CN111595469A - A Large FOV Multibeam Single Photon Detection System Using Ultra-Narrow Band Filtering - Google Patents

Abstract

The invention discloses a large-view-field multi-beam single photon detection system using ultra-narrow band filtering, which comprises a telescope system, an optical coupling device, an optical fiber array, an ultra-narrow band filter and a detector module which are sequentially arranged, wherein under the condition of a large view field, multi-beam echo photons are imaged on an image plane of the telescope system, the echo photons are coupled into the input end of the optical fiber array through the optical coupling device, and the echo photons are incident into the ultra-narrow band filter from the output end of the optical fiber array at a vertical angle and enter the detector module. The invention has the advantages that: the detection system can ensure that the central area and the edge area of the echo photon are both vertically incident to the effective area of the ultra-narrow band interference filter, solves the adverse effect caused by different incident angles, utilizes the filter to inhibit background noise to the maximum extent, improves the signal-to-noise ratio of the echo signal, and is favorable for being applied all day long.

Description

A Large FOV Multibeam Single Photon Detection System Using Ultra-Narrow Band Filtering

technical field

The invention belongs to the field of optical detection systems, and in particular relates to a large field of view multi-beam single-photon detection system using ultra-narrow band filtering.

Background technique

Single-photon detection systems have very important applications in long-distance ranging because of their very high sensitivity. With the gradual maturity of integrated and large-scale single-photon detection system technology, its application has been further extended to the field of long-distance, fast-moving high-precision mapping and remote sensing such as airborne and spaceborne. The multi-beam single-photon detection technology can integrate dozens or even hundreds of single-photon detections together, and use array single-photon detection devices or large-scale integrated unit single-photon detection devices to achieve simultaneous detection of echo photon signals of multiple channels. Compared with the traditional single-photon mapping remote sensing system, multi-beam single-photon detection can support mapping and remote sensing with a larger field of view, improve the work efficiency of the system, and even achieve fast imaging capabilities.

Under the condition of a large field of view, the system can accept echo photons with a larger angular range, which corresponds to a larger imaging area on the image plane of the telescope light collection system. Therefore, an array device or a large-scale integrated unit device is required for detection. But in fact, the comparison of the two conditions is not only the change of the imaging area, but also the incident angle of the echo photons irradiated to the detection device also has a significant change.

Compared with ordinary field of view conditions, the echo photon incident detection device under large field of view conditions cannot be approximately regarded as normal incidence under ideal conditions, but the incident angle gradually increases from the central area to the outside. If a single-photon detection system with more than 100 beams is used, the difference between the incident angles of photons at the edge and the center can be up to close to 10 degrees. For example, the incident angle of the 1# and 4# echo beams located at the edge is 80 degrees, and the incident angle of the 2# and 3# echo beams located in the center is 90 degrees. For the convenience of explanation, only the cases of 1# to 4# four beams are marked in Figure 2. The actual number of beams can reach more than hundreds. The incident angle in the central area is 90 degrees, and as it expands to the edge (usually spherical) The angle of incidence changes gradually. This angle difference brings a serious problem in practical application.

In the mapping and remote sensing applications based on single-photon detection, the background noise is very high, especially in the strong light environment, due to the need to work under all-weather conditions. The background noise light has the characteristics of wide spectral distribution, and the light source used in the system is usually a laser with narrow linewidth, so there is a significant wavelength difference between the background noise light and the echo signal photons. In order to separate the echo photon signal from the high background noise, it is usually necessary to use an ultra-narrowband filter to suppress the background noise. The transmission bandwidth of the ultra-narrowband filter is generally as low as 0.1 nm or less. However, the use of such ultra-narrowband filters is relatively limited. First, the echo photons need to have narrow linewidth wavelength characteristics, which requires the system to use ultra-narrow linewidth light sources; secondly, such ultra-narrowband filters Using the principle of interference, it is very sensitive to the incident angle, and the transmission wavelength can only be guaranteed at an angle that is highly approximately perpendicular to its surface. For example, the light source used in the system is 1550.1nm, when the incident angle of the echo photon is 90 degrees, the transmission center wavelength of the ultra-narrowband filter design is 1550.1nm, and the bandwidth is 0.1nm, which ensures strong suppression of background noise photons of other wavelengths. , while having better transmittance to echo photons. However, under the condition of a large field of view, the angle of the incident filter of the echo photons located in the non-central area may become 85 degrees, and the corresponding transmission center wavelength will be shifted by more than 0.2 nm, for example, it becomes 1549.9nm, which exceeds the design bandwidth of the filter, so that the echoed signal photons cannot be transmitted through the filter. The design and processing of the filter requires precise coating on the two surfaces and requires strict parallelism. Therefore, it is technically difficult to design an integrated filter array that is spliced together at multiple angles in a one-to-one correspondence with the array arrangement of APDs. In practical application conditions, the use of ultra-narrowband filters is almost inevitable.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a large field of view multi-beam single-photon detection system using ultra-narrowband filtering according to the shortcomings of the above-mentioned prior art. The receiving angle is oriented to ensure that the center area and edge area of the echo photon can enter the effective area of the ultra-narrowband filter at a vertical angle, and the filter can be used to the maximum extent to suppress background noise and improve the signal-to-noise ratio of the echo signal.

