Transmitting device with a scanning mirror covered by a collimating cover element

Abstract

A transmitting device, preferably containing at least two laser diodes and a scanning mirror, which is deflectable about its center (MP) and is arranged in a housing with a transparent cover element. The cover element is formed, at least in a coupling-out region, by a section of a monocentric hemispherical shell (HK) with a center of curvature (K) and is arranged to cover the scanning mirror in such a way that the center of curvature (K) of the hemispherical shell (HK) and the center (MP) of the scanning mirror coincide, and is formed in a coupling-in region by an optical block, comprising a toroidal entrance surface, in the special form of a cylindrical surface, at least one toroidal exit surface and at least two first mirror surfaces arranged between them, for deflecting and pre-collimating the laser beams.

Claims

1. A transmitting device comprising: a housing with a transparent cover element; at least one laser diode serving to emit at least one laser beam with a beam axis and with different angles of radiation along a fast axis and along a slow axis, wherein, in the case of at least two laser diodes, said at least two laser diodes being arranged side by side in the direction of their slow axis forming a row and having parallel beam axes; a scanning mirror capable of being deflected about its center MP and arranged inside the housing, wherein the beam axis of the at least one laser beam is directed at the transparent cover element in such a way that the at least one laser beam impinges on the center MP after the at least one laser beam passes through the transparent cover element within a coupling-in region, and that the at least one laser beam passes through the transparent cover element again within a coupling-out region after being reflected at the scanning mirror; the transparent cover element having a coupling-in region, in which; a toroidal entrance surface in a form of a cylindrical surface is provided for pre-collimating the at least one laser beam in a direction of the fast axis only, and either at least one toroidal exit surface is provided for pre-collimating the at least one laser beam in both directions of the slow axis and of the fast axis, or at least one toroidal exit surface in a special form of a cylindrical surface is provided for pre-collimating the at least one laser beam in a direction of the slow axis only; and the transparent cover element having a coupling-out region comprising a section of a monocentric hemispherical shell HK with a center of curvature, wherein the transparent cover element is arranged to cover the scanning mirror in such a way that the center of curvature K and the center MP of the scanning mirror coincide.

2. The transmitting device according to claim 1, wherein the transparent cover element is formed by a shell and an optical block integrated into the transparent cover element or adjacent to it, wherein the section of the monocentric hemispherical shell HK is formed on the shell and the toroidal entrance surface shaped as cylindrical surface, the at least one toroidal exit surface, and, in the case of at least two laser diodes, first mirror surfaces are formed on the optical block, the first mirror surfaces being respectively assigned to the at least two laser diodes for deflecting each of the at least two laser beams to the center MP.

3. The transmitting device according to claim 2, wherein the shell is a part of the monocentric hemispherical shell (HK).

4. The transmitting device according to claim 2, wherein the transmitting device has the at least two laser diodes and wherein the first mirror surfaces are planar surfaces inclined relative to each other so that the at least two laser beams are deflected at different angles.

5. The transmitting device according to claim 4, wherein the optical block has a second mirror surface for folding the at least two laser beams.

6. The transmitting device according to claim 2, wherein the transmitting device has the at least two laser diodes and wherein one first mirror surface is a parabolic surface (PS), so that the at least two laser beams are deflected at different angles.

7. The transmitting device according to claim 6, wherein the optical block has a second mirror surface for folding the at least two laser beams.

8. The transmitting device according to claim 1, wherein the transparent cover element is manufactured monolithically.

9. The transmitting device according to claim 1, wherein only one laser diode is present and a first mirror surface for deflecting one laser beam to the center (MP) of the scanning mirror is assigned to the one laser diode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIGS. 1A-1C are schematic diagrams showing a first exemplary embodiment of a transmitting device;

(3) FIGS. 2A-2B are schematic diagrams showing a second exemplary embodiment of a transmitting device;

(4) FIGS. 3A-3B are schematic diagrams showing a third exemplary embodiment of a transmitting device;

(5) FIG. 4 shows a design of the second exemplary embodiment of a transmitting device in a perspective view, and

(6) FIG. 5 shows a design of the third exemplary embodiment of a transmitting device in a perspective view.

