What problems should be paid attention to when shooting high-quality holograms?

Holography reproduces objects by recording interference patterns, so how to clearly record interference fringes is the key to success:

1. The recording material should have high resolution, preferably >; 3000 line pairs /mm, but the sensitivity of such a high-resolution silver salt photosensitive material is very low, which requires long exposure. Other photosensitive materials are less sensitive and require exposure time of tens of minutes.

2. Because the exposure time is long and the stability is very high, it should be carried out on a shock-absorbing optical platform to reduce the interference of airflow, the vibration of sound waves, and the thermal expansion of the subject, optical devices and photosensitive materials caused by temperature changes during exposure, because as long as the displacement of 1/4 wavelength occurs, the interference pattern will be completely destroyed!

3. Need a single longitudinal mode laser, that is, only one wavelength laser output, rather than multiple multimode laser outputs that are very close to each other. Only such a laser has a sufficiently long coherence length.

4. The laser power should be as high as possible, but the high-power single longitudinal mode laser is very expensive and needs to shoot holograms, but not all lasers are suitable, and the phenomenon of "cutting bread" will appear when shooting with multi-longitudinal mode laser. Single longitudinal mode high power pulsed laser can shoot portraits.

5. The exposure of the recording material has an optimal value, and the diffraction efficiency has a functional relationship with the exposure, which needs to be comprehensively considered according to the light intensity and the sensitivity of the recording material. Both overexposure and underexposure have low diffraction efficiency.

6. The optical paths of the object light and the reference light reaching the holographic recording material should be as equal as possible.

In a word, holography is a comprehensive application of physical and chemical knowledge, which requires high experimental skills besides theory. People who want answers are not for exams, but for science.

Biochemists engaged in holographic photography.