Abstract:
An optical lens comprising a first lens (L 1 ), a second lens (L 2 ), a third lens (L 3 ), a fourth lens (L 4 ), and a fifth lens (L 5 ) that are sequentially arranged on a common optical axis in the transmission direction of an incident light. Both the first lens (L 1 ) and the fifth lens (L 5 ) are negative meniscus lenses. Both the second lens (L 2 ) and the third lens (L 3 ) are positive meniscus lenses. The fourth lens (L 4 ) is a biconvex lens. The optical lens is applicable in an optical system of a laser processing apparatus. When an employed processing wavelength is different from a monitoring wavelength, imaging color differences in a monitoring system can thus be eliminated, specifically, when a wavelength in the infrared range is employed as a laser processing wavelength while a red wavelength serves as the monitoring wavelength, improved imaging effects are provided in the monitoring system, thus ensuring the quality of laser processing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to the field of optics, and more particularly relates to an optical lens applied to a laser processing. 
       BACKGROUND OF THE INVENTION 
       [0002]    With the increasingly growing of the laser processing technology, a full monitoring of laser processing process (laser marking or laser cutting) is desired, so as to ensure the processing quality. Currently, the common monitoring method is to use CCD monitoring system to monitor the whole process. Compared with the conventional processing system in which focusing is performed with the naked eye at the beginning of processing, the CCD monitoring system can monitor the whole process. By monitoring the entire process, the parameters can be adjusted immediately in case of quality problems, thus ensuring the quality of processing. 
         [0003]    The current CCD monitoring system has a “poor” vision at the wavelength in the far infrared light, and it has a higher sensitivity of the band in the red light region, thus the CCD monitoring system usually employ red light to work. However, when the system uses far-infrared wavelength laser to process, there is chromatic aberration in the imaging of the CCD monitoring system, which cannot faithfully reflect the processing in real-time. 
       SUMMARY OF THE INVENTION 
       [0004]    Accordingly, it is necessary to provide an optical lens, which can be adapted to the working wavelength of the far-infrared region, while it can eliminate the imaging chromatic aberration in the monitoring system when using the monitoring wavelength in the red light region. 
         [0005]    An optical lens includes, successively coaxially arranged along a transmission direction of an incident light: a first lens being a negative meniscus lens and having a first surface and a second surface; a second lens being a positive meniscus lens and having a third surface and a fourth surface; a third lens being a positive meniscus lens and having a fifth surface and a sixth surface; a fourth lens being a biconvex lens and having a seventh surface and a eighth surface; and a fifth lens being a negative meniscus lens and having a ninth surface and a tenth surface; wherein two surfaces of each lens are a light incident surface and a light outgoing surface of the lens, respectively; the first surface to the tenth surface are successively arranged along the transmission direction of the incident light; the first surface, the second surface, the third surface, the fourth surface, the fifth surface, the sixth surface, the eighth surface, and the ninth surface are convex surfaces towards the transmission direction of the incident light, and the seventh surface is a convex surface against the transmission direction of the incident light. 
         [0006]    In one embodiment, the first surface has a radius of curvature of −56 mm±5%; the second surface has a radius of curvature of −300 mm±5%; the first lens has a central thickness of 6 mm±5%. 
         [0007]    In one embodiment, the third surface has a radius of curvature of −110 mm±5%; the fourth surface has a radius of curvature of −80 mm±5%; the second lens has a central thickness of 12 mm±5%. 
         [0008]    In one embodiment, the fifth surface has a radius of curvature of −4000 mm±5%; the sixth surface has a radius of curvature of −90 mm±5%; the third lens has a central thickness of 22 mm±5%. 
         [0009]    In one embodiment, the seventh surface has a radius of curvature of 300 mm±5%; the eighth surface has a radius of curvature of −200 mm±5%; the fourth lens has a central thickness of 22 mm±5%. 
         [0010]    In one embodiment, the ninth surface has a radius of curvature of −150 mm±5%; the tenth surface has a radius of curvature of ∞; the fifth lens has a central thickness of 4 mm±5%. 