(7) A transmitting device according to the invention contains in all embodiments, as shown for example in FIGS. 1A to 1C, either a single laser diode 1.1 or at least two laser diodes 1.1, . . . , 1.n, which each emit a laser beam S.sub.1, . . . , S.sub.n with a beam axis A.sub.1, . . . , A.sub.n and with different angles of radiation in a fast axis fa and a slow axis sa.

(8) If the transmitting device contains at least two laser diodes 1.1, . . . , 1.n, they are arranged side by side in the direction of their slow axis sa, forming a row, and the beam axes A.sub.1, . . . , A.sub.n are parallel to each other. Compared to an arrangement in which the beam axes enclose an angle with each other, they can thus be arranged closer together and no adjustment is required to set the angular position.

(9) Moreover, the transmitting device contains a scanning mirror 2, which is deflectable about its center MP and is arranged in a housing 3 with a transparent cover element 4. The beam axis A.sub.1, . . . , A.sub.n of the at least one laser beam S.sub.1, . . . , S.sub.n is directed at the cover element 4 in such a way that, after passage of the at least one laser beam S.sub.1, . . . , S.sub.n through the cover element 4 within a coupling-in region 4.1, it impinges on the center MP, and that the at least one laser beam S.sub.1, . . . , S.sub.n, after reflection at the scanning mirror 2, passes through the cover element 4.2 again within a coupling-out region 4.2.

(10) It is essential to the invention that the cover element 4 has a toroidal entrance surface 5.1 in the coupling-in region 4.1, for pre-collimating the at least one laser beam S.sub.1, . . . , S.sub.n in the direction of the fast axis fa, a respective first mirror surface 5.3.sub.1, . . . , 5.3.sub.n assigned to the at least two laser diodes 1.1, . . . , 1.n, for deflecting the laser beams S.sub.1, . . . , S.sub.n to the center MP, and at least one toroidal exit surface 5.2.sub.1, . . . , 5.2.sub.n, for pre-collimating the at least one laser beam S.sub.1, . . . , S.sub.n in the direction of the slow axis sa. A toroidal surface is understood to be the surface or a section of the surface of a body that can be created geometrically by rotating a planar figure about an axis of rotation that is in the same plane as the figure itself. Such a body will also be called a toroid. Important special cases or limit cases of a toroid are torus, sphere and circular cylinder as well as cylindrical bodies with any (especially parabolic) cross-section. Surfaces and sections of surfaces of such special or limit cases are therefore also regarded as examples of toroidal surfaces. It is common practice for the person skilled in the art to slightly modify the surface for the correction of image errors.

(11) A toroidal (refracting or reflecting) optical surface generally influences the beam shape differently in two mutually perpendicular directions. In the special or limit case of a cylindrical lens (whose cross-sectional shape need not be spherical), the beam shape remains unaffected in one direction. In the special or limit case of an ordinary spherical lens, it is influenced equally in both directions.

(12) It is further essential to the invention that the cover element 4 is formed, at least in the coupling-out region 4.2, by a section of a monocentric hemispherical shell HK and that the cover element 4 is arranged to cover the scanning mirror 2 in such a way that the center of curvature K of the imaginary monocentric hemispherical shell HK (hereinafter referred to only as hemispherical shell HK) and the center MP of the scanning mirror 2 coincide. Monocentric means that the centers of curvature of the two surfaces of the hemispherical shell HK coincide. Manufacturing and assembly-related tolerances, long-term drifts as well as tolerance deviations between the position of the center of curvature K and the center MP lead to a deteriorating beam quality, but are tolerable within limits.

(13) Completely independent of an angle of incidence α.sub.1, . . . , α.sub.n, at which the at least one laser beam S.sub.1, . . . , S.sub.n impinges on the scanning mirror 42 with respect to the perpendicular L of the undeflected scanning mirror 42, the beam axis A.sub.1, . . . , A.sub.n after reflection at the scanning mirror 42, regardless of its position during the deflection, always impinges perpendicularly on the section of the hemispherical shell HK formed in the coupling-out region 4.2.

