APPARATUS FOR ADJUSTING THE DIRECTION OF A LIGHT BEAM EMITTED BY A LASER TUBE

Abstract: The apparatus (1) in reference comprises an axially-centering member (9) in the tubular envelope (10) of which two portions (10a, 10b) are provided which are adapted to house a first lens-holding group in which a biconvex lens (13) is mounted and a second lens-holding group in which a biconcave lens (21) is mounted. The biconvex lens (13) can move axially inside the axially-centering member (9) while the biconcave lens (21) is provided with a floating movement for the correction of focusing errors induced in the equipment on which the axially-centering member (9) is mounted.

Description: Apparatus for adjusting the direction of a light beam emitted by a laser tube The present invention relates to an apparatus for adjust- ing the direction of a light beam emitted by a laser tube . It is known that the use of light-in-weight alignment apparatuses based on the use of laser tubes is becoming more and more propagated in the most different fields of the technique. In fact such apparatuses are adapted to project a light beam to a long distance, which beam, intercepting the desired object, defines an area on the same which has a circular profile and a very high luminous intensity and which is called spot. Owing to the very narrow light beam emitted by a laser, the spot diameter can be kept very reduced even when remarkable distances are concerned. For the above reasons laser tubes are more and more used in technical fields where it is necessary to carry out a precise short- or middle-distance alignment, above all in the absence of precise reference points. Alignment apparatuses based on a light beam emitted by a laser tube can therefore be applied for example to scrapers when a furrow that must extend a long distance in a rectilinear direction has to be marked out on the ground.. Likewise such apparatuses are used when tunnels have to be bored in order to keep the tunnel side walls perfectly aligned with each other. In the field of the mechanical industry such apparatuses are applied to machine tools for example in order to determine the cutting line of a given mechanical work- piece in a very precise manner. A further typical example is given by firearms in particular of the small type, where such apparatuses, once applied, allow the shooter not to bring again the sight of the arm barrel into alignment with its own eye. A still further application example for these alignment apparatuses is offered in surgery, above all in operating theatres, where it is necessary to establish the pαsition that a patient must take, in a \/ e ry precise manner. The above mentioned examples only relate to some fields in which alignment apparatuses based on laser tubes are used; actually, there are many other fields that are not mentioned here for the sake of brevity. The laser beam alignment apparatuses presently on the market are numerous and they have different confo mations. However they substantially consist of a tubular envelope in which a laser tube is elastically housed. A box- shaped envelope accommodates the necessary means for supplying the laser tube with electricity, such as for example batteries and transformers. The laser tube- containing envelope is finally provided with adjusting means enabling the emitted light beam to be directed in a horizontal and vertical direction; in fact, if the j equipment is mounted on a non perfectly straight tool or if the fastening means on such a tool involves rough work tolerances, the light beam coming out of the laser tube would have a deflection that would cause the tool to act along a deviated direction with respect to the desired one . Among the various apparatuses of the known type for adjusting the direction of the light beam emitted by a laser tube, one will be hereinafter described in its essential features; it has proved to be particularly efficient above all owing to the high distance to which it succeeds in projecting a spot of a very reduced diameter and with very clear outlines, by means of limited powers. Such an apparatus substantially comprises a sleeve provid¬ ed with inner and outer screw threads and adapted to be mounted in coaxial relation with the tubular body carrying the laser tube, at the outlet end of the latter. With the inner threaded portion of the sleeve are engaged, by screwing, a first lens-holding disk which can be axially moved inside the sleeve and a second lens-holding disk susceptible of being locked to the sleeve erd opposite the laser tube. Each of said lens-holdirg disks carries a respective biconvex lens. The spacing of one lens with respect to the other which takes place when the first lens-holding disk is caused to move backwards and forwards by screwing inside the sleeve, establishes the desired focal length that is the distance that a spot of a reduced diameter and bright luminosity is wished to reach. As to the correction of the ray deflection, an adjusting system is provided which involves the displacement of the laser tube in the horizontal and vertical direction. More particularly, the adjusting means in the horizontal direction comprises a double-headed micrometric screw disposed in the rear part of the tubular envelope infce which the laser tube is housed. Such an envelope, r at its opposite end, is rotatably mounted on a pivot, so that when a rotation is imparted to the adjusting screw, the oscillation of the whole envelope about said pivot takes place. As to the adjusting means in the vertical direction, it substantially comprises an annular casing supporting the extension neck of the front capillary of the laser tube. On the upper part of said casing a thread¬ ed tang is provided which is in engagement with an adjusting screw provided with a hollow shank and an inner thread; acting on said screw a vertical displacement of the annular casing is caused and, consequently, of the extension neck of the front capillary of the laser. However this adjusting means of the known type has some drawbacks. In fact it was found that o n adjusting the focal length of the optical alignment apparatus the light beam emitted by the laser tube underwent some deflections. The causes for these