Bi-telecentric lens and camera

Abstract

The invention discloses a double telecentric lens and a camera, belonging to the field of optical devices, comprising: a first objective lens group and a second objective lens group arranged along an optical path, the first objective lens group consisting of four lenses, which are: a first objective lens, a second objective lens, a third objective lens and a fourth objective lens in sequence along the optical path; the first objective lens and the third objective lens are identical double convex lenses, and the second objective lens and the fourth objective lens are identical meniscus lenses; the second objective lens group consists of five lenses, which are: a fifth objective lens, a sixth objective lens, a seventh objective lens and an eighth objective lens in sequence along the optical path; the fifth objective lens, the sixth objective lens and the seventh objective lens are all meniscus objective lenses, and the eighth objective lens is a cemented lens consisting of a double convex objective lens and a meniscus objective lens; the entire device has a streamlined structure, a small number of lenses, and can be applied to a working distance with a large range of variation, and can be applied to a working distance in the range of 100 mm to 300 mm without changing the lens; the double telecentric structure design has high telecentricity, small distortion, and constant magnification, which is conducive to accurate measurement of machine vision.

Description

Technical Field

[0001] The invention relates to the field of optical devices, and in particular to a double telecentric lens and a camera. Background Art

[0002] In the machine vision precision measurement system, the optical lens is an important component. Ordinary industrial lenses have problems such as different magnifications, aberrations, and large distortions caused by changes in object distance. With the development of technology, the requirements for industrial lenses are becoming more and more precise. In order to meet the requirements of high-precision detection, the bi-telecentric lens can keep the image magnification basically unchanged within a certain depth of field. However, the bi-telecentric lens can usually only be used within a fixed working distance and a small depth of field, and cannot be used in scenes with large changes in working distance.

[0003] In order to be applied to a larger working distance range, a dual telecentric lens and camera are urgently needed, which can meet the needs of different working distance changes with only one lens to be suitable for different production work scenarios. Summary of the invention

[0004] To achieve the above objectives, one of the objectives of the present invention is to provide a new technical solution with wide application range, high measurement precision and strong stability.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A bi-telecentric lens, comprising:

[0007] The first objective lens group and the second objective lens group are arranged along the optical path,

[0008] The first objective lens group is composed of four lenses, which are: a first objective lens, a second objective lens, a third objective lens and a fourth objective lens in order along the optical path; the first objective lens and the third objective lens are identical double convex lenses, and the second objective lens and the fourth objective lens are identical meniscus lenses;

[0009] The second objective lens group is composed of five lenses, which are: the fifth objective lens, the sixth objective lens, the seventh objective lens and the eighth objective lens along the optical path; the fifth objective lens, the sixth objective lens and the seventh objective lens are all meniscus objective lenses, and the eighth objective lens is a cemented lens composed of a double convex objective lens and a meniscus objective lens.

[0010] The beneficial effects of the present invention are as follows: along the optical axis from the object side to the image side, there are the first objective lens group and the second objective lens group, wherein the first objective lens group is composed of four lenses, the first objective lens and the third objective lens are the same double convex lenses, the second objective lens and the fourth objective lens are the same meniscus lenses, wherein the first objective lens and the second objective lens, as well as the third objective lens and the fourth objective lens are composed of two pairs of identical lenses, which is beneficial to eliminating the spherical aberration and chromatic aberration of the optical system at different working distances and realizing object-side telecentricity; the second objective lens group is composed of five lenses, which are used to adjust the imaging and realize image-side telecentricity; the whole equipment has a double telecentric structure design, a simple structure, a small number of lenses, and can be applied to a working distance with a large range of variations. By fine-tuning the image distance, the working distance can be changed within 100mm-300mm; the telecentricity is high, the distortion is small, and the magnification is constant, which is beneficial to the precise measurement of machine vision.

[0011] On the basis of the above technical solution, the present invention can also be improved as follows:

[0012] Furthermore, the first objective lens and the second objective lens are spaced and correspondingly fitted to each other, and the third objective lens and the fourth objective lens are spaced and correspondingly fitted to each other.

