WO2024106966A1

WO2024106966A1 - Dual photodiode radiometer

Info

Publication number: WO2024106966A1
Application number: PCT/KR2023/018431
Authority: WO
Inventors: 이동훈; 신동주; 박성종
Original assignee: 한국표준과학연구원
Priority date: 2022-11-16
Filing date: 2023-11-16
Publication date: 2024-05-23
Also published as: KR20240071738A

Abstract

The present invention pertains to a dual photodiode radiometer comprising: a base substrate set on the optical path of to-be-measured light emitted from a light source; a first optical sensor unit installed in an incident area of the base substrate, on which the to-be-measured light is incident, so as to receive the to-be-measured light; and a second optical sensor unit that is installed, adjacent to the first optical sensor unit, in the incident area of the base substrate and receives the to-be-measured light, and has a different spectral sensitivity than the first optical sensor unit. The dual photodiode radiometer according to the present invention generates information about the to-be-measured light from the ratio between optical signals acquired using a plurality of photodiodes, and thus has the advantage of being able to obtain more accurate measurement values regardless of the type of light source or changes in spectral distribution.

Description

Dual photodiode radiometer

The present invention relates to a dual photodiode radiometer, and more specifically, to a dual photodiode radiometer using a plurality of optical sensors with different spectral sensitivities.

A radiometer, in its most general sense, is a device that measures optical radiation. The primary use of a radiometer is to characterize a radiation source by measuring or monitoring the optical radiation emitted by the source.

Photodiode-based radiometers are widely used in applications due to their advantages of high sensitivity, fast response, and simple structure. However, photodiode-based radiometers require separate additional equipment to measure spectral distribution or wavelength characteristics depending on the type of light source being measured, and when changing the filter to expand the usable area, calibration is required for each combination of individual filters and detectors ( calibration) must be performed.

The present invention was created to improve the above problems, and is a dual photo diode radiometer that uses a plurality of photo diodes and can obtain information about the light to be measured from the ratio of the optical signals obtained from the photo diodes. The purpose is to provide.

A dual photodiode radiometer according to the present invention for achieving the above object includes a base substrate set on the optical path of the measurement target light emitted from a light source, and the base into which the measurement target light is incident so as to receive the measurement target light. A first optical sensor unit installed in the incident area of the substrate, and installed in the incident area of the base substrate adjacent to the first optical sensor unit to receive the light to be measured, and a spectral spectrum different from that of the first optical sensor unit. A second optical sensor unit having sensitivity is provided.

The spectral sensitivity of the first and second optical sensors linearly increases as the wavelength value of incident light increases within a preset light wavelength range.

The second optical sensor unit includes a photo diode installed in the incident area of the base substrate, and a light-receiving surface of the photo diode that receives the light to be measured is coated to change the transmittance of the wavelength of light incident on the light-receiving surface for each wavelength. It is desirable to have a transmission filter layer.

The spectral response ratio of the first and second optical sensor units monotonically increases or monotonically decreases as the wavelength of the light to be measured increases within the set light wavelength range.

Meanwhile, the dual photo diode radiometer according to the present invention may further include an optical filter unit installed on the optical path of the light to be measured between the light source and the base substrate to filter the light incident on the base substrate.

The optical filter unit may include a broadband filter having a predetermined transmittance in the set optical wavelength region.

The optical filter unit may be equipped with a band-pass filter having a predetermined center wavelength and spectral band to be analyzed.

The optical filter unit may include a transmission filter having a spectral transmittance corresponding to a preset weighting function.

The center wavelength of the bandpass filter may be varied according to a preset variable pattern.

Meanwhile, the dual photo diode radiometer according to the present invention is provided with an accommodating space inside which the base substrate is accommodated, and an entrance opening is provided on the side opposite to the incident area of the base substrate so that the light to be measured is incident on the base substrate. It may be provided with a formed case and a diffusion plate installed on the entrance side to diffuse the measurement target light incident on the base substrate.

The dual photodiode radiometer according to the present invention calculates information about the light to be measured from the ratio of optical signals acquired using a plurality of photodiodes, so more accurate measurement values can be obtained regardless of the type of light source or changes in spectral distribution. There is an advantage.

