CN115469433A - Spectrum confocal displacement sensor dispersion lens - Google Patents

Abstract

The invention relates to a dispersive lens of a spectrum confocal displacement sensor, which is of an inverse teledistance structure, wherein a diaphragm is arranged on a first surface of a front group lens facing to an image space; the front group lens comprises a first lens which is a biconcave lens, and the focal length of the first lens is negative; the rear group lens comprises a second meniscus convex lens, a third biconvex lens, a fourth meniscus convex lens and a fifth lens which are sequentially arranged from the image space to the object space, and the focal length of the rear group lens is positive; the first lens and the fourth lens are made of the same glass material, and the second lens, the third lens and the fifth lens are made of the same glass material. The chromatic dispersion lens structure provided by the invention can correct the spherical aberration effectively and generate the nearly linear axial chromatic dispersion, and can obtain a larger image space numerical aperture; the negative lens is added at the image space to form a reverse distance structure, so that the longer integral length of the dispersion lens caused by the smaller numerical aperture at the image space is reduced; the dispersion lens only adopts two glass materials, so that the processing complexity and the production cost are reduced.

Description

Spectrum confocal displacement sensor dispersion lens

Technical Field

The invention belongs to the technical field of optical measurement, and particularly relates to a dispersion lens of a spectral confocal displacement sensor.

Background

The spectrum confocal displacement sensor is more and more emphasized in the field of precision detection, and compared with other detection methods, the spectrum confocal displacement sensor has the following characteristics: firstly, the method belongs to non-contact measurement, and does not damage a measured object during detection; secondly, the corresponding relation between the wavelength and the height or distance is established, and the height information is obtained by detecting the wavelength, so that the method can be used for detecting the three-dimensional shape information of the object; thirdly, the height and the distance can be obtained without axial scanning, and the detection speed is high.

The dispersive lens is an important component in the spectrum confocal displacement sensor, the axial dispersion range of the dispersive lens determines the measurement range of the sensor, and the numerical aperture determines the maximum measurement inclination angle and the transverse resolution of the sensor. According to the Schottky formula of the refractive index of glass, a single lens cannot generate linear axial dispersion, and in order to obtain a larger dispersion range and numerical aperture, the conventional spectral confocal dispersion lens adopts a larger number of lenses and a larger glass type (see the literature: design of a spectral confocal displacement sensor linear dispersion objective lens [ J ]. Chinese laser, 2019,46 (07): 219-225.). The chinese invention patent CN114136215A discloses a large-angle spectrum confocal measurement lens, which utilizes 7 lenses to design a dispersion lens, adopts various glass materials, and is difficult to assemble due to excessive lens quantity and glass types, and meanwhile, the production cost of the product is high, which is not favorable for popularization and application of the spectrum confocal displacement sensor.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the high-performance spectrum confocal displacement sensor dispersion lens which is small in image-side numerical aperture, large in object-side numerical aperture, compact in volume and long-axis dispersion.

The technical scheme for realizing the aim of the invention is that the spectral confocal displacement sensor dispersion lens is an inverse teledistance structure and comprises a diaphragm, a front group lens and a rear group lens which are sequentially arranged into the diaphragm, the front group lens and the rear group lens from an image space to an object space;

the diaphragm is arranged on the first surface of the front group of lenses facing the image space;

the front group lens comprises a first lens which is a biconcave lens, and the focal length of the front group lens is negative;

the rear group lens comprises a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from an image space to an object space, and the focal length of the rear group lens is positive; focal lengths of the second lens, the third lens, the fourth lens and the fifth lens are all positive; the second lens is a meniscus convex lens which is convex to the object space, the third lens is a double convex lens, and the fourth lens and the fifth lens are meniscus convex lenses which are convex to the image space;

the focal length of the dispersion lens is f, the focal length of the first lens is f1, and f1 meets the condition that-2 f is less than f1 < -1.9f; the focal length of the second lens is f2, and f2 satisfies 5f < f2 < 6f; the focal length of the third lens is f3, and f3 satisfies 4f < f3 < 5f; the focal length of the fourth lens is f4, and f4 satisfies 6f < f4 < 7f; the focal length of the fifth lens is f5, and f5 satisfies 5f < f5 < 6f;

the refractive index ND1 of the first lens meets ND1 > 1.5, and the Abbe number VD1 meets VD1 > 60; the refractive index ND2 of the second lens meets ND2 > 1.8, and the Abbe number VD2 meets VD2 > 20; the refractive index ND3 of the third lens meets ND3 > 1.8, and the Abbe number VD3 meets VD3 > 20; the refractive index ND4 of the fourth lens meets ND4 > 1.5, and the Abbe number VD4 meets VD4 > 60; the refractive index ND5 of the fifth lens meets ND5 > 1.8, and the Abbe number VD5 meets VD5 > 60.