[0013] The beneficial effect of adopting the above further scheme is that the first objective lens and the second objective lens are a pair, the third objective lens and the fourth objective lens are a pair, and the two pairs of identical objective lenses are conducive to eliminating the spherical aberration and chromatic aberration of the optical system at different working distances.

[0014] Furthermore, the bi-telecentric lens also includes an aperture, which is installed between the sixth objective lens and the seventh objective lens, wherein the interval length between the first objective lens and the second objective lens and the interval length between the third objective lens and the fourth objective lens are both 1.5 mm, the interval length between the second objective lens and the third objective lens is 2.8 mm, the interval length between the fourth objective lens and the fifth objective lens is 118 mm, the interval length between the fifth objective lens and the sixth objective lens is 46.5 mm, the interval length between the aperture and the sixth objective lens is 1.5 mm, the interval length between the aperture and the seventh objective lens is 5.4 mm, and the interval length between the seventh objective lens and the eighth objective lens is 18.9 mm.

[0015] The beneficial effects of adopting the above further scheme are: the aperture is an entity in the optical system that limits the light beam and is used to limit the light beam or the size of the field of view (imaging range); the distance between each objective lens is determined to ensure that the dual telecentric lens meets the requirements of precise measurement.

[0016] Further, the focal length of the first objective lens is 179.2 mm, the focal length of the second objective lens is -312.4 mm, the focal length of the third objective lens is 179.2 mm, the focal length of the fourth objective lens is -312.4 mm, the focal length of the fifth objective lens is 451.7 mm, the focal length of the sixth objective lens is -18.1 mm, the focal length of the seventh objective lens is 19.4 mm, and the focal length of the eighth objective lens is 43.6 mm.

[0017] The beneficial effect of adopting the above further scheme is that, by clarifying the focal lengths of the above eight objective lenses, the working distance of the equipment in the range of 100mm-300mm can be met, and high telecentricity, small distortion, and constant magnification can be achieved, which is conducive to the requirements of precise measurement of machine vision.

[0018] Furthermore, the left radius length of the first objective lens and the third objective lens is 201 mm, the right radius length is -169 mm, and the thickness is 14 mm, and the left radius length of the second objective lens and the fourth objective lens is -169 mm, the right radius length is -1120 mm, and the thickness is 7 mm.

[0019] Further, the left radius length of the fifth objective lens is 34.5mm, the right radius length is 41.1mm, and the thickness is 3.5mm; the left radius length of the sixth objective lens is 8.31mm, the right radius length is 4.23mm, and the thickness is 3.5mm; the left radius length of the seventh objective lens is -18.6mm, the right radius length is -8.11mm, and the thickness is 4.2mm; the left radius length of the biconvex objective lens of the eighth objective lens is 52.1mm, the right radius length is -14.5mm, and the thickness is 5mm; the left radius length of the meniscus objective lens of the eighth objective lens is -14.5mm, the right radius length is -34.3mm, and the thickness is 4.5mm.

[0020] The beneficial effect of adopting the above further scheme is: by clarifying the radius and thickness of each objective lens in the first objective lens group and the second objective lens group, the size of each objective lens can be clarified, and then its focal length and light beam refraction range can be clarified to ensure the working range of the equipment.

[0021] Furthermore, the object distance range of the bi-telecentric lens is 100mm-300mm, the image distance range is 22mm-18mm, the object field of view of the bi-telecentric lens is Φ80mm, the magnification is 0.14X, the image plane size is 2 / 3"CCD, the effective aperture is F8, the optical distortion is <0.05%, and 100lp / mm>0.3.

[0022] Furthermore, the operating wavelength of the bi-telecentric lens is visible light of 486nm-656nm.

[0023] Furthermore, the first objective lens and the third objective lens are made of H-K9L glass, the second objective lens and the fourth objective lens are made of H-F4 glass, the fifth objective lens is made of K-K9L glass, the sixth objective lens is made of H-ZF7LA glass, the seventh objective lens is made of H-ZK3 glass, and the eighth objective lens is made of H-ZK9B / H-ZF7LA glass.

[0024] The beneficial effect of adopting the above further scheme is that the above conditions are the control range within which the device can work normally.

[0025] A second object of the present invention is to provide a camera, comprising the above-mentioned bi-telecentric lens, wherein the bi-telecentric lens is installed in the camera.

