Optical beam shaping unit, distance measuring device and laser illuminator

Abstract

An optical beam shaping unit for shaping a beam bundle. The optical beam shaping unit has at least one ball lens for shaping the beam bundle, wherein the ball lens allows a large portion of the light incident on the ball lens to pass through, and wherein the optical beam shaping unit has at least one optical unit which has a positive effective focal length and which is arranged in a beam path with the ball lens.

Claims

1. An optical beam shaping unit for shaping a beam, the optical beam shaping unit comprising: at least one spherical lens for shaping the beam, wherein the spherical lens allows a major portion of light that is incident on the spherical lens to pass; at least one optical unit with a positive effective focal length, which is arranged in one beam path with the spherical lens; at least one light source for producing the beam; and a detector apparatus for detecting an incident beam, wherein the spherical lens and/or the optical unit are adapted to be displaceable in a z-direction with respect to a coordinate system xyz to set a divergence of the beam downstream of the optical unit, wherein the z-direction corresponds to a propagation direction of the beam, and wherein the at least one spherical lens is adapted to image the beam in the direction of the optical unit.

2. The optical beam shaping unit as claimed in claim 1, wherein the optical unit is a converging lens, a mirror or a lens system.

3. The optical beam shaping unit as claimed in claim 1, wherein the light source emits a laser beam as the beam, or wherein the light source is a laser diode.

4. The optical beam shaping unit as claimed in claim 1, wherein the light source emits the beam in a wavelength range Lambda_B and the spherical lens allows a major portion of light that is incident on the spherical lens in the wavelength range Lambda_B to pass.

5. The optical beam shaping unit as claimed in claim 1, wherein the light source is adapted to be displaceable in the z-direction.

6. The optical beam shaping unit as claimed in claim 1, further comprising at least one further spherical adapted to guide the incident beam onto the detector apparatus.

7. The optical beam shaping unit as claimed in claim 6, further comprising one optical additional unit for guiding the incident beam onto the further spherical lens.

8. A laser illuminator comprising an optical beam shaping unit as claimed in claim 1.

9. A distance measuring device with an optical beam shaping unit for shaping a beam, the optical beam shaping unit comprising: at least one spherical lens for shaping the beam, wherein the spherical lens allows a major portion of light that is incident on the spherical lens to pass; at least one optical unit with a positive effective focal length, which is arranged in one beam path with the spherical lens; at least one light source for producing the beam; and a detector apparatus for detecting an incident beam, wherein the spherical lens and/or the optical unit are adapted to be displaceable in a z-direction with respect to a coordinate system xyz to set a divergence of the beam downstream of the optical unit, wherein the z-direction corresponds to a propagation direction of the beam, and wherein the at least one spherical lens is adapted to image the beam in the direction of the optical unit.

10. The distance measuring device of claim 9, wherein the spherical lens comprises a ball lens.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows a schematic illustration of a distance measuring device in accordance with an exemplary embodiment; and

(3) FIG. 2 shows a schematic illustration of an optical beam shaping unit in accordance with an exemplary embodiment; and

(4) FIG. 3 shows a schematic illustration of an optical beam shaping unit in accordance with an exemplary embodiment; and

(5) FIG. 4 shows a schematic illustration of a radiation pattern of a light source according to an exemplary embodiment of the invention; and

(6) FIG. 5 shows a schematic illustration of an optical beam shaping unit in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

(7) FIG. 1 shows a schematic illustration of a distance measuring device 100 with an optical beam shaping unit in accordance with an exemplary embodiment. The distance measuring device 100 comprises a spherical lens 102, which is embodied to shape a ray bundle 106, in the present case a laser beam, which is emitted by a light source 104. The ray bundle 106 is indicated schematically as an arrow in FIG. 1. In reality, the ray bundle 106 is a ray bundle made up of a plurality of partial ray bundles.

(8) The spherical lens 102 is arranged between the light source 104 and an optical unit 108, such as a converging lens. The spherical lens 102 here images the ray bundle 106 in a suitable manner on the object plane or image plane of the optical unit 108. The optical unit 108 is embodied to collimate the ray bundle 106 which is imaged by the spherical lens 102.

(9) The spherical lens 102 has a diameter between 0.5 mm and 8 mm depending on the exemplary embodiment.

