Optical illumination and inspection system for wafer and solar cell defects

An optical inspection system for observing physical defects in a crystalline substrate structure comprising:

• a source of collimated light beam,
• means disposed in the path of said collimated light beam for filtering said collimated light beam to pass specific wavelengths of said collimated light beam,
• means disposed in the path of said collimated light beam for diffusing said collimated light beam at said specific wavelengths and directing the diffused light onto and illuminating said crystalline substrate structure,
• and observation means directed onto said crystalline substrate structure and responsive to said collimated light and said diffused light for providing an image of said crystalline substrate structure wherein physical defects in said crystalline substrate structure are apparent in said image,
• wherein said physical defects are cracks in said crystalline substrate structure,
• wherein said source of collimated light produces light in the near infrared spectrum, and wherein said diffused light directed onto said crystalline substrate structure by said diffusing means illuminates said crystalline substrate structure to produce shadows representative of said cracks which are apparent in said image of said observation means, and
• wherein said source of near infrared collimated light is a quartz-halogen lamp, said filtering means is a long pass filter, and said diffusing means is a structure having a reflective surface disposed in the path of the filtered collimated light for diffusing and reflecting the filtered collimated light rays onto said crystalline layer structure at a plurality of separate angles.