Light spot generating device

p0001The invention relates to a light spot forming apparatus according to the preamble of claim 1.

p0002Such light spot forming devices are generally used for scanning, where, for example, by means of a mirror wheel, a light beam, particularly a laser beam directed onto a surface to be scanned and there performing a periodic scan, generated in particular circular light spot. The light deflector can preferably produce about F-θ lenses a V-shaped scanning of the light beam (DE-PS 36 00 578) or by means of a concave mirror a parallel to itself shifted driving beam (DE-PS 23 40 688).

p0003In Abtastproblemen where the sensing surfaces, mounted for example on objects Code marks may be located in very different distances from the light spot forming device, the in-focus on the surface of the imaging surface light spot depending on the distance of the imaging surface of the light deflector on a very different size. Since it but on the other hand, in the scanning of existing example of the bar code on it arrives that the size of the light spot is in a predetermined relation to the width of code bar, you have the point light source is already using a zoom lens, ie a lens with variable focal length, on the imaging surface ready (US Patent No. 4,920,255) in order regardless of the distance between the light deflector and the imaging surface always to produce the same spot size on the imaging surface. Known zoom lenses consist of a plurality of lenses arranged in the optical axis direction slidably with each other, to change the focal length can. However, such zoom lenses are expensive and bulky, above all, in the optical axis direction, because the space for the axial displacement of lenses must be available.

p0004The aim of the present invention is to provide a light spot forming apparatus of the initially mentioned type, can be produced without using a plurality of, relative to each other in the optical axis direction movable lenses of the imaging surface in the light spots of different size, and preferably also of different shape.

p0005To achieve this object the features of the characterizing portion of claim 1 are provided.

p0006The inventive idea is thus to be seen in the fact that instead of a spherical or parabolic optics two in the area of ​​the radiation beam passageway crossed cylindrical optics are used, the focal length change is brought about in that each cylindrical lens is equipped along its cylindrical axis with veränderrlichen focal lengths, so that the by shifting two crossed in the field of light passage cylindrical optics in the direction of its cylinder axis, ie easily different focal lengths can be implemented perpendicular to the optical axis. Especially advantageous proves to be that the two cylindrical optics in the places where they are acted upon by the imaging light beam, while the same focal length can have, so that they total act as a parabolic or spherical optics, but may also have different focal lengths, so that instead of a circular light spot also elliptical light spots can be generated with different eccentricities. In the arrangement of two cylindrical optics is only necessary to ensure relative to each other that the cylinder axis, at least substantially perpendicular to one another are provided at the locations where they are acted upon by the imaging light beam, so that the two cylindrical optics areas at these locations together have the effect of a parabolic or spherical optics ,

p0007According to claims 2 and 3, the cylindrical optical cylindrical lens or cylindrical mirror can be. Cylindrical mirrors are preferred for manufacturing reasons.

p0008Further, the cylindrical optics according to claims 4 and 5 may be linear or circular. The circular shape is preferred for reasons of space and also to achieve a simple adjustability. To this end, a lot of different cylindrical lens focal lengths can be accommodated on a circular disk according to claim 6 in a compact manner. By placing the disc on a rotating shaft can also be done easily, the adjustment to different focal lengths.

p0009The optical axes at each point of the cylinder along the cylinder axis optics may be arranged relative to the axis of rotation according to claims 7 to 10th

p0010Particularly preferred is the embodiment defined in claim 11, because in this way the preparation of the cylinder mirror discs is facilitated by injection molding. The injection mold half which forms the cylinder mirror can be withdrawn in a simple manner in the direction of the axis of rotation of the cylinder mirror after its injection molding.

p0011With the device according to the invention any focal length changes along the cylinder axis can ultimately be made. Preferred, however, are the embodiments according to claims 12, 13th

p0012If on the total circumference of the circular disk a continuous increase or decrease in the focal length, is given at a point on the circumference an abrupt change in focal length according to claim 14th

p0013The embodiment defined in claim 15, the production is facilitated, on the other hand required for the generation of a sharp light spot optical accuracy is guaranteed.

