A Simple Guide to Creating Computer-Generated Holograms for Green Laser Projections

If you have ever dreamt of creating holograms for applications such as projecting circles with angles of 1.5 and 10 degrees when illuminated with a green laser, you are not alone. While the concept might seem complex, understanding the key steps and technical details involved can simplify the process. In this guide, we will break down the steps required to create these types of holograms.

Understanding the Basics of Holograms

A hologram is an optical phenomenon that captures a three-dimensional image through the interference of light waves. Computer-generated holograms (CGHs) are created using algorithms and are then projected using lasers, optical elements, and other tools. For this specific application, you will need to follow a few key steps to ensure accurate and detailed holograms.

Building the Holograms

Step 1: Determine the Desired Pattern

The first step is to determine the pattern you want to project. For this example, you desire to project 1.5 and 10-degree circles. This pattern will serve as the basis for your hologram.

Step 2: Calculate the Phase Shifts

Once you have the desired pattern, you need to calculate the phase shifts that will create this pattern. This involves taking the inverse Fourier transform of the pattern you want. Essentially, you are breaking down the pattern into its wave components and then reconstructing it in a way that will create the specific image you want.

Step 3: Encode the Phase Shifts on a Suitable Medium

The phase shifts need to be encoded onto a suitable medium, such as fine-grain film. Unlike traditional film that absorbs light, the material used should scatter light to create the holographic effect. This fine-grain film needs to be developed to ensure it does not absorb but scatters light effectively.

Technical Considerations

The accuracy of the pattern is critical, especially when working with light wavelengths. You will not be able to print the pattern directly using an ink jet printer due to the need for high precision. Instead, you will need to use specialized tools and techniques to ensure the pattern is accurate to the order of a wavelength of light. This is where the concept of holographic optical elements (HOEs) comes into play. HOEs are designed to manipulate light to create the desired optical effect.

DIY vs. Professional Solutions

While it is possible to create holograms in your garage or workshop, it is a highly technical task. If you are a physics graduate with experience in a laser lab, you will have a good starting point. However, accurately recording holograms requires significant technical knowledge, including a deep understanding of Fourier transforms. Additionally, you need to minimize vibrations in your optical setup to less than a wavelength of light. Building an optical bench with low expansion materials and pneumatic isolation can be a significant undertaking.

There are professional companies that can create these holograms for you. An hour-long video exists that goes through the entire process in detail, which you might want to watch. If you find the process too complex or find it challenging to understand the technical details, you can easily send the requirements to one of these companies and request a quote.

Conclusion

Creating holograms, especially for specific applications like projecting circles with precise angles, is a task that requires a fair amount of technical expertise. If you are willing to invest the time and effort to learn the necessary skills, it is certainly possible to create your own computer-generated holograms. However, for those without a background in physics or optical engineering, outsourcing might be the better option. Regardless of your approach, the ability to create holograms opens up a world of possibilities in fields such as aerospace, entertainment, and more.