KR101101538B1 - Optical sensor device - Google Patents

Abstract

An optical sensor device couples the light emitter 24, the light receiver 26, and the light beam emitted by the light emitter 24 into and out of the window pane and guides the light receiver 26 to the light receiver 26. It includes a sensor unit having a lens plate 12 used. The lens plate 12 has Fresnel lens structures 18a and 18b and Fresnel reflector structures 20a and 20b on the first face 12a facing the light emitter 24 and the light receiver 26. And a Fresnel reflector structure 22a, 22b on the second side 12b on the opposite side facing the window pane. This configuration is particularly suitable for use as a rain sensor. Sensor devices without light emitters are suitable for use as light sensors.

Description

Optical sensor device {OPTICAL SENSOR DEVICE}

The present invention relates to an optical sensor device adapted to be coupled to a windshield, in particular a windshield of a motor vehicle.

Sensor devices of this type are mainly used as rain sensors in automobiles for the automatic operation of windshield wipers and as light sensors for controlling the backs of vehicles. The use of conventional lenses affecting the beam path, for example the lens of the rainwater detection sensor, which is presented in EP 1 068 112 B1 inclined towards the windshield, requires a relatively large amount of space.

The use of holographic structures allows to realize smaller configurations, for example as known from WO 03/026937 A1. These sensors are based on the optical diffraction principle using diffractive elements, and thus have the drawback of substantially lower effective luminous efficiency and higher sensitivity to stray light caused by this principle.

DE 196 08 648 C1 proposes an optical sensor device in which the light entrance surface of the optical waveguide unit is configured in the form of a Fresnel lens. However, since the surface of the optical waveguide in which the lens is constructed is perpendicular to the window glass surface, this optical sensor device requires a very large amount of space.

The basic disadvantages of prior art rainwater sensing light sensor devices or daylight sensor devices are identified in terms of the high production costs and disadvantageous ratios of sensor dimensions to the size of the surface area detected by use.

The present invention provides an optical sensor device that requires very little structural space in the case of optimal light conditions and has as low sensitivity as possible to objects and external light in the front region.

To this end, in the first embodiment of the optical sensor device, a lens plate is used for coupling a light emitter, a light receiver, and a light beam emitted by the light emitter into and out of the window glass and guiding the light beam to the light receiver. A sensor unit is provided that includes. The lens plate comprises a combination Fresnel structure having a Fresnel lens structure and Fresnel reflector structure on the first side facing the light emitter and the receiver, and a Fresnel reflector structure on the second side opposite to the window pane. This configuration is particularly suitable for use as rainwater detection sensors.

In this case, the sensor unit in the lens plate has two separate combined Fresnel structures adjacent to each other, with oppositely arranged Fresnel reflector structures. The light emitter is positioned at the focal point of one Fresnel lens structure and the light receiver is positioned at the focal point of the other Fresnel lens structure. The light flux emitted by the light emitter is paralleled by one combinatorial Fresnel structure, passes vertically through the lens plate, is guided at an angle to the pane by a suitable Fresnel reflector structure, and is totally reflected by the pane, It is coupled to the lens plate by a Fresnel reflector structure associated with the other combinatorial structure, vertically passes through the lens plate, and is directed to the other combinatorial Fresnel structure and focused on the light receiving portion by the other combinatorial Fresnel structure. The fact that all of the optically active elements are concentrated in the lens plate requires minimal space. At the same time, a useful large sensor surface on the pane is obtained.

In a second embodiment of the optical sensor device, there is provided a sensor unit comprising a light receiver and a lens plate used to couple a light beam incident on the window pane to the outside of the window pane and to guide the light beam to the light receiver. The lens plate includes a combination Fresnel structure having a Fresnel lens structure and a Fresnel reflector structure on a first side facing the light receiver, and a Fresnel reflector structure on a second side on the opposite side facing the pane. This configuration is particularly suitable for use as a light sensor.

In this case, the beam of light impinging parallel to the glazing passes through the glazing at a predetermined angle, then is coupled to the lens plate by a Fresnel reflector structure, vertically passes through the lens plate and is guided to the combinatorial Fresnel structure, the other combinatorial Focused on the receiver by the Fresnel structure. Here too, since all of the optically active elements are concentrated in the lens plate, a minimum space requirement is obtained. At the same time, an excellent direction detection effect on the light to be detected is obtained.

In an advantageous embodiment of the rainwater detection / light sensor, both configurations of the light sensor device are combined and share a common lens plate in which the combined Fresnel structure and the Fresnel reflector structure are formed.