[0026] The beneficial effect of adopting the above further solution is that the camera adopting the above double telecentric lens can achieve a working distance within 100mm-300mm by fine-tuning the image distance, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The optical path diagram of the present invention with a working distance of 300 mm;

[0028] Figure 2 The optical path diagram of the present invention with a working distance of 200 mm;

[0029] Figure 3 The optical path diagram of the present invention with a working distance of 200 mm;

[0030] Figure 4 This is the spot diagram of the present invention when the working distance is 100 mm;

[0031] Figure 5 This is the spot diagram of the present invention when the working distance is 200 mm;

[0032] Figure 6 This is the spot diagram of the present invention when the working distance is 300 mm;

[0033] Figure 7 This is the field curvature distortion diagram of the present invention when the working distance is 100 mm;

[0034] Figure 8 This is the field curvature distortion diagram of the present invention when the working distance is 200 mm;

[0035] Fig. 9 This is the field curvature distortion diagram of the present invention when the working distance is 300 mm;

[0036] Fig.10 This is a modulation transfer function (MTF) diagram of the present invention when the working distance is 100 mm;

[0037] Fig.11This is a modulation transfer function (MTF) diagram of the present invention when the working distance is 200 mm;

[0038] Fig.12 This is a modulation transfer function (MTF) diagram of the present invention when the working distance is 300 mm.

[0039] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0040] 1. First objective lens; 2. Second objective lens; 3. Third objective lens; 4. Fourth objective lens; 5. Fifth objective lens; 6. Sixth objective lens; 7. Seventh objective lens; 8. Eighth objective lens. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings, which is not intended to limit the scope of the present invention.

[0042] Example 1: Figure 1-3 As shown, an embodiment of a bi-telecentric lens disclosed in the present invention comprises:

[0043] The first objective lens group and the second objective lens group are arranged along the optical path,

[0044] The first objective lens group is composed of four lenses, which are: the first objective lens 1, the second objective lens 2, the third objective lens 3 and the fourth objective lens 4 along the optical path; the first objective lens 1 and the third objective lens 3 are the same double convex lenses, and the second objective lens 2 and the fourth objective lens 4 are the same meniscus lenses;

[0045] The second objective lens group consists of five lenses, which are: the fifth objective lens 5, the sixth objective lens 6, the seventh objective lens 7 and the eighth objective lens 8 along the optical path; the fifth objective lens 5, the sixth objective lens 6, the seventh objective lens 7 are all meniscus lenses, and the eighth objective lens 8 is a cemented lens composed of a double convex objective lens and a meniscus lens.

[0046] The first objective lens 1 and the second objective lens 2 are spaced apart and correspondingly fitted to each other, and the third objective lens 3 and the fourth objective lens 4 are spaced apart and correspondingly fitted to each other.

[0047] Specifically, the leftmost side in the figure is the object side, the rightmost side is the image side, the lines are the light beam paths, and along the optical axis from the object side to the image side are the first objective lens 1, the second objective lens 2, the third objective lens 3, the fourth objective lens 4, the fifth objective lens 5, the sixth objective lens 6, the seventh objective lens 7 and the eighth objective lens 8. The first objective lens 1 and the third objective lens 3 are identical double convex lenses, the second objective lens 2 and the fourth objective lens 4 are identical meniscus lenses, the convex edge of the first objective lens 1 and the concave edge of the second objective lens 2 are spaced apart and correspondingly bonded to form a pair, the convex edge of the third objective lens 3 and the concave edge of the fourth objective lens 4 are spaced apart and correspondingly bonded to form a pair, the fifth objective lens 5, the sixth objective lens 6 and the seventh objective lens 7 are all meniscus objective lenses, and the eighth objective lens 8 is a cemented lens composed of a double convex objective lens and a meniscus objective lens.

[0048] It should be understood that the use of two pairs of identical lenses is conducive to eliminating the spherical aberration and chromatic aberration of the optical system at different working distances and achieving object-side telecentricity; the second objective lens group consists of five lenses, which are used to adjust the imaging and achieve image-side telecentricity; this equipment can achieve a working distance change within 100mm-300mm by fine-tuning the image distance; the overall structure is streamlined, the number of lenses is small, and it can be applied to a working distance with a large range of changes, and it can be applied to a working distance in the range of 100mm-300mm without changing the lens; the double telecentric structure design has high telecentricity, small distortion, and constant magnification, which is conducive to the precise measurement of machine vision.