The realization of the object of the present invention is accomplished by the following technical solutions:

A large field of view multi-beam single-photon detection system using ultra-narrow-band filtering, the detection system includes a telescope system, an optical coupling device, an optical fiber array, an ultra-narrow-band filter and a detector module arranged in sequence. Under the conditions, the multi-beam echo photons are imaged on the image plane of the telescope system, the echo photons are coupled into the input end of the optical fiber array through the optical coupling device, and the echo photons are transmitted from the optical fiber array. The output end is incident on the ultra-narrowband filter at a vertical angle and enters the detector module.

The input end of the fiber array is composed of a plurality of single-path fibers, and the output end of the fiber array is composed of a plurality of pigtails corresponding to the single-path fibers one-to-one.

The receiving angle direction of the single-channel optical fiber at the input end of the optical fiber array is gradually processed from the central area to the edge area.

The output end of the optical fiber array is a flexible optical path, so that the output end corresponding to each beam matches the design angle of the ultra-narrowband filter.

The output ends of the fiber array are integrated, and the echo photons passing through the fiber array are filtered by the single ultra-narrow filter.

The wavelengths of the echo photons are different, the echo photons of different beams are classified through the output end of the optical fiber array, and the classified echo photons are filtered by several interference filters respectively.

The detector module is a single detector or an array detector.

The advantages of the invention are: the detection system can ensure that the center area and the edge area of the echo photons are perpendicular to the effective area of the ultra-narrow-band interference filter, solve the adverse effects caused by different incident angles, and maximize the use of the filter The chip suppresses background noise and improves the signal-to-noise ratio of the echo signal, which is beneficial for applications throughout the day.

Description of drawings

Fig. 1 is the echo photon collection schematic diagram under the condition of large field of view of the present invention and under ordinary conditions;

Fig. 2 is the change schematic diagram of the incident angle of echo photon under the condition of large field of view of the present invention;

3 is a schematic diagram of an ultra-narrowband filter of the present invention for suppressing background noise;

FIG. 4 is a schematic diagram of photon detection with a large field of view and a high signal-to-noise ratio achieved by coupling an optical fiber array with an ultra-narrowband interference filter according to the present invention.

Detailed ways

Below in conjunction with the accompanying drawings, the features of the present invention and other related features will be described in further detail by embodiments, so as to facilitate the understanding of those skilled in the same industry:

As shown in Figure 1-4, the labels in the figure are: Telescope system 1, image plane 2, fiber array 3, ultra-narrowband filter 4, APD array detector 5.

Embodiment: As shown in Figures 1-4, this embodiment specifically relates to a large field of view multi-beam single-photon detection system using ultra-narrowband filtering. The detection system includes a telescope system 1, an optical coupling device, and an optical fiber array arranged in sequence. 3. Ultra-narrowband filter 4 and APD array detector 5. The optical fiber array 3 is an optical fiber device with a larger effective receiving area formed by integrating hundreds of optical fiber end faces.

The telescope system 1 is an optical system capable of magnifying the viewing angle of a distant object. After the incident parallel beam passes through the telescope system 1, it is still a parallel beam.

The optical coupling device is a photon collection and beam space control system, which is composed of a single or multiple mirrors or lenses, and is used to collect the returned echo photons in space and couple them into the fiber array 3 .

The input end of the fiber array 3 is composed of a plurality of single-path fibers, and the output end of the fiber array 3 is composed of a plurality of pigtails corresponding to the single-path fibers. Since the input end of the fiber has a certain numerical aperture, it has a larger acceptance angle for the coupled light beam.

