How to choose right Spectroradiometer & integrating sphere system
As far as we known that there have several type spectroradiometer, such as CCD spectroradiometer, mechanical scanning spectrophotometer etc. Generally, the type of spectrometer depend on what’s kind of lamp will be test, because the spectrometer is designed according to light-emitting characteristics. There have two kind of spectrometer in the market: one is Fast CCD Spectroradiometer; another is Single/Double Color Mechanical Scanning Spectrophotometer. In the practice, the CCD Spectroradiometer suitable for single LED, LED luminaires; and the traditional Mechanical Scanning Spectrophotometer suitable for CFL, HID lamp etc.
Why say the CCD Spectroradiometer suitable for single LED, LED luminaires, because it’s decided by light-emitting characteristics of LED. As we know the LED lumen output is not stable and attenuation is more worse than other lamp, when lighting on the LED, the lumen output at beginning is totally different from twenty minutes later, so this is require the test device have fast test speed; on the other hand, as LED lamp is mainstream lighting products at market, the production line test occupy a large part, so there appeared CCD spectroradiometer. Comparing LED products, the light-emitting characteristics of LED and HID lamp is totally different LED lamp, sometimes, we noticed that the light is very weak when light on the CFL, but after lighting some time, the light became stronger, so when testing this kind of lamp, the test device need longer time, and this test result is accuracy and reliable. The CCD spectroradiometer working with a optical fiber to measuring colorimetric parameters and luminous flux; the mechanical scanning spectrophotometer working with a optical fiber and detector, it measuring luminous flux working with detector; it measuring colorimetric parameters working with optical fiber. Generally speaking, the mechanical scanning spectrophotometer have high test accuracy but test time is longer, the test accuracy mentioned here focus on optical resolution, wavelength accuracy, stray light, and linear dynamic range so on. The mechanical scanning spectrophotometer mainly apply on the high request industry, but due to it need long test time which don’t suitable testing big changed sample caused by time and production line.
The traditional spectrometers are mechanical scanning spectrophotometer, mechanical scanning spectrometer using a monochromator to scanning wavelength , single photoelectric receiver photoelectric conversion, testing is slow, one by one wavelength serial output mode, the test time is relatively long, it can’t meet fast site test. The biggest weak point of mechanical scanning spectrometer is the mechanical axis and the transmission are easy get wear and tear after long time use, it will effect the wavelength accuracy and repeatability. With the development of electronic and mechanical technology, there appeared rapid mechanical scanning monochromator spectrophotometer which application with Sync-Skan synchronization sweep picking technique, the spectrum measurement from 380nm~780nm just need few seconds to finish test, it’s faster than traditional mechanical scanning system which need a few minutes to measure time, and test accuracy remain unchanged. Under the Sync-Skan technique, High-speed raster scan driver structure and high-speed A / D sampling synchronously working together, the fixed pulse signal sent from the MPU control both motor and A / D, the motor push grating movement to obtain the spectral power data for each wavelength.
With the continuous improvement of the performance of the detector array and computer technology, it solved the problem of transient spectroscopy measurements, making CCD array spectrometer developed rapidly, because it is a multi-channel parallel measurement, no mechanical scanning, reliability and a substantial increase in measurement speed. CCD spectrometer dispersive element includes a prism and grating. Grating feature is available for the entire spectral range of linear spectral dispersion, there is a spectrum of overlapping class times; prismatic features a spectral class overlap problem does not exist, high luminous flux, there are a lot of non-linear dispersion. According to the actual situation of the visible CCD array spectrometer which using planar grating as dispersive element, so basically the same band of the measured spectral resolution. Visible light CCD array spectrometer system consist of condensing system, part of the flat field spectrograph, solid state array detector, fast A / D converter and computer data processing. Compared with mechanical scanning spectrophotometer, CCD fast spectrometer has some advantages: small size (no mechanical rotating structure) and measuring fast.