CN111522135B

CN111522135B - Large-aperture catadioptric lens suitable for triangulation

Info

Publication number: CN111522135B
Application number: CN202010205079.7A
Authority: CN
Inventors: 王皓
Original assignee: Beijing Guotai Blue Shield Technology Co ltd
Current assignee: Beijing Guotai Blue Shield Technology Co ltd
Priority date: 2020-03-20
Filing date: 2020-03-20
Publication date: 2022-02-11
Anticipated expiration: 2040-03-20
Also published as: CN111522135A

Abstract

The invention provides a large-aperture catadioptric lens suitable for triangulation, which comprises: the spherical lens comprises a first square aspheric lens, a second square spherical reflector, a third circular spherical lens, a fourth circular spherical lens, a fifth circular spherical lens and a sixth lens; wherein, on the light path, the first square aspheric lens is arranged in front of the second square spherical reflector so as to be reflected by the second square spherical reflector through the first square aspheric lens; and the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens are arranged in sequence, so that the light reflected by the second square spherical reflector passes through the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens in sequence.

Description

Large-aperture catadioptric lens suitable for triangulation

Technical Field

The invention relates to the field of dynamic volume measurement, in particular to a large-aperture catadioptric lens suitable for triangulation.

Background

In dynamic volume measuring equipment based on a Position Sensitive Detector (PSD) and a triangulation method, emitted laser is irradiated on the surface of a measured object through an emitting prism, diffuse emission light on the surface of the measured object is reflected by a receiving prism through the receiving prism, and then is converged on a PSD surface through a receiving objective lens. Because the PSD has a certain dark current noise, the PSD driving circuit and the signal collecting circuit inevitably have a certain noise, and the measurement accuracy of the whole device is influenced and restricted by the signal-to-noise ratio of the effective signal of the system, the strength of the effective signal needs to be improved as much as possible.

Increasing the amount of incoming light to the receiving objective can significantly increase the effective signal strength of the system. From the optical path of the apparatus, it is known that the amount of light entering the receiving objective lens is affected by both the size of the working surface of the receiving objective lens and the size of the aperture of the receiving objective lens. Because the working surface of the receiving prism is rectangular, the caliber of the existing common objective lens is generally circular, and when the caliber is smaller than the long edge of the prism, a certain light inlet quantity loss can be caused; when the aperture of the objective lens is larger than the long edge of the prism, the relative aperture of the objective lens is too large, the aberration of the system is increased, the number of lenses in the optical system is too large, the transmittance is reduced, the expected effect is difficult to achieve, the total length of the system is obviously increased, and the volume and the weight of the objective lens are too large.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a large-aperture catadioptric lens suitable for triangulation aiming at the defects in the prior art, solve the problem that the combination of a receiving prism and an objective lens of dynamic volume measurement equipment based on PSD and triangulation is insufficient in light inflow, and simultaneously reduce the volume and the weight of the objective lens as much as possible.

According to the present invention, there is provided a large aperture catadioptric lens suitable for triangulation comprising: the spherical lens comprises a first square aspheric lens, a second square spherical reflector, a third circular spherical lens, a fourth circular spherical lens, a fifth circular spherical lens and a sixth lens; wherein, on the light path, the first square aspheric lens is arranged in front of the second square spherical reflector so as to be reflected by the second square spherical reflector through the first square aspheric lens; and the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens are arranged in sequence, so that the light reflected by the second square spherical reflector passes through the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens in sequence.

Preferably, the sixth lens is a surface glass of the PSD.

Preferably, a large aperture catadioptric lens suitable for triangulation is used in a dynamic volumetric measurement device based on PSD and triangulation.

Preferably, the lens focal length of the large-aperture catadioptric lens suitable for triangulation is 75 mm.

Preferably, the aperture stop of the large-aperture catadioptric lens suitable for triangulation is a first square aspheric lens.

Preferably, the size of the first square aspherical lens is preferably 30mm × 70 mm.

Preferably, the surfaces of the first square aspheric lens, the third round spherical lens, the fourth round spherical lens and the fifth round spherical lens are plated with antireflection films with transmittance not less than 99%.

Preferably, the surface of the second square spherical reflector is plated with a high reflection film with the reflectivity of more than or equal to 99%.

Preferably, the first square aspheric lens is coated with an anti-reflection film and an anti-oil-stain protective film.

Preferably, the fifth round spherical lens is coated with a narrow-band filter film.

The invention solves the problem that the dynamic volume measuring equipment based on PSD and triangulation has insufficient light-in quantity of the combination of the receiving prism and the objective lens, and simultaneously reduces the volume and the weight of the objective lens as much as possible.

Drawings

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

fig. 1 schematically shows a structural diagram of a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the present invention.

Fig. 2 schematically shows a graph of the optical transfer function (MTF) of a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the invention.

Fig. 3 schematically shows a circumscribed circle energy diagram of a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the invention.

It is to be noted, however, that the appended drawings illustrate rather than limit the invention. It is noted that the drawings representing structures may not be drawn to scale. Also, in the drawings, the same or similar elements are denoted by the same or similar reference numerals.

Detailed Description

In order that the present disclosure may be more clearly and readily understood, reference will now be made in detail to the present disclosure as illustrated in the accompanying drawings.