1 is a conceptual diagram of a dual photo diode radiometer according to an embodiment of the present invention,

Figure 2 is a cross-sectional view of the dual photo diode radiometer of Figure 1;

Figure 3 is a graph of the spectral responsivity of the first and second optical sensor units of the dual photo diode radiometer of Figure 1;

Figure 4 is a graph of the spectral response ratio of the first and second optical sensor units of the dual photo diode radiometer of Figure 1;

Figures 5 to 8 are graphs showing the function of the optical filter unit of the dual photo diode radiometer of Figure 1.

Hereinafter, a dual photo diode radiometer according to an embodiment of the present invention will be described in detail with reference to the attached drawings. Since the present invention can be subject to various changes and can have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components. In the attached drawings, the dimensions of the structures are enlarged from the actual size for clarity of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component without departing from the scope of the present invention, and similarly, the second component may also be named a first component.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

1 and 2 show a dual photo diode radiometer 100 according to the present invention.

Referring to the drawing, the dual photo diode radiometer 100 includes a case 110, a base substrate 120 installed inside the case 110, and a measurement object installed on the base substrate 120 and emitted from a light source. First and second

optical sensor units

130 and 140 for receiving light, and installed on the optical path of the light to be measured between the light source and the base substrate 120, filter the light incident on the base substrate 120. It is provided with a filter unit 150 and an analysis module (not shown) that analyzes the photocurrent signal provided from the first and second

optical sensor units

130 and 140.

The case 110 is installed on the optical path of the light to be measured emitted from the light source, and a receiving space 111 in which the base substrate 120 is accommodated is formed therein. Additionally, an entrance port 112 is formed on the front of the case 110 to allow the light to be measured to enter the receiving space 111. Meanwhile, in the illustrated example, the case 110 is shown as having a cylindrical structure, but the case 110 is not limited to this and may be formed in various shapes such as a square column or an oval.

In addition, the case 110 has a diffusion plate 113 installed on the entrance port 112 side to diffuse the measurement target light incident on the receiving space 111. Since the diffusion plate 113 is a diffuser commonly used in the related art to diffuse incident light, detailed description will be omitted.

The base substrate 120 is set on the optical path of the light to be measured emitted from the light source, and is installed on the rear inner surface of the case 110. The base substrate 120 has an incident area 121 on the front surface opposite the entrance opening 112, where light to be measured is incident.

The first optical sensor unit 130 is provided with a first photo diode 131 installed in the incident area 121 of the base substrate 120 where the measurement target light is incident so as to receive the measurement target light. . The first photodiode 131 is an optical sensor that receives light to be measured and generates a photocurrent signal corresponding to the light to be measured. The photocurrent signal of the first photodiode 131 is transmitted to the analysis module.

The second optical sensor unit 140 is installed in the incident area 121 of the base substrate 120 adjacent to the first optical sensor unit 130 and receives the light to be measured. It has a different spectral responsivity from that of the unit 130. The second optical sensor unit 140 includes a second photo diode 141 and a transmission filter layer 142.

The second photodiode 141 is installed in the incident area 121 of the base substrate 120 and receives light to be measured to generate a photocurrent signal. Here, the second photo diode 141 is installed in the incident area 121 adjacent to the first photo diode 131, and a light receiving surface for receiving the light to be measured is provided on the front side. At this time, it is preferable that the second photo diode 141 uses the same optical sensor as the corresponding first photo diode 131.

The transmission filter layer 142 is coated on the light-receiving surface of the second photo diode 141 to change the transmittance according to the wavelength of light incident on the light-receiving surface. The transmission filter layer 142 is formed as a non-metallic dielectric layer coating on the light-receiving surface of the second photo diode 141 to achieve a desired spectral transmittance.

The spectral transmittance and spectral reflectance of the corresponding transmission filter layer 142 may be designed to be different from each other. Meanwhile, the transmission filter layer 142 is not limited to this, and any variable means that can change the transmittance according to the wavelength of light incident on the second photo diode 141 can be applied. The spectral sensitivities of the first optical sensor unit 130 and the second optical sensor unit 140 are set to be different from each other by the above-described transmission filter layer 142.

