DE102014116852A1 - Optoelectronic sensor with a receiving element - Google Patents

Abstract

Optoelectronic sensor having a receiving element (2) and a receiving lens (4), and an optical filter element (6) which is arranged between the receiving element (2) and the receiving lens (4), wherein the optical filter element (6) at least one convex or concave surface (8) such that the received light rays pass through the filter element (6) at the surface (8) at each entry point at a right angle.

Description

The present invention relates to an optoelectronic sensor having a receiving element and a receiving lens and an optical filter element, which is arranged between the receiving element and the receiving lens.

In optoelectronic sensors interference filters are used. The task of the filter is to specifically filter light of certain frequencies. Typically, this blocks wavelengths from the near-infrared (NIR) or passes only the wavelengths emitted by a transmitter through the bandpass filter to the receiving element, with the aim of improving the signal-to-noise ratio and reducing sensitivity to stray light sources. Interference filters are usually applied to a glass substrate deposited dielectric layers, which are derived for the application in optoelectronic sensors significantly at least two tasks.

First, the process of mounting interference filters is often cumbersome due to the thin and force sensitive glass plates and must also be considered for downstream assembly processes.

Second, the filtering effect depends on the optical path length the beam takes through the filter. This results in a dependence of the center wavelength, quality and half width of the filter on the angle of the incident rays. In particular, band filters should only be irradiated by beam bundles with the smallest possible angular spectrum for optimum operation. Therefore, the ideal mounting location according to the prior art in front of the receiving lens, which, however, counteracts the miniaturization in the opto-mechanical design and is connected by the necessary large surface of the filter with additional costs.

It is therefore an object of the invention to provide an optical filter element which has an improved filtering effect. Another object is to provide a cheaper filter element. Another object is to provide a more compact optoelectronic sensor.

The object is achieved according to claim 1 by an optoelectronic sensor having a receiving element and a receiving lens and an optical filter element which is arranged between the receiving element and the receiving lens, wherein the optical filter element has at least one convex or concave surface, so that the received light beams Run through the filter element on the surface at each entry point in a vertical angle.

The receiving element is for example a receiving diode. In front of the receiving element is at a distance the receiving lens. The receiving lens is designed as a converging lens and focuses the light onto the receiving element. The received light occurs bundled after the receiving lens on the receiving element.

Between the receiving element and the receiving lens according to the invention, the optical filter element is arranged. The filter element has at least one convex or concave surface. On the convex or concave surface, the filter is effective through a filter layer. In this case, the convex or concave surface is arranged such that the received light rays after the receiving lens pass through or penetrate the filter element or the filter layer of the filter element at right angles or at right angles.

As a result, the filter element is equally effective for all light beams. Each light beam is filtered identically by the filter.

Since the filter element is arranged between the receiving lens and the receiving element, the filter element can be made smaller in area than a filter element which is arranged directly in front of the receiving lens, since the filter element only has to be made slightly larger than the receiving element, depending on which position the filter element is arranged between the receiving element and the receiving lens. As a result, the filter element can be made cheaper and easier. Since the filter element is more compact, better quality can be provided over the entire area of the filter element.

The filter element may be, for example, a bandpass filter, an infrared filter, a near infrared filter, etc.

In a further development of the invention, the sensor is a light barrier or a light sensor. A light barrier can be designed as a through-beam sensor. In this case, the light transmitter and the light receiver are arranged opposite one another and an interruption of the light beam leads in the evaluation unit of the light receiver to an object detection signal. In the case of a reflection light barrier, the light emitter and the light receiver are located on the same side of a surveillance area, usually in a single housing. Opposite a retroreflector is arranged, which reflects the light emitted by the light emitter back through 180 ° in the light receiver.

In a light scanner light transmitter and light receiver are arranged in a common housing. The light rays emitted by the light emitter are reflected or remitted on an object. The received light can be evaluated energetically. If a certain threshold is exceeded, an object detection signal is output.

However, the light sensor can also be designed as Triangulationstaster. In a Triangulationstaster the receiving element is spatially resolved and arranged the light emitter spaced from the receiving element. A light spot emitted by the light emitter is returned by an object, imaged via the reception lens onto the spatially resolving reception element. Depending on the distance of the object, the light spot is imaged at different positions, it being possible to infer the distance of the object from the position of the light spot on the receiving element.

