本文設計波段400 – 1000 nm Offner系統光譜儀，設計前須選定光源發散角、光譜成像大小、凹面鏡曲率、光柵條紋間距、繞射階數，以上述規格設計Offner系統架構，定義解像方向為X方向、解光譜方向為Y方向，光行進方向為Z方向。
本文分成使用點光源分析及狹縫光源分析，點光源大小X方向1 nm、Y方向1 nm，分析使用像素數為512 × 512，像素大小為3.9 μm × 3.9 μm。狹縫光源大小為X方向20 μm、Y方向20 μm，並在光源前方設置X方向0.6 mm、Y方向20 μm的狹縫，分析使用像素數為155 × 155、310 × 310，像素大小分別為12.9 μm × 12.9 μm及6.45 μm × 6.45 μm，此兩像素數依市面實際偵測器像素大小換算而得。
為了能精確分析波段的成像品質，將波段分波長400 nm、550 nm、700 nm、850 nm、1000 nm分別分析，經分析偵測器接收光線位置大多於聚焦縱深內，為了使波段聚焦能力更佳，將偵測器擺放位置及角度進行校正。
校正前光源X、Y方向斑點半高全寬約14 μm、總光譜解析度達1.62 nm，狹縫光源之X、Y方向斑點半高全寬達26 μm，總光譜解析度達2.64 nm。MTF圖可評估光學系統品質，應用MTF為0.3對應空間頻率及線對寬作為系統成像品質依據。校正前點光源X、Y方向之MTF為0.3對應空間頻率約為100 cycle/mm，對應線對寬達10 μm，狹縫光源X、Y方向之MTF為0.3對應空間頻率約為46 cycle/mm，對應線對寬度達21 μm。
經過校正波段400 – 1000 nm更能有效聚焦於偵測面，偵測器位置不僅於聚焦縱深內，且幾乎貼合最小斑點大小擬合曲線，點光源X、Y方向斑點半高全寬約10 μm、總光譜解析度達1.02 nm，狹縫光源之X、Y方向斑點半高全寬達24 μm，也近乎還原光源大小，總光譜解析度達2.36 nm。校正後點光源X、Y方向之MTF = 0.3對應空間頻率約為125 cycle/mm，對應線對寬達8 μm，狹縫光源X、Y方向之MTF = 0.3對應空間頻率約為50 cycle/mm，對應線對寬達20 μm。

Design of an Offner system spectrometer used for 400 – 1000 nm wavebands is introduced in this paper. It refers the divergence angle of the light, spectral imaging size, radius of concave mirror, grating pitch and the diffraction orders. X coordinates presents the slit image direction, Y is the spectral resolution direction and Z is the light propagation direction.
Point and slit light source are used for the performance analysis. In this paper, the point light source uses a detector of 512 × 512 pixel number and 3.9 μm × 3.9 μm pixel size. The slit light source uses two detectors of 155 × 155 and 310 × 310 pixel number, and 12.9 μm × 12.9 μm and 6.45 μm × 6.45 μm pixel size with a slit put in front of light source. The size of slit is 0.6 mm in X and 20 μm in Y and the size of the light source is 20 μm x 20 μm in both.
Five wavelengths, which are 400 nm, 550 nm, 700 nm, 850 nm, and 1000 nm specitied to analyze the quality of image. The results show that most of positions where detectors receive lights are located in the depth of focus. For a better ability of focus quality, correction for imaging plane positioning of detectors are involved.
After correction, the imaging location are not only within the depth of focus, but are also approaching the minimum spot size. In point source, the FWHM spot size is smaller than 10 μm, and the total spectral resolution of the system is better than 1.02 nm. In slit source, the FWHM spot size is smaller than 24 μm, and the total spectral resolution of the system is better than 2.36 nm.
In this paper, 0.3 MTF corresponds a basis of the performance for spatial frequency and pitch check image quality. In point source, MTF of 0.3 corresponds to a spatial frequency of 125 cycle/mm and a grating pitch of 8 μm. In slit source, MTF of 0.3 corresponds to a spatial frequency of 50 cycle/mm and a grating pitch of 20 μm.

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