Abstract:
An object of the invention is to provide a laser line-generator that generates a straight line with the both end portions as bright as the central portion, and a laser line-generator module that integrates the laser line-generator with a laser light source. A columnar transparent medium has an entrance boundary surface  10  for taking in laser light and an exit surface  20  for emitting the taken laser light linearly. At least one of the entrance boundary surface  10  and the exit surface  20  is composed of a curved surface, and a curve forming the curved surface includes two or more inflection points F.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical component used for a laser marker and the like. The present invention specifically relates to a laser line-generator that converts a point light source of laser light to a line light source, and a laser line-generator module that integrates the laser-line generator with a laser light source. 
     2. Description of the Related Art 
     A straight line generated by a laser line-generator using a conventional cylindrical lens has a characteristic that the both end portions are darker than the bright central portion. Therefore, in a reference setting operation of providing a long reference line, the both ends are difficult to see, which causes a decrease in workability.  FIG. 10  is a principle diagram of a laser-line generator using a semi-cylindrical rod lens. A semi-cylindrical rod lens MR having a radius R is set with an optical axis Z as a central axis, and a screen S is placed at a predetermined distance in parallel with an entrance boundary surface of the semi-cylindrical rod lens MR. Incoming light L 1  by a laser parallel beam is incident on the entrance boundary surface  10  in parallel with the optical axis Z, and outgoing light L 2  refracted on an exit surface  20  draws a straight line on the screen S. 
     The incoming light L 1  is incident at an incidence angle θ 1  with respect to a normal line P to the exit surface, and becomes the outgoing light L 2  as a result of being refracted at a refraction angle θ 2 . The incidence angle θ 1  of the incoming light L 1  is small near the optical axis Z, and increases as the incoming light L 1  becomes away from the optical axis Z and a distance X between the optical axis Z and the incoming light L 1  approaches the radius R. This being so, the refraction angle θ 2  of the incoming light L 1  incident near the optical axis Z is small, and the outgoing light L 2  draws a bright straight line without much dispersion. However, as the incoming light L 1  becomes away from the optical axis Z and the distance X increases, the incidence angle θ 1  rapidly increases, and the refraction angle θ 2  increases too, so that the incoming light L 1  is greatly refracted. This causes large dispersion of the outgoing light L 2 , and the interval between adjacent outgoing light beams widens and an outgoing light density drops. As a result, a dark straight line is drawn. 
       FIG. 11  is a luminance characteristics chart showing a relation between straight line brightness and a deflection angle (W=θ 2 −θ 1 ) formed by the outgoing light with the optical axis. In a deflection angle curve D, the deflection angle W rapidly increases as the incoming light L 1  becomes away from the optical axis Z and the distance X between the incoming light L 1  and the optical axis Z approaches the distance of the radius R. The curve stops at the point of the deflection angle W where total reflection occurs. A luminance curve B varies in accordance with this deflection angle curve D, in such a manner that the luminance is highest when the incoming light L 1  is on the optical axis Z and decreases as the distance X approaches the distance of the radius R.  FIG. 12  is a straight line drawing schematic view schematically showing straight line drawing. The incoming light L 1  enters the semi-cylindrical lens MR, and the outgoing light L 2  greatly disperses at the both ends and decreases in light quantity, so that a straight line with the both end portions darker than the central portion is generated. Japanese Patent Application Laid-Open No. 2003-329454 describes a mechanism of automatically correcting vertical and horizontal line light emission positions of a laser marker that includes a laser light source, a collimating lens, and a cylindrical lens. 
     SUMMARY OF THE INVENTION 
     The present invention was conceived to solve the problem mentioned above, and has an object of providing a laser line-generator that generates a straight line with the both end portions as bright as the central portion, and a laser line-generator module that integrates the laser line-generator with a laser light source. 
     A laser line-generator of the present invention is a laser line-generator using a columnar transparent medium. The columnar transparent medium has an entrance boundary surface for taking in laser light and an exit surface for emitting the taken laser light linearly, wherein at least one of the entrance boundary surface and the exit surface is composed of a curved surface, and a curve forming the curved surface includes two or more inflection points. 
     A laser line-generator of the present invention is a laser line-generator using a columnar transparent medium. The columnar transparent medium has an entrance boundary surface for taking in laser light and an exit surface for emitting the taken laser light linearly, wherein at least one of the entrance boundary surface and the exit surface is composed of a curved surface, and a curve forming the curved surface includes two or more inflection points. The inflection points exist neither on the entrance boundary surface nor the exit surface but outside of the extension of the entrance boundary surface and the exit surface. 