In a further development of the invention, the sensor is a sensor according to the time of flight method. In this case, a short light pulse or a group of light pulses is emitted by the light transmitter. The one or more light pulses are reflected or remitted by an object and received by the receiving element of the light receiver. From a downstream evaluation unit, the duration of the light from sending to receiving evaluated and calculated from the distance of the object.

In a development of the invention, a second surface, which is spaced apart from the first surface, is a plane, convex or concave surface. The first surface is opposite the receiving lens and the second surface is facing the receiving element.

For example, if the first surface is a convex surface and the second surface is a concave surface, the convex and concave surfaces having a common radius origin, the filter element has a curvature, the thickness of the filter element being constant.

However, it can also be provided that the first surface is a convex surface and the second surface is a concave surface, wherein the convex and concave surfaces have a different radius origin, so that the filter element has a curvature, wherein the thickness of the filter element is different.

However, it may also be provided that the first surface is a convex surface and the second surface is a planar surface. This creates a filter element which itself has a lens effect. The filter layer is formed by the first surface.

Furthermore, it can be provided that the first surface is a planar surface and the second surface is a concave surface. In this case, a filter element is also formed, which itself has a lens effect. The filter layer is formed by the second concave surface.

According to a preferred embodiment, the first or the second surface of the filter element has a spherical surface. A spherical surface is part of a spherical surface. The filter element is a rotationally symmetrical body, which is associated according to this embodiment of a rotationally symmetrical receiving lens. According to this embodiment, the light energy can be concentrated to the smallest possible light spot. This improves the sensor sensitivity and allows a higher distance accuracy with triangulation probes. The receiving element is for example a receiving diode with a small receiving surface. For example, the receiving area is less than 1 mm ² .

In a preferred embodiment, the filter element is arranged within the focal length of the receiving lens. According to this embodiment, the light energy can be concentrated to the smallest possible light spot. This improves the sensor sensitivity and allows a higher distance accuracy with triangulation probes. As a result, the receiving element can be made very small, for example in the case of a light barrier.

In a further development of the invention, the filter element is arranged outside the focal length of the receiving lens. As a result, the receiving element can be formed flat with a larger extent. This is useful, for example, if a planar image sensor is to be used as the receiving element, for example a CCD or CMOS image sensor. Furthermore, according to this embodiment, a planar position-sensitive receiving element can also be used.

For example, if the first surface is a concave surface and the second surface is a convex surface, the convex and concave surfaces having a common radius origin the filter element has a curvature, wherein the thickness of the filter element is constant.

However, it can also be provided that the first surface is a concave surface and the second surface is a convex surface, wherein the convex and concave surface have a different radius origin, so the filter element has a curvature, wherein the thickness of the filter element is different.

Furthermore, it can be provided that the second surface is a planar surface and the first surface is a concave surface. In this case, a filter element is also formed, which itself has a lens effect. The filter layer is formed by the first concave surface.

However, it may also be provided that the second surface is a convex surface and the first surface is a planar surface. This creates a filter element which itself has a lens effect. The filter layer is formed by the second convex surface.

In a further development, the filter element is made of glass and a cover glass of the receiving element. As a result, the filter element is mechanically coupled directly to the receiving element. As a result, the spatial assignment of the filter element is set to the receiving element, whereby the components no longer need to be aligned with each other. The receiving element is already produced with the coverslip and then fixed in a sensor.

In a particular embodiment, the receiving lens is a cylindrical lens and the filter element is a cylindrical body. The receiving element is formed by a plurality of receiving elements arranged in series. However, it can also be arranged a line-shaped or a strip-shaped receiving element. Such an arrangement is advantageous, for example, in the case of a barcode scanner or a light grid.

The invention will be explained below with regard to further advantages and features with reference to the accompanying drawings with reference to embodiments. The figures of the drawing show in:

1 an optoelectronic sensor according to the prior art;

2 to 9 each embodiment of the sensor according to the invention;

10 a cylindrical lens and a filter element as a cylindrical body;

11 a sensor as a light barrier;

12 a sensor as a reflection light barrier;

13 a sensor as a light sensor;

14 a sensor as Triangulationslichttaster;

15 a sensor according to the light transit time method.

In the following figures, identical parts are provided with identical reference numerals.

