Television – Special applications – Flaw detector
Reexamination Certificate
1997-12-03
2001-08-14
Garber, Wendy R. (Department: 2612)
Television
Special applications
Flaw detector
C348S132000, C348S371000, C348S370000, C250S495100
Reexamination Certificate
active
06275256
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of digital photography, and in particular to infrared illumination systems for digital infrared cameras used for example in surveillance, machine vision, and microscopy to image objects having spectrally reflecting surfaces.
BACKGROUND OF THE INVENTION
It is known to employ digital cameras to capture infrared information from a scene having specular surfaces, for example a part on an assembly line, or a specimen in a microscope. It is also known to use a source of artificial infrared illumination to aid in the capture of such images. A problem occurs in such image capture situations because the specular reflections of the source of infrared illumination wash out the detail in the image in the neighborhood of the specular reflection. Furthermore, in applications such as surveillance, it would be preferable if the source of such illumination remained unnoticed by the subject. Conventional flash systems capable of producing substantial infrared light also produce appreciable quantities of visible light. If the visible light from such a flash is filtered to produce an infrared flash, the resulting flash apparatus is inefficient, since a considerable portion of the energy produced by the flash is wasted. In applications such as machine vision and microscopy, it is desirable that the source of illumination be highly uniform and extended in space (non point source) to minimize the intensity of specular reflections. However, in applications where the object needs to be close to the lens, there is scant room for an extended light source. Therefore, it is also desirable for the light source to be compact, a requirement that is in apparent conflict with the need for the light source to be extended.
U.S. Pat. No. 4,866,285, issued Sep. 12, 1989, to Simms discloses a light source for an infrared film camera having one or more infrared diode light sources. It has been found that due to the point source nature of the infrared diodes, the illumination from such a light source is non-uniform at the subject and the point source nature of the diodes causes intense specular reflections from an object having specularly reflecting surfaces. There is therefore a need for an improved, energy efficient, uniform source of infrared illumination for infrared electronic photography.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, an illuminator for a digital camera includes a body of transparent material defining a cavity with an opening for locating a taking lens of the camera and an opening for locating an object to be photographed with the digital camera. A plurality of light emitting diodes (LEDs) are uniformly distributed throughout the body of transparent material with respect to the surface of the cone. A power supply applies power to the LEDs so that their brightnesses are equal. In a preferred embodiment of the invention, the body of material is infrared transmissive, the LEDs are infrared emitting diodes, the cavity is a cone shaped cavity, and the surface finish of the cavity is a flat finish.
These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.
ADVANTAGEOUS EFFECT OF THE INVENTION
The present invention has the advantage of providing a uniform, energy efficient illumination of the photographic subject resulting in few noticeable specular reflections.
REFERENCES:
patent: 4866285 (1989-09-01), Simms
patent: 5443597 (1995-08-01), Kitchloo et al.
patent: 5461417 (1995-10-01), White et al.
patent: 5701015 (1997-12-01), Lungershausen et al.
Baker Joseph L.
Olczak Eugene G.
Szumla Thomas
Close Thomas H.
Eastman Kodak Company
Garber Wendy R.
Tillery Rashawn N.
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