         [0011]    In one embodiment, an interval at a optical axis between the second surface of the first lens and the third surface of the second lens is 4 mm±5%; an interval at the optical axis between the fourth surface of the second lens and the fifth surface of the third lens is 1.5 mm±5%; an interval at the optical axis between the sixth surface of the third lens and the seventh surface of the fourth lens is 0.5 mm±5%; an interval at the optical axis between the eighth surface of the fourth lens and the ninth surface of the fifth lens is 10 mm±5%. 
         [0012]    In one embodiment, the optical lens further includes a sixth lens being a planar lens; wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are successively coaxially arranged along the transmission direction of the incident light. 
         [0013]    In one embodiment, the sixth lens has a central thickness of 4 mm±5%. 
         [0014]    In one embodiment, the sixth lens has an eleventh surface as a light incident surface and a twelfth surface as a light outgoing surface, an interval at a optical axis between the tenth surface of the fifth lens and the eleventh surface of the sixth lens is 2 mm±5%. 
         [0015]    The above-mentioned optical lens can be applied to an optical system of a laser processing apparatus, which uses wavelength in the far-infrared region as the wavelength for laser processing. When using the red light wavelength as the monitoring wavelength, the monitoring system can achieve a better imaging effect, thus ensuring the quality of laser processing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other objects, advantages, purposes and features will become apparent upon review of the following specification in conjunction with the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0017]      FIG. 1  is a schematic diagram of an optical lens according to one embodiment of the present invention; 
           [0018]      FIG. 2  is a graphic diagram showing field curvature and distortion of the optical lens of  FIG. 1 ; 
           [0019]      FIG. 3  is a graphic diagram showing a dispersion pattern of the optical lens of  FIG. 1 ; and 
           [0020]      FIG. 4  is a graphic diagram showing a modulation transfer function (M.T.F) of the optical lens of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0021]    Reference will now be made to the drawings to describe, in detail, embodiments of the present invention. 
         [0022]    It should be noted that, in the present specification, the propagation direction of the light is from the left side to the right side of the drawing. The positive or negative curvature radius of the lens is determined by taking a relative positional relationship between an intersection point of the curved surface and the principal optical axis and a center of the spherical surface of the curved surface. If the center of the spherical surface is in the left of the intersection point, the radius of curvature has a negative value, if, on the other hand, the center of the spherical surface is in the right of the intersection point, the radius of curvature has a positive value. In addition, one side on the left of the lens is referred as the object side, and the other side on the right of the lens is referred as the image side. A positive lens is a lens in which the central thickness thereof is greater than the thickness of the edge, and a negative lens is a lens in which the central thickness thereof is less than the thickness of the edge. 
         [0023]      FIG. 1  is a schematic diagram of an optical lens according to one embodiment of the present invention, and for illustrative purposes, only portions related to implementation of the disclosure are shown. The optical lens includes a first lens L 1 , a second lens L 2 , a third lens L 3 , a fourth lens L 4 , and a fifth lens L 5 , which are successively coaxially arranged along a transmission direction of the incident light. 
         [0024]    The first lens L 1  includes a first surface Si and a second surface S 2 , the second lens L 2  includes a third surface S 3  and a fourth surface S 4 , the third lens L 3  has a fifth surface S 5  and a sixth surface S 6 ; the fourth lens L 4  has a seventh surface S 7  and a eighth surface S 8 ; and the fifth lens L 5  has a ninth surface S 9  and a tenth surface S 10 . Two surfaces of each lens serve as a light incident surface and a light outgoing surface, respectively. The first surface Si to the tenth surface S 10  are successively arranged along the transmission direction of the incident light. 
         [0025]    The first lens L 1  is a negative meniscus lens. The first surface S 1  of the first lens L 1  is a convex surface towards the image, and the first surface S 1  has a radius of curvature of −56 mm. The second surface S 2  is a convex surface towards the image, and the second surface S 2  has a radius of curvature of −300 mm. The first lens L 1  has a central thickness d 1  (i.e., a thickness of the first lens L 1  along the principal optical axis) of 6 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the first lens L 1  is made of Nd 1.76:Vd27 (refractive index: dispersion coefficient). 
         [0026]    The second L 2  is a positive meniscus lens. The third surface S 3  of the second lens L 2  is a convex surface towards the image, and the third surface S 3  has a radius of curvature of −110 mm. The fourth surface S 4  is a convex surface towards the image, and the fourth surface S 4  has a radius of curvature of −80 mm. The second lens L 2  has a central thickness d 3  of 12 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the second lens L 2  is made of Nd 1.69:Vd56. 