1 shows a part of an optoelectronic sensor 1 According to the state of the art. According to 1 is on a circuit board 30 or a board a receiving element 2 arranged. Spaced to the receiving element 2 is a reception lens 4 arranged. The receiving element 2 is within the focal length 24 at the focal point of the receiving lens 4 arranged. In front of the reception lens 4 is an optical filter 32 arranged. Incident light therefore first penetrates the filter 32 , whereby unwanted light components are filtered out. Unfiltered light is shown as a continuous line. Filtered light is shown with a dot-dot-dash line. Subsequently, the incident light from the receiving lens 4 on the receiving element 2 focused.

2 shows an optoelectronic sensor 1 according to the present invention with a receiving element 2 and a receiving lens 4 and an optical filter element 6 which is between the receiving element 2 and the receiving lens 4 is arranged, wherein the optical filter element 6 at least one convex or concave surface 8th so that the received light rays are the filter element 6 on the surface 8th go through at each entry point in a vertical angle.

The receiving element 2 is for example a receiving diode, which on a circuit board 30 or circuit board is arranged. In front of the reception element 2 is located at a distance the receiving lens 4 , The reception lens 4 is designed as a converging lens and focuses the light on the receiving element 2 , The received light occurs after the receiving lens 4 fan-shaped on the receiving element 2 ,

Between the receiving element 2 and the receiving lens 4 is the optical filter element according to the invention 6 arranged. The filter element 6 has at least one convex or concave surface 8th on. On the convex or concave surface 8th the filter is effective through a filter layer. Here is the convex or concave surface 8th arranged such that the received light beams to the receiving lens 4 the filter element 6 or the filter layer of the filter element 6 traverse or penetrate perpendicularly or at right angles.

According to 2 and the following figures is a second surface 10 leading to the first surface 8th is spaced, a plane, convex or concave surface. The first surface 8th stands thereby the receiving lens 4 opposite, or is the receiving lens 4 facing and the second surface 10 stands thereby the receiving element 2 opposite or is the receiving element 2 facing.

For example, according to 2 the first surface 8th a convex surface and the second surface 10 a concave surface, wherein the convex and concave surfaces have a common radius origin, so has the filter element 6 a curvature, wherein the thickness of the filter element 6 is constant.

However, it can also according to 3 be provided that the first surface 8th a convex surface and the second surface 10 is a flat surface. This creates a filter element 6 , which itself has a lens effect. The filter layer is through the first surface 8th educated.

Further, it may be provided as in 4 shown that the first surface 8th a flat surface is and the second surface 10 a concave surface is. It is also a filter element 6 formed, which itself has a lens effect. The filter layer is through the second concave surface 10 educated.

However, it may also be provided as in 5 shown that the first surface 8th a convex surface and the second surface 10 is a concave surface, the convex and concave surfaces having a different radius origin. So has the filter element 6 a curvature, wherein the thickness of the filter element 6 is different.

According to the 2 to 9 has the first surface 8th or the second surface 10 of the filter element 6 a spherical surface. A spherical surface is part of a spherical surface. The filter element 6 is a rotationally symmetrical body, according to this embodiment of a rotationally symmetrical receiving lens 4 assigned.

According to the 2 to 5 is the filter element 6 within the focal length 24 the receiving lens 4 arranged. According to this embodiment, the light energy can be concentrated to the smallest possible light spot.

According to the 6 to 9 is the filter element 6 outside the focal length of the receiving lens 4 arranged. This allows the receiving element 2 be formed flat with a larger extent. This is useful, for example, if a flat image sensor as a receiving element 2 For example, a CCD or CMOS image sensor is to be used. Further, according to this embodiment, a planar position-sensitive receiving element 2 be used.

According to 6 is, for example, the first surface 8th a concave surface and the second surface 10 a convex surface, wherein the convex and concave surfaces have a common radius origin. According to 6 has the filter element 6 a curvature, wherein the thickness of the filter element 6 is constant.

According to 7 It is intended that the first surface 8th a concave surface and the second surface 10 is a convex surface, wherein the convex and concave surfaces have a different radius origin, so has the filter element 6 a curvature, wherein the thickness of the filter element 6 is different.

According to 8th It is intended that the second surface 10 a flat surface is and the first surface 8th a concave surface is. It is also a filter element 6 formed, which itself has a lens effect. The filter layer is through the first concave surface 8th educated.