p0014Preferred changes the radii of the circular surfaces takes you to claim 16th

p0015In order to realize a space-saving folded beam paths, in particular in the use of cylindrical mirrors, the embodiment of claim 17 is advantageous.

p0016The point light source is preferably designed according to claim 18th

p0017The invention is described in the following example with reference to the drawing; shows in this<dl id="dl0001"><dt>figure 1</dt><dd>a schematic perspective view of the basic principle of the light spot forming device according to the invention with two straight cylinder lenses </dd><dt>Figures 2a and 2b</dt><dd>Views generated in the imaging surface light spots in the direction of line II-II of Figure 1, as they can be produced by different displacement of the two cylindrical lenses according to Figure 1,</dd><dt>figure 3</dt><dd>a view in the direction of the axis of a mirror wheel of a working cylinder with two mirror-circular disks light spot forming device according to the invention with a mirror wheel as light deflector, a further embodiment is shown in dashed lines,</dd><dt>figure 4</dt><dd>a view of the object of Fig. 3 in the direction of arrow IV of Figure 3,</dd><dt>figure 5</dt><dd>a perspective view of a cylindrical mirror-disc according to the invention obliquely from the front in an enlarged scale,</dd><dt>figure 6</dt><dd>an enlarged axial section of an embodiment of a cylindrical mirror-disc, as illustrated by dashed lines in Fig. 3, 4, and</dd><dt>figure 7</dt><dd>an axial section similar to Figure 6 a further embodiment of a cylindrical mirror-disc, which also still one half of the mold used in injection Greeting methods illustrated during axial withdrawal of the injection molded cylindrical mirror-disc.</dd></dl>

p0018Of Figure 1 is based on a as light bulb 26 symbolized with an arranged behind nip point light source 11 is a narrow parallel imaging light bundle 19 having a circular cross-section, which for example has a diameter of 0.5 to 1 mm and a cylindrical lens 12 perpendicular to its cylinder axis 17, and parallel to the perpendicular to the cylinder axis 17 of the optical axis 15 impinge.

p0019A short distance behind the first cylindrical lens 12 is a second cylindrical lens 13, whose cylinder axis 18 to the cylinder axis 17 of the first cylindrical lens 12 is relatively at a right angle and which is also arranged with its optical axis 15 so that the light emerging from the cylindrical lens 12 imaging light beam 19 'parallel to the optical axis 15 impinge on the surface of the cylindrical lens. At a distance behind the second cylindrical lens 13 is an imaging surface 14 is provided on which the two crossed cylindrical lenses 12, 13 together produce a light spot 23, which is a sharp image of the point light source eleventh

p0020According to change the cylindrical lenses 12, 13 their focal length along the cylinder axes 17, 18 continuously, as from the one end to the other decreasing curvature of the cylindrical lens surfaces is illustrated by a. In addition, the two cylindrical lenses 12, 13 in the direction of the double arrows 27, 28, or 17 or 18 is displaced in the direction of the cylindrical lens axis, that selectively places different focal lengths can be moved to the location of the imaging light beam 19, 19 '.

p0021The operation of the light spot forming device described is as follows:

p0022By suitable displacement of the cylindrical lenses 12, 13 in the direction of the double arrows 27, 28 can for the imaging light beams 19, 19 'each have a desired focal length of the cylindrical lenses 12, 13 are selected such that either circular light spots 23 different sizes according to FIG 2 a or elliptical light spots 23 ', 23' 'of different sizes according to figure 2 b can be realized. To circular light spots get 23 different sizes according to FIG 2 a, have the focal lengths of the cylindrical lenses 12, 13 at the locations where they have the same focal length of the imaging light beams 19, 19 'crosses. The elliptical light spots 23 ', 23' 'with various eccentricity of Figure 2 b can be achieved in that the imaging beam traverses 19, 19' Make more or less different focal lengths of the two cylindrical lenses 12,. 13

p0023In order to achieve a correct focus of the light spots 23, 23 ', 23' 'on the imaging surface 14, the overall arrangement of the cylindrical lenses 12, 13, or the point light source 11 in the direction of the double arrow 29, ie, the optical axis 15 slidably in a suitable holder be arranged, except that the linear displacement of the cylindrical lenses 12, 13 in the direction of the double arrows 27, 28 must remain possible.

