Qiang Hao Dec Holography

* A hologram is a recording which contains both intensity and phase information. * By using a reference beam, we can record the direction of the object light. * After we take the image, develop it and re-put it in the exact same position where we took it, we can regain the same lively image by using the same the reference beam. Introduction

What do we want to do in this lab? Experiment Plans 1). Get the stress patterns of a can. 2). Estimate the coherence length of the light. 3). Double exposure.

The set-up we used throughout the lab Experiment Setup Important!!

Experiment setup

Experiment results Experiment 1: Stress Patterns. Put a weight on the top of a can, take a picture of the can with the exposure time to be 1.5 minutes. Then put off the weight and take a picture on the same film with the same exposure time. Since the can should not be moved when we putting off the weight, it is filled with water.

Experiment results Important!!

Stress patterns Experiment results

Experiment 2: Coherence Length. Replace the can by a ruler. Use the cylindrical mirror. Remove the lens in front of the mirror. The beam on the ruler should be as intense and as even as possible. Find out two dark points on the ruler. Measured the path difference of the two marks, and this equals to the coherence length. Experiment results

Actually, we can see the millimeter marks clearly. Here, we try to take a picture of the dark point of the ruler we found, but actually, it is hard to take a clear picture of that.

Experiment 3: Double Exposure Experiment results

In this lab, we use the technique called hologram to take images which can show us three dimensional aspects of the object. There are total three different experiments. The first one is stress pattern. By applying a stress on a can, and take the images both the stressed can and the unstressed can, we get the interference pattern. The lines show how the weights applied on the can. The second one is to measure the coherence length of the light. This can be calculated as the path difference of the two dark parts on the ruler. In our measurement, we have this value to be about 35.5cm. The third experiment is double exposure of two different objects. By this method, we can take the image which is impossible in our daily life. Conclusions

Reference  [1] The Holography lab manual.  [2] Wikipedia.

Thanks!