[0049] Preferably, the aperture position is set between the sixth objective lens 6 and the seventh objective lens 7.

[0050] Preferably, the first objective lens 1, the second objective lens 2, the third objective lens 3, the fourth objective lens 4, the fifth objective lens 5, the sixth objective lens 6, the seventh objective lens 7 and the eighth objective lens 8 are all placed vertically, and the center points of the lenses are on the same horizontal line.

[0051] Based on Example 1, Example 2: Figure 1-3 As shown, the bi-telecentric lens further includes an aperture, which is installed between the sixth objective lens 6 and the seventh objective lens 7, wherein the interval length between the first objective lens 1 and the second objective lens 2 and the interval length between the third objective lens 3 and the fourth objective lens 4 are both 1.5 mm, the interval length between the second objective lens 2 and the third objective lens 3 is 2.8 mm, the interval length between the fourth objective lens 4 and the fifth objective lens 5 is 118 mm, the interval length between the fifth objective lens 5 and the sixth objective lens 6 is 46.5 mm, the interval length between the aperture and the sixth objective lens 6 is 1.5 mm, the interval length between the aperture and the seventh objective lens 7 is 5.4 mm, and the interval length between the seventh objective lens 7 and the eighth objective lens 8 is 18.9 mm;

[0052] The focal length of the first objective lens 1 is 179.2 mm, the focal length of the second objective lens 2 is -312.4 mm, the focal length of the third objective lens 3 is 179.2 mm, the focal length of the fourth objective lens 4 is -312.4 mm, the focal length of the fifth objective lens 5 is 451.7 mm, the focal length of the sixth objective lens 6 is -18.1 mm, the focal length of the seventh objective lens 7 is 19.4 mm, and the focal length of the eighth objective lens 8 is 43.6 mm;

[0053] The intervals between the first objective lens 1 and the second objective lens 2 and between the third objective lens 3 and the fourth objective lens 4 are 1.5 mm, the intervals between the second objective lens 2 and the third objective lens 3 are 2.8 mm, the intervals between the fourth objective lens 4 and the fifth objective lens 5 are 118 mm, the intervals between the fifth objective lens 5 and the sixth objective lens 6 are 46.5 mm, the interval between the sixth objective lens 6 and the seventh objective lens 7 is where the aperture is located, the aperture is 1.5 mm away from the sixth objective lens 6, 5.4 mm away from the seventh objective lens 7, and the intervals between the seventh objective lens 7 and the eighth objective lens 8 are 18.9 mm.

[0054] The left and right radii of the first objective lens 1 and the third objective lens 3 are 201 mm / -169 mm, respectively, and the thickness is 14 mm. The left and right radii of the second objective lens 2 and the fourth objective lens 4 are -169 mm / -1120 mm, respectively, and the thickness is 7 mm.

[0055] The left and right radii of the fifth objective lens 5 are 34.5mm / 41.1mm respectively, and the thickness is 3.5mm. The left and right radii of the sixth objective lens 6 are 8.31mm / 4.23mm respectively, and the thickness is 3.5mm. The left and right radii of the seventh objective lens 7 are -18.6mm / -8.11mm respectively, and the thickness is 4.2mm. The left and right radii of the eighth objective lens 8 are 52.1mm / -14.5mm / -34.3mm respectively, and the thickness is 5mm / 4.5mm.

[0056] Specifically, the focal length, spacing, left and right radius and thickness of the above-mentioned objective lenses can clearly define the position and specific shape of each objective lens, thereby realizing the scenario of changing the working distance of the device, and through adjustment, one lens can meet the needs of different working distance changes, so as to be suitable for different production work scenarios.

[0057] Preferably, the left and right radii of each objective lens are the arc radii of its left outer surface and the arc radii of its right outer surface, where the circle center is positive on the right side of the objective lens center and negative on the left side; the thickness is the width at the center of each objective lens.

