Visible light double telecentric optical system

Abstract

The utility model relates to a visible light double telecentric optical system, which belongs to the technical field of industrial precision measurement, and solves the problems that the existing common industrial lens is difficult to meet the precision detection requirement, the sizes of object images on a detector are inconsistent due to different object distances when the same object is detected, and distortion is caused when the illuminance of the object images is not uniform along with the increase of a view field angle. In order to solve the technical problems, the visible light double-telecentric optical system comprises a first lens group, an aperture diaphragm and a second lens group which are sequentially arranged along the incident direction of light, so that main light of an object space and main light of an image space can be parallel to the optical axis of the visible light double-telecentric optical system to form double telecentricity, and the objective image is not similar to the actual object image. The entrance pupil and the exit pupil are respectively located at infinity of an object space and an image space, the MTF of the optical system is superior to 0.1 under a 208lp / mm line pair, the system distortion is superior to 0.3%, and the imaging quality is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of industrial precision measurement. Background Art

[0002] Existing ordinary industrial lenses are difficult to meet the needs of precision detection. When detecting the same object, different object distances will lead to inconsistent object image sizes on the detector. As the field of view angle increases, the cosine value of the field of view angle decreases, resulting in lower illumination in the off-axis field of view. The uneven illumination of the object image also causes distortion, causing the object image to lose similarity and the actual image to become curved. In addition, existing ordinary industrial lenses contain aspheric lenses, which are expensive and have a small lens curvature radius, resulting in thin edges and difficult processing and assembly. Telecentric optical systems are widely used in measurement and calibration in the machine vision industry due to their unique optical properties (high resolution, ultra-wide depth of field, ultra-low distortion, and unique parallel light design, etc.). Therefore, if telecentric optical systems can be applied to industrial detection, they can make up for the shortcomings of ordinary industrial lenses and meet the needs of precision detection in industry. Utility Model Content

[0003] In order to solve the technical problems in the above-mentioned prior art, the utility model proposes a “visible light double telecentric optical system”.

[0004] Visible light double telecentric optical system, such as Figure 1 As shown, it includes a first lens group 1, an aperture stop 2 and a second lens group 3 which are sequentially arranged along the incident direction of the light. The first lens group 1 includes:

[0005] The first lens 4 is a double convex cemented lens, the object side surface is convex, and the other surface is also convex;

[0006] The second lens 5 is a meniscus lens, the light incident side surface is convex, and the other surface is concave;

[0007] The third lens 6 is a double concave lens, the light incident side surface is concave, and the other surface is also concave;

[0008] The second lens group 3 includes:

[0009] The fourth lens 7 is a meniscus lens, the light incident side surface is concave, and the other surface is convex;

[0010] The fifth lens 8 is a double convex lens, the light incident side surface is convex, and the other surface is also convex;

[0011] The sixth lens 9 is a double convex cemented lens, the light incident side surface is convex, and the image side surface is convex;

[0012] The aperture stop 2 is located at the common focus of the third lens 6 and the fourth lens 7, so that the main light rays on the object side and the image side can be parallel to the optical axis of the visible light double telecentric optical system, forming a double telecentricity, and the entrance pupil and exit pupil are located at infinity on the object side and the image side respectively.

[0013] Technical effects:

[0014] The utility model discloses a visible light double telecentric optical system using white light illumination, with a resolution better than 0.01mm and a system magnification of 0.6; the aperture stop is located at the common focus of the third lens and the fourth lens, so that the principal rays of the object side and the image side are parallel to the optical axis, forming a double telecentricity, and then when the object distance is different when detecting the same object, the size of the object image on the detector is consistent and will not change; the telecentricity is better than 0.15°, and the telecentricity refers to the angle between the principal ray of the object side or the principal ray of the image side and the optical axis of the optical system, which has a greater impact on the measurement accuracy. The smaller the telecentricity, the smaller the measurement error; because the principal rays reaching the image plane from different fields of view are perpendicular to the image plane, the uniformity of the illumination of the object image is improved, such as Figure 2 As shown, the MTF of the utility model is better than 0.1 at a line pair of 208lp / mm. Figure 3 As shown, the system distortion is better than 0.3%, which improves the imaging quality; and the curvature radius of each lens is increased compared with the prior art, and spherical lenses are used to reduce the processing cost and the complexity of processing and assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the visible light double telecentric optical system.

[0016] Figure 2 It is an MTF curve diagram of an embodiment of the present utility model.

[0017] Figure 3 Schematic diagram of field curvature (left) and distortion (right) of an embodiment of the utility model. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0019] like Figures 1 to 3As shown, the utility model provides a "visible light double telecentric optical system", comprising a first lens group 1, an aperture stop 2 and a second lens group 3 arranged in sequence along the incident direction of light, wherein the air spacing between adjacent lens surfaces on the optical axis is as follows:

[0020] The air gap between the first lens 4 and the second lens 5 is 2.00-2.06 mm, the air gap between the second lens 5 and the third lens 6 is 2.21-2.23 mm, the air gap between the third lens 6 and the aperture stop 2 is 15.51-15.60 mm, the air gap between the aperture stop 2 and the fourth lens 7 is 29.41-29.65 mm, the air gap between the fourth lens 7 and the fifth lens 8 is 3.90-3.96 mm, and the air gap between the fifth lens 8 and the sixth lens 9 is 0.35-0.39 mm.

[0021] The first lens 4 includes a lens A401 and a lens B402. The center thickness of the lens A is 12.00-12.03 mm, the curvature radius of the light incident surface is 32.869-32.876 mm, and the curvature radius of the light exit surface is -22.822--22.823. The center thickness of the lens B is 12.00-12.02 mm, the curvature radius of the light incident surface is 22.822-22.823 mm, and the curvature radius of the light exit surface is 366.253-366.264.