Advantageous and suitable aspects of the optical sensor device according to the invention will be apparent from the dependent claims. Hereinafter, with reference to the accompanying drawings will be described in more detail the principle of the preferred embodiment.

According to the present invention, there is provided an optical sensor device which requires only a very small structural space in the case of optimum optical conditions and has as low sensitivity as possible to objects and external light in the front region.

Rainwater detection sensors typically consist of two identical light sensor units. This type of sensor unit is shown schematically in FIG. 1. The sensor unit is attached to the windshield 10 of the motor vehicle. The optically active element of the sensor unit is the lens plate 12. The lens plate 12 is optically coupled to the windshield 10 by a coupler layer 14.

On the first surface 12a facing away from the windshield 10, the lens plate 12 is provided with two identical Fresnel structures 16a, 16b arranged at a short distance from each other. Both Fresnel structures 16a and 16b are configured to be rotationally symmetric about axes A and B, respectively. The Fresnel structures 16a and 16b are divided into an inner side and an outer side, with the outer side having a larger radial echo distance from the axis A or B than the inner side. The inner portion is composed of Fresnel lens structures 18a, 18b, and the outer portion is composed of Fresnel reflector structures 20a, 20b. In the following, the Fresnel structures on the first face 12a of the lens plate 12 facing the windshield 10 are thus referred to as combined Fresnel structures 16a and 16b.

In particular, as can be seen in the detail enlarged view of FIG. 1A, both Fresnel lens structures 18a and 18b and Fresnel reflector structures 20a and 20b have a sawtooth profile and Fresnel reflector structures 20a and 20b ) Flanks are respectively oriented toward axes A and B, and steeper and longer than the corresponding flanks of Fresnel lens structures 18a and 18b.

On the second side 12b facing the windshield 10, opposite the combination Fresnel structures 16a, 16b, the lens plate 12 has two fres symmetrically mirrored with respect to the center plane M of the lens plate. Nel reflector structures 22a and 22b are provided. Like the Fresnel reflector structures 20a and 20b of the first face 12a, the Fresnel reflector structures 22a and 22b of the second face 12b are also made of precision surface forming parts that are alternately raised and concave.

The light emitter 24 is arranged at the focal point of the Fresnel lens structure 18a lying on the associated axis of rotation symmetry A. The light receiver 26 is disposed at the focal point of the Fresnel lens structure 18b lying on the associated axis of rotation B.

Light emitter 24 emits light in a particular frequency range, in which the term "light" is not limited to visible light, but more specifically radiation in the infrared range. The divergent light beam emitted by the light emitter 24 is reshaped into parallel light passing vertically through the lens plate 12 by the combined Fresnel structure 16a. Here, the combined Fresnel structure 16a is configured such that the light rays incident on the Fresnel lens structure 18a are only refracted, while the light rays incident on the Fresnel structure 20a are refracted and reflected (FIGS. 1 and FIG. See 1a). In the final analysis, all the rays are given in the same direction, resulting in a beam of rays that are all parallel.

As will be understood with reference to FIG. 1A, the (radial) position of the boundary between the Fresnel lens structures 18a and 18b and the Fresnel reflector structures 20a and 20b is such that the Fresnel lens is refracted by the light beam from the light emitter 24. It depends on the angle of incidence of the light beam of the light beam incident on the right flank (according to the drawing of FIG. 1A) of the structure 18a. The angles of inclination of these flanks are previously defined such that the refracted light beam passes vertically through the lens plate 12. If the radial distance from the axis A increases, this causes the angle of incidence to become smaller and smaller. At the point where the angle of incidence falls below a predetermined value (ie, the light enters the flank at too small an angle), a significant transition is provided for the Fresnel reflector structure 20a.

The parallel light beam passing through the lens plate 12 is reflected by the Fresnel reflector structure 22a at an angle with respect to the plane of the lens plate 12 and enters the coupler layer 14. Upon passing through the coupler layer 14, the light beam enters the windshield 10 and is totally reflected at the inner surface 10a opposite the windshield. The light beam then passes back through the windshield 10 to enter the coupler layer 14 and is deflected by the Fresnel reflector structure 22b to pass vertically through the lens plate 12. Combination Fresnel structure 16b ultimately transforms the parallel beam of light into a converging beam of light that impinges on receiver 26.

