The schematic for the experimental setup is shown in figure 1. Our setup uses a 635 nm laser as the light source, which is attenuated by a combination of neutral density filters in order to prevent over saturation. The light is then projected onto a 100 \(\mu\)m pinhole, generating a high quality uniform wavefront. To create a collimated beam, a converging lens is placed one focal length after the pinhole (in our case 15 mm). To eliminate higher order lobes, an iris is placed after the converging lens to only allow the central disk of the beam. After a creating a collimated plane wave, it is illuminated onto the sample, which generates a diffraction pattern. An objective lens is placed after the sample to focus the image onto the Charged Couple Device detector. The objective lens also increases the optical distance of the image, allowing us to acquire a far-field diffraction pattern within the size limitations of our workspace. The detector is connected to a computer where we will use built in software to control the device. A light image and a dark image will be taken so that contamination from the device can be subtracted from the final image.
In order to acquire a satisfactory image, and due to requirements of the Matlab program, an oversampling ratio of 30 is preferred. Calculating an over sampling ratio is not difficult, however in the experimental setup used, a lens is placed between the sample and the detector, which complicates the calculations. Instead, we plan to measure the oversampling ratio after taking the image and finding the distance between each peak, which is correlated to the oversampling ratio. We will adjust the distance between the detector, the second converging lens, and the sample in order to acquire an adequate image. All of this will be executed in darkness to prevent external saturation and great care will be taken to eliminate other sources of light such as that from computer monitors. The sample that we are using is a C. elegans larvae which is approximately 1 mm in size. It is transparent to the naked eye which should lead to interesting diffraction patterns that will hopefully allow us to observe its insides. The sample will be placed inside cover glass to keep it in place.