What Is a Holography Laser?

The first step of holographic technology is to use the principle of interference to record the light wave information of the object, that is, the shooting process: the subject is formed into a diffuse object beam under laser irradiation; the other part of the laser is used as a reference beam to be shot on the holographic negative and superimposed on the object beam Interference is generated, and the phase and amplitude of each point on the object's light wave are converted into spatially varying intensity, so that all the information of the object's light wave is recorded using the contrast and interval between the interference fringes ^[1] . The negative film with interference fringes is processed into a hologram, or hologram, after processing procedures such as development and fixing. The second step is to reproduce the light wave information of the object using the principle of diffraction. This is an imaging process: the hologram is like a For complex gratings, under coherent laser irradiation, the diffracted light waves of a linearly recorded sinusoidal hologram can generally give two images, namely the original image (also called the original image) and the conjugate image. The reproduced image has a strong three-dimensional sense and has a real visual effect. Each part of the hologram records the light information of the points on the object, so in principle, each part of it can reproduce the entire image of the original object. Multiple exposures can also record multiple different images on the same film. And can be displayed separately without interference.

1. The reconstructed three-dimensional image is conducive to preserving precious art materials for collection.

2. Every point is recorded on any point of the hologram when shooting, even if the photo is damaged.

3. The holographic photos have a strong three-dimensional sense and realistic images.

There are three types of projection technology:

1. Air projection and interaction technology: This invention was invented by a 29-year-old graduate student in science and engineering in Chad Dyne, Massachusetts, USA. It is a milestone in display technology. It can project images with interactive functions on the wall formed by airflow. This technology is based on the principle of mirage, projecting images on

The principle of holography is applicable to various forms of fluctuations, such as X-rays, microwaves, acoustic waves, and electronic waves, as long as these fluctuations have sufficient coherence when forming interference patterns. Optics

Introduction to Holographic Technology

Holographic technology

Holographic photography refers to a new type of photography technology that records all the information about the amplitude and bit of the reflected wave of the subject. Ordinary photography records the light intensity distribution on the surface of an object. It cannot record the phase information of the reflected light from the object, so it loses the three-dimensional sense. Holographic photography uses laser light as the illumination light source, and divides the light emitted by the light source into two beams, one beam is directly directed to the photosensitive sheet, and the other beam is reflected by the subject and then directed to the photosensitive sheet. The two beams of light are superimposed on the photosensitive film to cause interference. The sensitivity of each point on the photosensitive film varies not only with the intensity but also with the phase relationship of the two beams of light ^[5] . Therefore, holography records not only the intensity of the reflection on the object, but also the phase information. When the human eye directly looks at this photosensitive negative film, only interference fringes like fingerprints can be seen, but if a laser is used to illuminate it, the human eye can see the same three-dimensional stereo image of the original object through the negative film. Even if only a small part of a holographic picture is left, it can still reproduce all the scenes. Holography can be applied in many fields such as nondestructive testing, ultrasonic holography, holographic microscope, holographic memory, holographic film and television.

Holographic technical requirements

Shooting requirements, in order to take a satisfactory hologram, the shooting system must have the following requirements:

The light source must be a coherent light source

According to the previous analysis, holography is based on the interference principle of light, so the light source must be very coherent. The advent of lasers provides an ideal light source for holography. This is because the laser has good spatial coherence and time coherence. In the experiment, a He-Ne laser was used, and a small diffusive object was taken with it to obtain a good hologram.

Holographic technology

Holographic camera system must be stable

Because interference fringes are recorded on the holographic negative, and they are thin and dense interference fringes, even the smallest interference during the photographing process will cause the interference fringes to be blurred, and even make the interference fringes unrecordable. For example, if the film is shifted by one micrometer during the shooting, the fringes will be indistinguishable. For this reason, the holographic laboratory bench is required to be shockproof. All optical devices on the holographic stage are firmly fixed on the work surface steel plate with magnetic material. In addition, the air flow through the optical path, acoustic interference and temperature changes will cause changes in the surrounding air density. Therefore, no loud noises should be prohibited during exposure, and random walks should not be allowed to ensure that the entire laboratory is absolutely quiet. Our experience is that after each group has adjusted the light path, the students leave the experimental platform, stabilize for one minute, and then expose at the same time to get better results.

Object light and reference light should meet

The difference between the path lengths of the object light and the reference light should be as small as possible. The light path length of the two beams is the best, and the maximum cannot exceed 2cm. Use a string to measure the light path; 60 °, it is best to be about 45 °, because the interference angle is small, the interference fringes are thin, so the requirements for the stability of the system and the resolution of the photosensitive material are relatively low; It is required to be between 1: 1 and 1:10, and the light intensity ratio is measured by a silicon photocell.

Use high-resolution holographic negatives

Because fine and dense interference fringes are recorded on holographic negatives, high-resolution photosensitive materials are required. Photographic negatives for general photography can only record 50 to 100 stripes per millimeter due to the coarser particles of silver. The type I holographic dry plate produced by Tianjin Photographic Film Factory has a resolution of 3000 per millimeter, which can meet the holographic Photo requirements.

Holographic process

The rinsing process is also critical. We formulate according to the formulation requirements, and formulate the developing solution, stopping solution, fixing solution and bleaching solution. The above-mentioned several prescriptions require the preparation with distilled water, but experiments have proved that the preparation with pure tap water has also been successful. The rinsing process should be performed in a dark room. The chemical solution must not be exposed to light. Rinse at a temperature of about 20 ° C. Prepare the solution once and store it properly.