Stray light test

Performance the EP Stray Light Test with Potassium Chloride on UV-Vis Spectrophotometers, Technical Note, Agilent Technologies, Publ. 5988-0945EN, 2000. 

Table 3. Cutoff filters for stray-light tests. Path length 10 mm...

The performance verification tests required by major pharmacopoeias for UV-Vis spectrophotometers are listed in Table 10.1 [1-4]. The required performance tests include wavelength accuracy, stray light, resolution, and photometric... 

Table 20-1 gives the absorbance of a solution that you can prepare to test the accuracy of absorbance measurements on your spectrophotometer. Absorbance accuracy is affected by all components of the spectrophotometer, as well as stray light. Standards are also available to measure wavelength accuracy.9... 

Where possible the stray-light was estimated, the instrument readings were corrected for the turbidity of the water, and sample cells and caps were carefully matched, orientated and cleaned (the outside of the sample cell was polished with silicon), air bubbles were removed, etc. Note that during these tests turbidity-free water (as low as 0.02 FNU by filtering distilled water through a 0.45- xm-mcmbra n c filter) was used. Even under these conditions the instrumental error at low turbidity values was within +3% and +8% at a nominal value of 0.5 FNU and -1.3% to +10% at a nominal value of 1 FNU. 

To verify that a spectrophotometer is performing satisfactorily, the device must be shown to be able to operate within the specifications provided for it. Parameters to be tested include (1) wavelength accuracy, (2) spectral bandwidth, (3) stray light, (4) linearity, and (5) photometric accuracy. 

The goal for this analysis was to measure the prompt fluorescence decay time for each polycrystalline YSZ thickness. Results from this analysis are shown in Table 2. Visible fluorescence was observed through all three YSZ thicknesses at each of the tested laser wavelengths. It was not possible to measure the prompt fluorescence decay time for YAG Eu because the reduction of light intensity did not follow a simple exponential curve. This phenomenon is most likely caused by electrical noise, stray light, or the absorption and re-emission of fluorescence from the YSZ. 

Figure 4 Mielenz method. (Reproduced with permission from Mielenz KD, Weidener VR, and Burke RW (1982) Heterochro-matic stray light in UV absorption spectrometry A new test method. Applied Optics 2 a) 3354-3356.)...

A recurrent problem inherent to aU solar simulators is that they produce many parallel rays but in small quantities. However, prototypes, designed to operate outside, wiU then be subject to two important types of light beams a diffuse beam and a parallel beam (Matson et al., 1984). There will always be a margin of error on the textile behaviour in real conditions, compared to results obtained with the simulator. During testing, the room is plunged into darkness to avoid stray light. 

As seen in Section 3 excellent insight into surface quality, defects, and bulk purity can be obtained from scatter measurements. Also, astute analysis can result in simple, inexpensive in-process and final quality control procedures for production of a variety of surfaces, materials, and optics. As can be seen, much can be learned from visual examination of BRDF plots and raster scans. This is often sufficient for pass/fail tests of product quality. The data can also be analyzed in more detail using various formulas and computer programs. In addition, because the data are digital, they can be rapidly analyzed by computer in on-line process control applications. SORIC and leaders in the stray light community have developed a BRDF database (16, 17) for commonly used surfaces and materials employed by scientists and engineers (18,19, 20, 21, 22, 23). 

Practical aspects of the effects of, and tests for, stray light have been reported by Holiday and Reaven Saidel et at, in a study of absorption anomalies in the region 200-230 m/i with the Reckman DU spectrophotometer, cited some possibly misleading effects of stray light at the short-wavelength limit and suggested means of correction. 

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