Stray light, also referred to as flare, is any light that reaches the focal plane via a non-design optical path. It can cause contrast loss (decrease in dynamic range), false features (seeing ghost images), and changes in color; all of which can degrade the quality of the images captured and even interfere with the ability to detect objects in the scene.
Imatest provides both software and hardware for stray light testing. Our solution includes the following:
Learn more about the various components for our stray light testing solution below:
Imatest version 22.2 introduced the stray light (flare) analysis. Import images into Imatest to run the analysis, where Imatest can process the images into normalized stray light metric images. Various information and summary statistics can be derived from the resulting metric images. Outputs include the metric images themselves, as well as plots, videos, and standard output files (e.g., JSON and CSV). The stray light module is available in both Master and IT on our software store page. See also our stray light documentation for more detail.
The Imatest Motorized Gimbal allows for programmatic control over camera roll and yaw (or alternatively, pitch and yaw) which effectively provides control over the field angle and azimuth angle of a light source when properly set up and aligned. The Motorized Gimbal has 360-degree range for both axes and positional accuracy of 0.08 degrees. The Motorized Gimbal comes with a goniometer to help with leveling and alignment.
The Imatest Motorized Gimbal is available on the Imatest Store. See the Motorized Gimbal instructions page for additional details on how to get started with using the gimbal for stray light testing.
This fixture allows you to perform repeatable captures of a bright light source positioned at different angles in (or outside of) the camera’s field of view. The fixture consists of a matte black acrylic light shield with mounting hardware on a 120 cm x 60 cm optical breadboard with metric holes / spacing, shock absorbing feet. The main components of the fixture are a Motorized Gimbal and halogen fiber optic light source.
The halogen bulb covers both the visible and near-infrared spectrum. The fiber is paired with a collimation optic that focuses the light into a narrower beam, though still diverging. The fiber is mounted to a two-axis goniometer, useful for camera-to-source alignment. An extended, diverging light source such as this can be used for repeatable stray light testing so long as the setup (e.g., camera-to-source distance and alignment) remains constant. A benchtop stray light test fixture, including the Broadband Halogen Fiber Optic Illuminator and the Motorized Gimbal, is available on the Imatest Store.
Ideally, stray light testing should be done in a large, dark room to eliminate any potential for unwanted reflections. However, a blackout curtain may be used if a large, dark room is not available. The blackout curtains should not immediately surround the setup, but rather, there should be some space between the curtains and the setup (camera and light source) to further prevent unwanted reflections. The larger the enclosure, the better. Additional baffles may be used throughout the setup to further reduce extraneous reflections and ambient light. Imatest’s Blackout Curtain Fixture is available for purchase on the Imatest Store.
Imatest is developing a configurable light source designed for stray light testing. The design includes a 4” integrating sphere with a radiance monitor detector for highly uniform and controlled output. Attached to the integrating sphere are three ports for swappable LED engines. For example, LED engines corresponding to 5000K visible light, 850nm, and 940nm near-infrared light could be used to test for stray light in both the visible and near-infrared spectrum (other wavelengths are available). The integrating sphere acts as a diffusor that effectively blends the light from the separate LED engines into one uniform light source. The light source may include adjustable optics allowing for configurable divergence of the output beam (up to collimation), as well as an adjustable iris allowing for configurable source object size. A collimated, spatially uniform beam of light allows for controlled and repeatable stray light testing. This hardware component is still in development and is estimated to be ready in Q1 2023.
A concept render of the Imatest configurable light source designed for stray light testing. The design includes adjustable optics attached to an integrating sphere with a radiance monitor detector and three swappable LED engines
Imatest is developing a Motorized Test Stand that can be used for a variety of automated image quality testing purposes, including stray light testing. The Motorized Test Stand provides three axes of automated translational movement for sub-millimeter precision. When paired with a Motorized Gimbal and light source, the Motorized Test Stand can significantly aid with set up,camera-to-source alignment, and automated testing. This hardware component is still in development and is expected to be ready in 2023.
A concept render of the Imatest Motorized Test Stand paired with the Motorized Gimbal and configurable light source for stray light testing. The Motorized Test Stand provides three axes of translation which can aid in set up, camera-to-source alignment, and testing, along with variety of other image quality testing applications.
For more information on stray light and setting up your stray light test system, visit our stray light documentation. To purchase our stray light solution package, visit our store page.