Fresnel reflector structures 22a and 22b exhibit some special features, and with reference to FIG. 2, these features will now be described. The surface shaping portions of the Fresnel reflector structures 22a and 22b are generally serrated in cross section and are composed of a plurality of prismatic sections. The first flank 22 ₁ extends continuously straight from the base to the vertex, and the second flank consists of two sections 22 ₂ , 22 ₃ . The section 22 ₂ of the second flank (on the right side of FIG. 2) is less steep than the second section 22 ₃ , and the section 22 ₂ is also steeper than the first flank 22 ₁ . In other words, the Fresnel reflector structures 22a, 22b; 22 of the second face 12b are linear structures that deflect parallel beams in a particular direction.

The refractive indices n1 and n2 of each material forming the lens plate 12 and the coupler layer 14 are carefully matched, such as the angle of the flanks in the sawtooth reflector structures 22a and 22b. Light rays L passing through the lens plate 12 vertically are incident on the flank 22 ₁ at an acute angle α, totally reflected, and incident on the flank 22 ₂ at a predetermined angle β. In the configuration shown in Fig. 2, since the angle β is 90 degrees, the emission angle β also reaches 90 degrees. As a result, no refraction of light occurs in the flanks 22 ₂ .

The refractive indices n1 and n2 differ only slightly from each other. The condition for total reflection of the light beam on the flank 22 ₁ is that the angle of incidence must be greater than the arc sine value of the ratio of the refractive indices. Since the ratio of the refractive index is only slightly different from 1, the incident angle α should be relatively small. For example, a maximum angle of incidence of approximately 26 ° results in a combination of the material of polycarbonate for lens plate 12 and silicone rubber for coupler layer 14. This angle determines the minimum tilt of the reflector structure. The actual slope is determined so that the light rays exiting towards the windshield 10 have the angle needed for total reflection on the windowpane. The preferred entry angle for total reflection on the windshield 10 typically reaches approximately 45 °. This angle is appropriate for the requirements formed for the geometry of the Fresnel reflector structures 22a and 22b.

FIG. 3A also schematically illustrates the light transmission achievable using the geometry of the Fresnel reflector structures 22a and 22b shown in FIG. 2. No optical refraction occurs at the boundary layer between the lens plate 12 and the coupler layer 14. The result is non-optimal illumination of the sensor surface formed by the total reflection surface of the windshield 10.

The condition may be even more disadvantageous in FIG. 3B where the section 22 ₂ in the right flank of the tooth structure is much flatter. Since light rays are incident on the flanks 22 ₂ at angles other than 90 °, optical refraction occurs in the negative direction (right in FIG. 3B). The exiting beam of flux is much narrower than in FIG. 3A.

3c shows the optimum illumination conditions for the geometry. Here, the right flank of the tooth structure in this figure is continuous without being divided | segmented, and is formed steeply than the left flank. The photorefractive in the right flank occurs mathematically in the positive direction (left in FIG. 3C). The collision angle at which the light impinges on the left flank is also appropriate for the conditions for total reflection. The beams refracted by the right flank only touch the vertices of the adjacent tooth structure. This creates perfect illumination of the sensor surface on the windshield 10.

According to another approach, the principle of illumination described above, including the sensor surface as far as possible, is partially abandoned for improved external light suppression. In fact, it should be taken into account that external light (eg, sunlight) acting from outside the windshield 10 can likewise be incident on the receiver 26. Tests and simulations show that, within the schematic conditions discussed above, the construction of a substantially symmetrical tooth structure creates the best possible insensitivity to external light. An embodiment constructed in accordance with this approach is shown in FIG. 4.

A symmetrical configuration in this context is intended to mean that the left and right flanks are straight (without segmentation) and have the same angle of inclination with respect to the windshield 10 plane or the lens plate 12. In addition, the configuration of the "substantially" symmetrical tooth structure clearly includes deviations within the usual tolerance range, and is intended to take account of the difference in refractive index between the lens plate 12 and the coupler layer 14.

For the complete function of the configuration of the Fresnel reflector structures 22a and 22b described above, the reflector structures 22a and 22b in a form-fitting manner without the material of the coupler layer 14 containing bubbles or the like. It is essential to contact with the surface.

An embodiment of the light sensor device shown in FIG. 5 is a direction sensing daylight sensor. The sensor unit shown in this figure also has a lens plate 12 which acts as an optical element, in which case the lens plate is only a combination Fresnel structure 16 and a corresponding Fresnel reflector disposed on the opposite side of the structure. Only the structure 22 is provided. Combination Fresnel structure 16 is of the same configuration as the rainwater detection sensor device shown in Figs. 1 and 4 and thus includes (inner) Fresnel lens structure and (outer) Fresnel reflector structure, but in Fig. 5 Only fresnel lens structures are shown for simplicity.

