CN206369893U - A kind of fringe projection camera lens for three-dimensional measurement - Google Patents

Abstract

The utility model provides a fringe projection lens for three-dimensional measurement, which sequentially includes a front lens group with negative refractive power, a diaphragm and a rear lens group with positive refractive power from the object side to the image side; the front lens group consists of The object side to the image side include the first lens, the second lens and the third lens in sequence; the first lens is a meniscus lens with negative power; the second lens is a biconcave lens with negative power; the third lens is A double-convex lens with positive refractive power; the rear lens group from the object side to the image side sequentially includes the fourth lens, the fifth lens, the sixth lens and the seventh lens; the fourth lens is a double-convex lens with positive refractive power; the fifth lens is a biconcave lens with negative power; the sixth lens is a biconvex lens with positive power; and the seventh lens is a meniscus lens with negative power. The utility model provides a lens capable of realizing small distortion, small size, high light-passing performance and meeting the requirements of high-definition projection.

Description

A fringe projection lens for three-dimensional measurement

【Technical field】

The utility model relates to an optical lens, in particular to a stripe projection lens for three-dimensional measurement.

【Background technique】

There are many methods for three-dimensional measurement of structured light. The traditional method is to use computer-generated fringes and project the fringes to obtain the three-dimensional contour image of the target object, that is, to project the computer-generated fringe image onto the target object to obtain the three-dimensional contour of the target object. image, but this approach is limited by depth of focus, projected area and sharpness, and to some extent by lamp life.

In order to solve the inherent defects of the traditional fringe projection method in three-dimensional measurement, the method of using the acousto-optic fringe method instead of the fringe projection method for three-dimensional measurement came into being. The acousto-optic fringe method replaces the method of computer-generated grating fringes, and can project real interference fringes to the target object. It has a large depth of focus and true sinusoidal fringes, which is especially beneficial for three-dimensional measurement.

However, the projection lens of the traditional acousto-optic fringe method for three-dimensional measurement has weak light transmission performance and low resolution, which cannot meet the requirements of high light transmission ability and high definition of the three-dimensional measurement system.

【Content of utility model】

In order to overcome the deficiencies in the prior art. The utility model provides a fringe projection lens for three-dimensional measurement.

The technical solution of the utility model to solve the technical problem is to provide a striped projection lens for three-dimensional measurement. The striped projection lens for three-dimensional measurement includes a front lens group with negative focal power, a light stop and a rear lens group with positive power; the front lens group includes a first lens, a second lens and a third lens in sequence from the object side to the image side; the first lens is a meniscus with negative power lens with a convex surface facing the object side; the second lens is a biconcave lens with negative refractive power; the third lens is a biconvex lens with positive refractive power; the rear lens group from the object side to the image side includes the first Four lenses, the fifth lens, the sixth lens and the seventh lens; the fourth lens is a biconvex lens with positive power; the fifth lens is a biconcave lens with negative power; the sixth lens is A biconvex lens with positive refractive power; the seventh lens is a meniscus lens with negative refractive power, and the convex surface faces the object side; the fourth lens and the fifth lens are combined into a cemented lens; the first lens is close to The object side is an aspheric surface, and the seventh lens is an aspheric surface near the image side.

Preferably, the striped projection lens for three-dimensional measurement satisfies 76.36mm≤TTL≤79.92mm, where TTL is the distance from the outermost point on the object side of the first lens of the striped projection lens for three-dimensional measurement to the imaging plane.

Preferably, the striped projection lens for three-dimensional measurement satisfies the conditional formula 8.08≤TTL/EFL≤10.52, wherein TTL is the distance from the outermost point on the object side of the first lens of the striped projection lens for three-dimensional measurement to the imaging surface distance, EFL is the total focal length value of the fringe projection lens used for three-dimensional measurement.

Preferably, the striped projection lens for three-dimensional measurement satisfies the conditional formula 5.87≤TTL/FFL≤6.51, wherein TTL is the outermost point on the object side of the first lens of the striped projection lens for three-dimensional measurement to the imaging plane FFL is the distance from the outermost point on the image side of the first lens to the imaging plane.

