Optical sensor

An optical sensor includes a transmitter that emits light rays. Transmitting optics are installed downstream of the transmitter. An adjustment device is operatively arranged for reversibly adjusting, in three spatial directions, the relative position of the transmitter and the transmitting optics. A receiver receives light rays. An evaluation unit evaluates the received signals that are present at the receiver output.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an optical sensor, and more particularly to an adjustable optical sensor.

2. Related Art

In general, optical sensors can be embodied as light barriers, light scanners and distance sensors. In particular, the optical sensors can be barcode readers for detecting barcodes or, in general, for detecting markings with contrasting patterns.

Optical sensors of this type generally use transmitting optics or a standard optical system for generating a beam with the transmitting light rays emitted by the transmitter. To generate the desired beam with the transmitting light rays, in particular for focusing the beam and guiding the rays along a specific beam axis, the transmitting optics must be aligned relatively precisely and reproducibly.

During the process of manufacturing the optical sensor, the transmitter and the transmitting optics are installed inside a housing with an integrated optical sensor by using production steps that are typically carried out manually.

An optical sensor of this type is described in German patent document 198 44 238 A1. The optical sensor embodied as barcode reader is integrated into a housing, and an insert can be inserted into the housing for accommodating the optical components.

The housing insert is provided with a hollow-cylindrical receptacle in which the transmitter and the transmitting optics are positioned, one behind the other and spaced apart.

The disadvantage of this arrangement is that the installation locations for the transmitter and the transmitting optics are preset, thus making it impossible to adjust the beam course for the transmitting light rays. In particular, no subsequent corrections are possible in case of a faulty installation position of the components, because the transmitter and transmitting optics normally must be glued on for securing them inside the receptacle.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an optical sensor of the aforementioned type, which provides a reliable adjustment option with high flexibility for adjusting the beam guidance of the emitted light rays.

The above and other objects are accomplished according to the invention by the provision of an optical sensor comprising a transmitter that emits light rays, a receiver that receives light rays and an evaluation unit for evaluating the receiving signals present at the receiver output. An adjustment device is assigned to the transmitter, which permits a reversible adjustment in three spatial directions of the relative position of the transmitter and a transmitting optic installed downstream of the transmitter.

The device according to the invention makes it possible to preset the beam guidance of the transmitting light rays in a flexible manner. For this, the reversible adjustment is particularly advantageous because the beam guidance can be changed if necessary.

The beam profile for the transmitting light rays as well as their focussing position can be changed through adjusting the distance between transmitter and transmitting optics. A precise adjustment of the beam direction for the transmitting light rays is possible through positioning the transmitter or transmitting optics transversely to the transmitter axis.

The adjustment device of one advantageous embodiment comprises an optics holder in which the transmitting optics are positioned so as to be displaceable. In a first embodiment of the invention, the transmitting optics in the holder are positioned such that they can pivot in a plane that is oriented perpendicularly to the axis of the transmitting light beam, thus making it possible to adjust the beam direction of the transmitting light rays. The transmitter is positioned such that it can be displaced relative to the transmitting optics in order to preset the beam profile and focussing position of the transmitting light rays.

According to a particularly advantageous second embodiment of the invention, the transmitting optics inside the holder can be adjusted in all three spatial directions. As a result, the transmitter can be arranged locally secured inside the optical sensor. The beam direction in that case is preset through a pivoting movement of the optics holder transverse to the optical axis of the transmitter. Adjusting the beam profile and the focussing position is usefully achieved by deflection of the optics holder with respect to a predetermined reference point.

In each case, the optics holder is secured in a specified adjustment position with the aid of mechanical fixing and fastening systems, wherein the adjusted position can be released again at any time by activating the fixing and fastening systems.

In an exemplary embodiment, the present invention can be an optical sensor comprising: a transmitter that emits light rays; transmitting optics installed downstream of the transmitter; a receiver that receives light rays; an evaluation unit for evaluating the received signals that are present at the receiver output; and an adjustment device operatively arranged for reversibly adjusting, in three spatial directions, the relative position of the transmitter and the transmitting optics.

Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the invention is discussed in detail below. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention.

FIG. 1schematically shows the essential components of an optical sensor1according to the present invention, embodied as barcode reader. The optical sensor1is used for detecting barcodes2or, in general, for detecting markings with contrasting patterns. In principle, the optical sensor1can also be embodied as a light barrier, a light scanner, a distance sensor or the like.

The barcode reader according toFIG. 1comprises a transmitter4that emits light rays3and a receiver6that receives light rays5. The transmitter4, preferably a laser diode, is followed by transmitting optics7for generating a beam with the transmitting light rays3and focusing these rays.