     A laser module of the present invention is formed by directly incorporating a laser line-generator and a semiconductor laser onto an enclosure or a case of the semiconductor laser, and emits laser lightlinearly. 
     According to the present invention, a laser line-generator that generates a straight line with the both end portions as bright as the central portion can be obtained. By integrating this laser line-generator with a laser light source to form a laser line-generator module and incorporating the laser line-generator module into a laser marker, a decrease in workability can be prevented even when a long reference line is needed. This enables a laser marker with improved workability to be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an outline view showing a form of the first embodiment of a laser line-generator of the present invention. 
         FIG. 2  is a cosine function curve diagram showing a cosine function. 
         FIG. 3  is a luminance characteristics chart of a straight line corresponding to a deflection angle of the laser line-generator according to the first embodiment. 
         FIG. 4  is a schematic view of straight line drawing by the laser line-generator of the first embodiment. 
         FIG. 5  is a luminance characteristics chart of a straight line corresponding to a deflection angle of the laser line-generator according to the second embodiment. 
         FIG. 6  is a schematic view of straight line drawing by the laser line-generator of the second embodiment. 
         FIG. 7  is an outline view showing a form of the third embodiment of a laser line-generator of the present invention. 
         FIG. 8  is a luminance characteristics chart of a straight line corresponding to a deflection angle of the laser line-generator according to the third embodiment. 
         FIG. 9  is a schematic view of straight line drawing by the laser line-generator of the third embodiment. 
         FIG. 10  is a principle diagram of a laser line-generator using a semi-cylindrical rod lens. 
         FIG. 11  is a luminance characteristics chart of a straight line corresponding to a deflection angle of the semi-cylindrical rod lens. 
         FIG. 12  is a straight line drawing schematic view schematically showing straight line drawing by the semi-cylindrical rod lens. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of a laser line-generator according to the present invention are described below, with reference to drawings.  FIG. 1  is a laser line-generator outline view showing a form of a laser line-generator according to the first embodiment of the present invention.  FIG. 2  is a cosine function curve diagram showing a cosine function. This cosine function curve represents the case of a cosine function Y=A Cos(aX) where A=1 mm and a=2 mm −1 . In  FIG. 1 , a segment indicated by a circle shown in  FIG. 2  is cut out for a laser line-generator MC 1 . An entrance boundary surface  10  is a flat surface, whereas an exit surface  20  has the cut cosine function curve and includes inflection points F on both sides of an optical axis Z. Laser incoming light L 1  is incident on the entrance boundary surface  10  in parallel with the optical axis Z, and forms an incidence angle θ 1  with respect to a normal line P. The incoming light L 1  refracts at the exit surface  20 , and outgoing light L 2  is emitted at a refraction angle θ 2  with respect to the normal line P. 
       FIG. 3  is a luminance characteristics chart showing a relation between straight line brightness and a deflection angle W of the laser line-generator of the first embodiment. In a deflection angle curve D shown in  FIG. 3 , the refraction angle θ 2  varies monotonically as the incoming light L 1  on the entrance surface becomes away from the optical axis Z and the distance X between the incoming light L 1  and the optical axis Z increases, reduces its variation near the inflection points F, and exhibits extreme values at the inflection points F. In accordance with this, in the luminance curve B, the luminance is constant in a section where the variation of the refraction angle θ 2  is uniform, increases near the inflection points due to the reduced variation of the refraction angle θ 2 , and is at the maximum at the inflection points.  FIG. 4  is a straight line drawing schematic view schematically showing straight line drawing by the laser line-generator of the first embodiment. The incoming light L 1  is incident on the flat entrance boundary surface, and the outgoing light L 2  exits from the exit surface having the cosine function curve and draws a straight line on a screen S. The brightness is constant up to near the both end portions of the straight line, increases at the both end portions of the straight line since the dispersion of the outgoing light L 2  is reduced, and reaches a peak at the both ends. 
       FIG. 5  is a luminance characteristics chart showing a relation between straight line brightness and a refraction angle of a form of a laser line-generator according to the second embodiment of the present invention. An exit surface (not illustrated) formed by a cosine function curve in the second embodiment has a cosine function Y=A Cos(aX) where A=3.5 mm and a=0.2 mm −1 , and a segment cut out by a circle in  FIG. 2  does not contain the inflection points F on both sides of the optical axis Z. Accordingly,  FIG. 5  corresponds to a part of the deflection angle curve D and the luminance curve B between the inflection points on both sides shown in  FIG. 3 . The deflection angle curve D is a downward-sloping straight line indicating a monotonic variation of the deflection angle W, and the luminance curve B is a straight line indicating constant luminance.  FIG. 6  is a straight line drawing schematic view schematically showing straight line drawing by the laser line-generator of the second embodiment. The incoming light L 1  is incident on the flat entrance surface of a laser line-generator MC 2 , and the outgoing light L 2  exits from the exit surface having the cosine function curve between the inflection points and draws a straight line on the screen S. Because the variation of the deflection angle W is uniform, the outgoing light L 2  disperses evenly, and the brightness is constant to the both ends of the straight line. 
