Candela reproduction method and device based on virtual blackbody equivalent spectrum synthesis light source

Abstract

The present disclosure relates to a candela reproduction method and device based on a virtual blackbody equivalent spectrum synthesis light source, belonging to the technical field of optical metrology testing. The method comprises: calculating the spectral radiance distribution of an ideal blackbody based on the freezing point temperature of platinum; constructing a spectral synthesis light source composed of narrowband spectral light sources and homogenizing devices; determining the target spectral radiance distribution of the spectral synthesis light source for a preset human eye spectral light visibility efficiency function, so that the weighted integral value of the target spectral radiance distribution is equal to that of the ideal blackbody; adjusting the power of each narrowband light source in the spectral synthesis light source so that the spectral radiance distribution of the spectral synthesis light source reaches the target spectral radiance distribution p times; when the effective light emitting area of the outlet surface of the spectral synthesis light source is 1 / 60 square centimeters q times, the luminous intensity is determined to be p q candela, thus realizing a candela reproduction scheme consistent with the historical definition, compatible with multiple visual function models, and taking into account both theoretical rigor and engineering feasibility.

Description

Technical Field

[0001] This disclosure relates to the field of optical metrology and testing technology, and in particular to a method and apparatus for candela reproduction based on a virtual blackbody equivalent spectral synthesis light source. Background Technology

[0002] The candela (cd) is one of the seven base units in the International System of Units (SI) used to measure luminous intensity. The definition of the candela has evolved from a physical standard to a physical constant: In 1948, the candela was defined as the luminous intensity of a blackbody radiation source perpendicular to an area of ​​one-sixtieth of a square centimeter at the freezing point of platinum (the latest measurement is 2041.35 K); in 1979, the definition was updated to 1 candela for a light source emitting monochromatic radiation with a frequency of 540 × 10¹² Hz (corresponding to a wavelength of 555 nm) and a radiant intensity of 1 / 683 watt per steradian in a given direction; in 2019, with the SI becoming a full constant, the definition of the candela was further anchored to the optical efficiency constant. K cd =683 lm / W is a fixed constant. The optimal level of candela reproduction traced back to the cryogenic absolute radiometer has a relative standard uncertainty of 0.12%. A 2856K fixed-point blackbody based on the molybdenum-carbon alloy phase transition is used for candela reproduction, and its relative standard uncertainty reaches 0.1%, representing the optimal level traced back to the fixed-point blackbody.

[0003] However, the candela reproduction methods in related technologies have the following problems: 1) The reproduction method based on monochromatic lasers has geometric limitations: The method of reproducing candela by measuring the power of a 555 nm laser using an absolute radiometer relies strictly on the idealized assumptions of a "point source" and a "differential solid angle". When the measured solid angle is extended from a differential value to a finite value, the measured result as "average luminous intensity" deviates from the theoretically defined "differential luminous intensity", affecting the accuracy of the reproduction.

[0004] 2) The blackbody reproduction method is complex and costly: Platinum freezing point blackbody requires a highly uniform isothermal cavity to be achieved at extremely high temperatures. The experimental setup is complex and difficult to use as a routine transfer standard.

[0005] 3) Uncertainty introduced by differences in visual function models: There are multiple models of the human eye's spectral light efficiency function, and there are subtle differences between different models. Existing reproduction methods are difficult to be compatible with multiple visual functions at the same time.

[0006] 4) The challenge of synergistic control of spectral matching and spatial uniformity: Existing spectral synthesis methods often focus on matching in a single dimension, making it difficult to achieve a uniform distribution of the spatial light field while ensuring accurate spectral matching, which affects the reliability and reproducibility of the reproduction results. Summary of the Invention

[0007] To address at least some of the aforementioned technical problems, this disclosure provides a method and apparatus for candela reproduction based on a virtual blackbody equivalent spectral synthesis light source.

[0008] This disclosure provides a method for candela reproduction based on a virtual blackbody equivalent spectral synthesis light source, including: Using the freezing point temperature of platinum as the reference temperature, the reference spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band is calculated based on Planck's blackbody radiation formula. A virtual blackbody equivalent spectral synthesis light source is constructed; wherein the virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human eye's visual band and power that can be independently adjusted and controlled; the beam output from the narrowband spectral light source is guided into the homogenizing device for spatial mixing, forming a spatially uniform light field with adjustable spectral radiance distribution within a predetermined solid angle in a predetermined direction on the exit surface of the virtual blackbody equivalent spectral synthesis light source. For one or more preset human eye spectral luminous efficiency functions, the target spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source is determined, and the target spectral radiance distribution and the first weighted integral value of the preset human eye spectral luminous efficiency function are equal to the reference spectral radiance distribution and the second weighted integral value of the preset human eye spectral luminous efficiency function within a preset matching error threshold range. The power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source is independently adjusted so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source reaches the target spectral radiance distribution. p times; among which, p It is a real number greater than 0; When the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set to one-sixtieth of a square centimeter... q When the intensity is doubled, the luminous intensity of the virtual blackbody equivalent spectral synthesis light source in the predetermined direction is determined to be... p q Candela; among which, q It is a real number greater than 0.

[0009] Optionally, the preset one or more human eye spectral luminous efficiency functions include at least one of the following: the International Commission on Illumination (CIE) 2° field of view photopic spectral luminous efficiency function, the 2° field of view scotopic spectral luminous efficiency function, the 2° field of view mesopic spectral luminous efficiency function, the 2° field of view based on cone cells, the 2° field of view long-wavelength cone cell spectral response function, the 2° field of view mid-wavelength cone cell spectral response function, the 2° field of view short-wavelength cone cell spectral response function, the 10° field of view photopic spectral luminous efficiency function, the 10° field of view scotopic spectral luminous efficiency function, the 10° field of view mesopic spectral luminous efficiency function, the 10° field of view based on cone cells, the 10° field of view long-wavelength cone cell spectral response function, the 10° field of view mid-wavelength cone cell spectral response function, and the 10° field of view short-wavelength cone cell spectral response function; When the preset one or more human eye spectral light efficiency functions include at least two human eye spectral light efficiency functions, the weight or relative proportion of each human eye spectral light efficiency function is set respectively.

[0010] Optionally, the first weighted integral value and the second weighted integral value are equal within a preset matching error threshold range; the candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source further includes: When the virtual blackbody equivalent spectral synthesis light source includes more than one combination of narrowband spectral light sources, the combination method in which the number of narrowband spectral light sources in different combinations is less than a preset number threshold is taken as the narrowband spectral light source combination method in the virtual blackbody equivalent spectral synthesis light source.

[0011] Optionally, the step of independently adjusting the power of each of the narrowband spectral sources in the virtual blackbody equivalent spectral synthesis light source includes: The actual spectral radiance distribution of the uniform light field is detected using a spectroradiometer or radiance detector. The actual spectral radiance distribution is compared with the target spectral radiance distribution to obtain the deviation signal; Based on the deviation signal, adjust the driving current or output power of each of the narrowband spectral light sources until the actual spectral radiance distribution reaches the target spectral radiance distribution.

