CN-121829750-B - Very weak light radiance calibration system and method based on cascade integrating sphere

CN121829750BCN 121829750 BCN121829750 BCN 121829750BCN-121829750-B

Abstract

The invention discloses an extremely weak light radiation brightness calibration system and method based on a cascade integrating sphere, and belongs to the technical field of light radiation metering and photoelectric detection. The system comprises a first integrating sphere, a diaphragm barrel and a second integrating sphere, wherein the diaphragm barrel realizes large dynamic range light intensity adjustment through geometric attenuation, and the second integrating sphere is simultaneously connected with a reference detector and a to-be-calibrated high-sensitivity detector to realize on-line calibration and dynamic range bridging under the same radiance field. The light flux distribution is controlled by adjusting the aperture of the diaphragm, so that the measuring ranges of the two types of detectors are overlapped, and the light flux distribution is used for executing correction processing related to the non-ideal effect of the single photon detector and high-precision measurement of the extremely weak light radiance. The invention has compact structure and stable attenuation, can reproduce, and is suitable for weak light calibration and linearity test in the fields of quantum optics, night remote sensing and the like.

Inventors

LI JIANJUN
WANG WENTAO
KANG QING

Assignees

中国科学院合肥物质科学研究院

Dates

Publication Date: 20260505
Application Date: 20260311

Claims (10)

1. An extremely weak light radiance calibration system based on a cascade integrating sphere, which is characterized by comprising: The first integrating sphere is used for receiving light incident by the light source and forming a first radiance field; A first photodetector optically coupled to the first integrating sphere for measuring a first radiance field; the diaphragm barrel is connected between the first integrating sphere and the second integrating sphere, an adjustable diaphragm assembly is arranged in the diaphragm barrel, and the geometric attenuation of the luminous flux of the first radiance field entering the diaphragm barrel is realized by adjusting the adjustable diaphragm assembly; the second integrating sphere receives the geometrically attenuated luminous flux and forms a second radiance field, and is provided with at least two light outlets; The second light detector is optically connected to one light outlet of the second integrating sphere and is used for measuring a second radiance field; The third light detector is optically connected to the other light outlet of the second integrating sphere and is used for carrying out photon counting measurement on the extremely weak light signals in the second radiance field; And the aperture variable component is used for adjusting the luminous flux reaching the second light detector and the third light detector by changing the effective opening area of the corresponding light outlet, so that the second light detector is in a linear response interval and the third light detector is in an effective measurement interval.
2. The cascading integrating sphere based very weak light radiance calibration system of claim 1, wherein the adjustable aperture assembly comprises a front and a rear coaxially arranged adjustable diaphragms, and the geometric attenuation factor coupled from the first integrating sphere to the second integrating sphere is determined by changing the effective aperture of the front and rear adjustable diaphragms and the center distance between the front and rear adjustable diaphragms.
3. The cascade integrating sphere-based extremely weak light radiance calibration system according to claim 1, wherein the first light detector and the second light detector are silicon trap detectors calibrated through spectral responsivity tracing, and the luminous flux attenuation ratio from the first radiance field to the second radiance field can be determined by comparing output signals of the first light detector and the second light detector with known spectral responsivity of the first light detector and the second light detector, so that a traceable source attenuation relation inside the system is established.
4. The cascade integrating sphere based extremely weak light radiance calibration system according to claim 3, wherein the third light detector is a single photon detector, the calibration of which depends on setting up a function relation of reference radiance and counting rate based on a second radiance field reference value provided by the second light detector and determined by the traceable attenuation relation in a measurement range at least partially overlapped, and performing a correction process related to non-ideal effects of the single photon detector, wherein the correction process comprises solving an effective detection efficiency parameter of the single photon detector based on the radiance reference value provided by the reference detector and the counting output of the single photon detector in an overlapped measurement range, and correcting nonlinearity caused by dead time effects and/or post pulse effects.
5. The cascade integrating sphere based very weak light radiance calibration system of claim 1, wherein the aperture variable component is any one of an electrically adjustable diaphragm, an aperture wheel or an electrically variable aperture mechanism, and the ratio of light fluxes reaching each photodetector is independently adjusted by adjusting the aperture variable component while maintaining the second integrating sphere operating state.
6. The system for calibrating the ultra-weak light radiance based on the cascade integrating sphere according to claim 1, wherein the diaphragm tube is a hollow cylinder with an inner wall subjected to extinction treatment, and the geometrical attenuation mode of the diaphragm tube avoids the wavelength dependence and the aging effect of the optical filter, so that the attenuation multiple of the system is stable and reproducible for a long time.
7. The cascade integrating sphere based very weak light radiance calibration system of claim 1, wherein the second integrating sphere is further provided with a monitoring port for monitoring radiance stability.
8. An extremely weak light radiance calibration method based on a cascade integrating sphere, applied to the system of any one of claims 1-7, and characterized by comprising: Step1, optically connecting a light source with a light inlet of a first integrating sphere, forming a first radiance field in the first integrating sphere, and acquiring a measurement signal by using a first light detector; step 2, adjusting an adjustable aperture component in the aperture barrel to enable the attenuated luminous flux to enter the second integrating sphere and form a second radiance field, and acquiring a measurement signal of the second radiance field by utilizing the second optical detector; Step 3, determining a system attenuation relation from a first radiance field to a second radiance field based on measurement signals of the first light detector and the second light detector and known spectral responsivity of the measurement signals; Step 4, adjusting an aperture variable component in front of each light outlet of the second integrating sphere to enable the available measurement ranges of the second optical detector and the third optical detector to be at least partially overlapped; step 5, acquiring an original output signal of the third light detector under the condition of the second radiance field in the at least partially overlapped measuring range; and 6, determining a second radiance field reference value under the radiance reference constraint established by the first optical detector according to the system attenuation relation determined in the step 3, and correcting an original output signal of the second radiance field reference value by combining a non-ideal effect correction model of the third optical detector to obtain an absolute radiance value of a scaling parameter of the third optical detector and a measured target.
9. An electronic device, comprising: One or more processors; A memory for storing one or more programs; Wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the cascade integrating sphere based very weak light radiance calibration method of claim 8.
10. A computer readable storage medium having stored thereon executable instructions which when executed by a processor cause the processor to implement the cascade integrating sphere based very weak optical radiance calibration method of claim 8.

