A spectrophotometer linearity calibration device and method of use thereof

Abstract

The application discloses a kind of spectrophotometer linearity calibration device and its use method, it is related to photometer technical field.The device includes: the U-shaped section of upper flat plate, lower flat plate and U-shaped groove is mutually parallel;Two U-shaped grooves are opposite;Each U-shaped groove upper end is fixedly connected to upper flat plate by stand column, and lower end is fixedly connected to lower flat plate by stand column;It further includes that upper push rod penetrates upper flat plate and is fixed to upper flat plate, for driving upper flat plate to move up and down;Stand column penetrates parallel to upper flat plate upper flat plate;Upper vertical plate is vertically arranged on the lower surface of upper flat plate, and both sides are located in two U-shaped grooves respectively;Upper vertical plate moves up and down with upper flat plate;Lower push rod and upper push rod, lower flat plate and upper flat plate are respectively symmetrically arranged;Lower vertical plate is arranged opposite to upper vertical plate up and down.The device is based on single light source method, can avoid the influence of inconsistent light source in multiple light source method, linearity measurement can cover wide range of wavelength, and has smaller calibration error and higher calibration accuracy.

Description

Technical Field

[0001] This invention relates to the field of spectrophotometer calibration technology, and in particular to a spectrophotometer linearity calibration device and its usage method. Background Technology

[0002] Photometric linearity in a spectrophotometer refers to the degree to which the instrument's photometric measurement system maintains a linear relationship with the measured value of the light radiation power incident on the detector. Better photometric linearity indicates higher photometric accuracy, meaning the instrument can accurately reflect changes in incident radiation. Photometric data measured in a spectrophotometer is a relative value: it is relative to 100% or 0%, which are freely set. If a spectrophotometer's response is linear within the range of 0% to 100%, accurate photometric values ​​can be obtained. Due to the influence of nonlinear factors such as the detector, electronic circuitry, display, and stray light levels in the spectrophotometer, the photometric linearity of the entire system must be corrected to obtain accurate measurements.

[0003] Since 1897, various methods for measuring photometric linearity have been proposed, which can be broadly categorized into direct and indirect methods. Direct methods primarily involve superposition, while indirect methods include the inverse square distance method, the filter or filter combination method, and the polarizer method. The advantages of indirect methods are speed and simplicity; however, their disadvantages include complex error sources. The introduction of auxiliary quantities, such as the transmittance of the filter and the polarization degree of the polarizer, introduces additional errors, making it difficult to control the accuracy of the measurement results. For example, the traceability uncertainty of a standard neutral density filter at a higher-level metrology institution is typically 0.005; if a calibrated spectrophotometer is used, it can lead to even greater errors. The optical superposition method, based on physical principles, is a precise measurement method that avoids instrument-to-instrument transmission errors, is independent of sample preparation, and can be used across the entire photometric range. It is divided into multi-source and single-source methods. This invention employs a single-source method. The light source, spectrometer, collimator, and receiver components required for the measurement system all utilize the original spectrophotometer system. The nonlinear coefficient of the spectrophotometer can be obtained simply by placing the calibration device inside the sample chamber of the spectrophotometer and measuring it according to a certain method, thereby performing linear correction on the spectrophotometer.

[0004] Traditional single-source methods employ a pair of phase adjusters to split the emitted light into two beams, measure the power of each beam separately, and then use a beam combiner to combine the two beams and measure the combined beam's power. This method adds numerous optical components to the original optical path, such as polarizing mirrors, phase adjusters, polarizing beam splitters, and motorized shutters. These components all weaken the original beam power and introduce significant measurement errors; furthermore, inconsistencies in the motorized shutter speeds of the upper and lower beam paths also affect measurement accuracy. Summary of the Invention

[0005] To address the aforementioned technical problems in the prior art, this invention aims to provide a spectrophotometer linearity calibration device with smaller measurement errors and higher accuracy.

[0006] Specifically, in a first aspect, the present invention provides a spectrophotometer linearity calibration device, comprising an upper plate, a lower plate, and a U-shaped groove;

[0007] The upper plate, lower plate, and U-shaped groove have parallel cross-sections;

[0008] The two U-shaped grooves have openings facing each other; the upper end of each U-shaped groove is fixedly connected to the upper plate by at least one column, and the lower end is fixedly connected to the lower plate by at least one column.

[0009] It also includes the upper push rod, the upper upright plate, and the upper flat plate;

[0010] The upper push rod penetrates the upper plate and is fixed to the upper flat plate, which is used to drive the upper flat plate to move up and down; the column connecting the upper end of the U-shaped groove and the upper plate penetrates the upper flat plate; the upper flat plate is parallel to the upper plate.

