분광기의 광학벤치 (Optical Bench of spectrometer)

광학벤치란 무엇인가?

분광기에서 광학벤치는 광원에서 샘플을 향해 나아가거나 샘플에서 나온 빛을 검출기로 전달하는 광학적인 경로와 요소들의 집합입니다.

광학벤치의 용도별 종류

S: General-purpose bench for absorbance, reflectance, fluorescence
S 벤치는 흡광도, 반사도, 형광 등의 일반적인 광학 측정에 널리 사용되는 벤치
생화학, 화학, 환경 등 다양한 분야에서 사용되며, 특히 흡광 분석, 반사도 분석, 형광 분석과 같은 광학 측정에 적합

HR: High-resolution bench for laser characterization, atomic emission line analysis
HR 벤치는 높은 해상도의 광학 측정을 위해 고안된 벤치. 높은 해상도는 미세한 구조를 분석하고 정교한 측정이 가능
레이저 특성화 및 원자 발광선 분석과 같이 미세한 특성을 파악하는데 사용. 레이저 자체의 특성이나 원자 스펙트럼 등을 분석하는데 유용

QE: Quantum-Efficiency for low light level applications (Raman, fluorescence)
QE 벤치는 양자효율을 강조한 벤치로, 낮은 빛 수준에서도 정확하고 높은 민감도로 측정이 가능. 양자효율은 광원에서 나온 광자 중 검출기가 얼마나 많이 감지하는지를 나타내는 지표
라만 분석, 형광 분석과 같이 낮은 빛 수준에서의 측정에 사용. 낮은 빛에서도 정확한 분석을 수행하고자 할 때 유용

NIR: Near-infrared applications
NIR 벤치는 가까운 적외선(NIR) 영역의 측정을 위해 최적화된 벤치. NIR 영역은 일반적인 광선보다 더 긴 파장을 갖고 있어서 특정 물질들의 고유한 흡수 성질을 활용하는데 유용
식품, 약품, 농업 등에서의 원료 분석, 품질 관리 등 다양한 분야에서 사용. NIR 영역은 물질의 특성을 비파괴적 측정

Crossed Czerny-Turner Optical path

Most Compact of spectrometer designs, folded path results in smaller footprint

- mechanical drift scales with size, so smaller is mechanically more stable.
- less materials mean less weight, less machining, lower cost.
- aberrations (e.g. coma) manipulated to provide greater resolution. This overcomes the negative scaling of resolution with optical path-length

Light enters the optical fiber and is efficiently transmitted to the spectrometer. Once in the spectrometer, the divergent light emerging from the optical fiber is collimated by a spherical mirror. The collimated light is diffracted by a plane grating, and the resulting diffracted light is focused by a second spherical mirror. An image of the spectrum is projected onto a 1-dimensional linear CCD array, and the data is transferred to a computer through an A/D converter.

1. Fiber Connector (SMA/FC)
The SMA Connector secures the input fiber to the spectrometer. Light from the input fiber enters the optical bench through this connector.

2. Slit*
The Slit is a dark piece of material containing a rectangular aperture, which is mounted directly behind the SMA Connector. The size of the aperture regulates the amount of light that enters the optical bench and controls spectral resolution.
You can also use the HR2000 without a Slit. In this configuration, the diameter of the fiber connected to the HR2000 determines the size of the entrance aperture.
Only Ocean Optics technicians can change the Slit.

3. Filter*
The Filter is a device that restricts optical radiation to pre-determined wavelength regions. Light passes through the Filter before entering the optical bench. Both bandpass and longpass filters are available to restrict radiation to certain wavelength regions.
Only Ocean Optics technicians can change the Filter.

4. Collimating Mirror
The Collimating Mirror focuses light entering the optical bench towards the Grating of the spectrometer.
Light enters the spectrometer, passes through the SMA Connector, Slit, and Filter, and then reflects off the Collimating Mirror onto the Grating.

5. Grating*
The Grating diffracts light from the Collimating Mirror and directs the diffracted light onto the Focusing Mirror. Gratings are available in different groove densities, allowing you to specify wavelength coverage and resolution in the spectrometer.
Only Ocean Optics technicians can change the Grating.

6. Focusing Mirror
The Focusing Mirror receives light reflected from the Grating and focuses the light onto the CCD Detector or L2 Detector Collection Lens (depending on the spectrometer configuration).

7. L2 Detector Collection Lens*
The L2 Detector Collection Lens (optional) attaches to the CCD Detector. It focuses light from a tall slit onto the shorter CCD Detector elements.
The L2 Detector Collection Lens should be used with large diameter slits or in applications with low light levels. It also improves efficiency by reducing the effects of stray light.
Only Ocean Optics technicians can add or remove the L2 Detection Collection Lens.

8. CCD Detector (UV or VIS)
The CCD Detector collects the light received from the Focusing Mirror or L2 Detector Collection Lens and converts the optical signal to a digital signal.
Each pixel on the CCD Detector responds to the wavelength of light that strikes it, creating a digital response. The spectrometer then transmits the digital signal to the OOIBase32 application.