Custom optics

Smart manufacturing of custom prisms

By 12 October 2020 No Comments
custom prism

Are you looking for high-quality, custom prisms? Our unique manufacturing method enables you to have custom prisms, without high upfront costs or MOQs. But first, what are optical prisms and which type of prism is best suited for your particular goal?

Check our Addoptics datasheet for our most up-to-date capabilities and material properties.

What is an optical prism?

An optical prism is used to redirect light at a designated angle. Prisms can be used for ray deviation or for adjusting the orientation of an image. It is the design of the prism which determines how light interacts with the prism. As soon as light enters a prism it reflects off an individual surface, or several surfaces, before exiting. Light which enters a right angle prism reflects off a single surface, causing the light to redirect at 90°. However, when light enters a wedge prism the light is deviated through refraction as a result of varying substrate thickness.

Prisms and refraction

Understanding how an optical prism works is crucial in order to decide which type of prism is the best fit for your project. As such, we need to take a closer look at how light interacts with an optical surface.

This interaction is described by Snell’s Law of Refraction:

Law of Refraction

Here n1 is the index of the incident medium, θ1 is the angle of the incident ray, n2 is the index of the refracted medium and θ2 is the angle of the refracted ray.

Snell’s Law describes the relationship between the angles of incidence and transmission when a ray travels through media.

Prisms are notable for their ability to reflect a ray of light without the need for a special coating. This is done by total internal reflection (TIR). This occurs when the incident angle is higher than the critical angle (θc). Total internal reflection can only occur when light travels from a high index medium to a low index medium.

Snells law of refraction

Here n1 is the index of refraction for the medium where the ray originates, n2 is the index of refraction for the medium where the ray of light exits.

If a prism face does not meet TIR specifications for the desired angle (or angles), then a coating must be applied. As such, some applications require coated prisms, that would normally work well uncoated in other applications.

Types of prisms

Prisms can be divided into four types:

  • Dispersion prisms
  • Deviation / Reflection prisms
  • Rotation prisms
  • Displacement prisms

Dispersion prisms are made for dispersing light, as such they are not suited for any imaging applications. Deviation, rotation and displacement prisms are commonly used in imaging applications.

Optical prism applications

The number of surfaces, the angles of these surfaces and their position will shape the function of a custom prism. In order to understand how the most popular prisms work we can take a closer look at their usages in light reflection and refraction applications.

Right angle prism

This is one of the most commonly used prisms. The right angle prism can be used in various ways to achieve various results. The most common application of this type of prism is to use it for its single reflection that deviates the incident ray by 90°. Note that the produced image will then become left-handed, but – depending upon the position of the prism – it can be reverted or inverted.

Roof Prism

A roof prism has two reflecting surfaces, located 90° from one another. A roof prism functions like any other reflecting surface, except that handedness does not change. E.g. an amici roof prism is basically a right angle prism with a roof, as such the deviation of 90° occurs, but without changing parity. Roof prisms are mostly used together with other prisms in order to achieve the required result.

Combination prisms

Combination prisms are available in many shapes, sizes and applied coatings. Some common combination prisms are beamsplitters, Pechan roof prisms and porro systems.

Custom prisms by Addoptics

If you are looking for custom prisms in low-volume quantities Addoptics can help. Our unique manufacturing technology is perfectly suited for rapid prototyping and low volume manufacturing of custom optics.

With our technology you can have a handful of custom prisms created, where each prism can be unique in it’s design. Making our technology perfect for product testing and optimization, before moving on to production.

Benefits of Addoptics’ technology include:

  • Short lead-times (days instead of weeks)
  • No MOQs
  • High-grade polymer optics
  • Full design freedom

In need of custom prisms for your project? Contact us to discuss the possibilities.

Check our Addoptics datasheet for our most up-to-date capabilities and material properties.

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