The transmitting light rays3that are emitted by the transmitter4and the receiving light rays5that are reflected back by a barcode2are guided over a deflection unit. In an exemplary embodiment, the deflection unit is a motor-driven polygonal mirror wheel8with a predetermined number of facet-shaped mirror surfaces9.

As a result of the rotational movement of the polygonal mirror wheel8, the transmitting light rays3are periodically guided across a monitoring range10, which extends in a scanning plane. The monitoring range10extends across a specific angle region that is predetermined by the number of mirror surfaces9of the polygonal mirror wheel8.

The received signals present at the output of the receiver6are amplified in an amplifier that is not shown herein and evaluated in an evaluation unit30.

The received light rays5, which are reflected by the barcode2, are amplitude-modulated according to the sequence of black and white line elements in the barcode2. The received signals present at the output of the receiver6are correspondingly amplitude-modulated. The analog, amplitude-modulated receiving signals are evaluated in an evaluation unit30with a threshold value unit. Binary signal sequences are generated as a result, which are used to detect the barcode2through a comparison with stored contrast patterns for barcodss2.

A housing insert11is provided for accommodating the optical components of the optical sensor1according to the FIG.1. This insert is integrated into the optical sensor1housing, which is not shown herein.FIGS. 2 and 3show a detail of this housing insert11with an adjustment device for adjusting the relative position of the transmitter4and the transmitting optics7.

The adjustment device comprises an optics holder12for accommodating the transmitting optics7. The optics holder12, shown separately inFIG. 4, is positioned such that it can move on the housing insert11, whereas the transmitter4is locally secured to the housing insert11.

The detail of housing insert11that is shown inFIGS. 2 and 3shows another insert13with a bore14, in which the transmitter4is positioned. The housing insert11furthermore has a first and second holding part15a,15bfor positioning the optics holder12. The holding parts15a,15bare essentially cube-shaped elements that project perpendicularly from the bottom of the housing insert11.

The optics holder12can be a molded plastic part, the center piece of which forms a support element12afor accommodating the transmitting optics7. The transmitting optics7in this case are positioned on a bore16that extends through the support segment12a.

Holder segments12b,12cadjoin the longitudinal ends of the support segment12aand also form components of the optics holder12. The first holder segment12bhas a plate-shaped design and is positioned so as to be displaceable on the level support surface for the first holding part15a, which extends in a vertical plane and is assigned to the insert13. The first holder segment12bis connected via a flexible element12dto the support segment12a. The flexible element12dis formed by a structural weakness in the area where the wall thickness of the optics holder12is reduced considerably. The flexible element12dforms a resilient spring that can serve to bend the support segment12arelative to the first holder segment12b.

For a position change, the first holder segment12bcan be displaced on the support surface of the first holding part15a, wherein the displacement movement occurs in the vertical plane of the support surface and thus perpendicularly to the horizontally extending optical axis of the transmitter4. The second holder segment12cis positioned such that it can turn on the second holding part15b. The second holder segment12cis essentially a leg forming a right angle, wherein a rotary head17for the rotational positioning on the second holding part15bis provided on the front end of the leg, at the free end of the second holder segment12c. The leg of the holder segment12cforms a resilient element.

The optics holder12that is positioned on the holding parts15a,15badjoins the front of the insert13, so that the transmitting optics7in the insert13are positioned at a predetermined distance to the transmitting optics7in the optics holder12. The first holder segment12bis located inside a recess between the front portions of the insert13and the support surface of the holding part15a. A fixing screw18that extends through the side edge of insert13is used to secure the optics holder12in a certain adjustment position. The first holder segment12bin this case is secured in the recess between insert13and the first holding part15aby turning the fixing screw18.

The other side of the optics holder12is secured to the second holding part15bthrough the rotational positioning of the second holder segment12c. For this, the rotary head17is positioned on the second holder segment12c, inside an indentation19on the support surface of the second holding part15bthat faces the insert13and extends in a vertical plane. This indentation19extends in horizontal direction across the complete width of the second holding part15b. The indentation19has a constant semi-circular cross section in the longitudinal direction. The radius of the indentation19is adapted to the radius of the rotary head17.

The longitudinal axis of the optics holder12, arranged on the holding parts15a,15b, also extends in the horizontal direction, wherein the longitudinal axis of the optics holder12is positioned perpendicularly to the optical axis of the transmitter4.

The position of the optics holder12relative to the insert13can be changed as specified to adjust the relative position of the transmitter4and the transmitting optics7.