The optimized technical scheme is that ND1 is more than 1.5 and less than 1.6, VD1 is more than 60 and less than 70, ND2 is more than 1.8 and less than 1.9, VD2 is more than 20 and less than 30, ND3 is more than 1.8 and less than 1.9, VD3 is more than 20 and less than 30, ND4 is more than 1.5 and less than 1.6, VD4 is more than 60 and less than 70, ND5 is more than 1.8 and less than 1.9, and VD5 is more than 20 and less than 30.

According to the preferable technical scheme, the first lens and the fourth lens are made of the same glass material, the second lens, the third lens and the fifth lens are made of the same glass material, and the dispersion lens with better performance is obtained by only adopting two kinds of glass, so that the cost is effectively reduced, the dispersion range can reach 4mm or more, and the numerical aperture is larger than or equal to 0.5. The invention adopts two glass materials to generate near-linear axial dispersion, in order to reduce spherical aberration, two pieces of glass are divided into four pieces by using a method of bisection focal power, and a negative lens is added on an image space to form a reverse distance structure, so that the longer integral length of the dispersion lens caused by the smaller numerical aperture of the image space is reduced.

The dispersion lens provided by the invention adopts a reverse distance structure, the front group lens is a single lens, only one lens is adopted, the focal length is negative, the main functions are to increase the divergence angle so as to reduce the length of the whole system, simultaneously reduce the field angle of the rear group lens and reduce the incident height and deflection angle burden of light rays at the rear group. The rear group lens consists of four lenses, and the focal length is positive; the front two lenses consist of two meniscus lenses or a meniscus lens and a biconvex lens, and the curvature of the meniscus lens is bent to the image direction; the two rear lenses are two meniscus lenses, and the curvature is bent to the object space; the structure can correct spherical aberration and generate nearly linear axial dispersion, and can obtain larger image-side numerical aperture.

The diaphragm is arranged on the front surface of the first lens and does not change along with the difference of the wavelength.

Compared with the prior art, the invention has the beneficial effects that:

1. the dispersive lens adopts a reverse long-distance structure, the front group lens mainly has the functions of increasing a divergence angle and reducing a field angle of the rear group lens so as to reduce the incident height and deflection angle burden of light at the rear group, and the front group lens mainly has the functions of correcting spherical aberration and generating near-linear axial dispersion and can obtain larger object numerical aperture. The aperture is provided on a surface of the first lens facing the image side, and the size of the aperture does not change depending on the wavelength.

2. The dispersion lens provided by the invention can only adopt two glass materials, the first lens and the fourth lens are made of the same glass material, and the second lens, the third lens and the fifth lens are made of the same glass material, so that the processing complexity and the production cost are reduced.

Drawings

Fig. 1 is a schematic structural diagram of a dispersive lens of a spectral confocal displacement sensor according to an embodiment of the present invention;

in the figure, 1, a first lens; 2. a second lens; 3. a third lens; 4. a fourth lens; 5. a fifth lens; 6. and (4) a diaphragm.

Fig. 2 is a dot-column diagram of a dispersive lens of a spectral confocal displacement sensor according to an embodiment of the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining the drawings and the embodiment.

Example 1

Referring to fig. 1, a schematic structural diagram of a dispersion lens provided in this embodiment is shown; from the image space to the object space, the system sequentially comprises: a diaphragm 6, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5.

The first lens 1 is a biconcave lens, the second lens 2 is a meniscus convex lens, convex to the object side, the third lens 3 is a biconvex lens, and the fourth lens 4 and the fifth lens 5 are meniscus convex lenses, convex to the image side.

The focal length of the dispersion lens is f, the focal length of the first lens 1 is f1, and f1 meets the condition that-2 f is less than f1 < -1.9f; the focal length of the second lens 2 is f2, and f2 satisfies 5f < f2 < 6f; the focal length of the third lens 3 is f3, and f3 satisfies 4f < f3 < 5f; the focal length of the fourth lens 4 is f4, and f4 satisfies 6f < f4 < 7f; the focal length of the fifth lens 5 is f5, and f5 satisfies 5f < f5 < 6f.

