Sometimes it is necessary to make some analyses in the mm-cm scale. For this neither a common optics nor the microscopic solution with the relay lens is suited. We therefore evaluated the option to add some close-up lenses to a common lens.
Macroscopic scale
In the following setup we used a hyperspectral FireflEYE 496 blue and designed the optical path for a macro extension from Schneider-Kreuznach. In order to achieve an image size of 2x2mm, the necessary tube elongation had a length of 480mm.
With this length the optics needed to be stabilized with an aluminum frame. Although the first test have delivered satisfying results we thought the design to be impractical for the use even in a save environment of a laboratory.
Mounting adapter and close-up lenses (Schneider-Kreuznach)
Adding close-up lenses
After a further design study we found to use a common lens in combination with close-up lenses, also from Schneider-Kreuznach. For this we used the lens with the closest field of view available, i.e. the 50mm lens with a FOV of 6.5°. Using a mounting adapter on top of the 50mm lens allows to add a close-up lens, which directly results in a spot size in the mm-cm scale.
The advantage of this solution for the customer is huge. It now is possible to add a various number of the close-up lenses individually, meeting each requirement to the spot size in the macroscopic scale. The accuracy of the camera is not affected, because it is calibrated with the 50mm lens in our laboratory and the transmission rate of the close-up lenses is almost 100%.
“Bug report”
In order to demonstrate the potential of the macro setup onboard the S496 blue we used a colorful test bug and analyzed the quality of the sharpness and the spectral reflectance. The bug has a length of around 4cm and different parts of it were placed in the image spot of the camera.
Check out the images below and convince yourself on the spectral and spatial quality of the macroscopic solution.
Scale of the test bug
Front of the test bug with compound eye. The spectra represent the pixels inside the rectangles in the left image.
Belly of the test bug. The spectra represent the pixels inside the rectangles in the left image.
Belly of the test bug. The spectra represent the pixels inside the rectangles in the left image.