Meanwhile, it is preferable that the spectral sensitivities of the first optical sensor unit 130 and the second optical sensor unit 140 increase linearly as the wavelength value of incident light increases within a preset light wavelength range. Here, the set light wavelength range is 400 nm to 950 nm, but is not limited to this and can be set in various ways depending on the light to be measured.

Figure 3 shows a graph of the spectral responsivity of the first and second

optical sensor units

130 and 140 made of silicon photodiodes. Here, “A” is a graph of the spectral responsivity of the silicon photodiode, and “B” is the spectral responsivity of the silicon photodiode coated with the transmission filter layer 142. Referring to the drawing, the spectral sensitivity of a single silicon photodiode, such as the first optical sensor unit 130, may linearly increase as the wavelength of incident light increases in a set light wavelength region. In addition, like the second optical sensor unit 140, the silicon photodiode coated with the transmission filter layer 142 also has a linear increase in spectral sensitivity within the set light wavelength region, but has a spectral sensitivity different from that of a single silicon photodiode. indicates. Therefore, the second optical sensor unit 140 having a different spectral sensitivity from that of the first optical sensor unit 130 can be easily manufactured by coating the transmission filter layer 142 on the same photo diode as the first optical sensor unit 130. can do.

Meanwhile, Figure 4 shows a graph of the spectral response ratio of the first and second

optical sensor units

130 and 140. Referring to the drawings, the spectral response ratio of the first and second

optical sensor units

130 and 140 monotonically increases as the wavelength of the light to be measured increases within the set optical wavelength region so that an inverse function exists. Meanwhile, without being limited to this, the first and second

optical sensor units

130 and 140 may be designed so that the spectral response ratio monotonically decreases as the wavelength of the light to be measured increases within the set optical wavelength region.

The analysis module converts the photocurrent signal provided from the first and second

optical sensor units

130 and 140 into a digital signal, and analyzes the digital signal to calculate the radiation amount of light to be measured. The analysis module calculates the radiation amount (Φ) of the light to be measured through Equation 1 below.

Here, T(λ) is the spectral transmittance of the optical filter unit 150, and λ _min and λ _max are the minimum and maximum wavelength values of light passing through the optical filter unit 150. The irradiance of the light to be measured is within λ _min to λ _max , and is the spectral irradiance for the wavelength λ (

) can be calculated by integration.

Here, the photocurrent signals (i _A , i _B ) from the first optical sensor unit 130 and the second optical sensor unit 140 are the spectral irradiance (

) can be calculated by introducing the respective spectral sensitivities (S _A (λ), S _B (λ)) of the first optical sensor unit 130 and the second optical sensor unit 140, and the calculation formula is the following equation Same as 2.

Here, the spectral sensitivities (S _A (λ), S _B (λ)) increase linearly with respect to the incident light wavelength, so each spectral responsivity is expressed in Equation 3 below.

Here, a ₀ , a ₁ , b ₀ , b ₁ are constants determined from calibration measurements of the radiometer.

Meanwhile, since the ratio of spectral sensitivities of the first and second

optical sensor units

130 and 140 increases monotonically, the ratio of the spectral sensitivities is expressed in Equation 4 below.

And, if Equation 3 is substituted into Equation 2, the photocurrent signals of the first and second

optical sensor units

130 and 140 are expressed as Equation 5 below.

Meanwhile, the central wavelength (λ _c ) of the light source is expressed in Equation 6 below.

Here, X _λ (λ) can be substituted for any spectral measurement quantity.

Meanwhile, using Equation 1 and Equation 5, the photocurrent signals (i _A , i _B ) of the first optical sensor unit 130 and the second optical sensor unit 140,

Summarizing the equation for the center wavelength (λ _c ), the photocurrent signals of the first and second

optical sensor units

130 and 140 are expressed in Equation 7 below.

If the radiation amount (Φ) of the light to be measured is calculated based on Equation 7 above, it is as shown in Equation 8 below.

As described above,

If only the value of the center wavelength (λ _c ) is known, the radiation amount (Φ) of the light to be measured can be derived from the photocurrent signal value of the first and second

optical sensor units

130 and 140.

Meanwhile, the central wavelength (λ _c ) value can be calculated from the spectral response ratio (r(λ)) of the first and second

optical sensor units

130 and 140 as shown in Equation 9 below.