Preferably, the fringe projection lens used for three-dimensional measurement satisfies the conditional formula 0.32≤BFL/EFL≤0.40, wherein FFL is the distance from the outermost point on the image side of the first lens to the imaging plane, and BFL is the fringe used for three-dimensional measurement The distance from the outermost point on the image side of the seventh lens of the projection lens to the imaging plane.

Preferably, the striped projection lens used for three-dimensional measurement satisfies the conditional formula 18.06mm≤Fhou ≤44.80mm, wherein Fhou represents the focal length value of the rear lens group.

Preferably, the striped projection lens for three-dimensional measurement satisfies the conditional formula -1.11≤F rear/F front≤-0.54, wherein F front represents the focal length value of the front lens group.

Preferably, the fringe projection lens for three-dimensional measurement satisfies the conditional formula 72.45°≤FOV≤72.56°, where FOV represents the maximum field of view angle of the wide-angle lens.

Preferably, the first lens of the striped projection lens for three-dimensional measurement satisfies the conditional formula 0.05≤(d/h)/FOV≤0.06, where d represents the maximum convex surface of the first lens corresponding to the maximum field of view toward the object side. Clear aperture, h represents the imaging image height corresponding to the maximum field of view.

Preferably, the striped projection lens for three-dimensional measurement satisfies the conditional formula 2.96≤F glue/F rear ≤4.71, wherein F glue represents the focal length value of the cemented lens, and F front represents the focal length value of the front lens group.

The fringe projection lens used for three-dimensional measurement of the utility model adopts a compact structure with an ultra-short focal length and has a small TTL to maximize the field of view and projection area. At a distance of 1 meter, there is at least a 40-inch projection area so that a pair of The fringe pattern can cover a large surface as quickly as possible at one time, enabling the system to capture enough object information and achieve high-precision fringe patterns. The distortion rate is small, the MTF value of all spatial frequencies is as high as 80%, the light aberration only exists in the range from -0.025 to 0.025, and the imaging quality is more excellent.

At the same time, the side of the first lens close to the object side is an aspheric surface, and the side of the seventh lens close to the image side is an aspheric surface. The fringe projection lens for three-dimensional measurement can achieve a better aberration correction effect with fewer aspheric lenses, and at the same time save costs

Furthermore, the fringe projection lens for three-dimensional measurement provided by the utility model can realize the fringe projection lens for three-dimensional measurement with low cost, light weight, small distortion, small size, high light-passing performance and high-definition requirements.

【Description of drawings】

FIG. 1 is a structural schematic diagram of a first embodiment of a striped projection lens for three-dimensional measurement according to the present invention.

FIG. 2A is a color difference curve diagram of the first embodiment of a striped projection lens for three-dimensional measurement according to the present invention.

Fig. 2B is a curve diagram of the astigmatism field of the first embodiment of the fringe projection lens for three-dimensional measurement of the present invention.

Fig. 2C is the distortion aberration curve of the first embodiment of a fringe projection lens for three-dimensional measurement of the present invention

FIG. 3 is an MTF curve diagram of the first embodiment of a striped projection lens for three-dimensional measurement according to the present invention.

Fig. 4 is a radial energy curve diagram of the first embodiment of a striped projection lens for three-dimensional measurement of the present invention.

Fig. 5 is a schematic structural diagram of a second embodiment of a fringe projection lens for three-dimensional measurement according to the present invention.

FIG. 6A is a color difference curve diagram of a second embodiment of a striped projection lens for three-dimensional measurement according to the present invention.

FIG. 6B is a curve diagram of the astigmatism field of the second embodiment of the fringe projection lens for three-dimensional measurement of the present invention.

Fig. 6C is the distortion aberration curve of the second embodiment of a fringe projection lens for three-dimensional measurement of the present invention

FIG. 7 is an MTF curve diagram of a second embodiment of a fringe projection lens for three-dimensional measurement according to the present invention.

FIG. 8 is a radial energy curve diagram of the second embodiment of a fringe projection lens for three-dimensional measurement according to the present invention.