(14) As they pass through the cover element 4 within the coupling-in region 4.1, the laser beams S.sub.1, . . . , S.sub.n impinging on the cover element are, on the one hand, deflected and, on the other hand, pre-collimated in the direction of the fast axis fa and the slow axis sa of the laser diodes 1.1, . . . , 1.n in such a way that they impinge on the center MP of the scanning mirror 2 at the same small convergence angle in the direction of the fast axis fa and the slow axis sa, and are fully collimated after passing through the cover element 4 within the coupling-out region 4.2.

(15) Advantageously, the cover element 4 is formed by a shell 6 and an optical block 5 integrated into it as shown in FIG. 4. The cover element 4 may, also advantageously, be formed by a shell 6 and an adjacent optical block 5 as shown in FIG. 5. In this case, the section of the hemispherical shell HK is formed on the shell 6 and the toroidal entrance surface 5.1, the at least two first mirror surfaces 5.3.sub.1, . . . , 5.3.sub.n and the at least one toroidal exit surface 5.2.sub.1, . . . , 5.2.sub.n are formed on the optical block 5.

(16) The shell 6 advantageously constitutes a part of the hemispherical shell HK.

(17) FIGS. 1A to 1C show a first exemplary embodiment comprising, as an example, three laser diodes 1.1, 1.2, 1.3, including the laser beam S.sub.2 emitted by the laser diode 1.2 and the beam axes A.sub.1, A.sub.2, A.sub.3 of the laser diodes 1.1, 1.2, 1.3. The laser beams S.sub.1, S.sub.2, S.sub.3 are pre-collimated by refraction at the toroidal entrance surface 5.1.sub.1 in the direction of the fast axis fa. Here, the toroidal entrance surface 5.1.sub.1 represents a cylindrical surface.

(18) The number of first mirror surfaces 5.3.sub.1, 5.3.sub.2, 5.3.sub.3 present is equal to the number of laser beams S.sub.1, S.sub.2, S.sub.3 present. The first mirror surfaces 5.3.sub.1, 5.3.sub.2, 5.3.sub.3 are planar surfaces inclined to each other, with their size and the distance between their centers as well as the angle of inclination between the adjacent planar surfaces each being determined by the distance of the laser diodes 1.1, 1.2, 1.3. While the middle one of the three laser beams, S.sub.2, is deflected only in a plane containing the fast axis fa, the outer laser beams S.sub.1, S.sub.3 are also deflected in a plane perpendicular thereto so that all three laser beams S.sub.1, S.sub.2, S.sub.3 impinge on the center MP of the scanning mirror 2. The first mirror surfaces 5.3.sub.1, 5.3.sub.2, 5.3.sub.3 do not affect the collimation of the laser beams S.sub.1, S.sub.2, S.sub.3. Each of the first mirror surfaces 5.3.sub.1, 5.3.sub.2, 5.3.sub.3 is assigned a toroidal exit surface 5.2.sub.1, 5.2.sub.2, 5.2.sub.3. The toroidal exit surfaces 5.2.sub.1, 5.2.sub.2, 5.2.sub.3 can each be a cylindrical surface and therefore collimate only in the direction of the slow axis sa, but are preferably toroidal surfaces that collimate in the slow axis sa and additionally in the fast axis fa, so that the entrance surface 5.1 can have a lower refractive power. Spherical surfaces can be advantageously provided for this purpose if the beam angle of the laser beams S.sub.1, S.sub.2, S.sub.3 in the direction of the fast axis fa has already been adapted to the beam angle in the direction of the slow axis sa by the pre-collimation of the laser beams S.sub.1, S.sub.2, S.sub.3 at the toroidal entrance surface 5.1. The pre-collimated laser beams S.sub.1, S.sub.2, S.sub.3 should be slightly convergent to then be completely collimated by the refraction in the coupling-out region 4.2, which has a negative refractive power.

