Method for Improving Night Vision Device Depth of Field

摘要

It is known that when using Night Vision Devices (NVDs) to view objects close tothe observer, the depth of field, the volume of space that appears to be in focus, is extremely small. The depth of field of optical systems can be increased by slowing the system's f-number. A simple way to accomplish this is to add restrictive apertures onto the front of the objective lens. This noticeably increases NVD depth of field but causes a significant reduction in light gathering capability. This report addresses equations describing the phenomenon, assesses the tradeoffs that we are involved in using apertures to increase depth of field, and documents some experimental visual acuity data demonstrating an increased depth of field due to decreased lens aperture.