【detailed description】

In order to make the purpose, technical solutions and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Please refer to FIG. 1 , the utility model provides a fringe projection lens for three-dimensional measurement. The striped projection lens for three-dimensional measurement includes a front lens group with negative refractive power, a diaphragm, and a rear lens group with positive refractive power in sequence from the object side to the image side, and the front lens group includes sequentially from the object side to the image side. The first lens L1, the second lens L2 and the third lens L3. The rear lens group 30 includes a fourth lens L4 , a fifth lens L5 , a sixth lens L6 and a seventh lens L7 in order from the object side to the image side.

As shown in Figure 1, the fringe projection lens used for three-dimensional measurement is sequentially the first lens L1, the second lens L2, the third lens L3, the diaphragm R7 (FNO), and the fourth lens L4 from the object side to the image side. , the fifth lens L5, the sixth lens L6, the seventh lens L7, the color filter GF and the imaging surface IMA. The first lens L1 is a meniscus lens with negative refractive power, and its convex surface faces the object side. The side of the first lens L1 near the object side is an aspheric surface, and the side near the image side is a spherical plastic lens; the second lens L2 is a plastic lens with a negative light power biconcave lens, and both sides are spherical glass lens; the third lens L3 is a biconvex lens with positive power, which is a glass lens with both sides are spherical; the fourth lens L4 is a biconvex lens with positive power, It is a glass lens with spherical surfaces on both sides; the fifth lens L5 is a double-concave lens with negative refractive power, which is a glass lens with spherical surfaces on both sides, and the fourth lens L4 and the fifth lens L5 are combined into a cemented lens, which is glued together. Adhesive bonding forms a lens assembly, and the convex surface of the joint surface faces the image side; the sixth lens L6 is a biconvex lens with positive refractive power, and is a plastic lens with spherical surfaces on both sides; the seventh lens L7 is a plastic lens with negative optical power. A meniscus lens with a convex surface facing the object side, the seventh lens L7 is a plastic lens with an aspheric surface near the object side and a spherical plastic lens near the image side.

Table 1 The specifications of the fringe projection lens and its optical parameters for 3D measurement.

Form 1:

Aperture F 2.8 Entrance pupil diameter 3.37mm Maximum viewing angle 72.45° maximum spatial frequency 32lp/mm Total length TTL 76.36mm resolution 0.48Mp focal length f 9.45mm Diagonal size 0.378″ maximum distortion -3% Array size 800H×600V Imaging height y 6.92mm imaging area 7.68mm×5.76mm Projection area A 40 inches Projection distance l 1m

The relevant parameters in Table 2 are the surface type, radius of curvature, center thickness, semi-transparent aperture, and refraction of each surface of the fringe projection lens used for three-dimensional measurement from the object space (OBJ) to the image space (IMA). Rate and Abel constant and other related parameters.

Form two:

Table 3 is the detailed geometric parameters of the aspheric mirrors whose surface numbers are R1 and R13.

Form three:

According to Table 1, Table 2 and Table 3, we know that the fringe projection lens used for 3D measurement has a resolution of 800×600 pixels, and the optical format d is 0.378″ (7.68mm×5.76mm). The specific optical requirements are shown in the table 2. Among these requirements, the relationship between focal length and projection distance satisfies the equation:

f=l×d/A=1000×0.378/40=9.45mm

Among them, f represents the focal length, l represents the projection distance, d represents the optical format, and A represents the projection area.

Because the projected field of view is less than 80°, the calculation of the field of view by orthogonal projection satisfies the following equation:

ω represents half of the field of view, that is, the maximum field of view FOV=72.45°. y is the imaging height. As for the largest special frequency F satisfies:

F＝1/(2×s)＝1/(2×0.016)＝31.25lp/mm,

s represents the pixel size.

According to above-mentioned embodiment data, obtain the relevant data of following Table 4.