The center wavelength (λ _c ) value is calculated using the ratio of the photocurrent signals of the first and second

optical sensor units

130 and 140 measured as described above and the inverse function of the previously known spectral response ratio (r(λ)). It can be calculated.

That is, the dual photodiode radiometer 100 according to the present invention measures the ratio of the photocurrent signals of the first and second

optical sensor units

130 and 140 and the corresponding photocurrent signals, and determines the central wavelength of the light to be measured from the ratio of the photocurrent signals. can be calculated, and using this, the radiation amount value of the light to be measured can be obtained. Here, it is preferable that information on the spectral sensitivities of the first and second

optical sensor units

130 and 140 and the spectral transmittance of the optical filter unit 150 are written into the analysis module.

The optical filter unit 150 is installed inside the case 110 in front of the first and second

optical sensor units

130 and 140 and enters the first and second

optical sensor units

130 and 140 according to the type of light source to be measured. Filters the light to be measured.

As shown in FIG. 5, the optical filter unit 150 includes a broadband filter having a predetermined transmittance in the set optical wavelength region. In Figure 5, the black graph shows the wavelength range and transmittance of light that can be transmitted through the broadband filter, the orange graph shows the amount of radiation for each wavelength band of the light to be measured, and λ _min and λ _max are the minimum wavelength value in the set light wavelength range and This is the maximum wavelength value, and λc is the central wavelength of the light to be measured.

When measuring the radiation amount of a spectral light source or monochromatic light with a narrow line width, such as an LED or a laser, a broadband filter having a constant transmittance in a set light wavelength region can be set inside the case 110 for measurement. Since the transmittance of the optical filter unit 150 between the wavelengths λ _min and λ _max is constant, the transmittance is replaced with a constant value and can be replaced with 1 through calibration. At this time, it is possible to simultaneously measure the central wavelength and radiation quantity characteristics of the light to be measured through the first and second

optical sensor units

130 and 140. By setting the corresponding broadband filter, the dual photodiode radiometer 100 of the present invention can be used as a laser output meter or a monochromatic light radiometer.

Meanwhile, the optical filter unit 150 may be equipped with a band-pass filter having a predetermined center wavelength and spectral band to be analyzed, as shown in FIG. 6. In Figure 6, the black graph shows the wavelength range and transmittance of light that can be transmitted through the bandpass filter, the orange graph shows the amount of radiation for each wavelength band of the light to be measured, and λ _min and λ _max represent the wavelength range of light that can be transmitted. , are the minimum and maximum wavelength values within the spectral band area based on the set central wavelength.

When measuring the radiation amount of a certain wavelength range from a broadband white light source, the corresponding bandpass filter can be set inside the case 110 for measurement. Depending on the selection of the light transmission (T(λ)) area of the corresponding bandpass filter, the amount of radiation integrated in a specific wavelength area of the light to be measured can be measured through the first and second

optical sensor units

130 and 140. At this time, the light transmittance value of a certain bandpass filter can be replaced with 1 through calibration. Depending on the wavelength range of the target light to be measured, multiple bandpass filters with various center wavelengths and spectral bands can be replaced and used. Using the above-described bandpass filter, the dual photo diode radiometer 100 of the present invention can be used as a UV meter, an ultraviolet/visible/infrared selective radiometer, and a PPFD photosynthetic photometric meter.

Meanwhile, the optical filter unit 150 may include a transmission filter having a spectral transmittance corresponding to a preset weighting function. When measuring the amount of radiation defined by applying a specific weighting function, the measurement can be performed by setting the corresponding transmission filter inside the case 110. In Figure 7, the CIE XYZ tristimulus value for the light to be measured is measured using the corresponding transmission filter. In the figure, the orange graph on the upper side is a graph showing the radiation amount by wavelength of the light to be measured, and the lower graph shows the spectral transmittance of a filter set identically to the three types of CIE color matching functions. By measuring the radiation amount of the target light using each color matching function as a weighting function, the CIE XYZ tristimulus value and the color characteristics (color coordinates) of the target light source can be calculated from this.