[0011] The upper upright plate is vertically fixed to the lower surface of the upper flat plate, with its two sides located in two U-shaped grooves respectively; the upper upright plate moves up and down with the upper flat plate;

[0012] It also includes a lower push rod, a lower upright plate, and a lower flat plate;

[0013] The lower push rod and the upper push rod are symmetrically arranged vertically; the lower flat plate and the upper flat plate are symmetrically arranged vertically; the lower upright plate and the upper upright plate are arranged opposite each other vertically.

[0014] Secondly, this section also provides a method for using the aforementioned spectrophotometer linearity calibration device, and the specific calibration method for the spectrophotometer is as follows:

[0015] Step S1: Set the measurement beam;

[0016] Step S2: Set the spectrophotometer monochromator to the desired wavelength point λ1, and perform 0% line and 100% line calibration;

[0017] Wherein, 250nm≤λ1≤2500nm;

[0018] Step S3:

[0019] Fully open the upper and lower panels.

[0020] (1) Measure the distance L1 and the radiative flux Iab at this time. λ1 ;

[0021] (2) Move the lower plate up by L1 / 2 and measure the radiative flux Ia. λ1 ;

[0022] (3) Move the upper plate down by L1 / 2 and measure the radiative flux Ib. λ1 ;

[0023] (4) Close the upper and lower vertical plates and measure the stray radiation Id. λ1 ;

[0024] Step S4: Calculate the nonlinear error δ, using the following formula:

[0025] δ=(Iab λ1 -Ia λ1 -Ib λ1 -Id λ1 ) / 2;

[0026] Step S5: Return to step S2 to adjust wavelength point λ1, and measure the nonlinear error of all wavelength points in sequence.

[0027] Compared with the prior art, the spectrophotometer linearity calibration device provided by the present invention is based on the single light source method, which can avoid the influence of inconsistent light sources in the multi-light source method. The linearity measurement can cover a wide wavelength range and has a small calibration error and high calibration accuracy. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a spectrophotometer linearity calibration device in one embodiment of the present invention.

[0029] Figure 2 This is a U-shaped cross-sectional view of the U-shaped groove of the spectrophotometer linearity calibration device in one embodiment of the present invention.

[0030] Figure 3 This is a cross-sectional view of the light-shielding plate on the spectrophotometer linearity calibration device in one embodiment of the present invention.

[0031] Figure 4 This is a cross-sectional view of the lower light-shielding plate of the spectrophotometer linearity calibration device in one embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram showing the opening and closing state of the light inlet slit of the spectrophotometer linearity calibration device in one embodiment of the present invention.

[0033] Figure 6 This is a flowchart of a spectrophotometer leveling method in one embodiment of the present invention.

[0034] Figure 7 This is a flowchart of a spectrophotometer calibration method according to an embodiment of the present invention.

[0035] The labels in the diagram are for illustrative purposes only:

[0036] Lower plate - 11, column - 12, U-shaped groove - 13, upper plate - 14, upper light shield - 21, lower light shield - 22, lower push rod - 30, upper push rod - 31, stepper motor - 40, light inlet slit 50;

[0037] Upper vertical plate - 211, upper flat plate - 212, lower vertical plate - 221, lower flat plate - 222. Detailed Implementation

[0038] The technical solutions provided by the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0039] Example 1:

[0040] like Figure 1 As shown, this embodiment provides a spectrophotometer linearity calibration device, including an upper plate 14, a lower plate 11, and two U-shaped grooves 13; the U-shaped cross-sections of the upper plate 14, lower plate 11, and U-shaped grooves 13 are parallel to each other; the openings of the two U-shaped grooves 13 are opposite to each other; the upper end of the U-shaped groove 13 is fixedly connected to the upper plate 14 by at least one column 12, and the lower end is fixedly connected to the lower plate 11 by at least one column 12; all columns 12 are parallel to each other. The U-shaped cross-section of the U-shaped groove 13 is as follows: Figure 2 As shown.

[0041] It also includes an upper light-shielding plate 21 and a lower light-shielding plate 22. The upper light-shielding plate 21 includes an upper push rod 31, an upper upright plate 211 and an upper flat plate 212, and the lower light-shielding plate 22 includes an upper push rod 31, a lower upright plate 221 and a lower flat plate 222.