deflections are substantially two. One drawback is of mechanical origin and it relates to the threads provided on the sleeve and the lens-holder susceptible of moving backwards and forwards inside the former. In fact, a thread, however precise it may be, is never perfect so that the least error therein is transmitted, duly multiplied, to the spot so that it does not center the desired position. A further possibility of error is connected to the lenses themselves which, even if precise and of good construction, exhibit different optical characteristics depending upon the angular position they have, i.e. if a lens is caused to rotate about itself, in its new position it does not maintain the same optical characteristics as in its previous one. In this case too the error is multiplied at a certain distance so that the spot centers a point that actually does not correspond to the desired one. There are other adjusting systems based on the use of prisms which however lead to an aberration of the geometrical . figure of the luminous spot owing to the fact that at a certain distance, after carrying out the desired adjustment, the spot has an oval shape with out-of-focus outlines and with an increase of the spot area itself. The main object of the present invention is to obviate the above mentioned drawbacks rel'ative to the known art systems and to provide an apparatus for adjusting the direction of the light beam emitted by a laser tube which is adapted to perform a corrective deflection of the light beam without introducing any errors. A further object of the present invention is to make available an adjusting apparatus allowing the spot to keep very luminous and with perfectly clear outlines at a distance of about 600 meters, with minimum spot diameters and with the possibility for the spot to take all possible positions within a hypothetical circle having a radius of one meter. The foregoing and still further objects wh ' ich will become more apparent in the following are attained, according to the present invention, by an apparatusd) for adjusting the direction of the light beam emitted by a laser tube (8) which is characterized in that it comprises an axially-centering member (9) located in a suitable housing provided in a containing hull (3) and substantially consisting of a tubular envelope (10) comprising two inner portions (10a, 10b> of a different¬ iated diameter; a first lens-holding group housing a biconvex lens (13) which is mounted in the front portion of said axially-centering member (9) and is axially movable inside the latter; a second lens-holding group housing a biconcave lens (21) mounted in the rear portion of said axially-centering member (9) and consisting of a tubular body (19) terminating, at one end, in an outwardly spherical head (23), said spherical head (23) being rotatably accommodated in a housing counter-shaped thereto and obtained inside a spring ring (25) fastened to the inner walls of said second portion (10b); stop means adapted to prevent said tubular body (19) of the second lens-holding group from carrying out rotational movements about its own axis; adjusting means adapted to allow the first lens-holding group to move axially away from and close to said second lens-holding group; and adjusting means adapted to allow said second lens- holding group to carry out a floating displacement inside the spherical housing (24) of the spring ring(25). Further features and advantages of- the present invention will become more apparent from the detailed description of an apparatus for adjusting the direction of a light beam emitted by a laser tube given hereinafter by way of example only with reference to the accompanying drawings, in which : - Fig. 1 is a broken away perspective view of the apparatus according to the present invention; - Fig. 2 is a cross-sectional view to an enlarged scale of the apparatus in question; - Fig.3 is a sectional view taken along the line III- III in Fig. 2. Referring to the drawings, it has been generally indicated at 1 an apparatus for adjusting the direction of the light beam emitted by a laser tube. Such an apparatus is housed in a box-shaped body generally indicated at 2 and consisting of a hull 3 closed at its upper part by a cover 4 in turn divided into two distinct portions 5 and 6 articulated to each other at 7. The box-shaped body 2 is designed for housing, in addition to the adjusting apparatus 1, a laser tube 8, as well as ne respective electrical supply means such as a transformer, batteries and a connecting electrical circuit not shown in the figure as already known and Tonventional . According to the present invention the adjusting apparatus 1 comprises an axially-centering member generally indicated at 9. The axially-centering member 9 is substantially composed of a tubular envelope 10 inside which there are two portions 10a and 10b having L differentiated diameters. A first lens-holding group is mounted in the front portion 10a; it comprises a sleeve 11 provided with an inside step 12 adapted to axially hold a biconvex lens 13 and with an inner thread 14 engageable with a locking nut 16, after interposing a sealing ring 15 therebe.tween . Such lens-holding group is accomplished in such a way that it can axially move inside the first portion 10a of the axially-centering member 9. For the purpose, in the front part of the tubular body 10 provision is made for a pair of elongated apertures 17 into which respective screwslδ are introduced; they are designed for being tightened within threaded holes obtained in the sleeve 11. By loosening the screws " 18 the sleeve 11 is caused to slide axially without any possibilities of rotation inside the tubular body 10, so that the most appropriate position for projecting the focus of the optical system onto the desired point is achieved. In the second rear portion 10b of the axially-centering member 9 a second lens-holding group is mounted; it essentially consists of a tubular body 19 at one end of which a housing 20 is obtained for accommodating a bicon- cave lens 21 as well as a screw thread for the introduction of a locking nut 22 thereinto; said locking nut 22 is intended for holding the lens 21 rigidly located in its own housing 20. At