ISC NIRScan NIR Spectrometer User Manual

Overview

The ISC NIRScan is a compact NIR spectrometer based on DLP (Digital Light Processing) technology, covering two wavelength ranges: 900-1700nm (standard) and 1350-2150nm (extended). It uses a single-element InGaAs detector instead of a traditional linear array detector, achieving an excellent signal-to-noise ratio and programmable measurement capability in a compact form factor. This manual introduces the technical principle, hardware specifications and software operation of the NIRScan spectrometer series.

1. Introduction to NIR Spectroscopy

Near-infrared spectroscopy (NIRS) is a spectral analysis method based on the absorption of electromagnetic radiation by molecules in the 700-2500nm wavelength range. NIR radiation is absorbed through molecular vibration mechanisms — only chemical bonds whose dipole moment changes over time (such as O-H, N-H, C-H, S-H) can effectively absorb infrared radiation.

The most prominent absorption bands in the NIR region are related to the overtones and combination bands of fundamental vibrations:
- Transition from the ground state (ν = 0) to the second excited state (ν = 2) → first overtone
- Transition from the ground state (ν = 0) to the third excited state (ν = 3) → second overtone

The unique advantage of NIRS lies in its rapid, non-destructive nature; combined with chemometric methods, it can simultaneously predict the content of multiple components in a sample, and is widely used in agriculture, food, pharmaceutical and chemical industries.

2. Technical Principle of the DLP Spectrometer

2.1 Optical Architecture

The DLP-based NIR spectrometer adopts a post-dispersion architecture; the light path passes through the following in sequence:

Entrance slit → collimating lens group → band-pass filter → diffraction grating → focusing lens group → DMD → light-receiving lens → single-point InGaAs detector

Compared with the traditional linear array detector scheme, the DLP scheme uses a digital micromirror device (DMD) and a single-element InGaAs detector, equivalent to a 128-pixel linear array device at the same wavelength range and resolution.

2.2 Three Advantages of DLP Technology

  1. Higher-performance detector: the effective photosensitive area of a single-element InGaAs detector (diameter ϕ = 1 mm) is much larger than the individual small pixel of a linear array detector (typically 50 μm), giving a significantly higher signal-to-noise ratio.

  2. Programmable measurement modes: the high-resolution DMD (854 × 480 pixels) supports custom micromirror patterns, allowing flexible adjustment of wavelength sampling points and resolution.

  3. Hadamard encoding enhancement: by turning on multiple micromirror columns simultaneously for encoded measurement and recovering the spectrum with a matrix transform, the measurement time is greatly reduced under the same signal-to-noise ratio.

2.3 Specifications

Parameter Standard (STD) Extended (EXT)
Wavelength range 900-1700nm 1350-2150nm
Detector type Single-element InGaAs Single-element InGaAs
DMD resolution 854 × 480 854 × 480
Equivalent pixels 128 (Hadamard mode) 128 (Hadamard mode)
Communication interface USB 2.0 USB 2.0

3. Module Types

NIRScan offers multiple front-end modules to suit different measurement scenarios:

Module type Applicable scenario Measurement method
Diffuse reflectance module Solid powders, granules, fabrics Contact diffuse reflectance
Transmission module Transparent liquids, thin films Transmission / absorbance
Fiber input module Remote sampling, special geometry Fiber coupling to the spectrometer
Reflectance-transflectance spectrometer General multi-scenario use Switchable reflectance / transmission

4. Software Installation and Basic Operation

4.1 System Requirements

  • Operating system: Windows 10 or later (64-bit recommended)
  • USB interface: USB 2.0 or above
  • Storage: at least 500 MB of free space recommended for data storage

4.2 Installation Steps

  1. Download the companion software from the Pynect website.
  2. Extract to a folder with the same name under an all-English path.
  3. Double-click the executable to run (no installation required).
  4. Pay attention to the regional settings and font size to avoid overlapping interface text.

4.3 Measurement Workflow

  1. USB connection: connect the spectrometer to the computer with the supplied cable.
  2. Launch the software: wait for the connection progress bar to complete and confirm the model and serial number appear in the lower-left corner.
  3. Reference acquisition: place the reference (standard white reference or empty cuvette) according to the measurement mode, then click Reference Scan.
  4. Sample measurement: place the sample and click Scan.
  5. Data viewing: switch between reflectance/absorbance modes, or load historical data for comparison.

5. Spectral Analysis and Applications

5.1 Data Preprocessing

Before building a quantitative model, the raw spectrum usually needs the following preprocessing:
- Smoothing: Savitzky-Golay filtering to remove high-frequency noise.
- Derivative: first- or second-order derivatives to remove baseline drift and enhance peak resolution.
- Standard normal variate (SNV): remove the spectral offset caused by particle scattering.
- Multiplicative scatter correction (MSC): correct the effect of scattering on the spectrum.

5.2 Qualitative Analysis

Unsupervised methods such as principal component analysis (PCA) are used to cluster and classify samples, suitable for raw material identity verification and authenticity discrimination.

5.3 Quantitative Analysis

Supervised methods such as partial least squares regression (PLSR) are used to build a mathematical model relating the spectrum to the content of the target components, enabling simultaneous and rapid prediction of indicators such as moisture, protein and fat.

This article was compiled by Pynect.