[0042] The upper push rod 31 penetrates the upper plate 14 and is fixed to the upper flat plate 212, used to drive the upper flat plate 212 to move up and down; the column 12 connecting the upper end of the U-shaped groove 13 and the upper plate 14 penetrates the upper flat plate 212; the upper flat plate 212 is parallel to the upper plate 14. The upper upright plate 211 is vertically fixed to the lower surface of the upper flat plate 212, with its two sides located in the two U-shaped grooves 13 respectively; the upper upright plate 211 moves up and down with the upper flat plate 212.

[0043] The lower push rod 30 and the upper push rod 31 are arranged symmetrically in the vertical direction; the lower flat plate 222 and the upper flat plate 212 are arranged symmetrically in the vertical direction; the lower upright plate 221 and the upper upright plate 211 are arranged opposite each other in the vertical direction.

[0044] Both the upper upright plate 211 and the lower upright plate 221 are cuboids, with one convex and the other concave on their lower end faces, interlocking to block light. The thickness of the two upright plates, i.e., the height of the cuboids, is less than the width of the U-shaped groove, to ensure that the two end faces can move up and down within the U-shaped groove.

[0045] The gap between the upper plate 211 and the lower plate 221 is the light inlet slit 50.

[0046] Optionally, both the upper push rod 31 and the lower push rod 30 are electric push rods.

[0047] Optionally, both the upper push rod 31 and the lower push rod 30 are lead screws. To drive the two lead screws to move up and down, stepper motors 40 are respectively configured to drive the upper flat plate 212 and the lower flat plate 222 to move up and down through the lead screws.

[0048] Preferably, all columns 12 penetrate the upper plane plate 212 and the lower plane plate 222 to avoid displacement of the upper plane plate 212 affecting the accuracy and precision of the calibration.

[0049] Preferably, the upper end of each U-shaped groove is fixedly connected to the upper plate 14 by at least two columns 12; the lower end is fixedly connected to the lower plate 11 by at least two columns 12; the spectrophotometer linearity calibration device is symmetrical from left to right, that is, all the columns 12 are symmetrically distributed from left to right. Similarly, this symmetrical arrangement can also minimize structural errors, thereby reducing calibration errors and ensuring calibration accuracy and precision.

[0050] Preferably, if Figure 3 , Figure 4 As shown, the lower end of the upper plate 211 is protruding, and the upper end of the lower plate 221 is recessed, or the lower end of the upper plate 211 is recessed, and the upper end of the lower plate 221 is protruding. The protrusion and the recess interlock to ensure that the upper plate 211 and the lower plate 221 can be completely closed to block light without gaps or light leakage.

[0051] like Figure 5 As shown, the basic principle of the superposition method is the superposition property of light beams. An ideal photodetector has a very good linear response; for example, the readings Iab of the given radiant flux A and radiant flux B are equal to the readings of the two simultaneously superimposed fluxes Ia and Ib, i.e., Iab = Ia + Ib. If Iab ≠ Ia + Ib, it indicates that the spectrophotometer's response is nonlinear, which can be used to quantify nonlinear errors.

[0052] The light-entry slit 50 has three states. In the first state, both parts a and b of the light-entry slit 50 are fully open, meaning that both the upper light-shielding plate 21 and the lower light-shielding plate 22 are open, allowing the entire light beam to pass through the slit. In this state, the radiant flux Iab can be measured. In the second state, part a of the light-entry slit 50 is closed, and part b is open, meaning that the upper light-shielding plate 21 is closed, and the lower light-shielding plate 22 is open, allowing only the lower half of the light beam to pass through the slit. In this state, the radiant flux Ib can be measured. In the third state, part a of the light-entry slit 50 is open, and part b is closed, meaning that the upper light-shielding plate 21 is open, and the lower light-shielding plate 22 is closed, allowing only the upper half of the light beam to pass through the slit. In this state, the radiant flux Ia can be measured. Note that the opening or closing of the upper light-shielding plate 21 actually means the upper vertical plate 211 is open, and the opening or closing of the lower light-shielding plate 22 actually means the lower vertical plate 221 is open.

[0053] Ultraviolet-Vis-Near-Infrared (UVVis-NIR) spectrophotometers typically employ a dual-detector setup, consisting of a photomultiplier tube (PTU) and a PbS-lead sulfide (PbS) detector. The PTU receives UV and visible light signals, while the PbS detector receives near-infrared signals, with the detectors typically switching at a wavelength of 850 nm. The inconsistency in the linear responsivity of the two detectors can cause significant fluctuations in the response value around 850 nm. To obtain accurate measurement results, the two detectors must be leveled by moving the upper and lower light-shielding plates before using the device to further improve measurement accuracy.

[0054] Specifically, such as Figure 6 As shown, the leveling steps include:

[0055] Step 1: Fully open the upper plate 211 and the lower plate 221, and measure the distance L1 between the lower end face of the upper plate 211 and the upper end face of the lower plate 221.