its opposite end the tubular body 19 terminates in an outwardly spherical head 23. The spherical head 23 is rotatably located in a housing 24 counter-shaped thereto, obtained inside a spring ring 25. Said spring ring 25, for the purpose of allowing the necessary freedom of movement to the spherical head 23, is provided with threaded holes 26 in engagement with respective screws 27 housed in holes 28 provided on the tubular body 10 of the axially-centering member . Accord¬ ing to the present invention the apparatus 1 is provided with stop means adapted to prevent the tubular body 19, and consequently the biconcave lens 21 , from rotating about its own axis. Such a means substantially comprises a screw 29 susceptible of being screwed in a threaded hole 30 provided on the spherical head 23. The screw 29 also engages, by its head, with a longitudinal slit 31 carried by the spring ring 25. According to a further feature of the present invention, the inner part of th-e tubular body 19 is in the form of a cone in order to avoid any negative reflection effect of the light beam emitted by the laser tube inside the body itself. The apparatus according to the present invention is further provided with means adapted to allow a floating displacement of the second lens-holding group in the spherical housing 24 of the spring ring 25. To this end it should be noted that the box-shaped body 2 is provided with an inner block 32 which is of one piece construction with the bottom of hull 3 and with a pair of opposite posts 34 and 35 of one piece construction with the inner side walls of hull 3. Said means, adapted to allow the floating displacement of the second lens-holding group, comprises a first vertically-disposed operating screw 36 located in the cover, portion 6 covering the hull 3. To this end a substantially circular space 37 having a through hole 38 at the bottom is provided in this cover portion. The space 37 is used like a housing for a turret 39 inside which the operating screw 36 can be located; the rod 41 of the latter is screwed in a threaded hole carried by a strip 42 rigidly mounted on top of posts 34 and 35 in or¬ der toguide the displacements of screw 36 with respect to the second lens-holding group, with greater exactness. In addition, the rod 41 passes through a hole 43 worked in the rear portion of the tubular body 10 so that its free end is brought into contact with the tubular body 19 of the second optical group. The screw 36 is disposed in a coaxial relation with and in opposition to the bottom block 32 in .which a housing 44 is provided for accommodating a spring 45 adapted to act against the action exerted by the screw 36 (see Fig. 2). Referring particularly to Fig. 3 the adjusting means of the apparatus in question comprises a second operating screw 46 which also is located in a turret 47 disposed in a space .48 obtained on one side of the hull in the region of the post 35. The rod 49 of the screw ' 46 engages in a threaded hole 50 worked in a portion 51 of the turret 47 extending inside the hull 3 and passes through a hole 71 provided in the rear portion of the tubular envelope 10. So the free end of the screw 46 can come into a thrust relation with the tubular body 19 of the second lens-holding group. On the opposite side with respect o the screw 46 and in coaxial relation with the same, a housing 52 is provided in the post 34 and is adapted to accommodate a spring 53 acting against the action exerted on the tubular body 19 by the screw 46. ■ Advantageously and according to a further feature of the present invention, both turret 39 and turret 47 are respectively fixed to the cover portion 6 and to the hull 3 by screws identified at 54 and 55 respect¬ ively. Furthermore, each turret is provided with a number of longitudinal inner grooves 56 and 57 respectively , as well as with outer threads 58 and 59. The longitudinal grooves 56 and 57 are disposed at the same distance from each other over the whole circumferential extension of the turret itself and spring pegs 60 and 61 are destined to engage therewith, said pegs being located in appropriate housings 62 and 63 obtained transversely in the heads of the operating screws 36 and 46. In this way, acting on such screws it is possible to exactly establish the progress communicated to the screw itself and consequently the displacement degree imparted to the light beam coming out of the laser tube 8. Finally, in order to avoid the entering of dust or occasional movements of the operating screws 36 and 46, respective screw-covering members identified at 64 and 65 in Fig. 1 engage with the outer threads 58 and 59 of the turrets 39 and 47. After describing the apparatus in question mainly from a structural point of view, its operation appears very simple. - For adjusting the focal length it is sufficient to loosen the screws 18 and cause the first lens- holding group to slide axially up to the achievement of the desired position. After reaching this position, screws 18 are tightened again in order to avoid undesirable movements. As to the adjusting displacements of the second lens- holding group it is sufficient to unscrew the screw- covering members 64 and 65 and act on the operating screws 36 and 46 so that the tubular body 19 carrying the bi¬ concave lens 21 can take the desired position; it should be noted that during this floating movement of the second lens-holding group the lens 21 does not undergo any rotations about its own axis so that it is unable to insert error components in the direction that it gives to the light beam coming out of the laser tube 8. ' The invention thus attains the intended purposes-. Furthermore, it should be understood that the use, in the second lens-holding group, of a biconcave lens allows the optical group to take a more reduced axial dimension with respect to the present apparatuses providing the use of two biconvex lenses, while being equal the distance to which the spot is projected. Or alternatively, it is possible to obtain a smaller spot, the bulkiness and projection distance being equal. * Obviously many modifications and variations may be made to the apparatus in question without departing from the spirit and scope of the invention itself.

