Wells Research & Development

Library

Tests and Configurations

Common Configurations

Common Configurations

Afocal Module

This test setup is best suited for
Beam expanders, telescopes, or any lens combination designed to operate afocally.

Typical Setup

The setup above shows a 7X binocular under test.

The "L" bracket from the accessory kit is used to support the binocular in the photo.

Schematic Representation

OpticStudio hardware works in conjunction with PixelScope software. While no programming is needed, it is necessary to enter the parameters of the setup and the nominal parameters of the lens under test. The picture above shows how these parameters are entered.

Limitations

  • The clear aperture of the module should not be larger than the collimator. The standard 200 mm collimator is suitable for lenses with clear aperture up to about 20 mm.
  • The setup shown above is suitable for devices which are already in perfect collimation (or can be focused manually).

    Wells Research also supplies collimator tubes with adjustable focus.

  • The classical "lens bench" architecture does not lend itself to making off-axis measurements on afocal modules. The simplest strategy is to hold the afocal module stationary, and pivot the collimator and video telescope. This is possible with OpticStudio by using a pair of optional pivot mounts.

Tests possible with this setup

On-axis and off-axis tests
See note under "Limitations" above.

Plane of best focus
See note under "Limitations" above.

Image quality measurements
There are many ways to evaluate image quality, including MTF, 3-bar contrast, and visual examination of the PSF, just to name a few. These measurements are common to many different OpticStudio setups, so they are discussed in a separate chapter on measuring image quality.

Measuring EFL, BFL
These measurement are not applicable to an afocal module.

At the risk of stating the obvious, if the module can be disassembled it is possible to measure the EFL of the components separately.

Finding the Exit Pupil
This measurement is not supported by the standard OpticStudio. However, it is possible to visualize and plot pupil location vs field angle with the optional pivot mount.

Measuring Magnification
"Magnification" is the ratio of image height to object height. The EFL wizard in PixelScope makes it easy to do this with a few clicks of the mouse. For more information see measuring magnification.

Axial color
See note under "Limitations" above.