[0012] Optionally, the candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source is characterized by further comprising: Using a standard spectral radiance meter or radiance detector traceable to national metrological standards, the spectral radiance of the virtual blackbody equivalent spectral synthetic light source at the working wavelength of each of the narrowband spectral light sources is calibrated to obtain calibration results. The calibration results are recorded and used as the basis for tracing the source of the virtual blackbody equivalent spectral synthesis light source.

[0013] Optionally, the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set based on replacing precision apertures with different effective aperture areas or installing an effective aperture area adjustable aperture, wherein the effective aperture area is calibrated.

[0014] This disclosure also provides a candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source, comprising: The benchmark target determination module is used to calculate the benchmark spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band, based on Planck's blackbody radiation formula, using the platinum freezing point temperature as the benchmark temperature. A virtual blackbody equivalent spectral synthesis light source construction module is used to construct a virtual blackbody equivalent spectral synthesis light source. The virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human eye's visual band and power that can be independently adjusted and controlled. The beam output from the narrowband spectral light sources is guided into the homogenizing device for spatial mixing, forming a spatially uniform light field with adjustable spectral radiance distribution within a predetermined solid angle in a predetermined direction on the exit surface of the virtual blackbody equivalent spectral synthesis light source. The control and adjustment module is used to determine the target spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source for one or more preset human eye spectral luminous efficiency functions. The target spectral radiance distribution and the first weighted integral value of the preset human eye spectral luminous efficiency function are equal to the reference spectral radiance distribution and the second weighted integral value of the preset human eye spectral luminous efficiency function. The module also independently adjusts the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthetic light source so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source reaches the target spectral radiance distribution. p times; among which, p It is a real number greater than 0; The area setting and value output module is used to set the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source to one-sixtieth of a square centimeter. q The luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined and output based on the target spectral radiance distribution and the effective luminous area. p q Candela; among which, q It is a real number greater than 0.

[0015] Optionally, the light-diffusing device includes at least one of an integrating sphere, a diffuse reflector, a diffuse transmissive sheet, an optical fiber, a spatial light combiner, and a digital micromirror array, and the light-diffusing device includes a device that is assisted or enhanced by at least one of rotation, vibration, and scanning.

[0016] Optionally, the narrowband spectral light source includes at least one of a laser, a laser diode, a light-emitting diode, and a supercontinuum light source, and the narrowband spectral light source includes devices for eliminating speckle and limiting spectral bandwidth.

[0017] Optionally, the light homogenizing device includes an integrating sphere, and a precision aperture is provided at the light outlet of the integrating sphere; The narrowband spectral light source includes multiple laser diodes. The beams output by the multiple laser diodes are guided into the interior of the integrating sphere through space or optical fiber after passing through an anticoherence device. The candela reproduction device based on the virtual blackbody equivalent spectral synthesis light source further includes: a spectroradiometer or a radiance detector; the monitoring optical path of the spectroradiometer or radiance detector is aligned with the predetermined direction of the exit surface, and the spectroradiometer or radiance detector is used to detect the actual spectral radiance of the narrow band corresponding to the uniform light field and transmit it to the control and adjustment module.

[0018] The technical solution provided in this disclosure has the following advantages compared with the prior art: The candela reproduction method and apparatus based on a virtual blackbody equivalent spectral synthesis light source disclosed herein includes the following steps: using the platinum freezing point temperature as a reference temperature, calculating the reference spectral radiance distribution of an ideal blackbody with an emissivity of 1 within the human visual band based on Planck's blackbody radiation formula; constructing a virtual blackbody equivalent spectral synthesis light source; wherein the virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human visual band and whose power can be independently adjusted and controlled; the beam output from the narrowband spectral light sources is guided into the homogenizing device for spatial mixing; and the beam is then mixed within the virtual blackbody equivalent spectral synthesis light source. A uniform light field with adjustable spectral radiance distribution is formed within a predetermined solid angle in a predetermined direction on the exit surface of the source. For one or more preset human eye spectral luminous efficiency functions, the target spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source is determined. The first weighted integral value of the target spectral radiance distribution and the preset human eye spectral luminous efficiency function is equal to the second weighted integral value of the reference spectral radiance distribution and the preset human eye spectral luminous efficiency function. The power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source is independently adjusted so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source reaches the target spectral radiance distribution. p times; among which,p It is a real number greater than 0; when the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set to one-sixtieth of a square centimeter. q When the intensity is doubled, the luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined to be... p q Candela; among which, q For real numbers greater than 0, a method for reproducing the candela based on a virtual blackbody equivalent spectrum synthesis light source is provided. This method utilizes a multi-wavelength narrowband light source to precisely synthesize a virtual blackbody equivalent spectrum synthesis light source, achieving accurate equivalence of the spectral radiance of a platinum solidification point blackbody within a finite solid angle. This balances the rigor of the theoretical definition with the feasibility of engineering implementation, achieving high-precision reproduction and value transfer of the SI base unit, the candela. Specifically: 1) The candela reproduced by the technical solution provided in this disclosure is highly consistent with its historical definition: In the above technical solution, the spectral radiance of a platinum solidification point blackbody is used as the benchmark target, and the physical equivalent of the blackbody is achieved through spectral synthesis. The reproduction result has a natural consistency with the historical definition in 1948, and is also naturally compatible with the constant definition in 2019. Moreover, the operation is simple, the device is simple, and it is easy to use as a standard for daily transmission.

[0019] 2) Compatible with multiple visual function models: In the above technical solution, by matching integral equations, equivalence can be achieved for any preset human eye spectral light efficiency function, which solves the uncertainty problem caused by the differences between different visual function models.

[0020] 3) Solved the geometric measurement problem: In the above technical solution, by clearly defining the measurement within a predetermined solid angle and ensuring the high uniformity of the light field within that angle, the finite solid angle measurement value can effectively approximate the theoretical differential intensity, taking into account both theoretical rigor and engineering feasibility.

[0021] 4) Solved the problem of coordinated control of spectral matching and spatial uniformity: In the above technical solution, by setting a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human visual band and power that can be independently adjusted and controlled in the virtual blackbody equivalent spectral synthesis light source, and controlling and adjusting them, it is beneficial to achieve uniform distribution of spatial light field while ensuring accurate spectral matching, thereby improving the reliability and reproducibility of the reproduction results. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0023] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating a candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source provided in this embodiment of the disclosure; Figure 2 A schematic diagram of a candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source provided in this embodiment of the present disclosure; Figure 3 The relative distribution of spectral radiance in the 390nm to 760nm band of the ideal blackbody with the ideal freezing point of platinum used in the embodiments of this disclosure; Figure 4 The spectral luminous efficiency function of the human eye in the 2° field of view 390nm to 760nm band and the spectral response functions of long-wave, medium-wave and short-wave (LMS) cone cells used in the embodiments of this disclosure are: Figure 5 The 2° field-of-view human eye spectral luminous efficiency function and LMS cone cell spectral response function are used in the embodiments of this disclosure and are weighted by matching the relative distribution of spectral radiance in the 390nm to 760nm band of an ideal blackbody with a platinum freezing point. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0026] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0027] This disclosure provides a method and apparatus for candela reproduction based on a virtual blackbody equivalent spectral synthesized light source, achieving a candela reproduction scheme that is highly consistent with historical definitions, compatible with multiple visual function models, and has good engineering feasibility. The candela reproduction method and apparatus based on a virtual blackbody equivalent spectral synthesized light source provided in this disclosure are described below with reference to the accompanying drawings.