Claims: C L A I M S 1. An apparatus (1 ) for adjusting the direction of the light beam emitted by a laser tube (8) characterized in that it comprises an axially-centering member (9) located in a suitable housing provided in a containing hull (3) and substantially consisting of a tubular envelope (10) comprising two inner portions (10a, 10b) of a differentiated diameter; a first lens-holding group housing a biconvex lens (13) which is mounted in the front portion of said axially-centering member (9) and is axially movable inside the latter; a second lens- holdin-g group housing a biconcave lens (21) mounted in the rear portion of said axially-centering member (9) and consisting of a tubular body (19) terminating, at one end, in-an outwardly spherical head (23), said spherical head (23) being rotatably accommodated in a housing counter-shaped thereto and obtained inside a spring ring (25) fastened to the inner walls of said second portion (10b); stop means adapted to prevent said tubular body (19) of the second lens-holding group from carrying out rotational movements about its own axis; adjusting means adapted to allow the first lens-holding group to move axially away from and close to said second lens-holding group; and adjusting means adapted to allow said second lens-holding group to carry out a floating displacement inside the spherical housing (24) of the spring ring (25 ) . 2. An apparatus according to claim 1 characterized in that the inside of said tubular body (19) terminating in the outwardly spherical head (23) is of conical form. 3. An apparatus according to claim 1 characterized in that said stop means adapted to prevent said tubular body (19) of the second lens-holding group from carrying out rotational movements comprises a screw (29) fixed in a suitable threaded hole (30) of the spherical head (23), the head of said screw engaging between the edges of a slit (31) carried by said spring ring (25). 4. An apparatus according to claim 1 characterized in that said adjusting means adapted to allow the first lens-holding group to move axially comprises at least an elongated aperture (17) provided in the front portion of the ' axially-centering member (9), which cooperates with a fastening screw (18) tightened in a respective threaded hole obtained , in said lens-holding group. 5. An apparatus according to claim 1 characterized in that said adjusting means adapted to allow the second lens-holding group to carry out a floating displacement comprises a first upright operating screw (36) located in the upper portion of the hull (3) and acting by its free end against the tubular body (19) of the lens- holding group, in contrast to the action of spring means disposed at the bottom of the hull (3) and acting on the opposite portion of the tubular body (19) itself, and a second horizontal operating screw (46) located in a side wall of the hull (3) and acting, by its free end, against the tubular body (19) of the lens-holding group in contrast to the action exerted on the tubular body (19) itself by spring means located on the opposite side wall of the hull (3) 6. An.apparatus according to claim.5 characterized in that each of said operating screws (36, 46) is housed in a respective turret (39, 47) provided with a number of longitudinal inner grooves (56, 57) disposed at the same distance from each other over the whole circum¬ ferential extension of the turret' itself (39, 47), a spring peg (60, 61) located in an appropriate housing (62, 63) disposed transversely in the head of said operating screw (36, 46) engaging. ith said grooves (56, 57).

Inventors: PALA LUSSORIO RINALDO, PALA LUSSORIO, RINALDO
Applicants: PALA LUSSORIO RINALDO, PALA LUSSORIO, RINALDO
Application year: 1985
Main classification: G01B11
IPC codes: G01B11, H01S3