As shown in fig. 1, a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the present invention includes: a first square aspheric lens 1, a second square spherical reflector 2, a third round spherical lens 3, a fourth round spherical lens 4, a fifth round spherical lens 5 and a sixth lens 6; wherein, on the light path, the first square aspheric lens 1 is arranged in front of the second square spherical reflector 2, so that the first square aspheric lens 1 is reflected by the second square spherical reflector 2; and the third round spherical lens 3, the fourth round spherical lens 4, the fifth round spherical lens 5 and the sixth lens 6 are sequentially arranged, so that the light reflected by the second square spherical reflector 2 sequentially passes through the third round spherical lens 3, the fourth round spherical lens 4, the fifth round spherical lens 5 and the sixth lens 6.

In a preferred example, the sixth lens 6 is a surface glass of the PSD.

A large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the present invention can be advantageously used in dynamic volumetric measurement devices based on PSD and triangulation.

In a preferred example, the large aperture catadioptric lens is designed to have a focal length of 75mm, the aperture stop is a first square aspheric lens, and the first square aspheric lens preferably has a size of 30mm × 70 mm.

In a preferred example, the surfaces of the first square aspherical lens 1, the third circular spherical lens 3, the fourth circular spherical lens 4 and the fifth circular spherical lens 5 are uniformly plated with antireflection films having a transmittance of not less than 99%.

In addition, in a preferred example, the surface of the second square spherical reflector is plated with a high reflection film with the reflectivity of 99% or more so as to reduce the light energy loss of the laser.

In a preferred example, the first square aspheric lens is coated with an anti-reflection film and an anti-oil stain protective film to prevent lubricating grease and dust in the system from influencing the optical system.

In a preferred example, the fifth round spherical lens is coated with a narrow-band filter film to eliminate the influence of ambient light.

Fig. 2 schematically shows a graph of the optical transfer function (MTF) of a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the invention. The Fourier analysis method is used for describing the conversion relation from object plane light distribution to image plane light distribution, quantitatively reflecting the comprehensive effect caused by diffraction and aberration of the lens, and is an evaluation index which is recognized at present and can fully reflect the actual imaging quality of the system. The abscissa of the graph is the spatial frequency in units of line pairs per millimeter (lp/mm), and the ordinate is the transfer function of the lens, and the graph characterizes the image quality transfer condition of the lens under different spatial frequencies. The lines in fig. 2 represent the optical transfer functions at different fields of view, respectively, and corresponding spatial frequencies.

Fig. 3 schematically shows a circumscribed circle energy diagram of a large aperture catadioptric lens suitable for triangulation according to a preferred embodiment of the invention. The energy of the enclosing circle is represented by the ratio of the energy falling into the circle and the total energy, wherein the energy of the enclosing circle is centered on the chief ray on the image plane, and the distance from the point is taken as the radius to form the circle. The abscissa of the graph is the radius of the enclosing circle in microns and the ordinate is the ratio of the energy falling into the enclosing circle to the total energy.

As can be seen from fig. 2, the spatial frequency corresponding to the imaging quality of the optical system which achieves MTF of 0.6 is greater than 50 lp/mm. As can be seen from fig. 3, the light of all fields can be concentrated in a circle of diameter 40 μm around its principal ray.

Therefore, the invention solves the problem that the combined light-entering quantity of the receiving prism and the objective lens of the dynamic volume measuring device based on PSD and triangulation is insufficient, and simultaneously reduces the volume and the weight of the objective lens as much as possible.

It should be noted that the terms "first", "second", "third", and the like in the description are used for distinguishing various components, elements, steps, and the like in the description, and are not used for indicating a logical relationship or a sequential relationship between the various components, elements, steps, and the like, unless otherwise specified.

It is to be understood that while the present invention has been described in conjunction with the preferred embodiments thereof, it is not intended to limit the invention to those embodiments. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A large-aperture catadioptric lens suitable for triangulation is characterized by comprising a first square aspheric lens, a second square spherical reflector, a third round spherical lens, a fourth round spherical lens, a fifth round spherical lens and a sixth lens, wherein the sixth lens is surface glass of a PSD (phase-sensitive detector); wherein, on the light path, the first square aspheric lens is arranged in front of the second square spherical reflector, so that the light transmitted through the first square aspheric lens is reflected by the second square spherical reflector; and the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens are arranged in sequence, so that the light reflected by the second square spherical reflector passes through the third round spherical lens, the fourth round spherical lens, the fifth round spherical lens and the sixth lens in sequence.

2. A large aperture catadioptric lens for triangulation as claimed in claim 1, characterized by the fact that it is used in dynamic volumetric measurement devices based on PSD and triangulation.

3. A large aperture catadioptric lens for triangulation as claimed in claim 1, where the lens focal length of the large aperture catadioptric lens for triangulation is 75 mm.

4. The catadioptric large aperture lens for triangulation as claimed in claim 1, wherein the aperture stop of the catadioptric large aperture lens for triangulation is a first square aspheric lens.

5. A large aperture catadioptric lens suitable for triangulation as claimed in claim 1 where the first square aspheric lens has dimensions of 30mm x 70 mm.

6. The catadioptric lens with a large aperture suitable for triangulation of claim 1, wherein the first square aspheric lens, the third circular spherical lens, the fourth circular spherical lens and the fifth circular spherical lens are coated with an antireflection film with transmittance not less than 99%.

7. The catadioptric lens with large aperture suitable for triangulation of claim 1, wherein the second square spherical mirror is coated with a high reflective film with a reflectivity of 99% or more on the surface.

8. The catadioptric lens with large aperture suitable for triangulation of claim 1, wherein the first aspheric square lens is coated with an anti-reflective coating plus an anti-smudge protective coating.

9. The catadioptric large aperture lens for triangulation of claim 1 wherein the fifth circular spherical lens is coated with a narrow band filter.