As shown in 9 is provided that the second surface 10 a convex surface is and the first surface 8th is a flat surface. This creates a filter element 6 , which itself has a lens effect. The filter layer is through the second convex surface 10 educated.

Next is the filter element 6 for example, glass and a cover glass of the receiving element 2 , This is the filter element 6 directly with the receiving element 2 mechanically coupled.

As shown in FIG 10 is the receiving lens 4 a cylindrical lens and the filter element 6 a cylindrical body. Also the comments according to 2 to 9 can be formed as a cylindrical body, wherein the 2 to 9 correspond to a cross-sectional view. The receiving element 2 is in this case for example by a plurality of receiving elements arranged in series 2 educated. However, it can also be a line-shaped or a strip-shaped receiving element 2 be arranged.

According to 11 is the sensor 1 a photocell 12 , A photocell 12 can be designed as a through-beam sensor. There are light transmitters 34 and light receiver 36 arranged opposite and an interruption of the light beam leads in the evaluation of the light receiver 36 to an object detection signal. In a reflection light barrier according to 12 are light emitters 34 and light receiver 36 on the same side of a surveillance area, usually housed in a single housing. Opposite a retroreflekor is arranged, which by the light transmitter 34 emitted light reflected back by about 180 ° in the light receiver 36 ,

With a light sensor 14 according to 13 are light emitters 34 and light receiver 36 arranged in a common housing. The from the light transmitter 34 emitted light rays are reflected or remitted on an object. In this case, the received light of the light receiver 36 be evaluated energetically. If a certain threshold is exceeded, an object detection signal is output.

According to 14 the light sensor is designed as Triangulationstaster. For a triangulation button is the receiving element 2 designed to be spatially resolved and the light transmitter 34 spaced from the receiving element 2 arranged. One from the light transmitter 34 emitted light spot is returned by an object, via the receiving lens on the spatially resolving receiving element 2 displayed. Depending on the distance of the object, the light spot is displayed at different positions, wherein the position of the light spot on the receiving element 2 can be concluded on the distance of the object.

According to 15 is the sensor 1 a sensor according to the time of flight method. It is from the light transmitter 34 a short light pulse or a group of light pulses emitted. The one or more light pulses are reflected or remitted by an object and the receiving element 2 of the light receiver 36 receive. From a downstream evaluation unit, the duration of the light from sending to receiving evaluated and calculated from the distance of the object.

LIST OF REFERENCE NUMBERS

1

 optoelectronic sensor

2

 receiving element

4

 receiving lens

6

 optical filter element

8th

 first surface

10

 second surface

12

 photocell

14

 light sensor

28

 cylindrical lens

30

 PCB

32

 optical filter

34

 light source

36

 light receiver

Claims (9)

Optoelectronic sensor with a receiving element ( 2 ) and a receiving lens ( 4 ), and an optical filter element ( 6 ), which between the receiving element ( 2 ) and the receiving lens ( 4 ), characterized in that the optical filter element ( 6 ) at least one convex or concave surface ( 8th ), so that the received light beams the filter element ( 6 ) on the surface ( 8th ) at each entry point in a vertical angle. Sensor according to one of the preceding claims, characterized in that the sensor ( 1 ) is a light barrier or a light sensor. Sensor according to one of the preceding claims, characterized in that the sensor is a sensor ( 1 ) according to the time of flight method. Sensor according to claim 1, characterized in that a second surface ( 10 ) leading to the first surface ( 8th ) is a plane, convex or concave surface. Sensor according to one of the preceding claims, characterized in that the filter element ( 6 ) has a spherical surface. Sensor according to one of the preceding claims, characterized in that the filter element ( 6 ) within the focal length ( 24 ) of the receiving lens ( 4 ) is arranged. Sensor according to one of the preceding claims 1 to 5, characterized in that the filter element ( 6 ) out of focus ( 24 ) of the receiving lens ( 4 ) is arranged. Sensor according to one of the preceding claims, characterized in that the filter element ( 6 ) is made of glass and a cover glass of the receiving element ( 2 ). Sensor according to one of the preceding claims 1 to 8, characterized in that the receiving lens ( 4 ) is a cylindrical lens and the filter element ( 6 ) is a cylindrical body.

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