         [0027]    The third lens L 3  is a positive meniscus lens. The fifth surface S 5  of the third lens L 3  is a convex surface towards the image, and the fifth surface S 5  has a radius of curvature of −400 mm. The sixth surface S 6  is a convex surface towards the image, and the sixth surface S 6  has a radius of curvature of −90 mm. The third lens L 3  has a central thickness d 5  of 22 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the third lens L 3  is made of Nd 1.69:Vd56. 
         [0028]    The fourth lens L 4  is a biconvex lens. The seventh surface S 7  of the fourth lens L 4  is a convex surface towards the object, and the seventh surface S 7  has a radius of curvature of 300 mm. The eighth surface S 8  is a convex surface towards the image, and the eighth surface S 8  has a radius of curvature of −200 mm. The fourth lens L 4  has a central thickness d 7  of 22 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the fourth lens L 4  is made of Nd 1.69:Vd56. 
         [0029]    The fifth lens L 5  is a negative meniscus lens. The ninth surface S 9  of the fifth lens L 5  is a convex surface towards the image, and the ninth surface S 9  has a radius of curvature of −150 mm. The tenth surface S 10  is a plane with a radius of curvature of infinite (∞). The fifth lens L 5  has a central thickness d 9  of 4 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the fifth lens L 5  is made of Nd 1.6:Vd36. 
         [0030]    Further, intervals between each lens are configured as follows. Specifically, an interval d 2  at a optical axis between the light outgoing surface (the second surface S 2 ) of the first lens L 1  and the light incident surface (the third surface S 3 ) of the second lens L 2  is 4 mm with a tolerance of 5%, i.e., the interval d 2  can vary within ±5% of the expected value. 
         [0031]    An interval d 4  at the optical axis between the light outgoing surface (the fourth surface S 4 ) of the second lens L 2  and the light incident surface (the fifth surface S 5 ) of the third lens L 3  is 0.5 mm with a tolerance of 5%, i.e., the interval d 4  can vary within ±5% of the expected value. 
         [0032]    An interval d 6  at the optical axis between the light outgoing surface (the sixth surface S 6 ) of the third lens L 3  and the light incident surface (the seventh surface S 7 ) of the fourth lens L 4  is 0.5 mm with a tolerance of 5%, i.e., the interval d 6  can vary within ±5% of the expected value. 
         [0033]    An interval d 8  at the optical axis between the light outgoing surface (the eighth surface S 8 ) of the fourth lens L 4  and the light incident surface (the ninth surface S 9 ) of the fifth lens L 5  is 10 mm with a tolerance of 5%, i.e., the interval d 8  can vary within ±5% of the expected value. 
         [0034]    In one embodiment, the optical lens further includes a sixth lens L 6 . The first lens L 1 , the second lens L 2 , the third lens L 3 , the fourth lens L 4 , the fifth lens L 5 , and the sixth lens L 6  are successively coaxially arranged along the transmission direction of the incident light. 
         [0035]    The sixth lens L 6  includes an eleventh surface S 11  serving as the light incident surface and a twelfth surface S 12  serving as the light outgoing surface. As a protective component, the sixth lens L 6  is a planar lens, thus the radii of curvature of the eleventh surface S 11  and the twelfth surface S 12  are infinite. The sixth lens L 6  has a central thickness d 11  of 4 mm. In addition, an interval d 10  at the optical axis between the light outgoing surface (the tenth surface S 10 ) of the fifth lens L 5  and the light incident surface (the eleventh surface S 11 ) of the sixth lens L 6  is 2 mm. It should be understood that, the parameters above are expected values, and certain tolerances can be allowed to exist. The tolerance for the foregoing parameters is 5%, i.e., those parameters can vary within ±5% of the expected values. In one embodiment, the sixth lens L 6  is made of Nd 1.5:Vd64. 
