CN110672520A

CN110672520A - Outgoing prism structure for reducing stray light in volume scattering function measuring device

Info

Publication number: CN110672520A
Application number: CN201911011926.XA
Authority: CN
Inventors: 陶邦一; 吴超钒; 朱乾坤; 黄海清
Original assignee: Second Institute of Oceanography MNR
Current assignee: Second Institute of Oceanography MNR
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-01-10

Abstract

The invention discloses an emergent prism structure for reducing stray light in a volume scattering function measuring device, which belongs to the field of volume scattering function measurement. The invention combines the prism which has a specific shape and is easy to process with the attenuation module to form an emergent prism structure, thereby solving the problem of low signal-to-noise ratio caused by high stray light at the emergent end of the light path in the measurement of the rotary detector type volume scattering function.

Description

Outgoing prism structure for reducing stray light in volume scattering function measuring device

Technical Field

The invention relates to the field of measurement of volume scattering functions, in particular to an exit prism structure for reducing stray light in a volume scattering function measuring device.

Background

The volume scattering function is a very important water body intrinsic parameter in ocean optical remote sensing. In order to realize the optical closure of ocean remote sensing, the light quantity and the inherent quantity of the water body surface are indispensable, and the actually measured inherent quantity of the water body is relatively lacked in China. In the existing rotary type body scattering function measuring device, a body scattering function measurement at a wide angle is achieved by rotating an optical detector, the device generates scattering light by emitting a laser beam after passing through a water body to be measured, then a prism is used for guiding transmitted light to emit to a measuring area, or an optical trap is used for reducing the transmitted light energy in the measuring area to be negligible, so that the influence of the transmitted light on the scattering light is reduced, and the magnitude of the energy of the scattering light is much smaller than that of the transmitted light. In the method for guiding the transmitted light to emit by using the prism, on one hand, the reflected light returns to the measuring area along the original light path due to the reflectivity of the transmission surface, on the other hand, the diffuse reflection is formed due to the fact that the surface of the transmission surface is not smooth enough due to processing, and the stray light formed by the two aspects can affect the detection result of the scattered light.

Disclosure of Invention

The present invention is directed to provide an exit prism structure for reducing stray light in a bulk scattering function measuring device.

The purpose of the invention is realized by the following technical scheme: the outgoing prism structure for reducing stray light in a volume scattering function measuring device is formed by combining an attenuation module and a prism, light enters the prism after passing through the attenuation module, is refracted at an incident surface of the prism, is reflected at a reflecting surface of the prism, is partially reflected at an outgoing surface of the prism, the rest of light is emitted, and the reflected light returns through an original light path and passes through the attenuation module.

Preferably, the attenuation module and the prism are glued, of course, in a combination manner including, but not limited to, clamping by a clamp, etc., and the gluing has the advantages that no additional auxiliary device is needed, and the interface layer of the attenuation module and the prism is flat and dense.

Preferably, the attenuation module has a light absorption function, and the optical devices used in the attenuation module include, but are not limited to, neutral density plates, colored filters, and the like.

Preferably, the prism is made of glass with high uniformity and good transmittance, and the type of the prism includes but is not limited to BK7 glass.

Preferably, the prism has an entrance surface, a reflection surface, an exit surface, an observation surface and three absorption surfaces, the observation surface and the three absorption surfaces are located between the reflection surface and the exit surface, and the entrance surface and the reflection surface are located at the bottom of the prism and have included angles.

Preferably, the included angle between the incident surface and the reflecting surface is calculated according to the following equation:

wherein n is₂Denotes the refractive index of the prism, n₁Denotes the refractive index, θ, of the sample₁Denotes the angle of incidence with an absorption surface on the front side, theta₂Denotes the angle of the reflecting surface with respect to an absorbing surface on the rear side, theta₃Given according to the actual laser incidence, is a known number.

Preferably, the incident surface of the prism has good permeability, the surface precision of the prism is better than 1/2 lambda, and lambda is the incident laser wavelength; the reflecting surface has higher reflectivity, and the surface precision is better than 1/2 lambda.

Preferably, the processing method of the reflecting surface of the prism includes, but is not limited to, silver plating.

Preferably, the absorption surface of the prism has a high absorption rate, and the surface precision of the prism is better than 1/2 lambda.

Preferably, the processing mode of the absorption surface of the prism includes but is not limited to spraying high-absorption black paint.

The invention has the beneficial effects that: the prism with a specific shape and easy processing is combined with the attenuation module to form an emergent prism structure, stray light caused by that reflected light returns to a measurement area along an original light path due to the reflectivity of a transmission surface and stray light caused by that the surface of the transmission surface is not smooth enough to form diffuse reflection due to processing is prevented from entering the measurement area, and the problem of low signal-to-noise ratio caused by high stray light at the emergent end of a light path in the measurement of a rotary detector type body scattering function is solved.

Drawings

FIG. 1 is a schematic diagram of an exit prism structure of the present invention;

FIG. 2 is a perspective view of a prism of the present invention;

FIG. 3 is a front view of the prism of the present invention;

FIG. 4 is a top view of a prism of the present invention;

FIG. 5 is a left side view of the prism of the present invention;

FIG. 6 is a schematic view of the angle calculation of the incident and reflecting surfaces of the present invention;

fig. 7 is a diagram of the optical path within an exit prism structure of the present invention.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. In the following description and in the drawings, the same numbers in different drawings identify the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus consistent with certain aspects of the present application, as detailed in the appended claims. Various embodiments of the present description are described in an incremental manner.

