CN-121995602-A - Large-view-field relay system based on graded index lens and design method

Abstract

The invention discloses a large-view-field relay system based on a graded index lens and a design method thereof, and relates to the technical field of optics. On the premise of meeting the diffraction limit, the maximum effective field radius of the relay system is expanded to 0.15mm, and compared with the field of view of a single graded index lens, the relay system is improved by about 76%.

Inventors

• LIAO CHUNYAN
• BAI FUJUN
• Zhen Kun

Assignees

• 西北大学

Dates

Publication Date

20260508

Application Date

20260324

Claims (8)

1. 1. The large-view-field relay system based on the graded index lens is characterized by comprising an object plane (1), a graded index lens (2), an optical bonding layer (3), a plano-concave lens (4) and an image plane (5) which are coaxially and sequentially arranged; The graded index lens (2) is connected with the plano-concave lens (4) through an optical bonding layer (3).
2. 2. The graded index lens based large field relay system according to claim 1, wherein the graded index lens (2) is made of radial graded index material, the central refractive index is 1.62, the self-focusing constant is 0.6, and the fourth order coefficient is 0.21.
3. 3. The graded index lens based large field relay system according to claim 1, wherein the optical cement layer (3) is an ultraviolet curable glue with a refractive index of 1.5597.
4. 4. The graded index lens based large field relay system according to claim 1, wherein the plano-concave lens (4) is made of heavy lanthanum flint glass.
5. 5. The graded index lens based large field relay system according to claim 1, wherein the front end surface and the rear end surface of the graded index lens (2) are both planar, the front end surface of the plano-concave lens (4) is planar, and the rear end surface thereof is spherical.
6. 6. The design method of the large-view-field relay system based on the graded index lens is characterized by comprising the following steps of: S1, performing basic optimization on a large-view-field relay system; S2, expanding the field of view based on the basic optimized large-field-of-view relay system.
7. 7. The method for designing a large field-of-view relay system based on a graded index lens according to claim 6, wherein in S1, the basic optimization is specifically to optimize the central field-of-view and the paraxial field-of-view of the large field-of-view relay system so that the central point profile converges within the airy spot.
8. 8. The method for designing a large field-of-view relay system based on graded index lens according to claim 6, wherein in S2, the field expansion is specifically that the optimization weights of the fields of view of the large field-of-view relay system are all set to 1, the optimization weights of the central field of view are reduced, the optimization weights of the edge fields of view are raised, and the operand extraction is used to adjust the stehl ratio of the edge fields of view to be greater than or equal to 0.8.

Description

Large-view-field relay system based on graded index lens and design method Technical Field The invention relates to the technical field of optics, in particular to a large-view-field relay system based on a graded index lens and a design method. Background Micro fluorescence microscopy imaging technology is an important tool in modern neuroscience to resolve changes in specific nerve loops of animals under natural behavior. For deep brain regions (e.g., hippocampus, hypothalamus, etc.) located several millimeters deep below the cortex, beyond the imaging depth of conventional microscopes, a relay lens must be used to implant the excitation light and fluorescence signals into the brain. Gradient index lenses, by virtue of their small size, planar end face design, and radial self-focusing optical properties, become an indispensable relay element in deep brain imaging systems. In the prior art, there is a typical proposal of a micro objective lens combining a plano-convex lens with a high numerical aperture with a GRIN lens, wherein the design increases the Numerical Aperture (NA) of the system by utilizing the positive power of the plano-convex lens, and corrects the spherical aberration introduced by the plano-convex lens by utilizing the GRIN lens, so that the resolution is improved to the diffraction limit level, and the dendritic spiny structure of the hippocampal neuron is clearly observed. While the solution employing the front plano-convex lens improves resolution, the plano-convex lens causes a sharp accumulation of petzval curvature, which macroscopically manifests itself as a severe inward curvature of the system focal plane. Resulting in a smaller effective imaging field of view. Disclosure of Invention The invention provides a large-view-field relay system based on a graded index lens and a design method thereof, aiming at solving the problem that a single GRIN lens has serious physical constraints of petzval field curvature and off-axis astigmatism. The large view field relay system based on the graded index lens comprises an object plane, the graded index lens, an optical bonding layer, a plano-concave lens and an image plane which are coaxially and sequentially arranged; the graded index lens is connected with the plano-concave lens through an optical bonding layer. Further, the graded index lens uses a radial graded index material with a central refractive index of 1.62, a self-focusing constant of 0.6, and a fourth-order coefficient of 0.21. Further, the optical bonding layer adopts ultraviolet curing glue, and the refractive index of the ultraviolet curing glue is 1.5597. Further, the plano-concave lens adopts heavy lanthanum flint glass. Further, the front end surface and the rear end surface of the graded index lens are both plane, the front end surface of the plano-concave lens is plane, and the rear end surface thereof is spherical. Based on the system, the invention also provides a design method of the large-view-field relay system based on the graded index lens, which comprises the following steps: S1, performing basic optimization on a large-view-field relay system; S2, expanding the field of view based on the basic optimized large-field-of-view relay system. In S1, the basic optimization is specifically that the central view field and the paraxial view field of the large-view-field relay system are optimized so that the central point list is converged to be within the Airy spot. In S2, the view field expansion is specifically carried out by setting the optimization weight of each view field of the large view field relay system to be 1, reducing the optimization weight of the central view field, increasing the optimization weight of the edge view field, and extracting and adjusting the Style ratio of the edge view field to be greater than or equal to 0.8 by using an operand. The beneficial effects of the invention are as follows: (1) The field of view scope is greatly improved, namely, the maximum effective field of view radius of the relay system is expanded to 0.15mm on the premise of meeting the diffraction limit, and compared with the field of view of a single graded index lens, the relay system is improved by about 76%. (2) The excellent imaging contrast is maintained, the radius of the Airy spot is kept at 1.22 mu m, and the modulation transfer function value is stabilized above 0.3 at the spatial frequency (410 lp/mm) corresponding to the resolution limit, which far exceeds the resolvable threshold of the conventional photosensitive device 0.1. (3) The good engineering manufacturability is verified by Monte Carlo tolerance analysis, the probability (namely the yield) of the modulation transfer function being greater than 0.37 is stabilized to be more than 90% under the conventional processing and assembly tolerance, and the method has extremely high large-scale application potential. Drawings FIG. 1 is a schematic diagram of a large field-of-view relay system based on graded in