**6. Experimental measures**

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figure 1a.

**Figure 19.** ACPC VS PCPC using entry 1.

The ACPC works better than PCPC as the incidence angle increases if we use only entry 1 in the prismatic PCPC. Figure 19 show this behaviour for different incidence angles. The TIR that suffers light beam in the outer surface of the PCPC is not happening when incidence angle increases, this behavior explains the decrease of efficiency according to the incidence angle increases The division of the beam showed in figure 20 (b) is due to the prismatic effect when light reach the film in the outer side as shown basic raytrace in

**Figure 20.** Examples of collimated light entering entry 1 30º (a) and entry 2 30º (b).

new bending systems show a good way to reach all the lighting necessities.

The light guiding after PCPC is a good alternative to light far away from the collecting system, the use of a hollow light guide is demonstrated as a good way to transport light, and A CCD video photometer (Radiant Imaging Prometric 1400) is used to measure output light distribution in exit pupil with a Lambertian screen (Fig.21). We measure output light in two experimental assemblies changing the incidence angle between 0º and 75º increasing the source angle in steps of 15º. Firstly, we evaluate entry 1, and secondly entry 1+2 is evaluated.

**Figure 21.** Schematic diagram of experimental setup The HPCPC has the following parameters: input aperture diameter (entry1): 88 mm; output aperture diameter (Lambertian screen): 187 mm, L: 4000 mm, d: 260 mm.

Normalized light distribution map onto exit pupil is shown in the figures 22 to 28. The (a) figure represents the illuminance map obtained with the ray tracing software, the (b) figure represents the map obtained with the experimental setup. Figures 22 to 24 show data for using entry 1 and 25 to 28 show data using entry 1+entry 2 for some light angles.

**Figure 22.** 15º entry1. (a) Raytracing simulation, (b) Experimental measurement.

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Natural Lighting Systems Based on Dielectric Prismatic Film 177

**Figure 27.** 60º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 28.** 75º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

division of the beam showed in figure 27 due to the prismatic film structure.

material, it allow us to produce lighting products with unique properties.

**7. Conclusions** 

The circular peripheral wreath in figure 25 is due to the multiple internal reflections of the light inside the prismatic film. When we increase the angle of incidence, we can observe the

The present study shows the interesting combination of light transmission and reflection capabilities of dielectric prismatic film analysed in different guidance geometries and the approach of a collecting system for sunlight applications. Prismatic film can work as a perfect mirror or transparent material depending upon the angle that light strikes the

It is important to analyse the micro-structure prism imperfections in the form of the surfaces: imperfect corners (apex and valley), surfaces which are not optically flat or which deviate from the expected angle, optical inhomogeneities in the material and the existence of the curved area on the peaks prism which modify the optical behaviour of the prism film; this imperfections modify the optical path and therefore the rays can be directed to other directions instead of undergoing total internal reflections. In order to check the importance of prism rounding, the apex is analysed through Hough Transform by digital image processing. The peak curved radio obtained is despised because of the radius size obtained

**Figure 23.** 30º entry1. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 24.** 75º entry1. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 25.** 0º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 26.** 45º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 27.** 60º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

**Figure 28.** 75º entry1+entry2. (a) Raytracing simulation, (b) Experimental measurement.

The circular peripheral wreath in figure 25 is due to the multiple internal reflections of the light inside the prismatic film. When we increase the angle of incidence, we can observe the division of the beam showed in figure 27 due to the prismatic film structure.