Form four:

Wherein, EFL is the total focal length value of the fringe projection lens used for three-dimensional measurement, BFL is the distance from the outermost point on the image side of the seventh lens L7 of the fringe projection lens used for three-dimensional measurement to the imaging plane, and TTL is the distance from the image plane of the fringe projection lens used for three-dimensional measurement. The distance from the outermost point on the object side of the first lens L1 of the stripe projection lens for three-dimensional measurement to the imaging plane, FFL is the distance from the outermost point on the image side of the first lens L1 of the stripe projection lens for three-dimensional measurement to the imaging plane.

d represents the maximum aperture of the first lens facing the convex surface of the object side corresponding to the maximum viewing angle, and h represents the image height of the imaging corresponding to the maximum viewing angle.

F1, F2, F3, F5, and F6 represent the respective focal length values of the first, second, third, fifth, and sixth lenses, respectively. F Front and F Back represent the focal length values of the front lens group and the rear lens group respectively, and F glue represents the focal length value of the cemented lens.

Maximum Distortion=-3%, where Distortion is the distortion of the fringe projection lens used for three-dimensional measurement.

The first lens L1 satisfies the following conditional formula: (d/h)/FOV=0.05,

The first lens L1 satisfies the following conditional formula: Nd≥1.59, Vd≤29.45, high refractive index and high dispersion material, can fast light, and high dispersion material can effectively compensate the chromatic aberration value in the optical system, where Nd is the refractive index , Vd is Abbe's constant.

The second lens L2 adopts a high refractive index low dispersion material with a refractive index Nd≥1.75 and Abbe constant Vd≥60; the fourth lens L4 adopts a high refractive index low dispersion material with a refractive index Nd≥1.5 and Abbe constant Vd≥60; The sixth lens L6 adopts a high-refractive-index low-dispersion material with a refractive index Nd≥1.5 and an Abbe constant Vd≥60, which can effectively introduce 70°-80° field of view and light and reduce the aperture of the first lens to meet A better shadow effect is obtained in a shorter TTL value range to avoid excessive volume.

The third lens L3 satisfies the following conditional formula: Nd≥1.75, Vd≤27.5, high refractive index and high dispersion material, and the seventh lens L7 satisfies the following conditional formula: Nd≥1.50, Vd≤30, high refractive index and high dispersion material The material can quickly converge the incident light, and the high dispersion material can effectively compensate the chromatic aberration value in the optical system, where Nd is the refractive index and Vd is the Abbe constant.

The fourth lens L4 and the fifth lens L5 adopt a joint design to effectively improve the chromatic aberration of the optical system. Therefore, it is beneficial to improve the light transmission ability and image resolution ability of the entire optical system.

Please refer to Figure 2A-2C and Figure 3-Figure 4. Figure 2A is a chromatic aberration curve (also called a spherical aberration curve), which is determined by the wavelengths of commonly used red (C), green (D), and blue (F) light Indicates that the unit is mm. 2B is the astigmatism field curve diagram, which indicates the degree of image field curvature caused by astigmatism of the fringe projection lens used for three-dimensional measurement. It is represented by the commonly used green (D) light, and the unit is mm. The light aberration in the figure only exists from - In the range of 0.025 to 0.025, the imaging performance is excellent. FIG. 2C is a distortion curve diagram, which represents the magnitude of distortion under different viewing angles, in %, and the optical distortion of the fringe projection lens used for three-dimensional measurement is <-3%. Figure 3 is a graph of the MTF value, which shows the size of the lens resolution. The MTF value at all spatial frequencies is as high as 80%. The image point brightness of the lens imaging, where the field angle is zero degree is the highest image point brightness of the fringe projection lens imaging for three-dimensional measurement, and the maximum field angle is 72.45°.

Referring to Fig. 5, the difference between the stripe projection lens for three-dimensional measurement provided by the second embodiment of the present invention and the stripe projection lens for three-dimensional measurement provided by the first embodiment is that the second embodiment provides The total focal length of the stripe projection lens used for 3D measurement is 7.6mm, the TTL value is 79.92mm, and the maximum field of view FOV value is 72.56°. For specific parameters, please refer to Table 5, Table 6 and Table 7.

Table 5 is the specifications and optical parameters of the fringe projection lens for three-dimensional measurement provided by the second embodiment of the present invention.

