CN215219222U

CN215219222U - Curved surface narrowband optical filter

Info

Publication number: CN215219222U
Application number: CN202121303457.1U
Authority: CN
Inventors: 蔡鹏鹏
Original assignee: Hefei Chenhui Defence Technology Co ltd
Current assignee: Hefei Chenhui Defence Technology Co ltd
Priority date: 2021-06-10
Filing date: 2021-06-10
Publication date: 2021-12-17
Anticipated expiration: 2031-06-10

Abstract

The utility model discloses a curved surface narrow-band optical filter, which comprises an optical filter body, wherein the optical filter body comprises a substrate and a filter membrane plated on one side of the substrate; the filter film is of a spatial curved surface structure, the thickness of the filter film is uniform, the filter film is attached to the substrate, the included angle between the normal of any point a on the filter film and the incident ray A at any point a is smaller than theta, and theta meets the requirement

Wherein: lambda [ alpha ]₀The central wavelength of the incident light A, n is the equivalent refractive index of the film layer, and Δ λ is the allowable drift amount of the incident light A. The utility model discloses a strain original plane shape narrowbandThe optical sheet is made into a curved surface shape, so that incident parallel light can be incident on the curved surface optical filter in an approximately vertical mode after passing through the lens, and the central wavelength drift of the curved surface optical filter is small. The curved filter can have a narrow bandwidth, and can greatly weaken background radiation and reduce noise.

Description

Curved surface narrowband optical filter

Technical Field

The utility model relates to the field of optical technology, specifically a curved surface narrowband optical filter.

Background

Bandpass filters are basic optical elements that find application in a variety of optical technologies, particularly in laser technology. For example, in the laser detection technology, an optical lens is often used to collect incident light and focus the incident light on the surface of a photodetector, and a narrow-band filter is often added between the lens and the detector for filtering, so as to weaken sunlight and other background light radiation, reduce background noise, and improve signal-to-noise ratio.

The current narrow-band filter is generally designed into a plane shape, the central wavelength of a pass band is the wavelength of detection laser, the bandwidth is as small as possible in principle, but the narrow-band filter is severely limited by the central wavelength shift. In a receiving system, incident light inevitably passes through an optical filter in an inclined manner, and for obliquely incident laser, the central wavelength of the optical filter shifts towards a short-wave direction, so that only the bandwidth of the optical filter can be increased to ensure throughput, but the increased bandwidth can bring about serious background radiation, if the bandwidth is reduced, only a part of incident light with a small incident angle can pass through the optical filter to reach a detector, the intensity of a laser signal received by the detector can be weakened, in short, the central wavelength shifting phenomenon of the planar optical filter severely limits the bandwidth, prevents further reduction of the background radiation, and increases the difficulty of laser detection.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a curved surface narrowband light filter to solve the problem that proposes among the above-mentioned background art.

In order to achieve the above object, the utility model provides a following technical scheme:

the curved surface narrow-band optical filter comprises an optical filter body, wherein the optical filter body comprises a substrate and a filter film arranged on one side of the substrate;

the filter film is of a spatial curved surface structure, the optical filter is uniform in thickness and attached to the substrate, the included angle between the normal of any point a on the filter film and the incident ray A at any point a is smaller than theta, and theta meets the requirement of theta

Wherein: lambda [ alpha ]₀The central wavelength of the incident light A, n is the equivalent refractive index of the film layer, and Δ λ is the allowable drift amount of the incident light A.

As a further aspect of the present invention: the substrate and the filter film are spherical or paraboloid.

As a further aspect of the present invention: the normal of any point a on the filter film is parallel to the incident light ray a at the any point a, that is, the tangent plane of the any point a is perpendicular to the incident light ray a at the any point a, that is, θ is 0 °.

As a further aspect of the present invention: the filter film is made of high-refractive-index materials and low-refractive-index materials which are alternately distributed.

As a further aspect of the present invention: the high refractive index material is TiO₂Or HfO₂Or Nd₂O₅The low refractive index material is SiO₂Or MgF₂。

As a further aspect of the present invention: the filter film is arranged on the substrate by an evaporation plating or sputtering plating method.

Compared with the prior art, the beneficial effects of the utility model are that: the utility model discloses a make the shape of curved surface to original plane shape narrowband optical filter for incident parallel light can both incide on the curved surface optical filter with approximate vertically mode after passing through the lens on, makes the central wavelength drift volume of curved surface optical filter very little. The curved filter can have a narrow bandwidth, and can greatly weaken background radiation and reduce noise.

Drawings

FIG. 1 is a schematic diagram of an optical path of the optical filter according to the present embodiment;

FIG. 2 is a schematic diagram of a filter structure according to the present embodiment;

fig. 3 is a schematic diagram of an optical path of a conventional planar filter.