p0024In the preferred embodiment of Figures 3 and 4 a laser diode 11 generates a beam expanding lens 22, the imaging light beam 19 which impinges at an angle of approximately 20 ° to the edge portion of a cylindrical mirror-circular disc 21 about an axis perpendicular to the circular plane rotation axis 20 is rotatable. In the illustration beam 19 acted on by the edge region of the circular disk 21 is a circular concentric to the axis of rotation 20 arranged cylinder mirror 12 'having a circular cylinder axis 17'.

p0025Referring to Figure 5, the radius of curvature of the cylindrical mirror 12 'in the direction of the circumference changes continuously, in the direction of arrow in decreasing sense, so that at a peripheral location 16 a curvature jump, ie a step is created. In this way, taking the focal length of the cylinder mirror 12 'in the circumferential direction in the direction of arrow steadily. The radii of curvature may continuously change from 300 mm to 1200 mm, for example.

p0026So there is at each point on the circumference, a cylindrical mirror range of different focal lengths, the optical axis 15 of each of these areas is parallel to the axis of rotation 20th

p0027According to Figures 3 and 4, the imaging light beam 19 'is reflected and passes as optically already by the cylinder mirror 12' at a peripheral location of the cylinder mirror 12 influenced imaging light beam 19 'on the edge region of a further similar cylindrical mirror-disc 21, which is also parallel to an axis of rotation 20 to the optical axes 15 is rotatable and is arranged parallel to the first cylindrical mirror 12 '. The circular cylindrical mirror axis 18 'again extends concentrically to the rotation axis 20 of the cylindrical lens 13'.

p0028It is essential that the cylinder axis 18 'of the cylindrical mirror 13', where the imaging light beam 19 'impinges on the optical axis 17' of the cylindrical mirror 12 ', where the imaging light bundle 19 is incident, optically perpendicular, that is relatively crossed to her, so that the two powered cylinder mirror regions together have the effect of a spherical lens. How to Figures 3 and 4 detects the two cylindrical mirrors 12 ', 13' therefore applied at two offset by 90 ° to each other points from the imaging light beam 19 or 19 '.

p0029Of the cylindrical mirror 13 ', the imaging light beam 19' 'reflected to a mirror wheel 24, the axis of rotation 30 perpendicular to the through the imaging light beam 19, 19' as the imaging light beam 19 'is level' 'defined, 19th The light reflected from the mirror wheel 24 light beam 19 '' 'results due to the rotation of the mirror wheel 24 in the direction of arrow a V-shaped scanning and generates on a concave curved imaging surface 14 of the desired light spot 23 by appropriate rotation of the two cylindrical mirrors 12', 13 'about the pivot axes 20 may have different focal lengths of the cylindrical mirror 12', 13 'and implemented as different sizes and shapes of the light spot 23 in the sense of the figures 2 a, 2 b are obtained.

p0030While according to the representation in solid lines in Figures 3 and 4, the cylindrical mirror-circular disks 21 are formed as shown in FIG 5 that 12 'and 13' in such a way is at an end surface of the circular disk 21 of the groove-type cylindrical mirror, that the optical axis 15 at each circumferential location parallel to the rotation axis 20 and perpendicular to the respective end face of the circular disc 21 'can also be formed such that the cylindrical mirror 12', the cylindrical mirror-circular disks 21 by the dashed depictions in the figures 3 and 4 and according to figure 6, 13 'on the outer circumference of the cylindrical mirror-circular disks 21' are. In this case, the optical axes 15 to provide any circumferential location extensions of the radii of the circular disk 21 'at this point. The cylindrical mirror axes 17' and 18 'are back to the rotation axis 20' concentric circles, which, however, slightly radially outside the outer circumference of the cylindrical mirror -Kreisscheibe 21 'are.

