# Biophotons: A Hard Problem
## 6 Future Experimental Upgrade and Perspective  
For any experimental apparatus that aims to perform biophotonic measurements, possible improvements involve two approaches: increasing the number of detectors to enhance counts or enhancing the collection capacity. The first approach may be a double-edged sword. Biophotons are an endogenous production of a very small flux of photons, of the order of 100 ph/sec, within an energy range between 200 and 800 nm. Even in the darkest environment, a low background counter could have some spare counts per second. Increasing the number of detectors means increasing the sources of background noise and the covered solid angle, but this last can in practice be increased by a very small percentage, and therefore produce a modest gain in signal-to-noise ratio. In our opinion, enhancing the biophoton measurement capability of an experimental setup would be best achieved by improving its collection capacity. In this section, we introduce and assess various upgrades aimed at increasing the ability to collect luminescence biophotons in a scientific apparatus. Such improvements could also be applied to different apparatuses that aim to make measurements of rare low-background luminescence processes. A first improvement is the introduction of a Fresnel lens to the apparatus. The Fresnel lens is a \"sectioned\" convex lens with vertical parallel planes forming concentric rings. Refraction bends the light rays and makes them converge into a single focus. Placing a Fresnel lens in front of the emitting source (germinating plants, for example), luminescence photons can be focused to the counter (distances can be evaluated with a simulation), and thus the geometrical efficiency of the apparatus can be improved up to two orders of magnitude, as shown in Figure 8.  
A second improvement would be the building of an integrating sphere made with white Teflon. Teflon reflects more than 99% of the incident light in the visible energy range, so the light originally generated by the sample is reflected many times by the walls and finally reaches the hole where the photomultiplier is housed. In this way, it collects the emission coming from every part of the sample, and it is as if we have increased the solid angle of measurement by certain factors. The integrating sphere can be located inside a black PVC chamber to avoid any light contamination (see the right panel in Figure 8). The third improvement is the installation of light sources for calibration and validation testing of the experimental setup. Specifically, the best solution would be the installation of two light sources: one emitting coherent light and another emitting incoherent light. This can be of extreme importance as there are many works investigating the coherence state of biophotonic emission; we range from an analysis in terms of a totally chaotic field to those based on the presence of coherent and squeezed states. The introduction of coherent and incoherent light sources in the apparatus can provide a reference to compare the biophoton emission. So far, we mentioned the upcoming improvements. However, several further improvements may be made. One is the installation of an infrared camera to obtain fundamental information about growing cells. Such an improvement can be tested in lentils, but their chaotic vertical growth may produce an incomplete response collection. In cell cultures, where the layer is uniform, an infrared camera can collect more complete and clean information. Other improvements include the installation of devices and sensors to modify and monitor the temperature inside the chamber, the installation of irradiation systems, and the variation in atmosphere or pH and constituents of the soil of the plants to characterize the spectrometric response of germinating seeds. In this way, the lentil experiment represents a pioneering study on biophotons.