Description

Very weak light radiance calibration system and method based on cascade integrating sphere Technical Field The invention belongs to the technical field of optical radiation metering and photoelectric detection, and particularly relates to an extremely weak optical radiation brightness calibration system and method based on a cascade integrating sphere. Background In the fields of quantum information, remote sensing imaging, biological fluorescence detection, weak light communication and the like, traceable quantitative measurement of extremely weak light radiance is often required. Silicon trap detectors have been widely used as responsivity transfer detectors in radiometric calibration chains due to their high external quantum efficiency, good linearity and traceable spectral responsivity. However, due to dark current and current measurement noise, it is difficult to obtain a sufficient signal-to-noise ratio at picowatt levels and below, thereby limiting the usable dynamic range and lower measurement limit. The single photon detector (such as a Single Photon Avalanche Diode (SPAD)) can detect single photon events based on the photon counting principle, and has extremely high sensitivity under extremely low light conditions. However, the inherent nonlinear effects such as dead time, post pulse and the like cause saturation, nonlinear deviation and historical related errors (such as post pulse-induced related counting) between the observed counting rate and the incident photon flux, so that dead time/post pulse correction and parameter calibration are required to be introduced for quantitative measurement. In addition, existing single photon detector calibration generally requires independent devices or specific light source conditions, lacks a unified transfer link for online comparison with a traceable reference detector in the same radiance field, and thus is difficult to realize continuous splicing of dynamic ranges with silicon trap detectors. The existing light attenuation and light splitting scheme mainly comprises a Neutral Density (ND) filter stack, an optical fiber beam splitter, a single-stage integrating sphere, a fixed diaphragm and the like. The method has obvious limitations when the method is applied to extremely weak light and ultra-large dynamic range measurement, the attenuation coefficient of the ND filter changes along with wavelength, incidence angle and polarization state, reproducible attenuation characteristics are difficult to keep for a long time, the optical fiber beam splitter is sensitive to polarization, coupling modes and bending states, the splitting ratio is easily influenced by environmental disturbance, the splitting ratio is difficult to reproduce stably, the uncertainty of tracing is increased, the single-stage integrating sphere can provide a uniform radiance field, but the uniformity is deteriorated when the aperture ratio is increased, the attenuation capability is limited, and the effective dynamic range which is more than several orders of magnitude is difficult to cover while the uniformity is kept. Meanwhile, the reference detector and the single photon detector are often arranged in different light paths or different devices, so that on-line comparison calibration and dynamic range continuous splicing are difficult to realize in the same uniform radiance field, and systematic errors such as light path difference, environmental drift and the like are easy to introduce. Accordingly, there is a need for a system and method that (i) provides predictable and reproducible geometric attenuation, (ii) enables on-line scaling transfer of reference detectors and high sensitivity detectors within the same uniform radiance field, and (iii) supports single photon detector non-ideal effect correction and dynamic range continuous stitching. Disclosure of Invention The invention provides a cascade integrating sphere-based extremely weak light radiance calibration system and a cascade integrating sphere-based extremely weak light radiance calibration method, which realize large-order stable and predictable light intensity attenuation through a geometrically modelable multi-stage attenuation structure and a multi-detector port design on a second integrating sphere, realize on-line calibration and dynamic range bridging of a standard silicon trap detector and a single photon detector under the same integrating sphere radiance field, and realize quantifiable correction of dead time and post-pulse nonlinear behaviors of the single photon detector so as to realize continuous linear measurement under extremely weak light conditions. In order to achieve the above purpose, the invention adopts the following technical scheme: an extremely weak light radiance calibration system based on a cascade integrating sphere, comprising: The first integrating sphere is used for receiving light incident by the light source and forming a first radiance field; A first photodetector optically coupled to