The dual photodiode radiometer 100 of the present invention with the transmission filter set has the advantage of being able to design and apply a filter tailored only to the weighting function without considering the characteristics of the detector. When using multiple transmission filters with differently designed specifications, the present invention can also add a function that can identify the type of filter from the center wavelength value of the light to be measured. Using the above-described transmission band, the dual photo diode radiometer 100 of the present invention can be used as a photo illuminance meter, photoluminance meter, and colorimeter.

Meanwhile, the optical filter unit 150 may include a bandpass filter whose center wavelength is variable according to a preset variable pattern, as shown in FIG. 8. Here, the bandpass filter may be designed to have a relatively narrow spectral band of 10 nm or less. For example, the bandpass filter may be set to change the center wavelength in a variable pattern that increases or decreases at a constant speed or at preset intervals as time passes. In FIG. 8, the black graph shows the wavelength range and transmittance of light that can be transmitted in the bandpass filter, and the black column represents the wavelength range of light that can be transmitted, and is set to have a width corresponding to the set spectral band area. Additionally, the orange graph is a graph showing the radiation amount by wavelength of the light to be measured.

At this time, the band pass filter is capable of electro-optical scanning, and since a wavelength tunable band filter commonly used in the related art is applied, a detailed description will be omitted. By setting the above-described bandpass filter inside the case 110, the present invention can realize the function of a spectroradiometer. Moreover, the center wavelength of the bandpass filter can be monitored in real time using the first and second

optical sensor units

130 and 140 of the present invention, and sensitivity correction for each wavelength is not required, so when a single photodiode is used, Compared to other methods, it is possible to quickly and accurately measure the amount of radiation by wavelength of the light being measured.

As described above, the dual photo diode radiometer 100 according to the present invention filters the light to be measured through the optical filter unit 150, so that various types of radiometer functions can be implemented.

The description of the presented embodiments is provided to enable any person skilled in the art to use or practice the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not limited to the embodiments presented herein, but is to be construed in the broadest scope consistent with the principles and novel features presented herein.

Claims

A base substrate set on the optical path of the light to be measured emitted from the light source;

a first optical sensor unit installed in an incident area of the base substrate where the measurement target light is incident so as to receive the measurement target light; and

A second optical sensor unit installed in the incident area of the base substrate adjacent to the first optical sensor unit to receive the light to be measured, and having a different spectral sensitivity from the first optical sensor unit,

Dual photodiode radiometer.
According to paragraph 1,

The first and second optical sensors have spectral sensitivity linearly increasing as the wavelength value of incident light increases within a preset light wavelength range,

Dual photodiode radiometer.
According to claim 1 or 2,

The second optical sensor unit

a photo diode installed in the incident area of the base substrate; and

A transmission filter layer coated on the light-receiving surface of the photodiode that receives the light to be measured and changing the transmittance according to the wavelength of the light to be measured incident on the light-receiving surface.

Dual photodiode radiometer.
According to paragraph 2,

The spectral response ratio of the first and second optical sensor units monotonically increases or monotonically decreases as the wavelength of the light to be measured increases within the set light wavelength region,

Dual photodiode radiometer.
According to paragraph 2,

Further comprising: an optical filter unit installed on the optical path of the light to be measured between the light source and the base substrate and filtering light incident on the base substrate;

Dual photodiode radiometer.
According to clause 5,

The optical filter unit includes a broadband filter having a predetermined transmittance in the set optical wavelength region,

Dual photodiode radiometer.
According to clause 5,

The optical filter unit includes a bandpass filter having a predetermined center wavelength and spectral band to be analyzed,

Dual photodiode radiometer.
According to clause 5,

The optical filter unit includes a transmission filter having a spectral transmittance corresponding to a preset weighting function,

Dual photodiode radiometer.
In clause 7,

The bandpass filter has a center wavelength that varies according to a preset variable pattern,

Dual photodiode radiometer.
According to claim 1 or 2,

a case having an accommodating space therein for accommodating the base substrate, and having an entrance opening formed on a side opposite to an incident area of the base substrate so that the light to be measured is incident on the base substrate; and

Provided with a diffusion plate installed on the entrance side to diffuse the measurement target light incident on the base substrate,

Dual photodiode radiometer.