Form five

ω=36.28°, ω represents half of the field of view, and the maximum field of view FOV=2ω=72.56°.

The relevant parameters in Table 6 are the fringe projection lens used for three-dimensional measurement from the object space (OBJ) to the image space (IMA), the surface type of each surface of all lenses, the radius of curvature, the center thickness, the semi-transparent aperture, Refractive index and Abel constant and other related parameters.

Form six:

According to above-mentioned embodiment data, obtain the relevant data of following table seven.

Form seven:

Basic parameters EFL BFL TTL FFL d h Value (mm) 7.6 3 79.92 12.28 23.48 5.58 Basic parameters F1 F2 F3 F glue F6 F7 Value (mm) -24.925 -20.67 30.72 85.11 19.98 67.14 Basic parameters F front After F Value (mm) -33.52 18.06

The focal length of the stripe projection lens used for three-dimensional measurement satisfies 8.08≤TTL/EFL≤10.52, wherein TTL is the distance from the outermost point on the object side of the first lens of the stripe projection lens used for three-dimensional measurement to the imaging plane, and EFL is the distance Describe the total focal length value of the fringe projection lens used for three-dimensional measurement; 5.87≤TTL/FFL≤6.51, where FFL is the distance from the outermost point on the image side of the first lens to the imaging plane; 76.36mm≤TTL≤79.92mm, TTL is The distance from the outermost point on the object side of the first lens of the stripe projection lens for three-dimensional measurement to the imaging plane; 0.32≤BFL/EFL≤0.40, where BFL is the seventh lens image of the stripe projection lens for three-dimensional measurement The distance from the outermost point on the square side to the imaging surface; 18.06mm≤F rear ≤44.80mm, where F rear represents the focal length of the rear lens group; -1.11≤F rear/F front≤-0.54, where F front represents the front lens The focal length value of the group; 2.96≤F glue/F rear ≤4.71, where F glue represents the focal length value of the cemented lens.

Please refer to Fig. 6A-6C and Fig. 7, 8, the optical performance curve diagram of the second embodiment, the figure in its 6A is a chromatic aberration curve diagram (also called spherical aberration curve diagram), by commonly used red (C), green (D ), blue (F) three-color light wavelength to represent, the unit is mm. 6B is an astigmatism field curve diagram, indicating the image field curvature degree of imaging caused by astigmatism of the fringe projection lens used for three-dimensional measurement, represented by the commonly used green (D) light, and the unit is mm. FIG. 6C is a distortion curve diagram, showing the magnitude of distortion under different viewing angles, in %, and the distortion in the figure is <-6%. Figure 7 is a graph of the MTF value, which shows the size of the lens resolution. In the graph, the MTF value of all spatial frequencies is as high as 80%, and the ray aberration only exists in the range from -0.025 to 0.025, and the imaging quality is even better. . Fig. 8 is the energy diagram enclosed by the geometric light spots at different viewing angles, which represents the image point brightness of the lens imaging, where the viewing angle is zero degrees, which means that the image point brightness of the fringe projection lens imaging used for three-dimensional measurement is the highest, the maximum The field of view is 72.56°.

The utility model realizes the ultra-short focal length compact structure of the stripe projection lens used for three-dimensional measurement by rationally controlling the focal length distribution among the lenses, the TTL is kept minimum, and the viewing angle and projection area are maximized at the same time, at a distance of 1 meter A projected area of at least 40 inches allows a fringe pattern to cover a large surface as quickly as possible, enabling the system to capture sufficient object information and achieve high-precision fringe patterns. Especially suitable for three-dimensional measurement of structured light. The side of the first lens close to the object side is an aspheric surface, and the side of the seventh lens close to the image side is an aspheric surface. The fringe projection lens for three-dimensional measurement can achieve a better aberration correction effect with fewer aspheric lenses and save costs. .

At the same time, reasonable control of the focal power distribution ratio of the front and rear lens groups, on the one hand, helps to control the incident light height of the front lens group, so as to reduce the high-level aberration of the optical system and the outer diameter of the lens; on the other hand, it can reduce the The exit angle of the chief ray passing through the rear lens group improves the relative brightness of the optical system.

