle (θ

) of total internal reflection.

11. An apparatus as defined in claim 8, wherein said apparatus comprises means for emitting the measuring ray in pulses from the source (10, 11) of radiation and means for detecting the magnitude of the measuring radiation received by the detector element (14) during the pulse or thereafter, and means for comparing said magnitude with a predetermined set value.

12. An apparatus as defined in claim 11, additionally comprising

means for starting or stopping a windshield wiper based upon deviation of said magnitude from said predetermined set value.

13. An apparatus for detecting liquid and/or solid dirt on the surface of a transparent plate (1), in which apparatus radiation emitted by at least one source of electromagnetic radiation is transmitted inside of said plate (1) in the form of radiation undergoing total internal reflection at the surfaces (2, 3) of said plate, whereby the presence of liquid and/or dirt on the surface (2) and/or the surface (3) of the transparent plate (1) is detected from the intensity change of the totally reflected radiation, wherein

said apparatus has at least one radiation-emitting element (10, 11) placed relative to the surface (2) of the plate (1) so that the radiation is transferred from air to the measurement area of the surface of the plate (1) and the radiation emitted by said element is transmitted through the plate (1) without reflection when the plate is dry and/or clean, while a fraction of the radiation undergoes refraction from liquid droplets deposited on the surface (2) of the plate and/or undergoes total internal reflection from liquid droplets (4) deposited on the surface (3) of the plate and/or is scattered by droplets containing solid particles so as to make said fraction(s) of the radiation enter the inside of the plate (1) and become transferred inside of the plate (1) by total internal reflection at its surfaces (2, 3), and

said apparatus further has a radiation receiving detector means (14) adapted to receive the radiation travelling in the inside of the plate (1) by total internal reflection and to detect the presence of liquid/dirt deposited on the surface (2) and/or the surface (3) of the plate from the intensity increase of the received radiation, wherein

(a) said apparatus comprises two radiation-emitting elements of which one source (10) of radiation employed for detecting the liquid component is so aligned that the angle β

1 of the measuring ray to the surface (2) of the plate toward the detector means (14) is in the range 90°

-180°

, while the other source (11) of radiation employed for detecting the solid particles is so aligned that corresponding angle β

2 is in the range 0°

-90°

, or alternatively,

(b) the radiation employed for detecting the presence of solid particles is transmitted to the inside of the plate with the help of a transducer piece so as to make the radiation propagate inside of the plate by total internal reflection at the surfaces (2,

     3) of the plate, or

(c) said radiation receiving means comprise a radiation-sensitive detector means (14) mounted to the edge of the transparent plate (1), or

(d) the measurement is performed using a branched optical fiber (k1, k2) so that the radiation used for detecting solids is transmitted to the point of measurement via the same optical fiber (21) as used for taking the measuring radiation from the point of measurement to the detector element (14).

14. An apparatus as defined in claim 13, wherein said radiation receiving means comprise a transducer piece (12), which is made of a material transparent to the measuring radiation and incorporates a detector element (14) attached to it either directly or via a radiation transmitting element (20, 21) and/or a radiation collecting optical system (23), whereby the radiation traveling by total internal reflection in the inside of the plate (1) can exit from the plate (1) into the transducer piece (12) and further pass through the piece to the detector element (14).

15. An apparatus for detecting liquid and/or solid dirt on the surface of a transparent plate (1), in which apparatus radiation emitted by at least one source of electromagnetic radiation is transmitted inside of the plate (1) in the form of radiation undergoing total internal reflection at surfaces (2, 3) of said plate,

whereby the presence of liquid and/or dirt on the surface (2) and/or the surface (3) of the transparent plate (1) is detected from intensity change of totally reflected radiation, wherein

said apparatus has at least one radiation-emitting element (10, 11) placed relative to the surface (2) of the plate (1) so that the radiation is transmitted from air to a measurement area of the plate (1) and the radiation emitted by said element (10, 11) is transmitted through the plate (1) without reflection when the plate is dry and/or clean, while a fraction of the radiation undergoes refraction from liquid droplets deposited on the surface (2) of the plate and/or undergoes total internal reflection from the liquid droplets (4) deposited on the surface (3) of the plate and/or is scattered by contaminant droplets so as to make said fraction(s) of the radiation enter the inside of the plate and become transferred inside of the plate (1) by total internal reflection at its surfaces (2, 3), and

said apparatus further has a radiation receiving detector means (14) adapted to receive the radiation travelling inside of the plate (1) by total internal reflection and to detect the presence of liquid/dirt deposited on the surface (2) and/or the surface (3) of the plate from the intensity increase of the received radiation,

said apparatus comprises means for emitting the measuring ray in pulses from the source (10, 11) of radiation and means for detecting magnitude of measuring radiation received by the detector element (14) during the pulse or thereafter, and means for comparing said magnitude with a predetermined set value, and

said apparatus further comprises means for emitting the measuring ray from two sources (10, 11) of radiation in pulses at different instants of time and means for correspondingly receiving the pulses at different instants of time, whereby said apparatus is capable of accomplishing selective detection of both liquid and solid dirt deposited on the windshield of a vehicle, and thus performing demand-based starting and stopping of a windshield wiper and washer.