Detailed Comparison of Apogee Spectroradiometers
Apogee offers three models of miniature fiber optic spectroradiometers (Lab Spectroradiometers): PS-100, PS-200, and PS-300. Although all three models can be used for many of the same applications, there are differences between models that should be considered. The following table lists specification differences among models.
| Model | Sensitivity Range | Calibrated Range | Wavelength Resolution |
|---|---|---|---|
| PS-100 | 350 to 1150 nm | 350 to 1000 nm | 1.0 nm |
| PS-200 | 190 to 850 nm | 300 to 850 nm | 0.85 nm |
| PS-300 | 220 to 1100 nm | 300 to 1000 nm | 1.5 nm |
The main internal components of any miniature fiber optic spectroradiometer consist of an entrance slit, diffraction grating, optical bench (spectrograph), and detector. Apogee Lab Spectroradiometer models come with a standard slit size of 25 µm, providing an optimization between wavelength resolution and system throughput. Additionally, all Apogee Lab Spectroradiometer models incorporate the same charge coupled device (CCD) detector with 2048 pixels and pixel size of 14 µm wide x 200 µm tall. The component differences between Apogee Lab Spectroradiometer models are the diffraction grating and optical bench, setting the PS-100 apart from the PS-200 and PS-300, and allowing for its lower price.
The PS-100 uses a plane ruled diffraction grating, while the PS-200 and PS-300 feature a concave holographic grating. Ruled gratings are less expensive to manufacture, but generally have higher susceptibility to stray light due to surface roughness and groove imperfections. Holographic gratings can be manufactured with smoother surfaces, which inherently minimize stray light. Furthermore, the concave holographic grating found in the PS-200 and PS-300 eliminates aberrations (deviations in the raw spectrum as it is delivered to the detector), such as coma, astigmatism, spherical aberration, and field curvature.
The configuration of the optical bench brings together all the components listed above – yielding a system that properly delivers radiation to the detector. The PS-100 includes a configuration referred to as the crossed Czerny-Turner, which consists of two concave mirrors and a plane ruled diffraction grating. As radiation enters the slit the first mirror directs a collimated beam onto the diffraction grating. The second mirror is then used to focus the dispersed light from the grating onto the CCD detector. Due to the grating being used, the PS-200 and PS-300 come with a concave holographic configuration, which replaces the mirrors found in the crossed Czerny-Turner configuration with a single concave grating that disperses and focuses radiation from the entrance slit onto the detector. This results in minimized stray light and noise, while providing better system efficiency and throughput.
All Lab Spectroradiometer models come with interface software for use on Windows operating systems. The software is capable of collecting and displaying measurements of reflectance, transmittance, absorption, wavelength emissions, and both relative and absolute intensities. Ultimately, all models are an excellent choice for educational, laboratory, and field applications, while the PS-200 and PS-300 are better suited for research applications requiring higher accuracy and precision.