Q: create a local hemispherical irradiation model

Equipment for hemispherical imaging

Figure 1, reflecting sphere and camera(man). Ray tracing from a unit sphere to the imaging plane of a pinhole camera. 


An rgb camera is used to estimate the photon flux in the RGB bands of visible light.

In order to image the irradiation coming from the sky hemisphere, a reflecting sphere is used.

Software [Ray tracing], maps the RGB image to equal intervals in solid angle, and corrects for aberrations of the camera from the pinhole model.

A spectrometer with coaxial RGB camera is used to calibrate the RGB spectrum to the spectrometer readings.

The RGB segments are translated to spectrum segments [350:1100 nm], providing an estimated photon flux Nph(freq) as a function of solid angle.

Multiplication with freq * h gives the equivalent incoming energy flux.

Todo :

make permanent camera+ sphere+ tripod + logging of data

calibrate usb2000+ spectrometer to absolute photon count and simulate effects of RGB pass filters and quantum efficiency of RGB cameras. Calibrate cameras for geometric and radiometric non linearities.

Add picture of coaxial spectrometer_camera and the data it produces.

Option: Extend the coaxial spectrometer_camera device with servomotors to execute scanning patterns such as hemispherical scanning. Warning: avoid direct sunlight.