[0056] Step 2: Move the lower plate 221 upwards by L1 / 2, set the monochromator of the spectrophotometer to 750nm, and measure the radiant flux Ia; move the upper plate 211 downwards by L1 / 2, set the monochromator of the spectrophotometer to 1000nm, and measure the radiant flux Ib. There is no fixed order in which the radiant flux Ia and radiant flux Ib are measured.

[0057] Step 3: Adjust the upward displacement of the lower upright plate 221 to L2 and the downward displacement of the upper upright plate 211 to L3;

[0058] If the first error Δ1 > 0, then:

[0059] L2=(L1 / 2+1)mm; L3=(L1 / 2-1)mm;

[0060] otherwise,

[0061] L2=(L1 / 2-1)mm; L3=(L1 / 2+1)mm;

[0062] in,

[0063] Δ1 = Ia - Ib.

[0064] Step 4: Set the monochromator to 750nm and measure the radiant flux Ia at this time (i.e., Ia). 750 Ia λ=750 ) and radiation flux Ib (i.e., Ib 750 Ib λ=750 Set the monochromator to 1000 nm and measure the radiant flux Ia at this time (i.e., Ia). 1000 Ia λ=1000 ) and radiation flux Ib (Ib 1000 Ibλ=1000 ).

[0065] Similarly, measuring the radiative flux Ia 750 Radiative flux Ib 750 and measuring radiation flux Ia 1000 Radiative flux Ib 1000 There is no fixed order of precedence.

[0066] Step 5: Repeat steps 3 to 4 until the second error Δ2 < Δ1 / 2; where,

[0067] Δ2=|(Ia-Ib) λ=750 -(Ia-Ib) λ=1000 |=|(Ia 750 -Ib 750 )-(Ia 1000 -Ib 1000 )|.

[0068] After the leveling work is completed, as follows Figure 7 As shown, the nonlinear error at different fixed wavelength points can be measured, and the detector can be linearly corrected.

[0069] The steps are as follows:

[0070] Step S1: Set the measurement beam, specifically by installing the spectrophotometer linear calibration device in the spectrophotometer sample chamber, so that the light inlet is perpendicular to the measurement beam.

[0071] Step S2: Set the monochromator of the spectrophotometer to the desired wavelength point λ1, and use the spectrophotometer's built-in software to perform 0% line and 100% line calibration; where 250nm≤λ1≤2500nm.

[0072] Step S3: Measure the radiative flux at wavelength point λ1, including:

[0073] (1) Fully open the upper upright plate 211 and the lower upright plate 22, and measure the distance L1 and the radiant flux Ia (i.e., Iab) at this time. λ1 );

[0074] (2) Move the lower plate 221 up by L1 / 2 and measure the radiative flux Ia (i.e., Ia λ1 );

[0075] (3) Move the upper plate 211 down by L1 / 2 and measure the radiative flux Ib (i.e., Ib). λ1 );

[0076] (4) Close the upper plate 211 and the lower plate 221, and measure the stray radiation Id (i.e., Id). λ1 ).

[0077] Similarly, measuring the radiative flux Iab λ1 Radiative flux Ia λ1 and measurement of radiation flux Ib λ1 Stray radiation Id λ1 There is no fixed order of precedence.

[0078] Step S4: Calculate the nonlinear error δ, using the following formula:

[0079] δ=(Iab-Ia-Ib-Id) / 2=(Iab λ1 -Ia λ1 -Ib λ1 -Id λ1 ) / 2;

[0080] Step S5: Return to step S2 to adjust wavelength point λ1, and measure the nonlinear error of all wavelength points in sequence.

[0081] As can be seen from the above embodiments and accompanying drawings, compared with the prior art, the spectrophotometer linearity calibration device provided by the present invention is based on the single-source method. With its usage method, it can avoid the influence of inconsistent light sources in the multi-source method. The linearity measurement can cover a wide range of wavelengths and has small calibration error and high calibration accuracy.

[0082] Furthermore, electric push rods or stepper motors combined with lead screws can precisely control the up and down movement of the light-shielding plate; the columns penetrating the flat plate and the symmetrical distribution of multiple columns can ensure the stability of the relative position of the flat plate, which is conducive to reducing errors and improving accuracy in the calibration process; the end faces of the two plates can be fitted together to ensure complete light blocking and reduce calibration errors.