Further, the fringe projection lens for three-dimensional measurement provided by the utility model can realize the fringe projection lens for three-dimensional measurement with low cost, light weight, small distortion, small size, high light-passing performance and high-definition requirements. More plastic aspheric lenses are used to keep the weight and cost low.

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. Any modification, equivalent replacement and improvement within the principles of the utility model shall include the utility model.

Claims (10)

1. A fringe projection lens for three-dimensional measurement, characterized in that: from the object space to the image side, it comprises successively a front lens group with negative refractive power, a diaphragm and a rear lens group with positive refractive power; The front lens group sequentially includes a first lens, a second lens and a third lens from the object side to the image side; The first lens is a meniscus lens with negative power, and the convex surface faces the object side; the second lens is a biconcave lens with negative power; the third lens is a biconvex lens with positive power ; The rear lens group includes a fourth lens, a fifth lens, a sixth lens and a seventh lens in turn from the object side to the image side; The fourth lens is a biconvex lens with positive power; the fifth lens is a biconcave lens with negative power; the sixth lens is a biconvex lens with positive power; the seventh lens is a biconvex lens with Negative power meniscus lens with convex surface facing the object; The fourth lens and the fifth lens are combined into a cemented lens; The side of the first lens close to the object side is aspheric, and the side of the seventh lens close to the image side is aspheric. 2. The stripe projection lens for three-dimensional measurement according to claim 1, characterized in that: the stripe projection lens for three-dimensional measurement satisfies the conditional formula 76.36mm≤TTL≤79.92mm, and TTL is the The measured distance from the outermost point on the object side of the first lens of the fringe projection lens to the imaging plane. 3. The striped projection lens for three-dimensional measurement as claimed in claim 1, characterized in that: the conditional formula 8.08≤TTL/EFL≤10.52 is satisfied, wherein TTL is the first lens object of the striped projection lens for three-dimensional measurement The distance from the outermost point on the square side to the imaging plane, and EFL is the total focal length of the fringe projection lens used for three-dimensional measurement. 4. The striped projection lens for three-dimensional measurement as claimed in claim 1, characterized in that: the conditional formula 5.87≤TTL/FFL≤6.51 is satisfied, wherein TTL is the first lens of the striped projection lens for three-dimensional measurement The distance from the outermost point on the object side to the imaging plane, FFL is the distance from the outermost point on the image side of the first lens to the imaging plane. 5. The fringe projection lens for three-dimensional measurement according to claim 1, characterized in that: the conditional formula 0.32≤BFL/EFL≤0.40 is satisfied, wherein FFL is the distance from the outermost point on the image side of the first lens to the imaging plane , BFL is the distance from the outermost point on the image side of the seventh lens of the fringe projection lens used for three-dimensional measurement to the imaging plane. 6. The fringe projection lens for three-dimensional measurement according to claim 1, characterized in that: the conditional formula 18.06mm≤Fhou ≤44.80mm is satisfied, wherein Fhou represents the focal length value of the rear lens group. 7. The fringe projection lens for three-dimensional measurement according to claim 6, characterized in that: the conditional formula -1.11≤F rear/F front≤-0.54 is satisfied, wherein F front represents the focal length value of the front lens group. 8. The fringe projection lens for three-dimensional measurement according to claim 1, characterized in that: the conditional formula 72.45°≤FOV≤72.56° is satisfied, wherein FOV represents the maximum field of view angle of the wide-angle lens. 9. The striped projection lens for three-dimensional measurement according to claim 8, characterized in that: the first lens satisfies the conditional formula 0.05≤(d/h)/FOV≤0.06, wherein d represents the maximum angle of view corresponding to The maximum light aperture of the convex surface of the first lens facing the object side, and h represents the imaging image height corresponding to the maximum viewing angle. 10. The fringe projection lens for three-dimensional measurement as claimed in claim 1, characterized in that: the conditional formula 2.96≤F glue/F rear≤4.71 is satisfied, wherein F glue represents the focal length value of the cemented lens, and F front represents the front lens The focal length value of the group.