[0028] For example, Figure 1This is a flowchart illustrating a candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source, provided in an embodiment of this disclosure. (Reference) Figure 1 The candela reproduction method based on the virtual blackbody equivalent spectrum synthesis light source includes the following steps: S1. Using the freezing point temperature of platinum as the reference temperature, calculate the reference spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band based on Planck's blackbody radiation formula.

[0029] Using the platinum freezing point of 2041.35 K (corresponding to 1768.2 °C) as the reference temperature, the spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual wavelength range of 360 nm to 830 nm (or 390 nm to 760 nm) was calculated based on Planck's blackbody radiation formula. L e,λ ( l This serves as the benchmark for spectral matching, resulting in the benchmark spectral radiance distribution. Since 99.995% of the apparent luminous efficiency is concentrated in the 390 nm to 760 nm range, the spectral radiance distribution in this band is given particular attention. For clearer data illustration, an example is provided. Figure 3 The reference spectral radiance distribution in the range of 390 nm to 760 nm is shown. Similarly, the following text... Figure 4 and Figure 5 It only shows data in the range of 390 nm to 760 nm.

[0030] Planck's formula for blackbody radiation is:

[0031] in, h is Planck's constant. c The speed of light in a vacuum. k Boltzmann's constant, l The wavelength of light in air. n For standard air at light wavelength l The refractive index on T =2041.35 K.

[0032] S2. Construct a virtual blackbody equivalent spectral synthesis light source; wherein, the virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human eye's visual band and power that can be independently adjusted and controlled. The beam output from the narrowband spectral light source is introduced into the homogenizing device for spatial mixing, forming a spatially uniform light field with adjustable spectral radiance distribution within a predetermined solid angle in a predetermined direction on the exit surface of the virtual blackbody equivalent spectral synthesis light source.

[0033] Among them, the light homogenizing device includes one or more combinations of the following types: integrating sphere, diffuse reflector, diffuse transmissive sheet, optical fiber or spatial light combiner, digital micromirror array, and devices that can be assisted or enhanced by rotation, vibration, scanning, etc.

[0034] Narrowband spectral light sources include one or more combinations of the following types: lasers, laser diodes, light-emitting diodes, supercontinuum light sources, and necessary devices for eliminating speckle and limiting spectral bandwidth.

[0035] For example, the virtual blackbody equivalent spectral synthesis light source can employ an array of laser diodes with wavelengths covering 360 nm to 830 nm (or 390 nm to 760 nm), and the output power of each laser diode can be independently adjusted and controlled. The output of the laser diode array passes through an anticoherence device (such as a rotating diffuser or multimode fiber) to eliminate speckle effects, and is then guided through an optical fiber into the interior of an integrating sphere for spatial mixing. The inner wall of the integrating sphere is coated with a highly reflective, spectrally neutral diffuse reflective coating (such as polytetrafluoroethylene (PTFE) or barium sulfate). A precision aperture is provided at the exit port of the integrating sphere to define the effective emitting area of ​​the exit surface. A spatially uniform light field with adjustable spectral radiance distribution is formed within a solid angle of 2 degrees or 10 degrees in the direction normal to the exit surface.

[0036] In other embodiments, other types of homogenizing devices and narrowband spectral light sources can be used to construct virtual blackbody equivalent spectral synthesis light sources, which are not limited here.

[0037] S3. For one or more preset human eye spectral luminous efficiency functions, determine the target spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source. The first weighted integral value of the target spectral radiance distribution and the preset human eye spectral luminous efficiency function is equal to the second weighted integral value of the reference spectral radiance distribution and the preset human eye spectral luminous efficiency function within a preset matching error threshold range.

[0038] Among them, for one or more preset human eye spectral luminous efficiency functions F ( l Determine the target spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source constructed in S2. L e,λ_syn ( l ), such that: the first weighted integral value ∫ L e,λ_syn ( l )· F ( l ) dλ The second weighted integral value corresponding to the ideal blackbody in S1 is ∫ L e,λ ( l )· F ( l ) dλ They are equal within a preset matching error threshold range, thus obtaining the spectral luminous efficiency function of the human eye. F ( l A virtual blackbody equivalent spectral synthesized light source that matches the luminous intensity of the ideal blackbody in S1 in a predetermined direction under certain conditions.

[0039] For example, for a preset human eye spectral luminous efficiency function F ( l For example, the CIE 2° field of view photopic vision function. V ( l Using the preset human eye spectral luminous efficiency function, the target spectral radiance distribution is determined. L e,λ_syn ( l ), and it satisfies:

[0040] In this equation, the left side represents the first weighted integral value, and the right side represents the second weighted integral value. By setting the mathematical framework for matching this integral equation, the spectral luminous efficiency function of the human eye can be obtained. F ( l For example, the CIE 2° field of view photopic vision function. V ( l A virtual blackbody equivalent spectral synthesized light source that matches the luminous intensity of an ideal blackbody in the normal direction under the given conditions.

[0041] S4. Independently adjust the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source reaches the target spectral radiance distribution. p times; among which, p It is a real number greater than 0.

[0042] Specifically, by independently adjusting the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source constructed in S2, the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source is made to achieve the target spectral radiance distribution determined in S3. L e,λ_syn ( l ) of p times; among which, p It is a real number greater than 0. Specific adjustment methods will be illustrated with examples later.

[0043] S5. When the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set to one-sixtieth of a square centimeter... qWhen the intensity is doubled, the luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined to be... p q Candela; among which, q It is a real number greater than 0.

[0044] Specifically, when the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set to one-sixtieth of a square centimeter... q When the time is doubled, based on the equivalence condition already satisfied in S3, the target spectral radiance distribution is... L e,λ_syn ( l Based on the effective luminescent area, the luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined as follows: p q Candela, thus enabling the reproduction of candela. For example, q The value can be any candela value that needs to be reproduced, such as 1, 0.1, and 10.

