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Frequently Ask Questions

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Introducing Spectrometer

How to Calibrate wavelength for micro spectrometer?

Choose a light source with multiple wavelength characteristics, such as a mercury-argon lamp. After obtaining the light source's spectrum using a spectrometer, map the pixel values corresponding to the wavelength features to the actual wavelengths of the light source. This mapping creates a function that correlates pixel space with the actual spectrum. By applying this function, wavelength calibration can be achieved.

How is the signal-to-noise ratio (SNR) of the spectrometer calculated?

Using a broadband light source as the sample light source, first perform 100 scans in the absence of light and calculate the average baseline count for each pixel. Then, perform 100 scans under the sample light source and calculate the average and standard deviation of the output signal for each pixel. Finally, calculate the Signal-to-Noise Ratio (SNR) using the following formula: (SNR)ρ =(S-D)/σ ρ

SNR: Signal-to-Noise Ratio
S: the average intensity of the sample spectrum (with light)
D: the average value of the dark spectrum (without light)
σ: the standard deviation of the sample spectrum (with light)
ρ: the number of pixels.

How many components make up of a spectrometer?

A spectrometer is typically made up of 9 main components: the light source(Sample), entrance slit, collimating lens, diffraction grating or prism, focusing lens(Signal Intensity Enhanced), detector(CCD/CMOS), readout device, output interface(Signal Process Circuit), and software for data analysis.

How much does the detector cost?

Certain spectrometer detectors can be priced in the tens of thousands of dollars, while others may be available for just a few thousand dollars. For instance, cooled CCD detectors tend to have a significantly higher cost compared to uncooled CMOS detectors.

How to calculate the wavelength range?

To calculate the wavelength range of a spectrometer, you need the grating's groove density and the width of the detector. The range is then found by multiplying the width of a single detector element by the total number of elements and the spectral dispersion (in nm per pixel or mm).

What are application of spectrometers?

Spectrometers have diverse applications across various fields due to their ability to analyze and characterize light. Some key applications include:

- Chemical Analysis: Identifying and quantifying the composition of substances in fields such as chemistry and biochemistry.
- Environmental Monitoring: Analyzing air, water, and soil for pollutants and monitoring environmental changes.
- Astronomy: Studying the spectra of celestial objects to understand their composition, temperature, and motion.
- Medical Diagnostics: Analyzing biological samples for diagnostic purposes using techniques like spectroscopy.
- Material Science: Studying the optical properties of materials to understand their structure and behavior.
- Quality Control: Analyzing the composition of materials in manufacturing processes to ensure product quality.
- Color Measurement: Quantifying and controlling color in industries such as printing, textiles, and lighting design.
- Remote Sensing: Monitoring Earth's surface, vegetation, and atmospheric conditions using spectrometers on satellites.
- Food and Beverage Analysis: Analyzing the composition and quality of food and beverages.
- Forensic Analysis: Examining evidence in forensics, such as substances found at crime scenes.
- Art and Cultural Heritage Conservation: Analyzing pigments and materials in artwork for restoration and preservation.
- Pharmaceuticals: -Research and development in pharmaceuticals, including the analysis of drug compounds.
- Light Source Characterization: Characterizing the properties of light sources in various applications.
These applications highlight the versatility of spectrometers in providing valuable information for scientific research, industrial processes, and technological advancements across different disciplines.

What are factors decide the spectrometer performance?

Factors that decide spectrometer performance include the wavelength range, resolution, sensitivity, dynamic range, signal-to-noise ratio, accuracy of wavelength calibration, the precision of the spectral data, and the quality of the optical components like mirrors, gratings, and detectors.

What are important components of a spectrometer?

A spectrometer consists of a light source, an entrance slit to focus the light, a collimating lens to direct the light, a diffraction grating or prism to separate the light into its spectral components, a focusing lens to project the spectrum, a detector to capture the wavelengths, a readout device to process the signals, an output interface for data transfer, and software for data analysis and control. These components work in unison to measure and analyze the spectrum of light from a sample.

What are main factors can decide optical spectrometer resolution?

The resolution of an optical spectrometer is influenced by:

1. Entrance Slit Width: Narrow slits improve resolution by allowing a finer section of the spectrum to be analyzed but reduce light throughput.
2. Grating or Prism Dispersion: Higher grating density or prism quality separates light into its components more effectively, enhancing resolution.
3. Detector Pixel Density: More pixels allow the spectrometer to discern smaller wavelength differences, thus increasing resolution.
4. Focal Length: A longer focal length stretches the spectrum across more pixels, which can improve resolution by spreading out spectral features.
5. Optical Component Quality: Superior lenses and mirrors minimize aberrations and better focus the light, contributing to higher resolution.

What is a spectrometer used for? 

An incandescent light source is capable of producing white light, which, when passed through a spectrometer, disperses into a spectrum of multiple colors. While the human eye perceives it as white light, a spectrometer analysis reveals a display of rainbow colors. By exporting the data to a PC, one can read the spectrum, showcasing distinct wavelengths and intensity information contained within this seemingly white light.

What is called micro spectrometer or fiber optic spectrometer?

A micro-spectrometer or fiber optic spectrometer typically refers to a compact and miniaturized spectrometer that is designed for applications where space is limited or portability is a key requirement. These spectrometers are characterized by their small size and often utilize optical fibers to capture and transmit light to the spectrometer for analysis.

What is called modular spectrometer?