It should be noted that all the directional indications (such as up, down, left, right, front, and rear … …) in the embodiment of the present application are only used to explain the relative position relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indication is changed accordingly.

As shown in fig. 1 to 5, the present invention provides an exit prism structure for reducing stray light in a bulk scattering function measuring device, which has the following specific structure and functions:

1) the exit prism 20 structure is made up of the attenuation module 10 and the prism 20, in combination including but not limited to gluing. The attenuation module 10 has a light absorption function, and the present embodiment uses a neutral density sheet. The prism 20 has a total of seven facets including an entrance facet 1, a reflection facet 2, three absorption facets (3, 5, 7), a viewing facet 6, and an exit facet 4. The incident surface and the emergent surface respectively guide laser to be incident and emergent, the transmittance is good, the surface precision is better than 1/2 lambda (lambda is incident laser wavelength), so that the diffuse reflection can be reduced, and more light transmission is ensured (the same principle is applied to 1/2 lambda below); the reflecting surface is used for changing the direction of the light path and guiding the light path to leave the measuring area, the reflecting surface has higher reflectivity, the surface precision is better than 1/2 lambda, and the processing mode of the embodiment adopts a silver plating film; the absorption surface is used for absorbing stray light caused by diffuse reflection due to the fact that the surface of the emergent surface is not flat enough due to processing, the absorption rate is high, the surface precision is better than 1/2 lambda, and the processing mode of the embodiment adopts spraying of high-absorption black paint. The observation surface is used for observing the internal light path of the prism so as to evaluate the processing quality of the prism. The incident surface and the reflecting surface have a specific angle so that the laser light can be emitted perpendicularly to the exit surface to reduce the reflection intensity at the exit surface. As shown in fig. 6, the angle between the incident surface and the reflecting surface is calculated according to the following equation:

wherein n is₂Denotes the refractive index, n, of the prism 20₁Denotes the refractive index, θ, of the sample₁Denotes the angle of incidence with one of the absorption surfaces on the front side, i.e. absorption surface 5, theta₂Denotes the angle, θ, between the reflecting surface and one of the absorbing surfaces on the rear side (i.e., absorbing surface 3)₃Given according to the actual laser incidence, is a known number.

2) The attenuation module is added in front of the incident surface to inhibit stray light caused by the fact that the transmission surface has reflectivity and reflected light returns to the measurement area along the original optical path and stray light caused by diffuse reflection due to the fact that the surface of the transmission surface is not flat enough due to processing from entering the measurement area, and functions of the structure are described by taking the example that the attenuation module 10 has 1% transmittance. As shown in fig. 7, it is a light path diagram in the exit prism structure of the present invention, in which a solid line is incident laser light and a dotted line is reflected light. The incident laser light passes through the

attenuation module

10, 1% of light is transmitted, refracted at the incident surface 1 (light loss at the position is ignored), reflected at the reflection surface 2 (the reflection is regarded as 100% in analysis), 4% of light is reflected at the exit surface 3, the rest of light exits (absorption at the interface can be ignored), the reflected light returns through the original light path, then is attenuated by 1% through the attenuation sheet, finally, 4 ppm of light returns to the measurement area 30, at the moment, the returned light is reduced by 6 orders of magnitude, and the measurement result of scattered light cannot be influenced. Furthermore, the above analysis is based on the fact that the surfaces are flat, if the surface is not flat, diffuse reflection occurs on the surfaces, and the attenuation module 10 (combining the three absorption surfaces) greatly reduces the energy of the stray light of the diffuse reflection entering the measurement region.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. An exit prism structure for reducing stray light in a bulk scattering function measurement device, comprising: the emergent prism structure is formed by combining an attenuation module and a prism, light enters the prism after passing through the attenuation module, is refracted at an incident surface of the prism and is reflected at a reflecting surface of the prism, part of light is reflected at an emergent surface of the prism, the rest of light is emergent, and the reflected light returns through an original light path and passes through the attenuation module.

2. An exit prism structure according to claim 1, characterized in that: the attenuation module and the prism are formed by gluing.

3. An exit prism structure according to claim 1, characterized in that: the attenuation module has a light absorption function and is selected from a neutral density sheet and a colored filter.

4. An exit prism structure according to claim 1, characterized in that: the prism is made of BK7 glass.

5. An exit prism structure according to claim 1, characterized in that: the prism is provided with an incident surface, a reflecting surface, an emergent surface, an observation surface and three absorption surfaces, wherein the observation surface and the three absorption surfaces are positioned between the reflecting surface and the emergent surface, the incident surface and the reflecting surface are positioned at the bottom of the prism, and the incident surface and the reflecting surface form an included angle.

6. An exit prism structure according to claim 5, characterized in that: the included angle between the incident surface and the reflecting surface is calculated according to the following equation system:

7. An exit prism structure according to claim 5, characterized in that: the surface precision of the incidence surface and the reflection surface of the prism is better than 1/2 lambda, wherein lambda is the incident laser wavelength.

8. An exit prism structure according to claim 5, characterized in that: the processing mode of the reflecting surface of the prism adopts a silver plating film.

9. An exit prism structure according to claim 5, characterized in that: the surface precision of the absorption surface of the prism is better than 1/2 lambda.

10. An exit prism structure according to claim 5, characterized in that: the processing mode of the absorption surface of the prism adopts spraying high-absorption black paint.