[0058] Based on Example 1, Example 3: Figure 2-11 As shown, the object distance range of the double telecentric lens is 100mm-300mm, the image distance range is 22mm-18mm, the object field of view of the double telecentric lens is Φ80mm, the magnification is 0.14X, the image plane size is 2 / 3"CCD, the effective aperture is F8, the optical distortion is <0.05%, and 100lp / mm>0.3;

[0059] The working wavelength of the bi-telecentric lens is 486nm-656nm of visible light;

[0060] The first objective lens 1 and the third objective lens 3 are made of H-K9L glass, the second objective lens 2 and the fourth objective lens 4 are made of H-F4 glass, the fifth objective lens 5 is made of K-K9L glass, the sixth objective lens 6 is made of H-ZF7LA glass, the seventh objective lens 7 is made of H-ZK3 glass, and the eighth objective lens 8 is made of H-ZK9B / H-ZF7LA glass.

[0061] Specifically, the parameters of the above lenses are shown in the following table:

[0062]

[0063]

[0064] Through the above table, the test experiment was carried out, and the data is as follows:

[0065] like Figure 4-6 As shown, it is the spot diagram of the present invention, which is the RMS (Root mean square, which is the square root of the average value of the square of a set of statistical data) of each field of view at a working distance of 100mm, 200mm, and 300mm, respectively; in the figure, OBJ represents the object field of view, IMA represents the image field of view, and SPOT DIAGRAM is represented as a spot diagram, wherein the image in the figure represents the size of the diffuse spot presented at different positions of the object field of view on the image field of view; wherein the RMS root mean square radius of each field of view is smaller than the Airy disk radius, and the maximum RMS root mean square radius is 2.465μm, indicating that the imaging quality of the system is generally good and meets the design requirements of the object telecentric lens.

[0066] like Figure 7-9 As shown, it is the field curvature distortion diagram of the present invention, which is respectively at the working distances of 100mm, 200mm and 300mm. The maximum distortion of the system does not exceed 0.05%, which is beneficial to ensure the accuracy of machine vision detection and meet the detection requirements (FIELD CURVATURE in the figure represents field curvature, DISTORTION represents distortion, MILLIMTERS represents millimeters, and PERCENT represents percentage).

[0067] like Figure 10-12As shown, the Modulation Transfer Function (MTF) diagram of the present invention is shown, which shows that at working distances of 100mm, 200mm and 300mm, the MTF value of the full field of view at 110lp / mm is greater than 0.3, and the entire MTF curve is compact, close to the ideal MTF curve, the imaging rate, the system resolution is high, close to the diffraction limit, and the imaging performance is good (in the figure, MODULUS OF THE OTF is the contrast value, SPATIAL FREQUENCY IN CYCLES PER MM is the spatial resolution unit is line pairs / mm. POLYCHROMATIC DIFFRACTION MTF is the modulation transfer function MTF diagram).

[0068] It should be understood that the entire double telecentric lens structure is streamlined, with a small number of lenses. The working distance can be changed within 100mm-300mm by fine-tuning the image distance, and it can be used for working distances in the range of 100mm-300mm without changing the lens. The double telecentric structure design keeps the magnification of the lens basically unchanged within the range of working distance, with high telecentricity, small distortion, and constant magnification, which is conducive to precise measurement of machine vision.

[0069] On the basis of Example 1, Example 4, as Figure 1-12 A camera comprises the above-mentioned dual telecentric lens, and the dual telecentric lens is installed in the camera.

