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Dale BuralliFebruary 27, 20236 min read

Optical Assembly Provider - What to Look For

Optical assemblies are a critical part of a functional optical system. They consist of several components and mounting elements that must be aligned with precision, so it’s essential to carefully evaluate optical design manufacturing providers.

Here’s what you should look for when choosing an optical assembly provider for your optics project. We’ll start with the details of your optical design and what you should have hashed out when contacting an optical assembly provider for an estimate.

Optical Specifications

Optical specifications are necessary throughout a component or system’s design and manufacturing phases to reach performance requirements. They define the limits of the system’s performance and the time and cost necessary for manufacturing.

Both under-specification and over-specification can waste resources. It’s key to work within margins to ensure a successful finished product.

Manufacturing Specifications

Diameter Tolerance

The diameter tolerance of an optical component provides the acceptable range for the diameter and the mechanical tolerance for mounting. Though it doesn’t have a direct effect on performance, it can have an impact on the overall design and its functionality, by extension.

Radius of Curvature

The radius of curvature is the distance between the optical component’s vertex and the center of the curvature, which can be positive, zero, or negative, depending on the surface itself. The value determines the optical path length of the light rays that pass through the lens and the power of the surface.

Center Thickness Tolerance

The center thickness of a lens or other optical component is the thickness measured at the center, which can affect the optical performance. Combined with the radius of curvature, the thickness determines the optical path length of rays that pass through the lens.


Centering, centration, or decenter of a lens is a specification related to the beam deviation. Once this is determined, the wedge angle can be calculated. The centering is the physical displacement of the mechanical axis – the geometric axis of the lens – and the optical axis – the optical surfaces and the line that connects the center of curvature of the surfaces.

Angle Tolerance

Angle tolerance is relevant to projects that have beamsplitters or prisms. It refers to the angles between surfaces and determines the performance of the optical component. An autocollimator assembly can test the angle tolerance to ensure that the collimated beam hits the surface of normal incidence on each optical surface. The difference between the angles of the measured positions determines the angle tolerance.


Parallelism determines how parallel the two surfaces of the components are to one another. This is relevant to assemblies with windows or polarizers that require parallel surfaces for system performance without significant distortion, degrading the image or light quality.


Beveled edges protect the edges of glass components and prevent chipping during mounting. Small optical components may not need beveling, depending on the other specifications.

Clear Aperture

A clear aperture is the optical component’s diameter, designed according to predefined specifications. Manufacturers don’t guarantee the assembly’s specifications without this precise, clear aperture.

Surface Specifications

Surface Quality

An optical surface’s quality includes its appearance and manufacturing defects like scratches or warps. Though not all surface imperfections hamper performance, some can, such as surfaces at image planes and surfaces used with light at high power levels.

Surface Flatness

Surface flatness is a specification for accuracy that measures the deviation of a flat surface with a lens, prism, mirror, or other optical components. This is done using an optical flat, which is a precise surface for reference to compare the deviation of the manufactured component.

Surface Finish

Surface finish measures small-scale irregularities on a surface, usually due to the polishing process. Rough surfaces aren’t as durable as smooth surfaces and may not be ideal for some applications,


Power is a surface accuracy specification for curved surfaces (surfaces that have power). It’s tested similarly to flatness by comparing it against a reference surface. Any deviations will create Newton Rings, a series of rings demonstrating the deviation.

Material Specifications

Index of Refraction

The index of refraction is the ratio of the speed of light in a vacuum to the speed of light in a medium. This is important because the index of refraction for a glass optical component is an important property because the power is derived from the radius of curvature and the difference in the index of refraction on either side.

Abbe Number

The Abbe number quantifies the amount of dispersion a glass component exhibits, affecting focal lengths. Along with the index of refraction, the Abbe number is used by optical designers as degrees of freedom to design systems.

Laser Damage Threshold

The laser damage threshold is vital for laser optical assemblies, particularly with mirrors. This indicates the maximum amount of laser power a surface can withstand before the damage.

How to Choose an Optical Assembly Provider

Working with an experienced and knowledgeable optical assembly provider is crucial with all the components and specifications involved in optical assemblies. Here are the important qualities to look for:

Industry Experience and Expertise

Your optical assembly provider should have experience working on your industry’s optical assembly projects. This ensures that your provider can manufacture an assembly according to your specifications and industry-specific standards and adjust as needed to navigate challenges in the manufacturing process.

Some of these services may include:

  • Designing complete optical assemblies from start to finish
  • Improving a preliminary design concept or modifying an existing system
  • Designing optical components and mounting elements
  • Optimizing optical designs for mass production
  • Testing components individually and within complete assemblies

High-Quality Standards

It’s not enough to choose an optical manufacturer who provides services but one who’s committed to exceptional quality throughout the design process. A reputable optical assembly provider will have robust quality control processes in place with technology and documentation to ensure a successful finished product.


Depending on the industry, there are performance specifications and industry-regulated performance standards an assembly must meet. While some components are ideal, others are mission-critical and profoundly impact the final design, such as products for the aerospace industry.

A precision optical assembly supplier with industry experience should be able to determine your mission-critical components and adjust your design to improve performance, and provide proof of concept to minimize time and waste in the manufacturing process.


Virtually all custom optical assemblies will require compromises to balance the appropriate performance specifications with the cost of production. An experienced optical assembly manufacturer should be able to adjust your design to get the maximum performance out of the finished design for the most value.

This may include adjustments to:

  • Materials
  • Components
  • Performance and properties
  • Mounting and packaging
  • Size and weight
  • Production and fabrication

Optical Design Manufacturing with Apollo Optical Systems

Apollo Optical Systems is an industry leader. Leveraging a thorough understanding of the fundamentals, our design and manufacturing processes are guided by the philosophy that the best design comes from a thorough understanding of the problem and the technical principles that govern a successful finished product. We’ll work with you throughout the process, from prototyping to final assembly, to maximize performance without compromising quality or cost-effectiveness. Contact us today to discuss your custom optical assembly!

About Dale Buralli

Dr. Dale Buralli has served as the Chief Scientist for Apollo Optical Systems since 2003. In this role, Dr. Buralli is responsible for the design and optical modeling of various optical systems. These systems include virtual or augmented reality, ophthalmic and other imaging or illumination systems. Additionally, he provides support for optical tooling of lens molds and prototypes, including the development of custom software for both production and metrology. Dr. Buralli got his Ph.D. in optics from the University of Rochester in 1991. Now he is an Adjunct Professor of Optics at the University of Rochester’s Institute of Optics.