The light receiver 26 is disposed at the focal point of the Fresnel lens structure. The lens plate 12 is coupled to the windshield 10 by a coupler layer 14, and in the illustrated embodiment the tilt angle of the windshield 10 reaches approximately 27 °. With respect to the geometry of the Fresnel reflector structure 22, the same criteria as for the above-described embodiment of the rainwater detection sensor can be applied.

The daylight sensor is horizontally incident on the windshield 10, is inclined downward upon refraction upon incident on the window pane, and reacts to light impinging on the Fresnel reflector structure 22 through the coupler layer 14. The Fresnel reflector structure deflects the light beams and passes these light beams vertically through the lens plate 12 onto the combined Fresnel structure 16 that focuses on the light receiver 26.

In practice, a combination rainwater detection / light sensor is needed. Rainwater detection sensors include many sensor units of the type as shown in FIG. 1 or FIG. 4.

The sensor units are disposed adjacent to each other and share a common lens plate 12. The optically active structure of the daylight sensor shown in FIG. 5 is also disposed on the same lens plate 12. If necessary, other sensors are provided which can receive light from different directions. Non-directional ambient light can additionally be detected through a portion of the lens plate 12 that is non-optical or only optically active.

Lens plate 12 may be manufactured using conventional injection molding techniques. As an alternative, stamping techniques can be employed.

At least the non-optical active surface portion of the lens plate 12 to avoid malfunctions caused by light coupled to the interior and / or exterior in an undesirable manner, the possible causes will be discussed in more detail below. For example, refractive structures or reflective structures, such as retroreflective elements (so-called reflex reflectors), are provided. This causes light not incident on the optically active surface to be deflected in a "harmless" direction. As an alternative, printing that is opaque to light can be used to provide non-optical actives on one or both sides. In fact, not only the preferred parallel beam of light used for illumination of the windshield 10 at a 45 ° angle, but also the undesirable beam illuminates an object such as sand particles disposed in front of the windshield 10, This does not achieve any wetting. The light portion can be reflected back on these objects and possibly reach the light receiver 26 in this manner. Moreover, as already mentioned above, external light (eg, sunlight) acting from the outside may reach the light receiving portion 26. In addition, light from light emitter 24 may reach light receiver 26 directly (ie, without bypass through windshield 10) by multiple reflections if possible. All of these effects can lead to false wet perception.

1 is a schematic cross-sectional view of a sensor unit of a rainwater detection sensor.

1A is a schematic enlarged view of details of the bottom Fresnel structure of FIG.

2 is a schematic enlarged cross-sectional view of a Fresnel reflector structure.

3A-3C are corresponding schematic cross-sectional views of another embodiment.

4 is a schematic cross-sectional view of the light emitter side of a particular embodiment of a sensor unit in a rainwater detection sensor.

5 is a schematic cross-sectional view of a daylight sensor.

<Explanation of symbols for the main parts of the drawings>

10: windshield

12: lens plate

14: coupler layer

16, 16a, 16b: combination Fresnel structure

18a, 18b: Fresnel lens structure

22, 20a, 20b, 22a, 22b: Fresnel reflector structure

22 ₁ : first flank

22 ₂ , 22 ₃ : second flank

24: light emitter

26: Receiver

Claims (21)