(10) The light source 104, the spherical lens 102 and the optical unit 108 form a transmission channel 110 of the distance measuring device 100. In addition to the transmission channel 110, the distance measuring device 100 in accordance with the exemplary embodiment shown in FIG. 1 has a receiving channel 112, which comprises a further spherical lens 114 and a detector apparatus 116. The further spherical lens 114 and the further optical unit 122 are embodied to focus a ray bundle 118, which is reflected into the transmission channel 110 and is indicated here likewise as an arrow, onto the detector apparatus 116 for detecting the incident ray bundle 118. As a consequence of the detection, the detector apparatus 116 outputs a detector signal 120.

(11) In addition, an optical additional unit 122, for example in the form of a further converging lens, is connected upstream of the further spherical lens 114. The optical additional unit 122 is embodied to steer the incident ray bundle 118 in a suitable manner onto the object plane or image plane of the spherical lens 114.

(12) As can be seen in FIG. 1, the transmission channel 110 and the receiving channel 112 are arranged in mutually neighboring fashion. The two channels 110, 112 furthermore extend here substantially parallel with respect to one another. As a result, the structural form of the distance measuring device 100 can be kept as compact as possible.

(13) The light source 104 and the detector apparatus 116 are connected in each case to a device 124. The device 124 comprises a read unit 126 for reading the detector signal 120. The read unit 126 passes on the detector signal 120 to an ascertainment unit 128 for ascertaining a measurement value 130 that is representative of the distance using the detector signal 120.

(14) The device 124 comprises an optional control unit 132 for actuating the light source 104 by way of a corresponding actuation signal 134. By way of example, the control unit 132 transfers the actuation signal 134 additionally to the ascertainment unit 128, wherein the ascertainment unit 128 is embodied to ascertain the measurement value 130 furthermore using the actuation signal 134.

(15) FIG. 2 shows a schematic illustration of a beam path in an optical beam shaping unit in accordance with an exemplary embodiment, for example a distance measuring device 100 described previously on the basis of FIG. 1. The optical beam shaping unit has the spherical lens 102 and the optical unit 108, which in this case is designed in the form of an aspheric planoconvex lens. In contrast to FIG. 1, the ray bundle 106 is here illustrated as a ray bundle with the aperture ray 200 and the field ray 210. An object y in the object plane 220 is imaged by the spherical lens 102 onto the image plane 240 of the spherical lens 102, which results in an image height y′ in this image plane 240 of the spherical lens 102. The field rays 210 here exhibit a divergence 8 between the transmitter and the receiver. The field rays begin at the peripheral points of the object (i.e. in this case of the laser diode) and form the marginal rays of the divergence after the collimation.

(16) In summary, it can be noted that in accordance with the approach proposed here the first optical system is designed as a transparent, highly transmissive sphere. By setting the object distance (i.e. of the object plane of the source from the main plane of the spherical lens), a specific image distance (main plane of the spherical lens—image plane of the source) and consequently an imaging scale that is defined and variable within large limits is obtained in accordance with the imaging equation, which will be described further below. This means that the image size of the radiation source or receiving surface can be decreased or increased. With the same focal length (EFL) of the second optical system (here an aspheric individual lens), this results in a different divergence of the laser radiation and of the reception ray bundle.

(17) θ.sub.beam=y′f.sub.2′=image size of the first optical system/EFL of the second optical system; wherein the focal length f.sub.2′ in FIG. 2 corresponds to the distance between the main plane of the lens 108 and the plane 240.

(18) That means, if the imaging scale β′=y′/y=image size after imaging by the first optical system/object size of the source is less than 1, a decreased real image of the source will be produced and, with the same focal length f.sub.2′, a smaller resulting divergence will be obtained.

(19) If the structural length of the entire optical beam shaping unit (TOTR) is intended to be short, the first optical system should have an extremely short focal length.

(20) Ideally suited for this purpose is a sphere which is available as standard with diameters in the range 0.5 mm to 8 mm. Especially the diameters from 0.5 mm to 2 mm are of interest here (focal lengths with sapphire material from 0.3 mm to 1.2 mm).

(21) Due to the very short object back focal distances (object plane-main plane of the first optical system) and the small radiation apertures of the laser source, the optically effective area on the sphere is limited to an area near the axis. Only for this reason do the imaging aberrations of the sphere remain small. The remaining imaging aberrations (primarily spherical aberrations) are corrected by the aspheric shape of the second optical system, as is described in the exemplary embodiment.

(22) FIG. 3 shows a schematic illustration of a beam path in an optical beam shaping unit in accordance with an exemplary embodiment, for example a distance measuring device 100 described previously on the basis of FIG. 1. The optical beam shaping unit has the spherical lens 102 and the optical unit 108, which in this case is designed in the form of an aspheric planoconvex lens.

