Application of the hottest micro optical fiber spe

2022-08-09
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Application of micro fiber spectrometer in color measurement

spectroscopy is a technology for measuring the light intensity in ultraviolet, visible, near infrared and infrared bands. Spectral measurement has a wide range of applications, such as color measurement, concentration measurement of chemical components, luminescence and radiation analysis, etc

due to their huge volume and high price, traditional spectrometers limit their industrial application and can only be used for laboratory testing. This utilization requires the parts to be strongly machined at high temperature. The micro optical fiber spectrometer of avantes company in the Netherlands uses optical fiber as the signal acquisition device, so that the measurement is not restricted by factors such as location, environment and distance; Moreover, the volume is reduced to the size of a palm, and the cost is greatly reduced; In addition, its measurement speed is very fast and its measurement accuracy is high. These characteristics make it can be used in industrial analysis, which greatly expands the application field of spectrometer

background knowledge of color measurement

the color of an object can be expressed by CIE1976 (l*a*b*) color space. L* represents the brightness of the color. Positive a* values represent red and negative a* values represent green. Similarly, positive b* values represent yellow and negative b* values represent blue. The l*a*b* value can be derived from the CIE tristimulus values x, y, Z of the sample (object) and the tristimulus values xn, YN, Zn of the standard light source

the tristimulus values xn, yn and Zn of the standard light source are constants, which are only related to the type of standard light source selected

figure 1avasoftcolor color measurement software interface

CIE tristimulus values x, y, Z of object color are the relative power P of standard light source, reflectance R (or transmittance T) of object and CIE standard observation function X λ, y λ, z λ (2 degrees or 10 degrees) multiplied. The three stimulus values can be obtained by integrating the data length of the wave sphere disk in the visible light range (from 380 to 780nm, in 5nm steps)

chromaticity coordinates x, y, Z can be obtained by dividing the three stimulus values x, y, Z by their sum respectively:

another commonly used method to express color parameters a* and b* is to use hue angle (h*) and chromaticity (c*)

the measurement of hue angle starts from the red direction (+a*) h*=0 and increases counterclockwise:

chromaticity is defined as the length of the line segment from point a* = b* = 0 to the sampling point:

the commonly used parameter △ elab describing color difference is defined as:

Where, △ l*, △ a*, △ b* represents the difference between the reference color and the actually measured l*a*b* value

color measurement instrument

avantes company can provide users with two miniature spectrometer systems for color measurement

multi purpose color measurement spectrometer - avaspec2048

avaspec2048 is a miniature optical fiber spectrometer with simple operation, high measurement accuracy and medium price. It adopts a symmetrical czernyturner optical platform design. The signal light enters the optical platform through a standard SMA905 interface, is collimated by a spherical mirror, and then is divided by a plane grating, and is focused on a 2048 pixel CCD array through a second spherical mirror

Figure 2 main features of avaspec2048 spectrometer

avaspec2048

● fast response and high sensitivity

● high resolution and accurate measurement

● good thermal stability, with temperature drift coefficient of 0.1 pixel/℃

avaspec2048 color measurement system includes avaspec2048 spectrometer, avalighthal halogen lamp, standard reflection probe, white reference tile and avasoftcolor color measurement software (to be ordered together with avasoftfull full full function software). The convenience and flexibility of optical fiber makes it possible to measure the surface color of objects of any shape from a long distance, which overcomes the defects of color difference meter and spectrophotometer in the current market

in addition, the system can also carry out absorptivity, reflectance measurement, radiant luminescence measurement, etc. (you may need to choose other accessories), so as to realize multiple functions of one machine

mouse color measurement spectrometer - avamouse for color measurement of plane objects, avantes company has specially developed a low-cost mouse spectrometer avamouse. It consists of a built-in xenon lamp (flashing 35 times per second), an integrated photodiode array and a micro optical platform, which is connected to the computer through RS232 interface or USB interface

avamouse's main features

● designed for rapid color measurement - it can be used in laboratories and production workshops in coating, automobile painting, ink, plastic, textile, printing, paper and other industries

● lightweight and durable portable design - the body is as large as a mouse, light in weight and flexible in operation

● adopt 0/45 ° design - it can be used to measure the color of objects with high gloss

● it can be used with mix2match color matching software for computer color matching

Figure 3 avamouse spectrometer

color measurement software

no matter which spectrometer is used to measure color, avasoftfull full full function software and avasoftcolor color color measurement application software are required. Avantes also provides as161dll and colardll secondary development software and mix2match color matching software for industrial users

avasoftfull full full function software has friendly interface, simple operation and comprehensive functions. Users can set data acquisition parameters in the dialog box (such as detector integration time, automatic correction of dark background, signal averaging, spline interpolation and spectral smoothing). At the same time, the software also has the functions of automatic calibration of wavelength, calibration drift and periodic automatic storage, but the decay rate also ranks among the highest in the world

avasoftcolor color color measurement application software is developed for color measurement with spectrometer system. It can be used for reflective color measurement. AvaSoft color measurement application software can calculate CIE 1976 l*a*b* color parameters, as well as other commonly used parameters such as hue, chroma and X, y, Z values

these parameters can be displayed with a CIELab table (as shown in Figure 4), or as many as 8 color parameters can be monitored at the same time) over time (as shown in Figure 5). You can also save the measured l*a*b* value to the database, and then take a product color in the database as the reference color. By comparing the measured l*a*b* value with the reference color, the color difference (△ elab, △ l*, △ a*, △ b*) can be obtained

figure 4:cielab table

Figure 5: graph of parameters changing with time

the color of light source (such as LED) can also be measured by emission colorimetry. This measurement requires a radiation spectrum to calculate the color parameters x, y and Z. Through avasoftirad radiation measurement application software, absolute radiation measurement can be more accurate than relative radiation measurement mode (assuming an ideal blackbody light source with known color temperature). For the above reasons, radiation color calculation or "light color" calculation is one of the functions of radiation measurement application software

for ink and coating manufacturers, printing and dyeing plants, printing plants or other industries that need computer color matching, avantes provides mix2match color mixing and matching software. Its main function is to create a new color to compare and correct with the known color in the database, or create a new color to compare with the color in the shading file

mix2match software color matching steps:

1. Measure the original color

2. Computer generates an appropriate color mixing formula

3. Compare the generated sample color with the original color

4. Use the improved program to optimize the color mixing formula

to sum up, the emergence of avaspec2048 and avamouse portable micro spectrometer will bring new choices to the field of color measurement and make industrial color measurement possible. (end)

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