[0045] In some embodiments, the preset one or more human eye spectral luminous efficiency functions include at least one of the following: CIE 2° field of view photopic spectral luminous efficiency function, 2° field of view scotopic spectral luminous efficiency function, 2° field of view mesopic spectral luminous efficiency function, 2° field of view cone-based spectral luminous efficiency function, 2° field of view long-wavelength cone-based spectral response function, 2° field of view mid-wavelength cone-based spectral response function, 2° field of view short-wavelength cone-based spectral response function, 10° field of view photopic spectral luminous efficiency function, 10° field of view scotopic spectral luminous efficiency function, 10° field of view mesopic spectral luminous efficiency function, 10° field of view cone-based spectral luminous efficiency function, 10° field of view long-wavelength cone-based spectral response function, 10° field of view mid-wavelength cone-based spectral response function, and 10° field of view short-wavelength cone-based spectral response function; when the preset one or more human eye spectral luminous efficiency functions include at least two human eye spectral luminous efficiency functions, the weight or relative proportion of each human eye spectral luminous efficiency function can also be set separately.

[0046] Specifically, one or more preset human eye spectral luminous efficiency functions F ( lThis includes at least one of the following: CIE 2° field-of-view photopic spectral luminous efficiency functions, 2° field-of-view scotopic spectral luminous efficiency functions, 2° field-of-view mesopic spectral luminous efficiency functions, 2° field-of-view cone-based spectral luminous efficiency functions, 2° field-of-view long-wavelength cone-based spectral response functions, 2° field-of-view mid-wavelength cone-based spectral response functions, 2° field-of-view short-wavelength cone-based spectral response functions, 10° field-of-view photopic spectral luminous efficiency functions, 10° field-of-view scotopic spectral luminous efficiency functions, 10° field-of-view mesopic spectral luminous efficiency functions, 10° field-of-view cone-based spectral luminous efficiency functions, 10° field-of-view long-wavelength cone-based spectral response functions, 10° field-of-view mid-wavelength cone-based spectral response functions, and 10° field-of-view short-wavelength cone-based spectral response functions. For details, please refer to GB / T20151-2026 Photometry—The CIE system of physical photometry and ISO / CIE 23539:2023 Photometry — The CIE system of physical photometry. Documents such as photometry), CIE 170-2:2015, Fundamental Chromaticity Diagram with Physiological Axes — Part 2: Spectral Luminous Efficiency Functions and Chromaticity Diagrams, and CIE 170-1:2006, Fundamental Chromaticity Diagram with Physiological Axes; when the preset one or more human eye spectral luminous efficiency functions include at least two human eye spectral luminous efficiency functions, the weight or relative proportion of each human eye spectral luminous efficiency function can also be set separately.

[0047] The candela reproduction method based on virtual blackbody equivalent spectral synthesis light source provided in this embodiment can achieve equivalence for any preset human eye spectral luminous efficiency function, solving the uncertainty problem caused by the differences in different visual function models.

[0048] In other embodiments, the human eye's spectral luminous efficiency function F ( l It may also include other human spectral luminous efficiency functions known to those skilled in the art, but are not limited herein.

[0049] In some embodiments, the candela reproduction method based on a virtual blackbody equivalent spectral synthesized light source further includes: When the virtual blackbody equivalent spectral synthesis light source includes more than one combination of narrowband spectral light sources, the combination method in which the number of narrowband spectral light sources in different combinations is less than a preset number threshold is taken as the narrowband spectral light source combination method in the virtual blackbody equivalent spectral synthesis light source.

[0050] Specifically, for one or more preset human eye spectral luminous efficiency functions F ( l When a preset matching error threshold is set, there may be more than one combination of narrowband spectral light sources in the virtual blackbody equivalent spectral synthesis light source that meets the preset matching error threshold range. In this case, the combination with the fewest possible number of narrowband spectral light sources is preferred. That is, the combination with the fewest possible number of narrowband spectral light sources in different combinations is selected as the combination of narrowband spectral light sources in the virtual blackbody equivalent spectral synthesis light source, so that the uncertainty is minimized when adjusting the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source.

[0051] In some embodiments, the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source is adjusted independently, including: The actual spectral radiance distribution of a uniform light field is detected using a spectroradiometer or radiance detector. The deviation signal is obtained by comparing the actual spectral radiance distribution with the target spectral radiance distribution. Based on the deviation signal, adjust the driving current or output power of each narrowband spectral light source until the actual spectral radiance distribution reaches the target spectral radiance distribution.

[0052] Specifically, the power of each narrowband spectral source can be adjusted independently using a closed-loop feedback control method. This can be achieved by: using a spectroradiometer or radiance detector to detect the actual spectral radiance distribution of the uniform light field and obtaining a monitored value; then comparing the monitored value with the target spectral radiance distribution determined in S3. L e,λ_syn ( l The values ​​are compared to obtain the deviation signal; the driving current or output power of each narrowband spectral light source is adjusted according to the deviation signal until the monitored value reaches the target spectral radiance distribution. L e,λ_syn ( l ), to obtain the spectral luminous efficiency function of the human eye. F ( l A virtual blackbody equivalent spectral synthesized light source that matches the luminous intensity of the ideal blackbody in S1 in a predetermined direction under certain conditions.

[0053] In some embodiments, the candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source is characterized by further comprising: Using a standard spectroradiance meter or radiance detector traceable to national metrological standards, the spectral radiance of the virtual blackbody equivalent spectral synthetic light source at the working wavelength of each narrowband spectral light source is calibrated, and the calibration results are obtained. Record the calibration results, which will serve as the basis for tracing the source of the virtual blackbody equivalent spectral synthesis light source.

[0054] Specifically, in S4, a standard spectral radiance meter or radiance detector traceable to national metrological standards can be used to calibrate the actual spectral radiance of the virtual blackbody equivalent spectral synthesized light source at the working wavelength of each narrowband spectral light source, and obtain the calibration results; and record the calibration results, which can serve as the traceability basis for the virtual blackbody equivalent spectral synthesized light source.

[0055] In this embodiment of the disclosure, calibration is performed using a standard detector traceable to the national metrological standard to ensure that the measured values ​​of the reproduced results are traceable to the national standard and meet the metrological transfer requirements.

[0056] In some embodiments, the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set based on replacing precision apertures with different effective aperture areas or installing an effective aperture area adjustable aperture, and the effective aperture area is calibrated.

[0057] This setting makes it easy to accurately reproduce any candela value that needs to be reproduced.

[0058] The candela reproduction based on a virtual blackbody equivalent spectral synthetic light source provided in this embodiment has the following beneficial effects: 1) The candela reproduction results are highly consistent with the historical definition: In the above technical solution, the spectral radiance of the platinum freezing point blackbody is used as the benchmark target. The physical equivalent of the blackbody is achieved through spectral synthesis. The reproduction results are naturally consistent with the historical definition in 1948, and are also naturally compatible with the constant definition in 2019. Moreover, the operation is simple and the device is simple, which makes it easy to use as a standard for daily transmission.