In order to further improve the coupling efficiency of the echo photons entering the fiber array 3 under the condition of a large field of view, the input end of the fiber array 3 can be further processed by micromachining, so that the receiving angle of the single fiber at the input end of the fiber array 3 is oriented by The center area is gradually processed to the edge area, which better matches the incident angle of the incident echo multi-beam photons and improves the coupling efficiency.

After entering the fiber array 3, the echo photons of each beam propagate in the corresponding fiber together with the background noise light by utilizing the waveguide transmission characteristics of the fiber. The output end of the optical fiber array 3 is a flexible optical path, and it is convenient to strictly match the output end corresponding to each beam to the design angle of the ultra-narrowband filter 4 .

As shown in Figure 1-4, the output end of the fiber array 3 has the characteristics of a flexible optical path, and the output ends of the fiber array 3 can also be integrated to reduce the spatial output area of the multi-beam photonic signal, so as to filter light through a single ultra-narrow band The sheet 4 filters the echoed photons passing through the fiber array 3 . This can effectively suppress background noise and save the use of ultra-narrowband interference filters. Moreover, the ultra-narrowband filter 4 is a high-precision optical element, and there is a high probability of individual differences, that is, the parameters of different interference filters are different. If multiple filters are used in the overall system, Errors may exist that will affect system parameters.

As shown in Figure 1-4, the wavelengths of the echo photons are different. For example, the echo photons in the central area are 1550 nm and the echo photons in the edge area are 1064 nm. Classification, respectively use the corresponding ultra-narrowband filter 4 for filtering.

As shown in Figure 1-4, after passing through the ultra-narrowband filter 4, multiple single detectors can be used to detect photons of different beams according to the situation, or an array detector can be used to detect the echo photons of multiple beams at the same time. For detection, the APD array detector 5 is used in the embodiment of this case.

It should be noted that, the large field of view condition in this embodiment means that when echo photons enter the APD array detector 5 with a larger field of view receiving angle, they can still be effectively detected. (The original field of view receiving angle is mainly limited by the allowable angle of the ultra-narrowband filter 4, usually within 1 degree; in this embodiment, the field of view receiving angle is mainly limited by the field of view angle of the telescope system 1, which has a certain relationship with the target distance. Usually it can reach 10 degrees or more).

As shown in Figure 1-4, the working method of the large-field-of-view multi-beam single-photon detection system using ultra-narrowband filtering is as follows: under the condition of a large field of view, the multi-beam echo photons are on the image plane 2 of the telescope system 1 For imaging, the echo photons are coupled into the input end of the fiber array 3 through the optical coupling device. After the echo photons enter the fiber array 3, they are transmitted in the fiber, and the echo photons enter the ultra-narrowband filter 4 at a vertical angle from the output end of the fiber array 3 for filtering, and then enter the APD array detector 5 for detection.

Claims (7)

1. A large-view-field multi-beam single-photon detection system using ultra-narrow-band filtering is characterized in that the detection system comprises a telescope system, an optical coupling device, an optical fiber array, an ultra-narrow-band filter and a detector module which are sequentially arranged, under the condition of a large view field, multi-beam echo photons are imaged on an image plane of the telescope system, the echo photons are coupled into an input end of the optical fiber array through the optical coupling device, and the echo photons are incident to the ultra-narrow-band filter from an output end of the optical fiber array at a vertical angle and enter the detector module.

2. The system according to claim 1, wherein the input end of said optical fiber array is formed by a plurality of single-path optical fibers, and the output end of said optical fiber array is formed by a plurality of pigtails corresponding to said single-path optical fibers.

3. The system according to claim 2, wherein the receiving angle of said single-channel optical fiber at the input end of said optical fiber array is gradually changed from the central region to the edge region.

4. The system of claim 1 wherein the output ends of the fiber array are flexible optical paths to match the corresponding output ends of each beam to the design angle of the ultra-narrow band filter.

5. The large field of view multi-beam single photon detection system using ultra-narrow band filtering of claim 1 wherein the output ends of said fiber array are integrated and said echo photons passing through said fiber array are filtered by a single said ultra-narrow filter.

6. The system according to claim 1, wherein said echo photons have different wavelengths, said echo photons of different beams are classified by the output end of said fiber array, and said classified echo photons are filtered by a plurality of interference filters respectively.

7. The system of claim 1 wherein the detector module is a single detector or an array detector.

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