Penta Prisms

Penta Prism is a five-sided prism containing two reflecting surfaces at 45° to each other, and two refracting faces perpendicular to the entering and emerging beams. The important properties of Penta Prism are:

l The image is neither inverted nor reversed, just deviated by 90°.

l With the prism, a constant deviation angle applies to all rays transmitted by the useful aperture, regardless of the angles between these rays and the optical axis (or entrance and exit face normal).

Penta Prism

The deviation angle of 90° is thus independent of the orientation of the prism, making it especially important in applications in which the prism orientation cannot be precisely controlled. Due to geometry that total internal reflection cannot be used, the reflecting surfaces must be coated with a metallic or dielectric coating. The standard Penta Prism reflecting surfaces are coated with aluminum or enhanced aluminum(see Coating charpt). Sometimes, reflecting coating surfaces are with black painting.

Specification

Material: BK7 Grade A optical glass
Dimension Tolerance: ±2mm
90° Deviation Tolerance
Standard series: < 30 arc seconds
Precision series: <10 arc seconds
Flatness:
Standard series: l/2 at 632.8 nm
Precision series: l/4 at 632.8 nm
Reflectivity: R > 95% per face from 630 to 680 nm
Surface Quality: 60-40 scratch and dig

　

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