[0059] 2) Compatible with multiple visual function models: In the above technical solution, by matching integral equations, equivalence can be achieved for any preset human eye spectral light efficiency function, which solves the uncertainty problem caused by the differences between different visual function models.

[0060] 3) Solved the geometric measurement problem: In the above technical solution, by clearly defining the measurement within a predetermined solid angle and ensuring the high uniformity of the light field within that angle, the finite solid angle measurement value can effectively approximate the theoretical differential intensity, taking into account both theoretical rigor and engineering feasibility.

[0061] 4) Solved the problem of coordinated control of spectral matching and spatial uniformity: In the above technical solution, by setting a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human visual band and power that can be independently adjusted and controlled in the virtual blackbody equivalent spectral synthesis light source, and controlling and adjusting them, it is beneficial to achieve uniform distribution of spatial light field while ensuring accurate spectral matching, thereby improving the reliability and reproducibility of the reproduction results.

[0062] 5) Strong traceability: In the above technical solution, calibration is performed by using a standard detector that is traceable to the national metrological standard, ensuring that the value of the reproduced result is traceable to the national standard and meets the metrological transfer requirements.

[0063] This disclosure also provides a candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source, which can perform the steps of any of the candela reproduction methods based on a virtual blackbody equivalent spectral synthesis light source provided in the above embodiments, and achieve the corresponding beneficial effects. For details, please refer to the foregoing text, which will not be repeated here.

[0064] For example, Figure 2 This is a schematic diagram of a candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source, provided as an embodiment of this disclosure. (Reference) Figure 2 The candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source includes: a reference target determination module 21, used to calculate the reference spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band based on Planck's blackbody radiation formula, using the platinum freezing point temperature as the reference temperature; and a virtual blackbody equivalent spectral synthesis light source construction module 22, used to construct a virtual blackbody equivalent spectral synthesis light source. The virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human visual band and independently adjustable power. The beam output from the narrowband spectral light sources is guided into the homogenizing device for spatial mixing, and the beam is pre-mixed in a predetermined direction at the exit surface of the virtual blackbody equivalent spectral synthesis light source. A uniform light field with spatial uniformity and adjustable spectral radiance distribution is formed within a fixed solid angle. The control and adjustment module 23 is used to determine the target spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source for one or more preset human eye spectral luminous efficiency functions. The first weighted integral value of the target spectral radiance distribution and the preset human eye spectral luminous efficiency function is equal to the second weighted integral value of the reference spectral radiance distribution and the preset human eye spectral luminous efficiency function within a preset matching error threshold range. The module also independently adjusts the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source to ensure that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source reaches the target spectral radiance distribution. p times; of which pThe area setting and value output module 24 is a real number greater than 0, used to set the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source to one-sixtieth of a square centimeter. q The luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined and output based on the target spectral radiance distribution and effective luminous area. p q Candela; among which, q It is a real number greater than 0.

[0065] In this embodiment, the device adopts a modular design with clear division of functional modules, which facilitates actual construction and debugging and reduces the technical threshold for candela reproduction.

[0066] In some embodiments, the light homogenizing device includes at least one of an integrating sphere, a diffuse reflector, a diffuse transmissive sheet, an optical fiber, a spatial light combiner, and a digital micromirror array, and the light homogenizing device includes a device that is assisted or enhanced by at least one of rotation, vibration, and scanning.

[0067] Specifically, homogenizing devices include one or more combinations of the following types: integrating sphere, diffuse reflector, diffuse transmissive sheet, fiber or spatial light combiner, digital micromirror array, and devices that can be assisted or enhanced by rotation, vibration, scanning, etc.

[0068] In some embodiments, the narrowband spectral light source includes at least one of a laser, a laser diode, a light-emitting diode, and a supercontinuum light source, and the narrowband spectral light source includes devices for eliminating speckle and limiting spectral bandwidth.

[0069] Specifically, narrowband spectral light sources include one or more combinations of the following types: lasers, laser diodes, light-emitting diodes, supercontinuum light sources, and necessary devices for eliminating speckle and limiting spectral bandwidth.

[0070] In some embodiments, the homogenizing device includes an integrating sphere, and a precision aperture is provided at the light outlet of the integrating sphere; the narrowband spectral light source includes multiple laser diodes, and the beams output by the multiple laser diodes are guided into the interior of the integrating sphere through space or optical fiber after passing through an anticoherence device.

[0071] In some embodiments, the candela reproduction device based on the virtual blackbody equivalent spectral synthesis light source may further include: a spectroradiometer or a radiance detector; the monitoring optical path of the spectroradiometer or radiance detector is aligned with a predetermined direction of the exit surface, and the spectroradiometer or radiance detector is used to detect the actual spectral radiance of the narrow band corresponding to the uniform light field and transmit it to the control and adjustment module.

[0072] In this embodiment of the disclosure, a spectroradiometer or radiance detector monitors that the optical path is aligned with the predetermined direction of the exit surface, detects the spectral radiance of the narrow band corresponding to the uniform light field, and provides a feedback signal to the control and adjustment module, so that the actual spectral radiance distribution generated by the output of all laser diodes reaches the target spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source.

[0073] In this embodiment of the disclosure, the candela reproduction device based on the virtual blackbody equivalent spectral synthesis light source is a candela reproduction device based on an integrating sphere and a laser diode array. The corresponding candela reproduction method based on the virtual blackbody equivalent spectral synthesis light source may include the following steps: S101: Using the platinum freezing point temperature of 2041.35 K (corresponding to 1768.2℃ Celsius) as the reference temperature, the spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual wavelength range of 360 nm to 830 nm (or 390 nm to 760 nm) is calculated based on Planck's blackbody radiation formula. L e,λ ( l This serves as the benchmark for spectral matching, thus yielding the benchmark spectral radiance distribution. For example, the benchmark spectral radiance distribution curve can be found in [reference needed]. Figure 3 .

[0074] Planck's formula for blackbody radiation is:

[0075] in, h is Planck's constant. c The speed of light in a vacuum. k Boltzmann's constant, l The wavelength of light in air. n For standard air at light wavelength l The refractive index on T =2041.35 K.

[0076] S201: A virtual blackbody equivalent spectral synthesis light source is constructed using a laser diode array with wavelengths covering 360 nm to 830 nm (or 390 nm to 760 nm). The output power of each laser diode can be independently adjusted and controlled. The output of the laser diode array passes through an anticoherence device (such as a rotating diffuser or multimode fiber) to eliminate speckle effects, and is then guided into the interior of an integrating sphere via optical fiber for spatial mixing. The inner wall of the integrating sphere is coated with a high-reflectivity, spectrally neutral diffuse reflection coating (such as polytetrafluoroethylene (PTFE) or barium sulfate). A precision aperture is provided at the exit port of the integrating sphere to limit the effective emitting area of ​​the exit surface. A spatially uniform light field with adjustable spectral radiance distribution is formed within a solid angle of 2° or 10° in the direction normal to the exit surface.

