An Experimental Plenoptic CameraA standard 2D camera records only a flat projection of the 3D scene. It records the intensity of light rays striking pixels arranged in a 2D array. There is no information preserved about the way light travels from a point of the object to a pixel.
A plenoptic camera (also called light field camera) records a complete 4D light field of a 3D scene. Besides the radiance of a ray striking a pixel we also get information about the angle of incidence. Having this extra information we can calculate or render images at various distances from the lens. Changing distance between the lens and sensor (or film) is what we normally do to focus a camera. A recorded light field can be used to refocus an image by post processing.
The example images to the left are computed from the same single light field image. The example below shows that we can move a little bit to change perspective as well. Taking this further we can calculate a depth map or make a stereoscopic pair of images. And there is much more that can be done using this technique. For instance, if we know from where the ray bundles come we can block stray light or ghost images.
The resolution of my first images is not impressive. But they are produced by using home made micro lenses and the processing is not optimized. There is a lot of research going on in this field. By applying super resolution algorithms some scientists have been able to reach quite impressive resolution and image quality. Making the microlenses.
Light field cameras can be made in various ways. My camera is using the principles of the Plenoptic Camera 2.0. An array of micro lenses is mounted in front of the image sensor. Each micro lens produces a focused image of a portion of the scene. A specific point of the object is imaged by several micro lenses. Each one from a different angle.
A comprehensive explanation of the Plenoptic Camera 2.0 is available in this paper by the inventors Andrew Lumsdaine and Todor Georgiev:
The Focused Plenoptic Camera
Other important papers on the subject:
Fourier Slice Photography
High Dynamic Range Image Capture with Plenoptic 2.0 Camera
Light Field Superresolution
Todor Georgiev's site - a goldmine!
|The unprocessed light field image||Detail of the light field image|
The micro lens array is placed in front of the image sensor.
Making the microlenses.
|A Mamiya 645 AFD II with a ZD digital back was converted to a focused Plenoptic camera. It's really simple once you get the microlenses made. The microlens array is just dropped in between the IR cut filter and the sensor. There is a gap of about one millimeter where the lens array fits nicely.|