(19) The second exemplary embodiment shown in FIG. 2A and FIG. 2B differs from the first exemplary embodiment in that there is a second mirror surface 5.4 in the coupling-in region 4.1. The second mirror surface 5.4 only serves to fold the laser beams S.sub.1, S.sub.2, S.sub.3 in order to be able to minimize the space required and vary the position of the entrance surface 5.1 and the laser diodes 1.1, 1.2, 1.3.

(20) FIG. 4 shows a perspective view of a design of the second exemplary embodiment. It is clearly evident here that the shape of the cover element 4 has been adapted outside the coupling-in and coupling-out regions 4.1, 4.2 to minimize the space required.

(21) The third exemplary embodiment shown in FIGS. 3A and 3B is particularly advantageous for a larger number of laser diodes 1.1, . . . , 1.n or if the distances between the beam axes A.sub.1, . . . , A.sub.n are specified. Instead of having the same number of first mirror surfaces 5.3.sub.1, . . . , 5.3.sub.n as there are laser diodes 1.1, . . . , 1.n, there is only one first mirror surface 5.3.sub.1 here, which is a parabolic mirror surface PS with a focal point F.sub.PS and is arranged in such a way that the focal point F.sub.PS would coincide with the center of curvature K and the center MP if the refractive power of the, in this case, one toroidal exit surface 5.2.sub.1, arranged downstream, were theoretically neglected. Regardless of the distance between the laser diodes 1.1, . . . , 1.n and thus the beam axes A.sub.1, . . . , A.sub.n, the axis beams A.sub.1, . . . , A.sub.n are reflected into the focal point F.sub.PS and thus into the center MP of the scanning mirror 2. The parabolic mirror surface PS can be a toroidal parabolic mirror surface, which strictly speaking results in a focal line, which however contains a point where all axis beams A.sub.1, . . . , A.sub.n meet and which is understood to be the focal point F.sub.PS.

(22) The one toroidal exit surface 5.2.sub.1 is in this case an aspherical cylindrical surface, with the cylinder axes of the entrance surface 5.1 and the one exit surface 5.2.sub.1 being perpendicular to each other.

(23) The shell 6 and the optical block 5 can be manufactured individually and connected to each other, preferably by gluing. However, they are advantageously manufactured monolithically from one piece.

(24) A special case not shown in the Figures is a transmitting device with only one laser diode 1.1. There is no need here for a first mirror surface 5.3.sub.1, since the one beam axis A.sub.1 of the just one laser beam S.sub.1 can be directed directly at the center MP of the scanning mirror 2. In the coupling-in region 4.1 the laser beam S.sub.1 is then guided only over the entrance surface 5.1 and one exit surface 5.2.sub.1.

(25) All embodiments of a transmitting device according to the invention have the advantage that the entire beam beam shaping for collimation and the beam deflection of the laser diode beams S.sub.1, . . . , S.sub.n towards the scanning mirror 2 take place within the cover element 4, thus providing a compact, low-adjustment design.

LIST OF REFERENCE NUMERALS

(26) 1.1, . . . , 1.n laser diode 2 scanning mirror 3 housing 4 cover element 4.1 coupling-in region (of the cover element 4) 4.2 coupling-out region (of the cover element 4) 5 optical block 5.1 entrance surface (of the optical block 5) 5.2.sub.1, . . . , 5.2.sub.n exit surface (of the optical block 5) 5.3.sub.1, . . . , 5.3.sub.n first mirror surface (of the optical block 5) 5.4 second mirror surface (of the optical block 5) 6 shell S.sub.1, . . . , S.sub.n laser beam A.sub.1, . . . , A.sub.n beam axis (of the laser beam S.sub.1, . . . , S.sub.n) fa fast axis (of the laser diode 1.1, . . . , 1.n) sa slow axis (of the laser diode 1.1, . . . , 1.n) MP center (of the scanning mirror 2) L perpendicular HK monocentric hemispherical shell PS parabolic mirror surface F.sub.PS focal point of the parabolic mirror surface α.sub.1, . . . , α.sub.n angle of incidence