[0077] S301: For the preset human eye spectral luminous efficiency function F ( l For example, the CIE 2° field of view photopic vision function. V ( l As the target, determine the target spectral radiance distribution. L e,λ_syn ( l ), to satisfy:

[0078] Thus, the photopic visual function at the CIE 2° field of view is obtained. V ( l A virtual blackbody equivalent spectral synthesized light source that matches the luminous intensity of an ideal blackbody in the normal direction under the given conditions.

[0079] S401: The power of each laser diode is adjusted using a closed-loop feedback control method.

[0080] For example, a standard spectroradiometer traceable to national metrological standards can be used to detect the actual spectral radiance distribution of a uniform light field to obtain a monitored value; the monitored value is then compared with the target spectral radiance distribution determined in S301. L e,λ_syn ( l The difference is compared to obtain the deviation signal; the driving current of each laser diode is adjusted by the control and adjustment module according to the deviation signal until the monitored value reaches the target spectral radiance distribution.

[0081] At the same time, the same spectroradiometer can be used to absolutely calibrate the spectral radiance at the working wavelength of each narrowband spectral light source, and the calibration results can be recorded as a basis for traceability.

[0082] S501: The effective light-emitting area of ​​the exit surface is set to one-sixtieth of a square centimeter using a precision aperture. q times.

[0083] In this embodiment of the disclosure, q =1, meaning the effective luminous area is set to one-sixtieth of a square centimeter. Based on the equivalence condition already satisfied in S3, the target spectral radiance distribution... L e,λ_syn ( l Based on the effective luminescent area, the luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the normal direction is determined to be 1 candela.

[0084] In some embodiments, equivalence of any human eye spectral luminous efficiency function under ideal approximation conditions can also be achieved.

[0085] Specifically, in this embodiment, the virtual blackbody equivalent spectral synthesis light source uses a sufficient number of narrowband spectral light sources, whose wavelengths cover the entire human visual band of 360 nm to 830 nm (or 390 nm to 760 nm) with sufficiently fine intervals. Furthermore, the output power of each narrowband light source is precisely adjusted to achieve a target spectral radiance distribution of the synthesized light source. L e,λ_syn ( l The spectral radiance distribution at each wavelength position is similar to that of an ideal blackbody at the platinum freezing point. L e,λ ( l If they are close enough, that is, if they satisfy:

[0086] in e This is a preset matching error threshold, i.e., a preset allowable deviation. For example, this preset matching error threshold can be less than 0.01%.

[0087] In this case, for any pre-defined human eye spectral luminous efficiency function F ( l (Including but not limited to the CIE 2° field of view photopic spectral luminous efficiency function, 2° field of view scotopic spectral luminous efficiency function, 2° field of view mesopic spectral luminous efficiency function, 2° field of view cone-based spectral luminous efficiency function, 2° field of view long-wavelength cone-based spectral response function, 2° field of view mid-wavelength cone-based spectral response function, 2° field of view short-wavelength cone-based spectral response function, 10° field of view photopic spectral luminous efficiency function, 10° field of view scotopic spectral luminous efficiency function, 10° field of view mesopic spectral luminous efficiency function, 10° field of view cone-based spectral luminous efficiency function, 10° field of view long-wavelength cone-based spectral response function, 10° field of view mid-wavelength cone-based spectral response function, and 10° field of view short-wavelength cone-based spectral response function, all of which satisfy:)

[0088] When the effective luminescent area of ​​the exit surface is set to one-sixtieth of a square centimeter, the same as that of an ideal blackbody at its freezing point, the virtual blackbody equivalent spectral synthesized light source will provide a visual function for any of the aforementioned parameters. F ( l The luminescence intensity in the predetermined direction is the same as that of an ideal blackbody at the solidification point of platinum, which is 1 candela.

[0089] In this embodiment of the disclosure, when the spectral synthesis is sufficiently refined, it can fundamentally solve the uncertainty problem caused by the differences in different visual function models, and achieve candela reproduction of "one synthesis, equivalent everywhere".

[0090] In some embodiments, optimized matching can also be performed for multiple visual functions.

[0091] In this embodiment of the disclosure, a preset human eye spectral luminous efficiency function is used. F ( l This can include various methods, for example, simultaneously requiring the same photopic spectral luminous efficiency function as the CIE 2° field of view. V ( l ) and 2° field of view based on the spectral luminous efficiency function of cone cells V F ( l Equivalent to ) In this case, the target spectral radiance distribution L e,λ_syn ( l The following conditions must be met simultaneously:

[0092]

[0093] When the number of narrowband spectral sources in the virtual blackbody equivalent spectral synthesis light source is limited, the above set of equations may have multiple solutions.

[0094] The embodiments disclosed herein employ an optimization algorithm to prioritize the combination of the fewest narrowband spectral light sources, provided that a preset matching error threshold (e.g., 0.1%) is met, in order to reduce system complexity and cost.

[0095] In some embodiments, the virtual blackbody equivalent spectral synthesis light source can be a three-wavelength synthesis light source, and the spectral response functions of long-wavelength cone cells in the 2° field of view, the spectral response functions of medium-wavelength cone cells in the 2° field of view, and the spectral response functions of short-wavelength cone cells in the 2° field of view are precisely matched based on the three-wavelength synthesis light source.

[0096] Specifically, the virtual blackbody equivalent spectral synthesis light source constructed in this embodiment uses only three narrowband spectral light sources, with their center wavelengths set to 450 nm, 540 nm and 650 nm, respectively, corresponding to the sensitive regions of S cone, M cone and L cone in LMS cone cells.

[0097] Furthermore, the preset human eye spectral luminous efficiency function F ( l ) represents the CIE 2006 2° field-of-view LMS cone cell spectral response function, denoted as . l ( l ), m ( l ), s ( l For each cone cell channel, establish a weighted integral equation:

[0098]

[0099]

[0100] in l ( l ), m ( l ), s ( l () represents the CIE 2006 2° field of view LMS cone cell spectral response function, see [reference]. Figure 4 .

[0101] Subsequently, by adjusting the output power of the three narrowband light sources at 485 nm, 550 nm and 630 nm, the above three integral equations were made valid, with a relative deviation of less than 0.02%.

[0102] Because the LMS cone cell spectral response function is the same as other cone cell-based spectral luminous efficiency functions (such as... V F ( l The linear combination of the three cone cell channels, therefore, when the responses of all three cone cell channels are consistent with the ideal blackbody at the platinum freezing point, for any spectral luminous efficiency function based on cone cells... G ( l (can be represented as) l ( l ), m ( l ), s ( l The weighted integral of the linear combination of platinum (a blackbody with a solidification point) deviates from that of an ideal blackbody with a solidification point of less than 0.02%.

[0103] In this embodiment of the disclosure, a limited number of narrowband light sources are used, and high-precision equivalence of various visual functions based on cone cells can be achieved by independently matching the three channels of the LMS.