[0022] The center thickness of the second lens 5 is 8.00-8.03 mm, the radius of curvature of the light incident surface is 22.509-22.683 mm, and the radius of curvature of the light exit surface is -41.494--41.513;

[0023] The central thickness of the third lens 6 is 8.00 to 8.05 mm, the radius of curvature of the light incident surface is -88.946 to -89.032 mm, and the radius of curvature of the light exit surface is -11.732 to -11.936;

[0024] The center thickness of the fourth lens 7 is 7.00-7.03 mm, the curvature radius of the light incident surface is -651.313--651.081 mm, and the curvature radius of the light exit surface is 41.075-41.103;

[0025] The center thickness of the fifth lens 8 is 7.00-7.06 mm, the radius of curvature of the light incident surface is 298.647-299.364 mm, and the radius of curvature of the light exit surface is 51.264-51.369 mm;

[0026] The sixth lens 9 includes a lens C901 and a lens D902. The center thickness of the lens C is 4.73-4.76 mm, the radius of curvature of the light incident surface is 70.888-70.963 mm, and the radius of curvature of the light exit surface is 43.392-43.695. The center thickness of the lens D is 7.00-7.03 mm, the radius of curvature of the light incident surface is -43.392--43.695 mm, and the radius of curvature of the light exit surface is 295.459-295.867.

[0027] Preferably, the specific parameters of each lens are shown in the following table:

[0028]

[0029] The object working distance of this embodiment is 65mm, of which the distance from the last surface of the system to the image plane is 25mm, that is, the back intercept is 20mm, which leaves enough space for the mechanical connection between the optical system and the subsequent system or detector. For example, a CCD or CMOS camera is placed on the image plane to receive the object surface signal amplified by the visible light double telecentric optical system, thereby obtaining clear and high-magnification object surface information.

[0030] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

Claims

1. Visible light double telecentric optical system, characterized by: The invention comprises a first lens group (1), an aperture stop (2) and a second lens group (3) which are arranged in sequence along the incident direction of light, wherein the first lens group (1) comprises: The first lens (4) is a double convex cemented lens, the object side surface is convex, and the other surface is also convex; The second lens (5) is a meniscus lens, the light incident side surface is convex, and the other surface is concave; The third lens (6) is a biconcave lens, the light incident side surface is concave, and the other surface is also concave; The second lens group (3) comprises: The fourth lens (7) is a meniscus lens, the light incident side surface is concave, and the other surface is convex; The fifth lens (8) is a biconvex lens, the light incident side surface is convex, and the other surface is also convex; The sixth lens (9) is a double convex cemented lens, the light incident side surface is convex, and the image side surface is convex; The aperture stop (2) is located at the common focus of the third lens (6) and the fourth lens (7), so that the main light rays on the object side and the image side can be parallel to the optical axis of the visible light double telecentric optical system, forming a double telecentricity, and the entrance pupil and the exit pupil are respectively located at infinity on the object side and the image side.

2. The visible light double telecentric optical system according to claim 1, characterized in that: The air interval between the first lens (4) and the second lens (5) is 2.00-2.06 mm, the air interval between the second lens (5) and the third lens (6) is 2.21-2.23 mm, the air interval between the third lens (6) and the aperture stop (2) is 15.51-15.60 mm, the air interval between the aperture stop (2) and the fourth lens (7) is 29.41-29.65 mm, the air interval between the fourth lens (7) and the fifth lens (8) is 3.90-3.96 mm, and the air interval between the fifth lens (8) and the sixth lens (9) is 0.35-0.39 mm.

3. The visible light double telecentric optical system according to claim 1, characterized in that: The first lens (4) comprises a lens A (401) and a lens B (402), wherein the central thickness of the lens A (401) is 12.00 to 12.03 mm, the radius of curvature of the light incident surface is 32.869 to 32.876 mm, and the radius of curvature of the light emitting surface is -22.822 to -22.823 mm, and the central thickness of the lens B (402) is 12.00 to 12.02 mm, the radius of curvature of the light incident surface is 22.822 to 22.823 mm, and the radius of curvature of the light emitting surface is 366.253 to 366.264 mm; The center thickness of the second lens (5) is 8.00 to 8.03 mm, the radius of curvature of the light incident surface is 22.509 to 22.683 mm, and the radius of curvature of the light exit surface is -41.494 to -41.513; The third lens (6) has a central thickness of 8.00 to 8.05 mm, a light incident surface curvature radius of -88.946 to -89.032 mm, and a light exit surface curvature radius of -11.732 to -11.936 mm; The fourth lens (7) has a central thickness of 7.00 to 7.03 mm, a light incident surface curvature radius of -651.313 to -651.081 mm, and a light exit surface curvature radius of 41.075 to 41.103 mm; The fifth lens (8) has a central thickness of 7.00 to 7.06 mm, a light incident surface curvature radius of 298.647 to 299.364 mm, and a light exit surface curvature radius of 51.264 to 51.369 mm; The sixth lens (9) includes a lens C (901) and a lens D (902). The center thickness of the lens C (901) is 4.73-4.76 mm, the radius of curvature of the light incident surface is 70.888-70.963 mm, and the radius of curvature of the light exit surface is 43.392-43.

695. The center thickness of the lens D (902) is 7.00-7.03 mm, the radius of curvature of the light incident surface is -43.392--43.695 mm, and the radius of curvature of the light exit surface is 295.459-295.

867.

4. The visible light double telecentric optical system according to claim 1, characterized in that: The object working distance of the optical system is 65 mm, and the back focus is 20 mm.

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