Illumination in Imaging

It is not uncommon for a customer to struggle with contrast and resolution problems within an imaging system, while underestimating the power of proper illumination. In fact, the desired image quality can typically be met by improving the illumination scheme, rather than investing in higher resolution detectors, imaging lenses, and software. System integrators should keep in mind that proper light intensity in the final image is directly dependent upon component selection.

Every component affects the amount of light incident on the sensor and, therefore, affects the image quality of the system. The aperture (f/#) of the imaging lens has a direct impact on the amount of light incident on the camera. The illumination should be increased as the lens aperture is closed (i.e. higher f/#). High power lenses will usually require more illumination since the smaller areas viewed reflect less light back into the lens. The camera's minimum sensitivity is also important in determining the minimum amount of light required by the system. In addition, the CCD camera settings (gain, shutter speed, etc.) affect the sensitivity of the sensor. Fiber optic illumination usually involves an illuminator and a light guide, each of which should be integrated to optimize lighting at the object. The light intensity for the illumination products in this catalog is specified in terms of footcandles (English unit). Lux, the SI unit equivalent, can be related to footcandles as follows: