Grouping type spectrum confocal dispersion objective lens

Abstract

The invention discloses a grouped spectrum confocal dispersion objective lens, which comprises a light source incident end, a light source receiving end, a dispersion objective lens front lens group, an aperture diaphragm and a dispersion objective lens rear lens group, wherein the light source incident end and the light source receiving end are ports of the multimode optical fiber; the dispersion objective lens front lens group and the dispersion objective lens rear lens group respectively comprise at least one lens. The position of the aperture diaphragm between the dispersion objective lens front lens group and the dispersion objective lens rear lens group is adjustable, and the center of the aperture diaphragm is located on the optical axis; the rear lens group of the dispersion objective lens bears most dispersion requirements, and transmission light between the front lens group and the rear lens group is approximately collimated light. Performance parameters such as the measurement range and the light spot size of the dispersion objective lens can be independently adjusted to meet different measurement requirements, the length of the spectrum confocal dispersion objective lens can be flexibly adjusted, the assembling freedom degree is increased, and the spectrum confocal dispersion objective lens is made to be suitable for more complex measurement scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of optical objective lenses, and in particular relates to a grouped spectral confocal dispersion objective lens. Background Art

[0002] Spectral confocal sensor is an important non-contact photoelectric displacement sensor. Its highest accuracy can reach nanometer level by using color coding and confocal technology. Spectral confocal sensor can encode the three-dimensional information of the measurement surface into the spectral characteristics of the sample reflected light, and has the advantages of high measurement accuracy, high resolution, fast response speed, excellent stability, and large allowable tilt angle. It is very suitable for dimensional measurement or detection of precision parts.

[0003] The spectral confocal measurement system is mainly composed of a light source, a dispersive objective lens, and a detector. As the core component of the spectral confocal sensor, the optical performance of the dispersive objective lens directly affects the measurement performance of the sensor. Most of the currently available dispersive objective lenses use an integral structure to achieve the dispersion requirements. The lens groups are not interchangeable, and the parameters such as the length of the dispersive objective lens are fixed. Adjusting the measurement performance of the dispersive objective lens requires redesigning the optical system. Summary of the invention

[0004] In view of the shortcomings of the existing spectral confocal dispersive objective lens, the present invention provides a grouped spectral confocal dispersive objective lens, which can individually adjust the performance parameters of the dispersive objective lens, such as the measurement range and spot size, to meet different measurement requirements, and can flexibly adjust the length of the spectral confocal dispersive objective lens to increase the assembly freedom.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme:

[0006] The grouped spectral confocal dispersion objective lens of the present invention is characterized in that it comprises, in sequence: a light source incident end and a receiving end, a dispersion objective lens front lens group, an aperture stop, and a dispersion objective lens rear lens group;

[0007] The light source incident end and receiving end are ports of multimode optical fiber;

[0008] The front lens group of the dispersion objective lens has positive optical power and includes at least one lens;

[0009] The position of the aperture stop between the front lens group of the dispersion objective lens and the rear lens group of the dispersion objective lens is adjustable, and the center of the aperture stop is located on the optical axis;

[0010] The optical power of the rear lens group of the dispersion objective lens is positive and includes at least one lens;

[0011] The wide-spectrum white light emitted from the incident end and the receiving end of the light source passes through the front lens group of the dispersive objective lens, the aperture stop, and the rear lens group of the dispersive objective lens in sequence to form dispersed light with focal points of different wavelengths spread along the optical axis. The dispersed light is irradiated to the object to be measured and forms reflected light after being reflected by the object to be measured. The reflected light passes through the rear lens group of the dispersive objective lens, the aperture stop, and the front lens group of the dispersive objective lens in sequence to be received by the incident end and the receiving end of the light source.

[0012] The grouped spectral confocal dispersive objective lens of the present invention is also characterized in that the front lens group of the dispersive objective lens satisfies the constraint condition shown in formula (1):

[0013] (1)

[0014] In formula (1), i is the serial number of the lens in the front lens group of the dispersion objective lens; N is the total number of lenses in the front lens group of the dispersion objective lens, and satisfies N>0; D i is the effective light diameter of the i-th lens in the front lens group of the dispersion objective; is the focal length of the i-th lens in the front lens group of the dispersion objective; v i is the Abbe number of the i-th lens in the front lens group of the dispersive objective lens; j is the serial number of the lens in the grouped spectral confocal dispersive objective lens; M is the total number of lenses in the grouped spectral confocal dispersive objective lens, and M>N is satisfied; is the effective light diameter of the jth lens in the grouped spectral confocal dispersion objective; is the focal power of the jth lens in the grouped spectral confocal dispersion objective; is the Abbe number of the jth lens in the grouped spectral confocal dispersion objective; represents the absolute value; α is the set threshold and satisfies α∈[0,0.01].

[0015] Furthermore, the transmitted light between the front lens group of the dispersive objective lens and the rear lens group of the dispersive objective lens satisfies formula (2):

[0016] (2)

[0017] In formula (2), λ k is any wavelength within the working band of the grouped spectral confocal dispersion objective lens, and λ k ∈[λ s ,λ t ],λ s is the short-wavelength of the grouped spectral confocal dispersion objective in the working band, λ t is the long-wavelength of the grouped spectral confocal dispersion objective within the working band; The wavelength of light emitted from the front lens group of the dispersion objective is λ k The angle between the light ray and the optical axis; Indicates absolute value; Represents the upper limit of the absolute value of the angle between the light ray and the optical axis, in milliradian order.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention divides the lens part of the spectral confocal dispersive objective lens into a front lens group and a rear lens group, most of the dispersion is borne by the rear lens group, and the transmitted light between the two lens groups is approximately collimated light, so replacing the rear lens group can change the measurement range, and replacing the front lens group can change the spot size, that is, by replacing different lens groups, different measurement requirements can be met, thereby improving the practicality of the lens group and the scalability of the system; in addition, the influence of the distance between the two lens groups on the overall performance of the dispersive objective lens is reduced, so the interval length of the two lens groups can be flexibly adjusted, thereby enhancing the degree of freedom of assembly of the spectral confocal dispersive objective lens, and making the spectral confocal dispersive objective lens suitable for more complex measurement scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0021] Figure 2 is a wavelength-displacement curve diagram of the first embodiment of the present invention;

[0022] Figure 3 This is a multi-wavelength focused spot diagram of the first embodiment of the present invention;

[0023] Figure 4 It is an axial aberration curve diagram of the first embodiment of the present invention at a wavelength of 580nm.

[0024] Labels in the figure: 1-light source incident end and receiving end; 21-dispersive objective front lens group; 22-aperture stop; 23-dispersive objective rear lens group; 3-measured object; L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-fifth lens; L6-sixth lens; L7-seventh lens; L8-eighth lens; s1~s13 are 13 lens surfaces respectively. DETAILED DESCRIPTION

[0025] In this embodiment, a grouped spectral confocal dispersion objective lens comprises, in sequence: a light source incident end and a receiving end 1, a dispersion objective lens front lens group 21, an aperture stop 22, and a dispersion objective lens rear lens group 23;

[0026] Among them, the light source incident end and the receiving end 1 are ports of multimode optical fiber;

[0027] The front lens group 21 of the dispersion objective lens has a positive optical power and includes at least one lens;

[0028] The position of the aperture stop 22 between the dispersion objective lens front lens group 21 and the dispersion objective lens rear lens group 23 is adjustable, and the center of the aperture stop is located on the optical axis;

[0029] The optical power of the dispersion objective rear lens group 23 is positive and includes at least one lens;

[0030] The wide-spectrum white light emitted from the incident end 1 of the light source passes through the front lens group 21 of the dispersive objective, the aperture diaphragm 22, and the rear lens group 23 of the dispersive objective in sequence to form dispersed light with focal points of different wavelengths spread along the optical axis. The dispersed light is irradiated to the object to be measured 3, and is reflected by the object to be measured 3 to form reflected light. The reflected light passes through the rear lens group 23 of the dispersive objective, the aperture diaphragm 22, and the front lens group 21 of the dispersive objective in sequence, and is received by the receiving end 1.

[0031] The structural diagram of the first embodiment of the present invention is as follows: Figure 1 shown.

[0032] In this embodiment, the dispersive objective front lens group 21 includes: a negative optical focal length doublet lens composed of a first lens L1 and a first lens L2, and a positive optical focal length doublet lens composed of a third lens L3 and a fourth lens L4; the first lens L1 and the fourth lens L4 are spherical lenses with positive optical focal length; the second lens L2 and the third lens L3 are spherical lenses with negative optical focal length.

[0033] In this embodiment, the dispersion objective rear lens group 23 includes: a fifth lens L5, a negative optical power doublet lens composed of a sixth lens L6 and a seventh lens L7, and an eighth lens L8; the fifth lens L5, the seventh lens L7, and the eighth lens L8 are spherical lenses with positive optical power; the sixth lens L6 is a spherical lens with negative optical power.

[0034] In this embodiment, the glass materials of the first lens L1, the third lens L3, the fourth lens L4, and the sixth lens L6 satisfy the following requirements: 1.50< n d <1.70,50< v d <70; the glass material of the second lens L2, the fifth lens L5, the seventh lens L7, and the eighth lens L8 satisfies: 1.70< n d <1.90, 20< v d <40; where n d is the refractive index corresponding to d light, v d is the Abbe number corresponding to d light.

[0035] The specific surface parameters of this embodiment are shown in Table 1 below:

[0036]

[0037] In the grouped spectral confocal dispersive objective lens provided by the present invention, the dispersive objective lens front lens group 21 satisfies the constraint condition shown in formula (1):

[0038] (1)

[0039] In formula (1), i is the serial number of the lens in the front lens group 21 of the dispersion objective lens; N is the total number of lenses in the front lens group 21 of the dispersion objective lens, and satisfies N>0; D i is the effective light diameter of the i-th lens in the front lens group 21 of the dispersion objective lens; v is the focal length of the i-th lens in the front lens group 21 of the dispersion objective lens; i is the Abbe number of the i-th lens in the front lens group 21 of the dispersion objective lens; j is the serial number of the lens in the grouped spectral confocal dispersion objective lens; M is the total number of lenses in the grouped spectral confocal dispersion objective lens, and M>N is satisfied; is the effective light diameter of the jth lens in the grouped spectral confocal dispersion objective; is the focal power of the jth lens in the grouped spectral confocal dispersion objective; is the Abbe number of the jth lens in the grouped spectral confocal dispersion objective; represents the absolute value; α is the set threshold and satisfies α∈[0,0.01].

[0040] For the first embodiment of the present invention, the working band range is 420-740nm, with 580nm as the central wavelength. Figure 2 It can be seen that the dispersion in the entire working band is 4mm, and N=4, M=8, α is 0.003, satisfying α∈[0,0.01].

[0041] In the grouped spectral confocal dispersive objective lens provided by the present invention, the transmitted light between the dispersive objective lens front lens group 21 and the dispersive objective lens rear lens group 23 satisfies formula (2):

[0042] (2)

[0043] In formula (2), λ k is any wavelength within the working band of the grouped spectral confocal dispersion objective, and λ k ∈[λ s ,λ t ],λ s is the short-wavelength in the working band of the grouped spectral confocal dispersion objective, λ t It is the long-wave wavelength within the working band of the grouped spectral confocal dispersion objective; The wavelength of the light emitted from the front lens group 21 of the dispersion objective lens is λ k The angle between the light ray and the optical axis; Indicates absolute value; Represents the upper limit of the absolute value of the angle between the light ray and the optical axis, in milliradian order.

[0044] For the first embodiment of the present invention, the absolute value of the divergence angle of the outgoing light corresponding to the short wavelength of 420nm of the dispersive objective lens front lens group 21 is 0.13mrad, the absolute value of the divergence angle of the outgoing light corresponding to the intermediate wavelength of 580nm is 0.07mrad, and the absolute value of the divergence angle of the outgoing light corresponding to the long wavelength of 740nm is 0.12mrad, and β can be 0.2mrad.

[0045] In the grouped spectral confocal dispersive objective lens provided by the present invention, the dispersive objective lens front lens group 21 also satisfies formula (3):

[0046] (3)

[0047] In formula (3), S a is the primary spherical aberration coefficient of the front lens group 21 of the dispersion objective lens; p is the serial number of the lens surface in the front lens group 21 of the dispersion objective lens, and the cemented surface of the double cemented lens is regarded as a lens surface; P is the total number of lens surfaces in the front lens group 21 of the dispersion objective lens; y p u is the height of the marginal light on the surface of the pth lens in the front lens group 21 of the dispersion objective lens; p u is the tangent value of the angle between the incident light on the p-th lens surface in the front lens group 21 of the dispersion objective and the optical axis; p ' is the tangent value of the angle between the outgoing light on the p-th lens surface in the front lens group 21 of the dispersion objective and the optical axis; n p is the refractive index of the light at the incident point of the pth lens surface in the front lens group 21 of the dispersion objective lens; n p ' is the refractive index of the light at the exit of the p-th lens surface in the front lens group 21 of the dispersion objective lens; C p is the curvature of the p-th lens surface in the front lens group 21 of the dispersion objective; represents the absolute value; σ represents the upper limit of the primary spherical aberration coefficient of the dispersion objective front lens group 21, which is in the micron level.

[0048] In the grouped spectral confocal dispersive objective lens provided by the present invention, the dispersive objective lens rear lens group 23 satisfies formula (4):

[0049] (4)

[0050] In formula (4), S b is the primary spherical aberration coefficient of the dispersion objective rear lens group 23; q is the serial number of the lens surface in the dispersion objective rear lens group 23, and the cemented surface of the double cemented lens is regarded as a lens surface; Q is the total number of lens surfaces in the dispersion objective rear lens group 23; y qu is the height of the marginal light on the surface of the qth lens in the rear lens group 23 of the dispersion objective lens; q u is the tangent value of the angle between the incident light and the optical axis on the surface of the qth lens in the rear lens group 23 of the dispersion objective lens; q ' is the tangent value of the angle between the outgoing light on the surface of the qth lens in the rear lens group 23 of the dispersion objective lens and the optical axis; n q is the refractive index of the light at the incident point of the qth lens surface in the rear lens group 23 of the dispersion objective lens; n q ' is the refractive index of the light at the exit of the qth lens surface in the rear lens group 23 of the dispersion objective lens; C q is the curvature of the qth lens surface in the dispersion objective rear lens group 23; represents the absolute value; τ represents the upper limit of the primary spherical aberration coefficient of the dispersion objective rear lens group 23, which is in the micron level.

[0051] For Example 1 of the present invention, when 580nm is used as the central wavelength, the absolute value of the primary spherical aberration coefficient of the dispersive objective front lens group 21 is 4.6μm, and the absolute value of the primary spherical aberration coefficient of the dispersive objective rear lens group 23 is 3.6μm. σ and τ can be equal to 5μm, indicating that the spherical aberration generated by the dispersive objective front lens group 21 and the dispersive objective rear lens group 23 are very small. This embodiment has a good focusing effect on a wide spectrum light beam.

[0052] Figure 3 The black solid circle in the figure represents the size of the Airy disk, which are the light spots of 420nm, 500nm, 580nm, 660nm and 740nm on their respective focusing planes from left to right. It can be seen that the concentrated light spots corresponding to multiple wavelengths within the working band of this embodiment are significantly smaller than the Airy disk, which means that this embodiment reaches the diffraction limit.

[0053] Figure 4 : is the axial aberration curve of this embodiment. Taking the central wavelength of 580nm as an example, the curve in the figure shows that the axial aberration of this embodiment is very small, and the light beam can be perfectly focused by the dispersive objective lens.

[0054] In summary, the present invention divides the lens part of the spectral confocal dispersive objective lens into a front lens group and a rear lens group. Most of the dispersion is borne by the rear lens group, and the transmitted light between the two lens groups is approximately collimated light. Therefore, replacing the rear lens group can change the measurement range, and replacing the front lens group can change the spot size, that is, by replacing different lens groups, different measurement requirements can be met, thereby improving the practicality of the lens group and the scalability of the system; in addition, the influence of the distance between the two lens groups on the overall performance of the dispersive objective lens is reduced, so the interval length of the two lens groups can be flexibly adjusted, thereby enhancing the freedom of assembly of the spectral confocal dispersive objective lens, and being suitable for more complex measurement scenarios.

[0055] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A grouped spectral confocal dispersion objective lens, characterized in that: Including in order: A light source incident end and a receiving end (1), a dispersion objective lens front lens group (21), an aperture stop (22), and a dispersion objective lens rear lens group (23); The light source incident end and the receiving end (1) are ports of a multimode optical fiber; The front lens group (21) of the dispersion objective lens has a positive optical power and comprises at least one lens; The position of the aperture stop (22) between the dispersion objective lens front lens group (21) and the dispersion objective lens rear lens group (23) is adjustable, and the center of the aperture stop is located on the optical axis; The optical power of the dispersion objective rear lens group (23) is positive and comprises at least one lens; White light with a wide spectrum emitted from a light source incident end and a receiving end (1) passes through a dispersion objective lens front lens group (21), an aperture stop (22), and a dispersion objective lens rear lens group (23) in sequence to form dispersion light with focal points of different wavelengths spread along an optical axis. The dispersion light is irradiated onto a measured object (3), and after being reflected by the measured object (3), it forms reflected light. The reflected light passes through a dispersion objective lens rear lens group (23), an aperture stop (22), and a dispersion objective lens front lens group (21) in sequence to be received by the light source incident end and the receiving end (1).

2. The grouped spectral confocal dispersion objective lens according to claim 1, characterized in that: The dispersion objective lens front lens group (21) satisfies the constraint condition shown in formula (1): (1) In formula (1), i is the serial number of the lens in the front lens group (21) of the dispersion objective lens; N is the total number of lenses in the front lens group (21) of the dispersion objective lens, and satisfies N>0; D i is the effective light transmission diameter of the i-th lens in the front lens group (21) of the dispersion objective lens; is the focal length of the i-th lens in the front lens group (21) of the dispersion objective lens; v i is the Abbe number of the i-th lens in the front lens group (21) of the dispersion objective lens; j is the serial number of the lens in the grouped spectral confocal dispersion objective lens; M is the total number of lenses in the grouped spectral confocal dispersion objective lens, and satisfies M>N; is the effective light diameter of the jth lens in the grouped spectral confocal dispersion objective; is the focal power of the jth lens in the grouped spectral confocal dispersion objective; is the Abbe number of the jth lens in the grouped spectral confocal dispersion objective; represents the absolute value; α is the set threshold and satisfies α∈[0,0.01].

3. The grouped spectral confocal dispersion objective lens according to claim 1, characterized in that: The transmitted light between the dispersion objective lens front lens group (21) and the dispersion objective lens rear lens group (23) satisfies formula (2): (2) In formula (2), λ k is any wavelength within the working band of the grouped spectral confocal dispersion objective lens, and λ k ∈[λ s ,λ t ],λ s is the short-wavelength of the grouped spectral confocal dispersion objective in the working band, λ t is the long-wavelength of the grouped spectral confocal dispersion objective within the working band; The wavelength of the light emitted from the front lens group (21) of the dispersion objective lens is λ k The angle between the light ray and the optical axis; Indicates absolute value; Represents the upper limit of the absolute value of the angle between the light ray and the optical axis, in milliradian order.

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