In the figure: 1-optical filter body, 11-substrate, 12-optical filter film, 2-light-transmitting mirror and 3-photoelectric detector.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1-3, in an embodiment of the present invention, a curved surface narrowband optical filter includes an optical filter body 1, which includes a substrate 11 and a filter film 12 coated on one side of the substrate 11; the filter film 12 is of a spatial curved surface structure, the thickness of the filter film 12 is uniform, the filter film 12 is attached to the substrate 11, the included angle between the normal of any point a on the filter film 12 and the incident ray A at any point a is smaller than theta, and theta meets the requirement that theta

The substrate 11 is a spherical surface or a paraboloid, the filter film 12 is a high refractive index material and a low refractive index material which are alternately arranged, and the high refractive index material is TiO₂、HfO₂、Nd₂O₅The low refractive index material is SiO₂、MgF₂The filter film is coated on the substrate 11 by evaporation plating or sputtering plating.

Example 1

As shown in fig. 3, the current narrowband filter is generally designed in a planar shape, the center wavelength of the passband is the detection laser wavelength, and the bandwidth is as small as possible in principle, but is severely limited by the shift of the center wavelength. In a receiving system, the incident light inevitably passes through the optical filter obliquely, and for the laser light with oblique incidence, the central wavelength of the optical filter will shift to the short wave direction, and the shift amount is equal to:

wherein λ₀The central wavelength of the incident light, theta is the incident angle of the light (the included angle with the normal line of the optical filter), n is the equivalent refractive index of the film layer, and delta lambda is the drift amount of the central wavelength when the light is obliquely incident.

If a narrow band filter with the center wavelength of 1um is usedWhen the method is applied to a short-focus laser echo detection light path with the F number of 1, the incident angle of marginal rays of a converged light beam reaches 45 degrees, and n x of a film layer is assumed²If the bandwidth of the filter is ± 50nm, the drift amount will reach 50nm, that is, the incident light can be fully transmitted only when the bandwidth of the filter is ± 50nm, and the background radiation caused by the large bandwidth is unacceptable. If the bandwidth of the filter is reduced to ± 5nm (the common bandwidth), only a part of the incident light with an incident angle smaller than 13 ° (the drift amount is smaller than 5nm) can pass through the filter to reach the detector while the background radiation is greatly reduced, and the intensity of the laser signal received by the detector is also reduced.

As shown in fig. 1, the optical filter 1 of this embodiment is a spherical structure, the optical filter 1 is located between the transparent mirror 2 and the photodetector 3, the center of sphere of the optical filter 1 and the focal point of the transparent mirror 2 are both located on the photodetector, in this embodiment, the normal line of any point a on the substrate 11 is parallel to the incident light ray a at any point a, i.e. the tangent plane of any point a is perpendicular to the incident light ray a at any point a, i.e. θ is 0 °, when parallel light is incident, the refracted light passing through the transparent mirror 2 is perpendicular to the position of the optical filter 1, so that no central wavelength drift occurs, the bandwidth of the optical filter 1 can be narrow, and at the same time, enough light can be ensured to pass through the transparent mirror, and the background radiation is greatly reduced.

It is obvious to a person skilled in the art that the invention is not restricted to details of the above-described exemplary embodiments, but that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. The curved surface narrow-band optical filter is characterized by comprising an optical filter body (1), wherein the optical filter body (1) comprises a substrate (11) and an optical filter film (12) plated on one side of the substrate (11);

the filter coating (12) is of a spatial curved surface structure, the thickness of the filter coating (12) is uniform, the filter coating (12) is attached to the substrate (11), the included angle between the normal of any point a on the filter coating (12) and the incident ray A at any point a is smaller than theta, and theta meets the requirement that theta is equal to theta

2. A curved narrowband filter according to claim 1, wherein the filter film (12) is spherical or parabolic.

3. The curved narrowband filter according to claim 1, wherein a normal of any point a on the filter film (12) is parallel to the incident light ray a at the any point a, i.e. a tangential plane of any point a is perpendicular to the incident light ray a at the any point a, i.e. θ is 0 °.

4. The curved surface narrowband filter according to claim 1, wherein the filter film (12) is an alternating distribution of high refractive index material and low refractive index material.

5. The curved-surface narrowband optical filter according to claim 4, wherein the high-refractive-index material is TiO₂Or HfO₂Or Nd₂O₅The low refractive index material is SiO₂Or MgF₂。

6. The curved surface narrowband optical filter according to claim 1, wherein the filter film is disposed on the substrate (11) by evaporation plating or sputtering plating.