(23) In distance measuring devices, as small a divergence as possible of the laser radiation from a defined radiation surface AF of a light source 104 should generally be achieved, i.e. that due to the spherical lens 102, an image of decreased size of the radiation surface must be produced in the intermediate image plane ZBE.sub.sphere of the arrangement. In the exemplary embodiment, the spherical lens 102 is held in a mount 102a which is displaceable in the z-direction. If this assembly is displaced in the z-direction, i.e. if the distance Z.sub.LD is changed, the distance of the radiation surface AF from the main plane HH′.sub.sphere of the spherical lens 102 changes. Here, the location of the intermediate image ZBE.sub.sphere also changes in accordance with the known relation z′.sub.LD=f.sup.2sphere/z.sub.LD (paraxial imaging equation). The optical unit 108, which is mounted in a further mount 108a and embodied as a collimator, is likewise displaceable in the z-direction and is displaced such that the focal plane F.sub.colli of the collimator 108 again coincides with the intermediate image plane ZBE.sub.sphere of the spherical lens 102. This ensures clean collimation of the ray bundle exiting from the radiation surface AF. The result is a laser divergence which is proportional to the intermediate image in accordance with the formula: tan Θ=y.sub.LD/f′.sub.colli.

(24) Assuming, for example, 1:1 imaging of the exit surface AF into the ZBE.sub.sphere and if a spherical lens 102 of 1 mm diameter is selected, the result of a displacement of the spherical lens 102 in the z-direction of 1 mm is halving of the initial laser divergence.

(25) FIG. 5 shows a schematic illustration of a beam path in an optical beam shaping unit in accordance with an exemplary embodiment, for example a distance measuring device 100 described previously on the basis of FIG. 1. The optical beam shaping unit has the spherical lens 102 and the optical unit 108, which in this case is designed in the form of an aspheric planoconvex lens.

(26) This further exemplary embodiment is intended to show how it is possible, by way of the described arrangement, to vary the relation of meridional and sagittal extent of the laser beam in the far field.

(27) Due to their structure, semiconductor laser diodes have a laser exit opening in the direction of the slow axis (SA) of 80 μm to approximately 200 μm and in the direction of the fast axis (FA) of 1 μm to approximately 10 μm. The semiconductor laser diodes used in laser measurement technology have a strongly astigmatic radiation pattern. Typical radiation angles are here 6° to 15° in the SA and 20° to 25° in the FA. FIG. 4 qualitatively shows such a radiation pattern. The figure clearly shows how the relation S.sub.0/M.sub.0, . . . S.sub.4/M.sub.4 continuously changes in dependence on the z-position (Z.sub.0, . . . Z.sub.4).

(28) When using such semiconductor laser diodes in laser distance measuring devices or laser illuminators, the aim is to produce a beam cross-section that is as square as possible (Z.sub.1), but at least a predefined beam cross-section (Z.sub.2, . . . Z.sub.4).

(29) An arrangement for producing a predefined beam cross-section is shown in FIG. 5.

(30) The optical arrangement, for example a distance measuring device, is identical to the basic arrangement shown in FIG. 1. However, in this exemplary embodiment in accordance with FIG. 5, the laser diode, which is embodied as the light source 104, is arranged so as to be displaceable in the z-direction, wherein the location of the spherical lens 102 with respect to the collimator 108 is not variable and the intermediate image plane of the spherical lens ZBE.sub.sphere coincides with the focal plane F.sub.colli of the collimator 108.

(31) Due to the displacement of the laser diode 104 in the z-direction, always different beam cross sections of the laser aperture (S.sub.1-M.sub.1 . . . S.sub.4-M.sub.4) from FIG. 4 appear in the object plane OE.sub.sphere of the spherical lens 102. What are formed in the image plane of the spherical lens ZBE.sub.sphere in meridional and sagittal direction are proportional intermediate images. These are imaged (collimated) to the far field by the collimator 108. In dependence on the z-location (Z.sub.1 . . . Z.sub.4 in FIG. 4), laser cross sections having different meridional and sagittal extent ratio are therefore obtained. For example, if the laser diode 104 is displaced such that the z-position Z.sub.1 in FIG. 4 is positioned in the object plane of the spherical lens 102, the result is a square beam cross section in the far field.

(32) The exemplary embodiments described and shown in the figures are selected purely by way of example. Different exemplary embodiments may be combined with one another in full or in relation to individual features. It is also possible to supplement an exemplary embodiment with features of a further exemplary embodiment.

(33) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.