A prism is an optical element that alters the direction of light propagation by utilizing the principles of reflection or refraction. Typically crafted from transparent optical materials such as glass or quartz, it features specific geometric shapes—commonly right-angle prisms, pentagonal prisms, or roof prisms. By inducing reflection at its surface (usually a polished reflective face), it alters the established propagation path of incident light rays, thereby redirecting the optical path.

Compared to mirrors, the advantages of steering prisms lie in their structural stability, fixed and highly precise optical path deflection angles, and resistance to factors such as external vibrations and temperature changes that could compromise optical path stability. Consequently, they are widely used in optical systems requiring precise control over the direction of light paths.

Applications of Deflection Prisms

1. Altering the optical path direction to adapt to diverse inspection scenarios

In optical inspection equipment (such as industrial cameras, microscopes, surveying instruments, etc.), constraints from the inspection environment (e.g., confined spaces, unusual object positioning) sometimes prevent the lens from directly aligning with the target. A deflection prism alters the optical path direction through reflection (e.g., converting a horizontal path to vertical or adjusting the angle), enabling the device to observe or capture the target without modifying its overall layout. For instance, in industrial assembly line inspection, a deflection prism allows the camera to capture objects above a conveyor belt from the side or below, preventing spatial interference between the equipment and the conveyor.

2. Simplifying Deflection Mechanism Structure and Saving Assembly Space

The geometric design of the deflection prism integrates optical path deflection functionality, eliminating the need for additional complex mechanical transmission components (such as multi-mirror adjustment mechanisms). This not only simplifies the overall optical system structure but also significantly reduces the device's volume and assembly space requirements. For example, in portable optical instruments like handheld laser rangefinders, using a steering prism enables multiple optical path deflections within limited space, ensuring compactness and portability.

3. Ensuring High-Precision Assembly to Enhance Imaging Quality

Direction-changing prisms feature extremely high machining precision (e.g., flatness of reflective surfaces, angular tolerances), guaranteeing accuracy and stability of optical path deflection angles during assembly. This high-precision characteristic minimizes issues like optical path deviation and aberrations, thereby ensuring the optical system's imaging clarity and measurement accuracy. The application of steering prisms is particularly critical in telecentric lenses. Telecentric lenses require that the principal rays from either the object side or image side be parallel to the optical axis. Steering prisms precisely control the optical path direction, ensuring the lens maintains distortion-free, high-resolution imaging performance even at large fields of view. They are widely used in machine vision inspection, precision measurement, and other fields.

Types and Applications of Deflection Prisms

1. Right-Angle Prism: Achieves 90° or 180° deflection with a simple structure, commonly used for vertical optical path deflection.

2. Pentaprism: Enables precise 90° deflection unaffected by minor variations in incident light angle. Suitable for applications requiring stable deflection angles (e.g., telescopic sights, rangefinders).

3. Roof Prism: Achieves optical path deflection via two mutually perpendicular reflective surfaces (roof faces), minimizing lateral image inversion. Commonly found in binoculars.

The performance of steering prisms is also influenced by coating technology. Applying anti-reflective coatings or high-reflectivity coatings to the reflective surfaces reduces light reflection losses, enhances the optical path's transmission efficiency, and further optimizes imaging or signal transmission quality.