DE102006048297A1 - Opto-electronic sensor device i.e. light barrier, has polarization filter arranged between transmitter and transmitter optics that is designed as thin Fresnel lens, and analyzer arranged between receiver and receiver optics - Google Patents

Abstract

The device has a transmitter (1) for transmitting electromagnetic radiation, and a receiver (4) for receiving the radiation. A polarization filter (2) is attached to the transmitter for polarizing the radiation. An analyzer (5) is provided for analyzing the polarized radiation. A transmitter optics (3) and a receiver optics (6) are formed by a diffraction grating or by a Fresnel lens. The filter is arranged between the transmitter and the transmitter optics. The analyzer is arranged between the receiver and the receiver optics. The transmitter optics is designed as a thin Fresnel lens.

Description

The The invention relates to an optoelectronic sensor device, in particular Photocell, according to the preamble of claim 1.

The special application of the optoelectronic sensor device according to the invention are light barriers. Nonetheless, the principle of the invention is can also be used in other optoelectronic sensor devices, and always there, where polarized electromagnetic radiation is used.

Optoelectronic Sensor devices have a transmitter for emitting electromagnetic Radiation as well as a receiver for receiving the electromagnetic radiation. Transmitter and receiver in each case a transmitter optics and a receiver optics are assigned. In order to strongly reflecting or reflecting objects are reliably detected can (because of the big one Brightness is not always possible) Polarized light is used. For this purpose, the sender a polarizing filter and the receiver associated with an analyzer. This use of linear polarizers in photoelectric sensors for the suppression of noise strongly reflecting or reflecting objects is known.

The Problem with such optoelectronic sensor devices provides the transmitter and receiver optics dar. Here thick lenses are used so far. These are production-related in the inner structure tensions, which are negative affect the polarization of electromagnetic radiation. by virtue of this polarization disorders it is necessary that the Polarizing filter and the analyzer each in the range between the Transmitter or receiver optics and the reflection element must be arranged. This can be but the optics for a low-cost manufacture. On the other hand exists - like executed - the problem the stress birefringence.

From that Therefore, the invention is based on the object, an optoelectronic Sensor device, in particular light barrier, the specified above To create a way to make the overall look cost-effective and compact can.

The technical solution is characterized by the features in the characterizing part of claim 1.

The The basic idea of the invention lies in a low-tension, thin front screen with integrated Fresnel or diffraction structures. Thus, it is suggested the optics for Sender and receiver with polarizing filters by using Fresnel or diffraction structures as low-tension, thin-walled to perform optical components and the functions in a housing closure To unify component in the form of a windscreen without at the Use of polarized electromagnetic radiation the effect the polarization filter is permanently impaired. For the production this inexpensive Parts can conventional injection molding be used. Suitable materials are COC or PMMA Question, which is a relatively low stress optical birefringence and especially in thin-walled Components can be used for use in polarization optics.

The Training according to claim 2 hits before that the Transmitter optics and receiver optics by a one-piece Fresnel lens or formed by a one-piece diffraction grating are. This is a continuous closed windscreen with created integrated lens structures or line structures.

there is according to the training in claim 3, the Fresnel or diffraction structure of the device inside facing and the outside as a flat surface executed.

One embodiment an optoelectronic according to the invention Sensor device in the form of a light barrier will be described below with reference to Drawing described. This drawing shows a schematic representation the photocell.

The photocell initially has a transmitter 1 for emitting electromagnetic radiation. In front of the transmitter 1 there is a polarization filter 2 , And in front of this polarization filter 2 there is a transmitter optics 3 in the form of a Fresnel lens.

Immediately adjacent to the transmitter 1 there is a receiver 4 , In front of this receiver 4 there is an analyzer 5 and in front of this analyzer 5 a receiver optics 6 also in the form of a Fresnel lens. This Fresnel lens is the receiver optics 6 with the Fresnel lens of the transmitter optics 3 united to a double Fresnel lens.

The common double lens (Fresnel lens or diffraction lens) of the transmitter optics 3 as well as the receiver optics 6 is at the same time as Lichtaustritts- or light entrance window part of the light barrier housing.

The operation is as follows:
The transmitter 1 emitted electromagnetic radiation is first through the polarizing filter 2 polarized and then in the transmitter optics 3 parallelization. Because the transmitter optics 3 is designed as a thin Fresnel lens, this has only a relatively low voltage optical birefringence, so that the polarization of the electromagnetic radiation is virtually unaffected.

After hitting a reflector, the electromagnetic radiation is reflected back and first by means of the receiver optics 6 on the receiver 4 bundled. Because here too the receiver optics 6 in the form of the Fresnel lens does not affect the polarization of electromagnetic radiation, the analyzer 5 between the receiver optics 6 and the receiver 4 be arranged.

In the illustrated embodiment, the light barrier is formed with a reflector. Of course it is also possible for the recipient 4 on the opposite side (ie in the area of the reflector) to arrange.

1

transmitter

2

polarizing filter

3

transmitter optics

4

receiver optics

5

analyzer

6

receiver optics

Claims (3)

Optoelectronic sensor device, in particular light barrier, with a transmitter ( 1 ) for emitting electromagnetic radiation, with a receiver ( 4 ) for receiving the electromagnetic radiation, with a transmitter optics ( 3 ) and a receiver optics ( 6 ) as well as with the transmitter ( 1 ) associated polarizing filter ( 2 ) for polarizing the electromagnetic radiation and a receiver ( 4 ) associated analyzer ( 5 ) for the polarized radiation, characterized in that the transmitter optics ( 3 ) and the receiver optics ( 6 ) is formed by a Fresnel lens or by a diffraction grating and that the polarizing filter ( 2 ) between the transmitter ( 1 ) and the transmitter optics ( 3 ) and the analyzer ( 5 ) between the receiver ( 4 ) and the receiver optics ( 6 ) is arranged. Optoelectronic sensor device according to the preceding claim, characterized in that the transmitter optics ( 3 ) and the receiver optics ( 6 ) are formed by a one-piece Fresnel lens or by a one-piece diffraction grating. Optoelectronic sensor device according to one of previous claims, characterized in that the Fresnel or diffraction structure facing the inside of the housing and that the outside as a homogeneous, flat surface is trained.