         [0036]    The solution of the above embodiment will be more clearly described in the following brief descriptions: 
         [0037]    The firth lens L 1 : 
         [0038]    The first surface S 1 , radius of curvature of −56 mm; 
         [0039]    The second surface S 2 , radius of curvature of −300 mm; 
         [0040]    The central thickness, 6 mm; 
         [0041]    The material: 1.76/27; 
         [0042]    The second lens L 2 : 
         [0043]    The third surface S 3 , radius of curvature of −110 mm; 
         [0044]    The fourth surface S 4 , radius of curvature of −80 mm; 
         [0045]    The central thickness, 12 mm; 
         [0046]    The material: 1.69/56; 
         [0047]    The distance between the first lens L 1  and the second lens L 2 , 4 mm. 
         [0048]    The third lens L 3 : 
         [0049]    The fifth surface S 5 , radius of curvature of −400 mm; 
         [0050]    The sixth surface S 6 , radius of curvature of −90 mm; 
         [0051]    The central thickness, 22 mm; 
         [0052]    The material: 1.69/56; 
         [0053]    The distance between the second lens L 2  and the third lens L 3 , 0.5 mm. 
         [0054]    The fourth lens L 4 : 
         [0055]    The seventh surface S 7 , radius of curvature of 300 mm; 
         [0056]    The eighth surface S 8 , radius of curvature of −200 mm; 
         [0057]    The central thickness, 22 mm; 
         [0058]    The material: 1.69/56; 
         [0059]    The distance between the third lens L 3  and the fourth lens L 4 , 0.5 mm. 
         [0060]    The fifth lens L 5 : 
         [0061]    The ninth surface S 9 , radius of curvature of −150 mm; 
         [0062]    The tenth surface S 10 , radius of curvature of ∞; 
         [0063]    The central thickness, 4 mm; 
         [0064]    The material: 1.6/36; 
         [0065]    The distance between the fourth lens L 4  and the fifth lens L 5 , 10 mm. 
         [0066]    The sixth lens L 6 : 
         [0067]    The eleventh surface S 11 , radius of curvature of ∞; 
         [0068]    The twelfth surface S 11 , radius of curvature of ∞; 
         [0069]    The central thickness, 4 mm; 
         [0070]    The material: 1.5/64; 
         [0071]    The distance between the fifth lens L 5  and the sixth lens L 6 , 2 mm. 
         [0072]    An optical system employing the foregoing optical lens can perform laser processing using the red or infrared light having a wavelength in a range of from 1064 to 630 nm as the light source. In a laser processing apparatus equipped with a CCD monitoring system using red light as a monitoring light source, the color aberration in the CCD image can be avoided due to this optical lens, thus obtaining a better imaging effect and a better real-time monitoring of the processing. 
         [0073]    Next, the optical effects of the laser processing apparatus having the optical lens are explained with reference to  FIG. 2  to  FIG. 4  by choosing the far-infrared laser (λ=1064 nm) and the visible illumination light (λ=632 nm). 
         [0074]    The specific parameters of the optical lens are as follows: f=210 mm; Φ=30 mm; marking range: A=130*130 mm 2 , where f is the focal length of the optical lens, and Φ is the entrance pupil diameter. 
         [0075]      FIG. 2  is a graphic diagram showing field curvature and distortion of the optical lens. As can be seen from  FIG. 2  that, the axial chromatic aberration ΔCI=0.15-0.2, the magnification chromatic aberration ΔCII≈0, which are ideal. 
         [0076]      FIG. 3  is a geometrical aberration diagram of the lens. As can be seen from  FIG. 3  that, the geometric dispersion circle in all of the fields of view is about 0.01 mm, which is ideal. 
         [0077]      FIG. 4  is a graphic diagram showing a modulation transfer function (M.T.F) of the optical lens. As can be seen from  FIG. 4  that, when the resolution reaches 20 line pairs, M.T.F is 0.6, which is fully able to meet the requirements of laser processing. 
         [0078]    By using the optical lens according to the embodiment, light with a working band such as λ=1064 nm and the CCD visible band λ=632 nm can be focused on the same image plane, such that the whole laser processing procedure can be faithfully reflected in the CCD target plane, the entire marking process can be monitored to ensure that the entire marking process is accurate. 
         [0079]    Although the description is illustrated and described herein with reference to certain embodiments, the description is not intended to be limited to the details shown. Modifications may be made in the details within the scope and range equivalents of the claims.