Lens plate 12 used to couple light emitter 24, light receiver 26, and light beams emitted by light emitter 24 into and out of the window pane and to guide the light beams to light receiver 26. An optical sensor device adapted to be coupled to a window pane, comprising a sensor unit having: The lens plate 12 has Fresnel lens structures 18a and 18b and Fresnel reflector structures 20a and 20b on the first surface 12a facing the light emitter 24 and the light receiver 26. And a Fresnel reflector structure (22a, 22b) on the second side (12b) on the opposite side facing the window pane. Coupled to the window pane, comprising a sensor unit having a light receiver 26 and a lens plate 12 used to couple the light beam incident on the window pane to the outside of the window glass and guide the light beam to the light receiver 26. An optical sensor device adapted to ring, The lens plate 12 has a combination Fresnel structure 16 having a Fresnel lens structure and a Fresnel reflector structure on the first surface 12a facing the light receiver 26, and a second surface on the opposite side facing the window glass. And a Fresnel reflector structure (22) on (12b). 2. Optical sensor device according to claim 1, characterized in that the combined Fresnel structure (16a) of the first face (12a) reshapes the diverging beams into parallel beams. 3. The combined Fresnel structure (16a, 16b; 16) of the first surface (12a), according to claim 1 or 2, is coupled to a parallel light beam that is coupled to the outside of the pane and traverses the lens plate (12). Optical sensor device characterized in that the reshaping. 5. Optical sensor device according to claim 4, wherein the parallel beam of light passes vertically through the lens plate (12). 3. Optical sensor device according to claim 1 or 2, characterized in that the combined Fresnel structure (16a, 16b; 16) of the first face is a rotationally symmetrical structure for focusing divergent or parallel beams. 7. The Fresnel reflector structures 20a, 20b of the combination Fresnel structures 16a, 16b; 16 are Fresnel lens structures 18a, 18b of the combination Fresnel structures 16a, 16b; Optical sensor device, characterized in that it has a radial distance from the larger axis of rotation (A, B). 3. Optical sensor device according to claim 1 or 2, wherein the Fresnel reflector structures (22a, 22b; 22) of the second face (12b) are linear structures which deflect parallel beams in a particular direction. The coupler layer (14) of claim 1 or 2, wherein the lens plate (12) is in form-fitting contact with the Fresnel reflector structures (22a, 22b; 22) of the second surface (12b). Optical sensor device, characterized in that coupled to the windowpane. 3. Optical sensor device according to claim 1 or 2, characterized in that the Fresnel reflector structures (22a, 22b; 22) of the second surface (12b) reflect at the inner surface. The fresnel reflector structures (22a, 2b; 22) of the second surface (12b) are made of the first flank (22 ₁ ) in which reflection occurs and parallel beams enter and exit. An optical sensor device having two flanks (22 ₂ , 22 ₃ ) and having a sawtooth cross section. 12. Optical sensor device according to claim 11, wherein the second flanks (22 ₂ , 22 ₃ ) are traversed vertically. 12. An optical sensor device according to claim 11, wherein the refraction of light occurs in the second flank (22 ₂ , 22 ₃ ). 13. Light sensor device according to claim 12, characterized in that the second flank has two sections (22 ₂ , 22 ₃ ) having different inclinations, and the less steep section (22 ₂ ) forms an entrance surface. 14. An optical sensor device according to claim 13, wherein the second flanks (22 ₂ , 22 ₃ ) each form an entrance surface steeper than the first flank. 12. The optical sensor device according to claim 11, wherein the first and second flanks (22 ₁ and 22 ₂ and 22 ₃ respectively) are formed symmetrically with respect to each other. 2. The Fresnel lens structures 18a and 18b and Fresnel reflector structures 20a and 20b, wherein the Fresnel reflector structures 22a and 22b are disposed on the lens plate 12 on the opposite side. Two separate combinatorial Fresnel structures 16a, 16b are formed that contain each other, the light emitter 24 is positioned at the focal point of one Fresnel lens structure 18a, and the light receiver 26 is the other Fresnel. The light beams disposed at the focal point of the lens structure 18b and emitted by the light emitter 24 are paralleled by one combined Fresnel structure 18a, vertically pass through the lens plate 12, and on the opposite side of the fres The lens plate 12 is guided at an angle to the pane by the Nell reflector structure 22a and totally reflected by the pane and then by the Fresnel reflector structure 22b opposite the other combination Fresnel structure 16b. Is coupled to the lens plate 12 vertically And at least one sensor unit which is guided to another combinatorial Fresnel structure (16b) and focused by the other combinatorial Fresnel structure (16). 18. Optical sensor device according to claim 17, wherein the optical sensor device comprises a plurality of sensor units having a shared lens plate (12). The light beam incident on the window pane at a narrow detection angle, after passing through the window glass at a predetermined angle, is coupled to the lens plate 12 by a Fresnel reflector structure 22 opposite the window glass, and the lens An optical sensor device, characterized in that it passes vertically through the plate (12) and is guided to the combined Fresnel structure (16), which is focused to the receiver (26) by the combined Fresnel structure. A rainwater detection / light sensor, characterized in that the light sensor device according to claim 17 is combined with the light sensor device according to claim 19, which comprises a shared lens plate (12). 14. An optical sensor device according to claim 13, wherein the second flank has two sections (22 ₂ , 22 ₃ ) having different inclinations, and the less steep section (22 ₂ ) forms an entrance surface.

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