Plenoscope Passive Optical Rangefinder
Presently the military use a wide range of handheld, head mounted, and weapon-systems-mountable optical systems. These devices serve many functions; from visible and night vision imaging to target designation and ranging. Optical rangefinders employed by the military tend to be large and most utilize an active laser source. The increasing use of warning receivers and electro-optical devices capable of detecting these laser rangefinders could put friendly forces at risk and/or allow the enemy enough time to egress or otherwise avoid direct fire. It is therefore desirable to field a passive range-finding instrument which is compatible with current electro-optical imaging systems to allow the military to utilize a single integrated optical device to perform multiple optical tasks – imaging, targeting, and range-finding.
With a Phase I Small Business Innovation Research contract from the United States Marine Corp, Nanohmics set out to design an electro-optical imaging device capable of determining the range to individual objects in a scene without the use of active emitters or multiple apertures. The novel, automated, handheld imaging system is based on a plenoptic camera design, and will be simple to use, providing the range to selected objects in the field-of-view. The optical system can be adapted to visible imaging devices as well as infrared focal plane arrays. The system should be inexpensive, easy to use by the individual soldier, rugged, and low in maintenance. The user will be able to view objects in a real-time high resolution color image of the scene, and then switch to range mode and obtain real-time range to objects in a slightly lower-resolution grayscale image – even if those objects are moving. Nanohmics is developing a custom optical system along with embedded digital signal processing electronics and a unique opto-mechanical design; and developing firmware/software algorithms for determining range to objects within the system field-of-view.
Summary of Phase I results
scopes, and weapons fire-control systems. The result is effective, inexpensive, easy to use, rugged, and low maintenance optical systems for the Marine.
During the course of the Phase I program, Nanohmics completed an optimized design for a single-aperture passive rangefinder based on a realization of a plenoptic camera. The breadboard rangefinder integrated plenoptic camera components (main lens, microlens array, and image sensor) with advanced image-sensor readout electronics and computational post-processing capability. Nanohmics realized the hardware design of the principal components into a breadboard passive rangefinder device for evaluation by Marine Corps personnel. The breadboard rangefinder was used as a platform for testing the various range mapping and user interface features and modes that were developed during the packaging concept phase. Nanohmics engineers and scientists also completed a detailed theoretical and analytical performance and limitation determination along with developing initial algorithms for computing range image maps.
Potential Applications and Benefits
The combination of several optical tasks into a single optical system or device could have significant impact on the weight and number of devices carried by a squadron. For example, a day/night passive rangefinder based on Nanohmics’ Plenoscope™ technology could function as a surveillance scope, spotter scope, passive rangefinder, and perhaps even a rifle scope. The range-finding function of the Plenoscope™ could allow accurate real-time ballistic compensation for rifles, and could couple to fire-control systems for grenade launchers and other large caliber munitions. Simple addition of active components to the device would enable illuminator and designator functions, all integrated into a single device.
can achieve high accuracy at long ranges or can provide parallax-processing to provide views behind partially-obscuring objects like foliage, netting, or trees.
The underlying plenoptic camera technology realized in the Plenoscope™ offers interesting features and advantages for law enforcement, including enhanced surveillance and range-finding. Numerous commercial applications exist in the areas of inspection and quality control, where quantitative depth information in a scene is required. For commercial and consumer photography applications, the fact that a plenoptic camera records more information from a scene than a normal photographic camera allows post-processing tools to convert Plenoscope™ images into normal two-dimensional photographs with the focal distance and aperture stop (depth of focus) selected after the fact.