A modular spectrometer refers to a spectroscopy system that is designed with modular components, allowing users to customize and assemble the system according to their specific needs. In a modular spectrometer, individual modules or components, such as light sources, detectors, gratings, and optical elements, are separate and interchangeable. This modularity offers flexibility in configuring the spectrometer for different applications, wavelengths, or resolution requirements.

Product Technical Questions


Are user's manual and technical information also provided?

The user's manual and technical information can be downloaded by the QR code we provided in the package.


Can an optical fiber with an FC connector be connected to micro-spectrometers?

Our micro-spectrometers designed for optical fiber connection are equipped with an SMA connector. It's important to note that optical fibers utilizing an FC connector cannot be directly coupled to our micro-spectrometers.


Can micro-spectrometer A/D-converted values be converted to light levels?

Unfortunately, this cannot be achieved as the mini-spectrometer lacks coefficients for converting A/D-converted values into light levels.


How are micro-spectrometers driven?

The micro-spectrometer, designed with modularity in mind, features a CSI camera interface, allowing for seamless integration with a Raspberry Pi through the provided cable. This compact micro-spectrometer is engineered for convenience, requiring no external power source as it draws its power directly from the Raspberry Pi.


How are spectrophotometric measurements made in a mini-spectrometer?

The micro-spectrometer functions by spectrally separating incident light through a grating and arranging it one-dimensionally by wavelength. Subsequently, this processed light enters the image sensor, and the wavelength data is extracted by interpreting the electrical signals generated at each position where light is incident on the sensor. The image sensor comprises an array of photoelectric conversion elements and a circuit designed to transfer the resulting charges to an external device. Our offering includes micro-spectrometers equipped with a specific configuration, a driver circuit, and an interface circuit for seamless connection to either a Raspberry Pi or a mobile device.


How does the slit size affect detection?

Within micro-spectrometers, the slit size plays a crucial role in determining both resolution and throughput. A reduction in slit size, particularly in width, enhances resolution. However, this comes at the cost of decreased light levels available for measurement, leading to a decline in the throughput of the mini-spectrometer. The selection of the micro-spectrometer slit size involves a careful balance, considering these factors to optimize performance.


How is spectral resolution defined?

Two methods are commonly used to define spectral resolution. The first method, based on DIN standards using the Rayleigh criterion, quantifies how effectively the micro-spectrometer can distinguish wavelength differences between peaks with the same intensity that are adjacent to each other. According to this criterion, the valley between the two peaks must be measurable within 81% or less of the peak value.

Alternatively, a more practical approach to defining spectral resolution involves determining the spectral width using FWHM (full width at half maximum). This method directly characterizes the broadening of the spectrum at a point where the intensity is 50% of the spectral peak value. The resolution defined by the half-width (FWHM) is approximately 80% of the resolution value defined by the Rayleigh criterion. In the case of mini-spectrometers, spectral resolution is defined using the more practical half-width (FWHM) method.


How often is wavelength calibration needed? How can I do it?

SpectroChip micro-spectrometers are characterized by their absence of moving parts, resulting in exceptional stability. In typical environments, such as indoor settings, we believe there is no necessity for wavelength calibration. Users can confidently rely on the initially provided wavelength conversion factors without the need for recalibration.

For those seeking to verify wavelength precision, calibration lamps emitting well-known spectral lines can be employed. If there is a need to reacquire wavelength conversion factors with high precision, we recommend utilizing a high-precision monochromator.


I need to convert each pixel data of the image sensor into wavelength data. How can I do it?

The relationship between each pixel on the image sensor and the corresponding wavelength can be determined using the following 5-order approximate expression:

Wavelength [nm] = a0 + a1pix1 + a2pix2 + a3pix3 + a4pix4 + a5pix5

Here, a0~a5 represent the wavelength conversion factors specified in the final inspection sheet. These factors are internally stored in mini-spectrometers, excluding head-type mini-spectrometers. The variable pix can take any pixel number from 1 to the last pixel of the image sensor.

The evaluation software utilizes these factors to display data converted into wavelengths. It's important to note that values calculated using this approximate expression may exhibit slight variations when compared with the known wavelengths of spectral lines.


Is software for operating a mini-spectrometer available?

We have provided code examples on Github that can run a micro-spectrometer on a Raspberry Pi. These examples include basic functionalities for conducting measurements, such as setting measurement conditions, acquiring and storing data, and displaying charts.


What else can the evaluation software do besides basic functions?

The evaluation software is written in Python and is currently open source. Therefore, users can design their own UI interface according to their needs or control other devices through the Raspberry Pi to build their own spectroscopy measurement system


What is the definition of the stray light level?

Two methods are commonly employed to define stray light levels. One approach involves using white light transmitted through a long-pass filter that allows a specific wavelength as the measurement light. In this method, stray light is defined as the ratio of transmittance in the transmitted wavelength range to the blocked wavelength range. This method is suitable for evaluating the impact of stray light across a broad wavelength range, making it applicable to scenarios such as fluorescence measurement. However, it's important for users to note that the intensity profile of the white light used as the reference can influence the measurement values.

The second method utilizes reference light in a narrow wavelength range, such as light emitted from a monochromator or a spectral line lamp. In this case, stray light can be defined using the equation below, incorporating the reference light level and the amount of unnecessary light output at a position shifted from the peak wavelength of the reference light within a narrow wavelength range. This method, focusing on reference light in a narrow wavelength range, offers simplicity in measurement conditions, ensuring good reproducibility for quantitative evaluations.

SL = 10 × (log IM / IR)

-SL: represents stray light by means of reference light in a narrow wavelength range,
- IM is the amount of unnecessary light output at a position shifted from the peak wavelength of the reference light,
- IR is the reference light level.

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