[0104] In some embodiments, the 10° visual function can also be matched based on a three-wavelength synthetic light source.

[0105] In this embodiment of the disclosure, a preset human eye spectral luminous efficiency function is used. F ( l ) represents the CIE 2006 10° field-of-view LMS cone cell spectral response function, denoted as . l 10 ( l ), m 10 ( l ), s 10 ( l ).

[0106] The established weighted integral equation can refer to the weighted integral equation for matching the 2° field of view LMS cone cell spectral response function mentioned earlier, and simply replace the CIE 2006 2° field of view LMS cone cell spectral response function with the CIE 2006 10° field of view LMS cone cell spectral response function.

[0107] Subsequently, by adjusting the output power of the three narrowband light sources at 450 nm, 540 nm and 650 nm, the deviation of the response of the LMS cone cell spectral response function for a 10° field of view from that of an ideal blackbody with the same effective luminescent area at the solidification point is less than 0.1%.

[0108] Based on the same linear combination principle, when the responses of the three 10° field-of-view LMS cone cell channels are consistent with the ideal blackbody at the platinum freezing point, the deviation of the spectral luminous efficiency function based on the cone cells for any 10° field of view is also less than 0.1%.

[0109] Furthermore, embodiments of this disclosure also require a photopic spectral luminous efficiency function based on cone cells for a CIE 10° field of view. V F10 ( l The weighted integral result of ) deviates from that of an ideal blackbody at the freezing point of platinum by less than 0.1%. Because V F10 ( l ) can be represented as l 10 ( l ), m 10 ( l ), s10 ( l ) specific linear combinations ( V F10 ( l ) = a l 10 ( l ) + b m 10 ( l ) + c s 10 ( l ),in a , b , c (where the coefficients are known), when the responses of all three cone cell channels satisfy a deviation of less than 0.1%, CIE 1964 10° is based on the photopic spectral luminous efficiency function of cone cells. V F10 ( l The response deviation naturally meets the requirements, see [reference]. Figure 5 .

[0110] In this embodiment of the disclosure, by independently matching the three channels of LMS, high-precision equivalence of the LMS cone cell spectral response function and photopic vision function can be achieved simultaneously, which is suitable for application scenarios that need to consider both color vision and brightness vision.

[0111] In some embodiments, different effective luminous areas can be set. Specifically, by replacing precision apertures with different opening areas, the effective luminous area can be set to different values ​​such as 0.1 times, 10 times, etc., of one-sixtieth of a square centimeter, to respectively reproduce luminous intensities of 0.1 candela, 10 candela, etc. The effective opening area is calibrated by a precision length measuring device before use to ensure the accuracy of the geometric values.

[0112] In some embodiments, the function of the homogenizing device can also be implemented in different forms. Specifically, the homogenizing device is not limited to an integrating sphere, and can also adopt the following combinations: 1) Combination of diffuse reflector and spatial beam combiner: the beams output from multiple laser diodes are combined by the spatial beam combiner and then irradiated onto the diffuse reflector to form a uniform light field on the surface of the diffuse reflector; 2) Digital micromirror array: the spatial light field is homogenized by high-speed modulation; 3) Combination of rotating diffuser and fiber bundle: the uniformity is enhanced by introducing a time averaging effect through mechanical rotation.

[0113] In some embodiments, matching can also be performed for visual functions at different field-of-view angles. Specifically, for large field-of-view display applications, a preset human eye spectral luminous efficiency function is used. F ( l The CIE 1964 10° field of view photopic spectral luminous efficiency function can be used. V 10 ( l (and CIE 2006 10° field of view LMS cone cell spectral response function. When measuring in the direction of the normal to the exit surface of the integrating sphere, it is necessary to ensure that the uniformity of the light field brightness within a 10-degree solid angle meets the requirements to guarantee visual equivalence under large field of view conditions.)

[0114] Finally, the experimental verification results illustrate the effects that the candela reproduction method and apparatus based on the virtual blackbody equivalent spectral synthesis light source provided in this disclosure can achieve.

[0115] Specifically, the candela reproduction method and apparatus based on a virtual blackbody equivalent spectral synthetic light source provided in this disclosure were used to conduct a candela reproduction experiment. For example, three narrowband laser diodes (wavelengths at 485 nm, 550 nm, and 630 nm, respectively) were used, and the power of each laser was adjusted through closed-loop feedback control to match the spectral radiance distribution of the synthetic light source with that of a 2041.35 K blackbody within the corresponding wavelength band. Calibration was performed using a spectroradiometer or radiance detector traceable to national metrological standards (relative standard uncertainty 0.02%).

[0116] It should be noted that although the actual measured temperature of the platinum freezing point, 2041.35 K, has a standard uncertainty of approximately 0.4 K in experiments, the embodiments of this disclosure define the ideal blackbody temperature corresponding to the candela as 2041.35 K. This temperature value itself, as a defining constant, is unaffected by the measurement uncertainty. Therefore, the candela value reproduced in the embodiments of this disclosure depends only on the accuracy of the spectral synthesis and the calibration accuracy of the geometric parameters, and is decoupled from the actual measurement uncertainty of the platinum freezing point temperature.

[0117] Experimental results show that the relative standard uncertainty of the 1 candela luminous intensity reproduced by the embodiments of this disclosure can reach less than 0.05%, which is significantly better than the existing candela reproduction methods. This verifies the progress and feasibility of the candela reproduction method and device based on the virtual blackbody equivalent spectral synthesis light source provided by the embodiments of this disclosure.

[0118] In this embodiment, the spectral radiation characteristics of a platinum solidification point blackbody are reproduced by virtual blackbody equivalent spectral synthesis. Combined with precise geometric control and weighted equivalence of human visual functions, a candela reproduction method and apparatus that are highly consistent with historical definitions and compatible with multiple visual models are realized, and it also has good prospects for engineering applications.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0120] Furthermore, in this paper, the aforementioned reference temperature is set as the platinum freezing point to maintain consistency with the historical definition of the candela. However, it could also be set to one of the following: palladium freezing point, rhodium freezing point, iridium freezing point, molybdenum freezing point, tungsten freezing point, iron-carbon freezing point, cobalt-carbon freezing point, palladium-carbon freezing point, platinum-carbon freezing point, ruthenium-carbon freezing point, rhenium-carbon freezing point, molybdenum carbide-carbon freezing point, tungsten carbide-carbon freezing point, or any temperature at which significant observable spectral radiance is generated through blackbody radiation in the human visual band. Once the reference temperature is determined, the corresponding equivalent spectral synthesis light source can be prepared using the methods described in this paper.