[0070] It should be understood that the camera using the above-mentioned dual telecentric lens can achieve a working distance within 100mm-300mm by fine-tuning the image distance, and has wide applicability.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A bi-telecentric lens, It is characterized in that include: The first objective lens group and the second objective lens group are arranged along the optical path, The first objective lens group is composed of four lenses, which are arranged in order along the optical path: a first objective lens (1), a second objective lens (2), a third objective lens (3) and a fourth objective lens (4); the first objective lens (1) and the third objective lens (3) are identical double convex lenses, and the second objective lens (2) and the fourth objective lens (4) are identical meniscus lenses; The second objective lens group is composed of five lenses, which are, in order along the optical path, a fifth objective lens (5), a sixth objective lens (6), a seventh objective lens (7) and an eighth objective lens (8); the fifth objective lens (5), the sixth objective lens (6) and the seventh objective lens (7) are all meniscus objective lenses, and the eighth objective lens (8) is a cemented lens composed of a double convex objective lens and a meniscus objective lens; The focal length of the first objective lens (1) is 179.2 mm, the focal length of the second objective lens (2) is -312.4 mm, the focal length of the third objective lens (3) is 179.2 mm, the focal length of the fourth objective lens (4) is -312.4 mm, the focal length of the fifth objective lens (5) is 451.7 mm, the focal length of the sixth objective lens (6) is -18.1 mm, the focal length of the seventh objective lens (7) is 19.4 mm, and the focal length of the eighth objective lens (8) is 43.6 mm; The object distance range of the bi-telecentric lens is 100mm-300mm, the image distance range is 22mm-18mm, the object field of view of the bi-telecentric lens is Φ80mm, the magnification is 0.14X, the image plane size is 2 / 3"CCD, the effective aperture is F8, and the optical distortion is <0.05%.

2. The bi-telecentric lens according to claim 1, It is characterized in that The first objective lens (1) and the second objective lens (2) are spaced apart and correspondingly fitted to each other, and the third objective lens (3) and the fourth objective lens (4) are spaced apart and correspondingly fitted to each other.

3. The bi-telecentric lens according to claim 1, It is characterized in that The optical system further comprises an aperture, which is installed between the sixth objective lens (6) and the seventh objective lens (7), wherein the interval length between the first objective lens (1) and the second objective lens (2) and the interval length between the third objective lens (3) and the fourth objective lens (4) are both 1.5 mm, the interval length between the second objective lens (2) and the third objective lens (3) is 2.8 mm, the interval length between the fourth objective lens (4) and the fifth objective lens (5) is 118 mm, the interval length between the fifth objective lens (5) and the sixth objective lens (6) is 46.5 mm, the interval length between the aperture and the sixth objective lens (6) is 1.5 mm, the interval length between the aperture and the seventh objective lens (7) is 5.4 mm, and the interval length between the seventh objective lens (7) and the eighth objective lens (8) is 18.9 mm.

4. The bi-telecentric lens according to claim 1, It is characterized in that The left radius length of the first objective lens (1) and the third objective lens (3) is 201 mm, the right radius length is -169 mm, and the thickness is 14 mm; the left radius length of the second objective lens (2) and the fourth objective lens (4) is -169 mm, the right radius length is -1120 mm, and the thickness is 7 mm.

5. The bi-telecentric lens according to claim 1, It is characterized in that The fifth objective lens (5) has a left radius of 34.5 mm, a right radius of 41.1 mm, and a thickness of 3.5 mm. The sixth objective lens (6) has a left radius of 8.31 mm, a right radius of 4.23 mm, and a thickness of 3.5 mm. The seventh objective lens (7) has a left radius of -18.6 mm, a right radius of -8.11 mm, and a thickness of 4.2 mm. The eighth objective lens (8) has a double convex objective lens with a left radius of 52.1 mm, a right radius of -14.5 mm, and a thickness of 5 mm. The eighth objective lens (8) has a meniscus objective lens with a left radius of -14.5 mm, a right radius of -34.3 mm, and a thickness of 4.5 mm.

6. The bi-telecentric lens according to claim 1, It is characterized in that The working wavelength of the bi-telecentric lens is visible light of 486nm-656nm.

7. The bi-telecentric lens according to claim 1, It is characterized in that The first objective lens (1) and the third objective lens (3) are made of H-K9L glass, the second objective lens (2) and the fourth objective lens (4) are made of H-F4 glass, the fifth objective lens (5) is made of K-K9L glass, the sixth objective lens (6) is made of H-ZF7LA glass, the seventh objective lens (7) is made of H-ZK3 glass, and the eighth objective lens (8) is made of H-ZK9B / H-ZF7LA glass.

8. A camera, It is characterized in that The bi-telecentric lens comprises the bi-telecentric lens according to any one of claims 1 to 7, wherein the bi-telecentric lens is installed in the camera.

Images