Claims

1. A spectrophotometer linearity calibration device, characterized in that, include: Upper plate (14), lower plate (11) and two U-shaped grooves (13); The U-shaped sections of the upper plate (14), the lower plate (11), and the U-shaped groove (13) are parallel to each other; Two U-shaped grooves (13) have openings facing each other; the upper end of each U-shaped groove (13) is fixedly connected to the upper plate (14) by at least one column (12), and the lower end is fixedly connected to the lower plate (11) by at least one column (12). It also includes an upper push rod (31), an upper upright plate (211), and an upper flat plate (212); The upper push rod (31) penetrates the upper plate (14) and is fixed to the upper flat plate (212) to drive the upper flat plate (212) to move up and down; the column (12) connecting the upper end of the U-shaped groove (13) and the upper plate (14) penetrates the upper flat plate (212); the upper flat plate (212) is parallel to the upper plate (14). The upper plate (211) is vertically fixed to the lower surface of the upper flat plate (212), with its two sides located in two U-shaped grooves (13); the upper plate (211) moves up and down with the upper flat plate (212); It also includes a lower push rod (30), a lower upright plate (221), and a lower flat plate (222); The lower push rod (30) and the upper push rod (31) are arranged symmetrically in the upper and lower positions; the lower flat plate (222) and the upper flat plate (212) are arranged symmetrically in the upper and lower positions; the lower upright plate (221) and the upper upright plate (211) are arranged opposite each other in the upper and lower positions. The upper plate (211) has a protruding lower end and a recessed upper end, or the upper plate (211) has a recessed lower end and a protruding upper end, so that they fit together.

2. The spectrophotometer linearity calibration device as described in claim 1, characterized in that, Both the upper push rod (31) and the lower push rod (30) are electric push rods.

3. The spectrophotometer linearity calibration device as described in claim 1, characterized in that, Both the upper push rod (31) and the lower push rod (30) are lead screws; a stepper motor (40) is also included, which is used to drive the upper flat plate (212) or the lower flat plate (222) to move up and down through the lead screw.

4. The spectrophotometer linearity calibration device as described in claim 1, characterized in that, Each U-shaped groove (13) is fixedly connected to the upper plate (14) at its upper end by at least two columns (12) and to the lower plate (11) at its lower end by at least two columns (12); the spectrophotometer linearity calibration device is symmetrical from left to right.

5. The method of using the spectrophotometer linearity calibration device as described in claim 1, characterized in that, The calibration method for the spectrophotometer is as follows: Step S1: Set the measurement beam; Step S2: Set the spectrophotometer monochromator to the desired wavelength point λ1, and perform 0% line and 100% line calibration; Wherein, 250nm≤λ1≤2500nm; Step S3: Fully open the upper panel (211) and the lower panel (221). (1) Measure the distance L1 and the radiative flux Iab at this time. λ1 ; (2) Move the lower plate (221) up by L1 / 2 and measure the radiative flux Ia. λ1 ; (3) Move the upper plate (211) down by L1 / 2 and measure the radiation flux Ib. λ1 ; (4) Close the upper plate (211) and the lower plate (221) and measure the stray radiation Id. λ1 ; Step S4: Calculate the nonlinear error δ, using the following formula: δ=(Iar λ1 -Yes λ1 -One λ1 -Id λ1 ) / 2; Step S5: Return to step S2 to adjust wavelength point λ1, and measure the nonlinear error of all wavelength points in sequence.

6. The method of use as described in claim 5, characterized in that, It also includes the method for balancing the spectrophotometer, specifically: Step R1: Measure the radiative flux Ia and radiative flux Ib; Fully open the upper panel (211) and the lower panel (221). (1) Move the lower plate (221) up by L1 / 2, set the monochromator of the spectrophotometer to 750nm, and measure the radiant flux Ia; (2) Move the upper plate (211) down by L1 / 2, set the monochromator of the spectrophotometer to 1000nm, and measure the radiation flux Ib; Step R2: Adjust the upward displacement of the lower plate (221) to L2, and adjust the downward displacement of the upper plate (211) to L3; If the first error Δ1 > 0, then: L2=(L1 / 2+1)mm; L3=(L1 / 2-1)mm; otherwise, L2=(L1 / 2-1)mm; L3=(L1 / 2+1)mm; in, Δ1 = Ia - Ib; Step R3: (1) Set the monochromator to 750 nm and measure the radiant flux Ia. 750 and radiation flux Ib 750 ; (2) Set the monochromator to 1000 nm and measure the radiant flux Ia. 1000 and radiation flux Ib 1000 ; Step R4: Repeat steps R2 to R3 until the second error Δ2 < Δ1 / 2; where, Δ2=|(Ia 750 -Ib 750 )-(He 1000 -Ib 1000 )|。

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