Lens system designing is a crucial aspect of optical systems. Successful lens design supports not only a working model but also manufacturing, assembly, testing, and implementation. This is important for proof of concept. An initial design can be excellent in theory but may fall apart in later manufacturing stages.
Designing a lens system – or optical system – is far more involved than designing a single lens. There are considerations of cost, size, timeline, lens parameters, geometry, assembly setup, tolerance models, and more. All of the aforementioned can impact the final design and its performance in real-world applications.
Understanding Lenses and Lens Design
A lens can refer to a curved piece of glass or plastic, which you’ll see with eyeglasses, sunglasses, and contact lenses. This is the layperson’s understanding of a lens.
To a lens or optics designer, a lens is a device that collects and distributes light in the desired way.[1] For example, a camera has a range of lenses of different shapes and sizes that work together to the camera’s performance. In this context, the lenses are referred to as lens elements, and they’re within an optical system.
A lens or optical system can contain any number and combination of lens elements, mirrors, prisms, filters, diffraction gratings, rotating polygon scanners, holographic elements, or other types of optical components.
The designer must consider the performance and size requirements of the system, the light source that will be used with the lens (light bulbs, lasers, LEDs, etc.), and the type of detector, which is a device that reacts to light. More complex systems, such as those for infrared and ultraviolet light, will need more sources and detectors, but the lens design principles are the same.
Lens design may be involved with:
- Microscopes, telescopes, and binoculars
- Camera lenses
- Slide, movie, overhead, and video projectors
- Endoscopes for surgery
- Laser printers, office copiers, fax machines, and microfilm readers
- Product code laser scanners
- Laser-based optical readers for CD and CD-ROM
- Repair optics
- Projector lenses for integrated circuits
Lens Design Requirements
Optical systems have different requirements. They may include:
- Optical performance or image quality, which may be quantified by modulation transfer function, encircled energy, Strehl ratio, ghost reflection control, and pupil performance
- Physical requirements like weight, static volume, dynamic volume, center of gravity, and configuration
- Environmental requirements like temperature, pressure, vibration, and electromagnetic shielding ranges
Several constraints can affect the optical system, including the lens element center, edge thickness, air spaces between lenses, entrance and exit angles, and index of refraction.
Also, the cost of design and manufacturing are part of optical design. Depending on the application, the costs associated may significantly impact the final design. The manufacturing schedule and delivery may also factor into the design process.
Lens Design Process
The lens design process can vary according to the project, but the general steps include:[2]
Defining the Problem
Engineers or other professionals may conceptualize the optical system, but the optics designer must turn the concept into detailed optical specifications. The performance specs are included in this step and indicate how detailed of an image the lens should provide and other requirements.
Sometimes, the desired performance and requirements are contradictory, so compromises must be made to prioritize the most critical aspects of the system.
Entering the Pre-Design Stage
Once the specifications are set, the designer must make decisions about different aspects of the system, such as the size, number of elements, reflection vs. refraction, and more. This process may include rough sketches and graphical ray tracing or the use of graphical software tools.
Selecting a Starting Point
This is the stage when the concept comes to a realization. Software can be useful to leverage existing designs and troubleshoot design problems to create a system that performs as it should with few concessions. Graphical and approximate methods can be used to create the starting point.
Performing Initial Analysis
The starting point provides a baseline analysis to measure improvement over the specifications. Aberration analysis may be used in the design process to design and select variables to create the most effective final design.
Optimizing the Design
Once the variables are defined, such as the curvature, index of refraction, and thickness, that can be changed, the lens can be optimized. The variables are altered systematically to minimize errors while staying within the parameters. This phase is when changes take place to resolve conflicts and make final adjustments and tradeoffs.
Performing a Final Analysis
After the lens is optimized, the designer can see if the changes allow the system to perform as expected. If it’s not where it needs to be, the designer may need to return to the optimization phase to change design aspects. If the design is a complete failure, the designer may need to go back to the starting point.
Preparing for Fabrication
If the lens system does meet the requirements, it can be prepared for fabrication. The design is turned into practice to produce real-life lenses that meet the requirements for real-world use. Optical design software can be used at this stage as well. However, the process still needs the human eye of a designer to identify problems and determine priorities for a successful finished product.
Custom Lens Design at Apollo Optical Systems
Software helps with the optical design process. But, there’s no substitute for the knowledge, experience, and design intuition of an engineer. At Apollo Optical Systems, our design process is guided by the philosophy that optimized designs come from understanding the problem and the physical principles that can guide an optimal solution.
Our design process includes the customer in all phases of the development cycle, from prototyping to final manufacturing and assembly. You can rely on in-house design expertise and optical and mechanical design under one roof for an integrated solution. We provide design for manufacturing, design verification, tolerance analysis, and design for imaging and non-imaging systems. Contact us today for an estimate of your custom optical components and assemblies!
Sources:
[1] https://www.britannica.com/science/optics#:~:text=An%20optical%20system%20consists%20of,%2C%20and%20fibre%2Doptics%20bundles. [2] https://spie.org/news/engineering-an-optical-system?SSO=1