An operating element in the form of a rod-shaped lever20is provided to vary the position of the transmitting optics7in a vertical plane that extends perpendicularly to the optical axis of the transmitter4. The lever20is disposed in a bore21of a first holder segment12bof the optics holder12, wherein the bore21extends in axial direction through the first holder segment12b. The cross section of bore21narrows down in the center of the first holder segment12b. Starting with this narrowed down cross-section, the diameter of the bore21continuously expands toward the locations where it exits on the front and back of the first holder segment12b. A recess22that exits at the support surface is furthermore provided in the first holding part15afor accommodating the lever20. The recess22has an essentially hemispherical design, wherein its diameter at the support surface is somewhat larger than the diameter of the lever20. To adjust the position of the transmitting optics7, the lever20is inserted into the bore21of the first holder segment12b, so that the front end of lever20that projects over the first holder segment12bengages in the recess22in the first holding part15a.

The position of the lever inside the receptacle is changed through moving the back end of the lever20. In the process, the first holder segment12bis deflected in the plane for the support surface through the guidance of the lever20inside the bore21. As a result of the cone-shaped design of the bore21, the deflection movement of the lever20is continuously converted to a pivoting movement of the holder segment12band thus moves the complete optics holder12. With this pivoting movement, the optics holder12is pivoted relative to the pivoting axis predetermined by the rotary head17. In addition, the rotary head17is displaced in the second holding part15b, if necessary along the indentation19. As soon as the desired adjustment position of the optics holder12is reached, this holder is secured on the insert13with the fixing screw18.

An eccentric element23is provided for adjusting the position of the transmitting optics7in the direction of the optical axis for the transmitter4. The eccentric element23takes the form of an eccentric plate and is positioned on the side relative to the insert13, with the rotational axis extending in vertical direction. The outer surface of the eccentric plate rests against the back of the optics holder12, in the region of the support segment12aend, which is facing the second holding element12c. A wrench or similar tool is attached to the surface and used to turn the eccentric plate around the plate's rotational axis, which changes the contact pressure exerted onto the optics holder12in accordance with the shape of the eccentric plate.

The optics holder12is bent in the region of flexible element12dby changing the contact pressure. As a result, the support segment12ais pivoted in horizontal direction and the transmitting optics7are either moved toward or away from the transmitter4. The respectively adjusted position of the optics holder12is secured by the eccentric plate23since the eccentric plate23presses the first holder segment12bwith the rotary head17into the indentation19. As a result of the springy effect of the leg of the holder segment12c, a contact spring is formed that pushes against the eccentric plate23.

FIGS. 5 and 6show a different embodiment of an adjustment device for an optical sensor1. The transmitter4is again positioned inside an insert13, wherein the insert13has a bore14for accommodating the transmitter4. The optics holder12again holds the transmitting optics7and follows the insert13with the transmitter4.

The optics holder12is provided with a spherical head24, having a spherical outer surface. A bore25with the transmitting optics7disposed therein extends through the spherical head24. The optics holder12furthermore has a housing, consisting of two housing halves26a,26b, which are secured to each other, fitted one on top of the other, with fixing screws18′. Each housing half26a,26bhas a spherical half shell27a,27b. The spherical half shells27a,27bcomplement each other to form a spherical receptacle with the spherical head24disposed therein. The upper spherical half shell27acontains a circular opening28on the top. A lever20′ that is connected to a spherical head24and radially projects from the outer surface of the spherical head24extends through this opening28. Alternatively, the lever20′ can also be inserted into a bore in the spherical head24. The opening28has a smaller diameter than the lever20′, which functions as operating element.

To adjust the position of transmitting optics7, the fixing screws18′ on the housing are loosened slightly. As a result, the spherical head24fits with only slight friction against the walls of the spherical half shells27a,27band can be pivoted to the desired adjustment position by deflecting the lever20′. Following this, the adjusted position of spherical head24is secured by tightening the fixing screws18′. In principle, the holder inside the spherical half shells27a,27bcan also be designed to be self-holding, so that the fixing screws18′ can be omitted. For this, at least one spherical half shell27a,27bis made from a material having springy characteristics, so that the spherical head24can be locked in place as a result of the spring force exerted by the spherical half shell27a,27b.

The transmitting optics7inside the spherical head24can be pivoted inside the housing in a vertical plane that extends perpendicularly to the optical axis for the transmitter4. The distance between the transmitter4and transmitting optics7is adjusted by displacing the transmitter4in its position along the optical transmitter axis.