Most studio LED light sources use low power LEDs distributed over a diffuse light panel surface. This limits the panel size and increases the weight for large panels. MSL, on the other hand, uses very high power and tightly clustered LEDs which can be lensed for highly focused beams or diffused using familiar studio diffusion and other light modifiers. LED beam focusing options are available from 12 deg to 50 deg.

MSL computer control enables a range of possibilities. MSL control software includes MegaVision’s unique and powerful N-Shot Table™ The N-Shot Table enables automatic control of light power, exposure, and color for a series of image captures. Multiple images can be captured under different lighting automatically. For example, it is possible to capture under sunlight, 5,000K, and tungsten one after another without changing or moving the lights. With the computer controlling light color, power, and exposure, multiple shot captures under different lighting conditions are made as simple as a single capture.

Automatic multiple-shot captures enables unique possibilities for color capture using monochrome sensors. A reprise of legacy triple-shot color capture is possible using RGB lights (in lieu of RGB filters). But more interestingly, multi-shot capture using up to 10 color bands enables capturing color images of unprecedented color accuracy: 9-band color capture reduces the ΔE by a factor of 4 over the very best RGB color capture (whether single shot or multi shot).

For scientific exploration, MSL can be expanded beyond the visible. UV and IR lights can be added to provide hyperspectral imaging capabilities for scientific, industrial, forensic, medical, and academic imaging.

Lighting Configuration Options

Heads may be configured with varying combinations of visible, UV, and/or IR. Single heads may be joined together to create dual head units.

Advantages of MS LED illumination

1. MS LED’s provide highly specific, low maintenance, and very repeatable light. Spectral properties are consistent from shot to shot and year to year. Lumens/watt is stable, and much better than strobe, incandescent, HMI, or fluorescent.
2. Normal lifetimes exceed 50,000 hours for visible band LEDs and 10,000 hours for IR and UV LEDs.
3. Rapid switching times (< 50 µSec) allow pulse-width modulation and precise exposure durations.
4. High efficiency reduces heat and stress on the objects in the scene.
5. Elimination of unwanted IR wavelengths prevents registration difficulties caused by object motion due to heating during long exposures.
6. Because narrow-band LED’s emit no light outside the specified band, there is no need to filter IR light from the sensor. The IR cutting filter can be eliminated. Eliminating the IR filter removes an optical element from the image forming path and substantially increases light efficiency, enabling reduced exposure and greater S/N.

When using a monochrome sensor and narrow band illumination, the light is utilized more efficiently than white light. Ordinary color photography which employs broad- band white light uses great deal of unnecessary light energy. The majority of the light energy in white light is discarded by normal color camera filtration after the light has interacted with the objects in the scene. White light must be filtered at the camera after the scene is subjected to unnecessary light energy. With narrow band LED illumination, no filtration is required. The light energy is used more efficiently, and only enough light to properly expose the objects in the spectral band of interest is generated. Unused light energy is eliminated before it is created at the source of the light, rather than after the light hits the object in the scene. This means that the object is subject to less light stress, and the lighting system requires dramatically less power.

Color Capture With a Monochrome Sensor and LED Illumination

While the human color vision system is functionally tri-stimulus, our retinal spectral response curves can’t be replicated by a simple set of 3 band-pass filters. Nearly all color cameras rely on 3 band-pass filters, typically red, green, and blue. An average color accuracy of ΔE=3 over a broad range of colors (such as are found on an X-rite ColorChecker Color Target) is considered superb for 3-color cameras, and is very difficult to improve.

Somewhere in the range of 6-10 bands are required to acquire enough spectral information to make a good match to human vision. Attempts to make practical systems utilizing multiple band capture with color filters between the scene and the sensor have proved problematic for a number reasons. By coming at the problem from a different direction, namely, creating the color bands at the source of the light (using LED’s), the MSL solves the difficult practical problems of multiple filters. Capturing sufficient perfectly registered and highly repeatable spectral bands is an enabling technology for deploying semi-automated, high-quality color reproduction. With tri-stimulus capture, color matching over a practical range of commonly encountered dyes, pigments, plastics, and other materials is sufficiently poor that individual, scene-specific, localized color adjustments must be performed to obtain the
desired accuracy. This color-matching step is sufficiently time consuming and costly that it is practical to create high-quality color reproductions of only the most expensive originals.

The MSL approach can dramatically reduce the amount of labor-intensive postprocessing of the image data and provide highly accurate color reproduction of a very wide range of difficult subjects. Using Megavision’s patent pending process, the average color error of a 10-spectral-band color image over the range of ColorChecker colors is below the discrimination threshold of human vision: ΔE < 0.8 .