The refractive index ND1 of the first lens 1 satisfies ND1 > 1.5; the refractive index ND2 of the second lens 2 satisfies ND2 > 1.8; a refractive index ND3 of the third lens 3 satisfies ND3 > 1.8; a refractive index ND4 of the fourth lens 4 satisfies ND4 > 1.5; the refractive index ND5 of the fifth lens 5 satisfies ND5 > 1.8.

The abbe number VD1 of the first lens 1 satisfies VD1 > 60; the abbe number VD2 of the second lens 2 satisfies VD2 > 20; the abbe number VD3 of the third lens 3 satisfies VD3 > 20; the abbe number VD4 of the fourth lens 4 satisfies VD4 > 60; the abbe number VD5 of the fifth lens 5 satisfies VD5 > 60.

In the present embodiment, the parameters of each lens are as follows:

the focal length f1 of the first lens 1 is-34.27mm, ND1 is 1.5168, VD1 is 64.1987;

the focal length f2 of the second lens 2 is 97.14mm, ND2 is 1.8466, and VD2 is 23.7873;

the focal length f3 of the third lens 3 is 83.40mm, nd3 is 1.8466, vd3 is 23.7873;

the focal length f4 of the fourth lens 4 is 121.15mm, the nd4 is 1.5168, and the vd4 is 64.1987;

the fifth lens 5 has a focal length f5 of 97.46mm, ND5 of 1.8466 and VD5 of 23.7873.

According to the dispersion lens provided by the embodiment, the axial dispersion between the working wavelengths of 450-800 nm is 4.17mm, the object numerical aperture is 0.5, the overall length of the lens is 162mm, and the maximum aperture is 46mm.

Referring to fig. 2, a dot diagram of the dispersion lens provided in this embodiment shows that: under the wavelength of 450nm, 500nm, 600nm, 700nm and 800nm, the radius of the light spot is basically near the Airy spots, the spherical aberration is corrected, and the imaging quality is better.

Claims (2)

1. The utility model provides a confocal displacement sensor dispersion lens of spectrum which characterized in that: the lens is a reverse distance structure and comprises a diaphragm, a front group lens and a rear group lens which are sequentially arranged from an image space to an object space;

the diaphragm is arranged on the first surface of the front group of lenses facing the image space;

the front group of lenses comprises a first lens (1) which is a biconcave lens, and the focal length of the front group of lenses is negative;

the rear group lens comprises a second lens (2), a third lens (3), a fourth lens (4) and a fifth lens (5) which are sequentially arranged from an image space to an object space, and the focal length of the rear group lens is positive; focal lengths of the second lens, the third lens, the fourth lens and the fifth lens are all positive; the second lens is a meniscus convex lens which is convex to the object space, the third lens is a double convex lens, and the fourth lens and the fifth lens are meniscus convex lenses which are convex to the image space;

the focal length of the dispersion lens is f, the focal length of the first lens is f1, and f1 meets the condition that-2 f is less than f1 < -1.9f; the focal length of the second lens is f2, and f2 satisfies 5f < f2 < 6f; the focal length of the third lens is f3, and f3 satisfies 4f < f3 < 5f; the focal length of the fourth lens is f4, and f4 satisfies 6f < f4 < 7f; the focal length of the fifth lens is f5, and f5 satisfies 5f < f5 < 6f;

the refractive index ND1 of the first lens meets ND1 > 1.5, and the Abbe number VD1 meets VD1 > 60; the refractive index ND2 of the second lens meets ND2 > 1.8, and the Abbe number VD2 meets VD2 > 20; the refractive index ND3 of the third lens meets ND3 > 1.8, and the Abbe number VD3 meets VD3 > 20; the refractive index ND4 of the fourth lens meets ND4 > 1.5, and the Abbe number VD4 meets VD4 > 60; the refractive index ND5 of the fifth lens meets ND5 > 1.8, and the Abbe number VD5 meets VD5 > 60.

2. The spectral confocal displacement sensor dispersive lens according to claim 1, characterized in that: the first lens and the fourth lens are made of the same glass material, and the second lens, the third lens and the fifth lens are made of the same glass material.

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