1. Field of the Invention
The present invention relates to an apparatus and a method for inspecting a light transmittable material, such as a filmstrip, to detect a defect thereon.
2. Description Related to the Prior Art
In producing a filmstrip including cyan, magenta and yellow coloring layers, the filmstrip is examined. At the end of the examination, an unexposed filmstrip is developed as a sample film for determining whether there is a defect of optical sensitization (or a coloring defect) on the filmstrip. The coloring defect means that a color has a higher density at a position on the filmstrip, where a sensitivity of a photosensitive material in each of the photosensitive layers has increased. The following are examples of possible causes increase in the sensitivity of the photosensitive material: an excessive pressure during rubbing and pressing the filmstrip, a fogging in static light or another light, a fogging by contacting with sensitizer-like material, faults of coating materials to vary densities thereof, and a fault of bases to vary densities thereof.
As the developed filmstrip is inspected with eyes for detecting of the defect, so much time is necessary for the inspection, and the determination whether the filmstrip has the defect is dependent on a subject of an inspector. Further, if the inspector is exhausted, he cannot carry out the precise determination. Especially, the coloring defect in yellow is more hardly found with eyes than that in red and blue.
The problem will be resolved if an inspection light is scanned on the filmstrip for the inspection. A light density of the inspection light becomes lower at an position of the coloring defect. However, a dust on the filmstrip makes it impossible to detect the defect with precision. Namely, as the dust diffuses the inspection light, the light density becomes lower at a position where there is dust on the filmstrip. Accordingly, it is hardly determined whether the decrease of the light density is caused by the defect or the dust. Further, the dust sometimes cannot be removed even if the cleaning of the filmstrip is carried out before the inspection.