p0031When placed in the beam path to the figures 3 and 4, the axes of rotation 20 'of the cylinder mirror discs 21' must be perpendicular to the rotation axes 20 of the embodiment shown in solid lines. Incidentally, also here the condition that the image of the light beams 19, 19 'is acted upon locations on the circumference of the circular plate 21' each 90 ° offset from each other.

p0032The cylindrical mirror 12 ', 13' may be located on the periphery of a cylindrical mirror-circular disc 21 '' as well as the results of FIG. 7 In this case, the optical axes 15 of at any peripheral location, for example at an angle α of 45 ° to the axis of rotation 20 ''. Also any other angle α (see also Fig. 3, 4) between 0 and 90 ° is also conceivable.

p0033The embodiment of Figure 7 has the advantage that when producing the cylinder mirror-circular disc 21 '' in an injection form, the cylindrical mirrors 12 'and 13' forming mold half 25 in the direction of the axis of rotation 20 '' Top of the circular disc 21 '' problems can be lifted. It is therefore expedient to design the cylinder mirror-circular disc 21 '' is so designed that relative to the rotational axis 20, there are no undercuts, so that the circular disc 21 'can be' produced in a single injection molding operation without burrs.

p0034In the preferred embodiment, the light spot forming device according to the invention with cylindrical mirror-circular disks 21, 21 ', 21' 'is the key advantage is that the different focal length settings of the two cylindrical lenses 12', 13 'not only independently, but also by a simple rotational movement about the axes 20, 20 ', 20' 'can be realized.

p0035To focus the light spot, the arrangement of the laser diode 11 and the beam expander 22 in the direction of the double arrow 29 may be 'slidably disposed according to FIGS. 3 and 4

LIST OF REFERENCE NUMBERS

p0036<dl id="dl0002" compact="compact"><dt>11</dt><dd>Point light source (laser diode)</dd><dt>12</dt><dd>cylindrical lens</dd><dt>12 '</dt><dd>cylindrical mirror</dd><dt>13</dt><dd>cylindrical lens</dd><dt>13 '</dt><dd>cylindrical mirror</dd><dt>14</dt><dd>imaging surface</dd><dt>15</dt><dd>optical axis</dd><dt>16</dt><dd>peripheral location</dd><dt>17</dt><dd>cylinder axis</dd><dt>17 '</dt><dd>cylinder axis</dd><dt>18</dt><dd>cylinder axis</dd><dt>18 '</dt><dd>cylinder axis</dd><dt>19</dt><dd>Imaging light bundle</dd><dt>19 '</dt><dd>Imaging light bundle</dd><dt>19 ''</dt><dd>Imaging light bundle</dd><dt>20</dt><dd>axis of rotation</dd><dt>21</dt><dd>Cylindrical mirror-disc</dd><dt>21 '</dt><dd>Cylindrical mirror-disc</dd><dt>21 ''</dt><dd>Cylindrical mirror-disc</dd><dt>22</dt><dd>Beam expander</dd><dt>23</dt><dd>light spot</dd><dt>23 '</dt><dd>light spot</dd><dt>23 ''</dt><dd>light spot</dd><dt>24</dt><dd>mirror wheel</dd><dt>25</dt><dd>mold</dd><dt>26</dt><dd>light bulb</dd><dt>27</dt><dd>double arrow</dd><dt>28</dt><dd>double arrow</dd><dt>29</dt><dd>double arrow</dd><dt>29 '</dt><dd>double arrow</dd><dt>30</dt><dd>axis of rotation</dd></dl>