[0121] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for candela reproduction based on a virtual blackbody equivalent spectral synthesis light source, characterized in that, include: Using the freezing point temperature of platinum as the reference temperature, the reference spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band is calculated based on Planck's blackbody radiation formula. A virtual blackbody equivalent spectral synthesis light source is constructed; wherein the virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human eye's visual band and power that can be independently adjusted and controlled; the beam output from the narrowband spectral light source is guided into the homogenizing device for spatial mixing, forming a spatially uniform light field with adjustable spectral radiance distribution within a predetermined solid angle in a predetermined direction on the exit surface of the virtual blackbody equivalent spectral synthesis light source. For one or more preset human eye spectral luminous efficiency functions, the target spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source is determined, and the target spectral radiance distribution and the first weighted integral value of the preset human eye spectral luminous efficiency function are equal to the reference spectral radiance distribution and the second weighted integral value of the preset human eye spectral luminous efficiency function within a preset matching error threshold range. The power of each narrowband spectral source in the virtual blackbody equivalent spectral synthesis light source is independently adjusted so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthesis light source reaches the target spectral radiance distribution. p times; among which, p It is a real number greater than 0; When the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set to one-sixtieth of a square centimeter... q When the intensity is doubled, the luminous intensity of the virtual blackbody equivalent spectral synthesis light source in the predetermined direction is determined to be... p q Candela; among which, q It is a real number greater than 0.

2. The candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source according to claim 1, characterized in that, The preset one or more human eye spectral optical efficiency functions include at least one of the following: a 2° field of view photopic spectral optical efficiency function, a 2° field of view scotopic spectral optical efficiency function, a 2° field of view mesopic spectral optical efficiency function, a 2° field of view based on cone cells, a 2° field of view long-wavelength cone cell spectral response function, a 2° field of view mid-wavelength cone cell spectral response function, a 2° field of view short-wavelength cone cell spectral response function, a 10° field of view photopic spectral optical efficiency function, a 10° field of view scotopic spectral optical efficiency function, a 10° field of view mesopic spectral optical efficiency function, a 10° field of view based on cone cells, a 10° field of view long-wavelength cone cell spectral response function, a 10° field of view mid-wavelength cone cell spectral response function, and a 10° field of view short-wavelength cone cell spectral response function. When the preset one or more human eye spectral light efficiency functions include at least two human eye spectral light efficiency functions, the weight or relative proportion of each human eye spectral light efficiency function is set respectively.

3. The candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source according to claim 1, characterized in that, The candela reproduction method based on the virtual blackbody equivalent spectral synthesis light source further includes: When the virtual blackbody equivalent spectral synthesis light source includes more than one combination of narrowband spectral light sources, the combination method in which the number of narrowband spectral light sources in different combinations is less than a preset number threshold is taken as the narrowband spectral light source combination method in the virtual blackbody equivalent spectral synthesis light source.

4. The candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source according to claim 1, characterized in that, The step of independently adjusting the power of each of the narrowband spectral sources in the virtual blackbody equivalent spectral synthesis light source includes: The actual spectral radiance distribution of the uniform light field is detected using a spectroradiometer or radiance detector. The actual spectral radiance distribution is compared with the target spectral radiance distribution to obtain the deviation signal; Based on the deviation signal, adjust the driving current or output power of each of the narrowband spectral light sources until the actual spectral radiance distribution reaches the target spectral radiance distribution.

5. The candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source according to claim 4, characterized in that, Also includes: Using a standard spectral radiance meter or radiance detector traceable to national metrological standards, the spectral radiance of the virtual blackbody equivalent spectral synthetic light source at the working wavelength of each of the narrowband spectral light sources is calibrated to obtain calibration results. The calibration results are recorded and used as the basis for tracing the source of the virtual blackbody equivalent spectral synthesis light source.

6. The candela reproduction method based on a virtual blackbody equivalent spectral synthesis light source according to claim 1, characterized in that, The effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source is set based on replacing precision apertures with different effective aperture areas or installing an adjustable aperture with an effective aperture area, and the effective aperture area is calibrated.

7. A candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source, characterized in that, include: The benchmark target determination module is used to calculate the benchmark spectral radiance distribution of an ideal blackbody with an emissivity of 1 in the human visual band, based on Planck's blackbody radiation formula, using the platinum freezing point temperature as the benchmark temperature. A virtual blackbody equivalent spectral synthesis light source construction module is used to construct a virtual blackbody equivalent spectral synthesis light source. The virtual blackbody equivalent spectral synthesis light source includes a homogenizing device and a set of narrowband spectral light sources with wavelengths covering the human eye's visual band and power that can be independently adjusted and controlled. The beam output from the narrowband spectral light sources is guided into the homogenizing device for spatial mixing, forming a spatially uniform light field with adjustable spectral radiance distribution within a predetermined solid angle in a predetermined direction on the exit surface of the virtual blackbody equivalent spectral synthesis light source. The control and adjustment module is used to determine the target spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source for one or more preset human eye spectral luminous efficiency functions. The target spectral radiance distribution and the first weighted integral value of the preset human eye spectral luminous efficiency function are equal to the reference spectral radiance distribution and the second weighted integral value of the preset human eye spectral luminous efficiency function within a preset matching error threshold range. The module also independently adjusts the power of each narrowband spectral source in the virtual blackbody equivalent spectral synthetic light source so that the actual spectral radiance distribution of the virtual blackbody equivalent spectral synthetic light source reaches the target spectral radiance distribution. p times; among which, p It is a real number greater than 0; The area setting and value output module is used to set the effective luminous area of ​​the exit surface of the virtual blackbody equivalent spectral synthesis light source to one-sixtieth of a square centimeter. q The luminous intensity of the virtual blackbody equivalent spectral synthesized light source in the predetermined direction is determined and output based on the target spectral radiance distribution and the effective luminous area. p q Candela; among which, q It is a real number greater than 0.

8. The candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source according to claim 7, characterized in that, The light-diffusing device includes at least one of integrating sphere, diffuse reflector, diffuse transmissive sheet, optical fiber, spatial beam combiner, and digital micromirror array, and the light-diffusing device includes devices that are assisted or enhanced by at least one of rotation, vibration, and scanning.

9. The candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source according to claim 7, characterized in that, The narrowband spectral light source includes at least one of a laser, a laser diode, a light-emitting diode, and a supercontinuum light source, and the narrowband spectral light source includes devices for eliminating speckle and limiting spectral bandwidth.

10. The candela reproduction device based on a virtual blackbody equivalent spectral synthesis light source according to claim 7, characterized in that, The light homogenizing device includes an integrating sphere, and a precision aperture is provided at the light outlet of the integrating sphere; The narrowband spectral light source includes multiple laser diodes. The beams output by the multiple laser diodes are guided into the interior of the integrating sphere through space or optical fiber after passing through an anticoherence device. The candela reproduction device based on the virtual blackbody equivalent spectral synthesis light source further includes: a spectroradiometer or a radiance detector; the monitoring optical path of the spectroradiometer or radiance detector is aligned with the predetermined direction of the exit surface, and the spectroradiometer or radiance detector is used to detect the actual spectral radiance of the narrow band corresponding to the uniform light field and transmit it to the control and adjustment module.

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