       FIG. 5  is a luminance characteristics chart showing a relation between straight line brightness and a refraction angle of a form of a laser line-generator according to the second embodiment of the present invention. An exit surface (not illustrated) formed by a cosine function curve in the second embodiment has a cosine function Y=A Cos(aX) where A=3.5 mm and a=0.2 mm −1 , and a segment cut out by a circle in  FIG. 2  does not contain the inflection points F on both sides of the optical axis Z. Accordingly,  FIG. 5  corresponds to a part of the deflection angle curve D and the luminance curve B between the inflection points on both sides shown in  FIG. 3 . The deflection angle curve D is a downward-sloping straight line indicating a monotonous variation of the deflection angle W, and the luminance curve B is a straight line indicating constant luminance.  FIG. 6  is a straight line drawing schematic view schematically showing straight line drawing by the laser line-generator of the second embodiment. The incoming light L 1  is incident on the flat entrance surface of a laser line-generator MC 2 , and the outgoing light L 2  exits from the exit surface having the cosine function curve between the inflection points and draws a straight line on the screen S. Because the variation of the deflection angle W is uniform, the outgoing light L 2  disperses evenly, and the brightness is constant to the both ends of the straight line. 
       FIG. 7  is a laser line-generator outline view showing a form of a laser line-generator according to the third embodiment of the present invention. A cosine function curve in the third embodiment represents a cosine function Y=A Cos(aX) where A=8.9 mm and a=0.393 mm −1 . The segment cut out by the circle shown in  FIG. 2  is applied to the entrance boundary surface  10  which has the inflection points F on both sides of the optical axis Z, whereas the exit surface  20  is a flat surface. The laser incoming light L 1  is incident on the entrance boundary surface  10  in parallel with the optical axis Z, and forms the incidence angle θ 1  with respect to a normal line P 1 . The incoming light L 1  refracts at the exit surface  20 , and the outgoing light L 2  is emitted at the refraction angle θ 2  with respect to a normal line P 2 . 
       FIG. 8  is a luminance characteristic chart showing a relation between straight line brightness and a refraction angle of the laser line-generator of the third embodiment. In the refraction angle curve D shown in  FIG. 8 , the refraction angle θ 2  gradually decreases as the incoming light L 1  on the entrance boundary surface becomes away from the optical axis Z and the distance X between the incoming light L 1  and the optical axis Z increases, and exhibits extreme values at the inflection points F. In accordance with this, in the luminance curve B, the luminance slightly increases as the refraction angle θ 2  gradually decreases, and is at the maximum at the inflection points.  FIG. 9  is a straight line drawing schematic view schematically showing straight line drawing by the laser line-generator of the third embodiment. The incoming light L 1  is incident on the concave entrance boundary surface, and the outgoing light L 2  exits from the flat exit surface and draws a straight line on the screen S. The dispersion of the outgoing light L 2  gradually decreases and so the brightness gradually increases up to near the both end portions of the straight line, and the outgoing light L 2  has no dispersion and the brightness reaches a peak at the both ends of the straight line. 
     The first to third embodiments describe the case where the entrance boundary surface is a flat surface and the exit surface is a cosine function curved surface having two inflection points, the case where the entrance boundary surface is a flat surface and the exit surface is a cosine function curved surface whose two inflection points exist not on the exit surface but outside of the extension of the exit surface, and the case where the entrance surface is a cosine function curved surface having two inflection points and the exit surface is a flat surface. These entrance boundary surfaces and/or exit surfaces may have a curved surface formed by a curve of a cosine function and the like where the curve forming the curved surface includes two or more inflection points or where the two or more inflection points exist not on the entrance boundary surface or the exit surface but outside of the extension of the entrance boundary surface or the exit surface. Furthermore, the laser line-generator according to the present invention and a semiconductor laser may be directly incorporated onto an enclosure or a case of the semiconductor laser to form a laser line-generator module (not illustrated) that emits laser light linearly. 
     As described above, according to the present invention, a laser line-generator that generates a straight line with the both end portions as bright as the central portion can be obtained. By integrating this laser line-generator with a laser light source to form a laser line-generator module and incorporating the laser line-generator module into a laser marker, a decrease in workability can be prevented even when a long reference line is needed. This enables a laser marker with improved workability to be provided.