Method and apparatus for inspecting lightness on the surface of an object

An apparatus for inspecting lightness of the surface of an object having at least first and second surface portions different in lightness, comprising:

• first means for taking an image of the first and second surface portions of the object under appropriate illumination,
• first memory means for memorizing said taken image,
• second memory means for memorizing normal image of the surface of the object as a reference image,
• third means for accumulating lightness of each pixel of said taken image in accordance with addressing of each pixel of said reference image at each pixel belonging to first and second pixel regions corresponding to the first and second surface portions, said third means setting the accumulated lightness as first and second accumulated lightness data respectively,
• fourth means for counting the number of pixels of said taken image in accordance with addressing of each pixel of said reference image at each pixel belonging to said first and second pixel regions and for setting said respective counted numbers as first and second counted pixel data respectively,
• fifth means for dividing said first accumulated lightness data by said first counted pixel data to be set into a first dividend data and for dividing said second accumulated lightness data by said second counted pixel data to be set into a second divided data, and
• sixth means for taking a lightness difference of said first divided data and lightness of each pixel of said taken image belonging to said first pixel region and for taking a lightness difference of said second divided data and lightness of each pixel of said taken image belonging to said second pixel region, said sixth means determining a fault portion of said taken image as lightness fault data in accordance with said respective lightness difference.

An apparatus for inspecting lightness of the surface of an object having at least first and second surface portions different in lightness, comprising:

• first means for taking an image of first and second surface portions of said object under appropriate illumination;
• memory means for memorizing the image of the first and second surface portions;
• second means for preliminary memorizing values defining respective regions of the first and second surface portions and for determining to which of the memorized values respective pixels of the image belong;
• third means for defining, on a basis of the determination of the memorized values, a first reference lightness of the first surface portion in accordance with lightness of all the pixels of the image corresponding with the first surface portion and for defining, on a basis of the determination of the memorized values, a second reference lightness of the second surface portion in accordance with lightness of all the pixels of the image corresponding with the second surface portion;
• and
• fourth means for calculating a difference between the first reference lightness and each lightness of the pixels of the image corresponding with the first surface portion and a difference between the second reference lightness and each lightness of the pixels of the image corresponding with the second surface portion and for determining the quality in lightness of the surface of said object on a basis of the calculated differences.

A method of inspecting lightness of the surface of an object having at least first and second surface portions different in lightness, comprising the steps of:

• a) taking an image of the first and second surface portions of said object under appropriate illumination;
• b) memorizing the image of the first and second surface portions;
• c) preliminarily memorizing values defining respective regions of the first and second surface portions and determining to which of the memorized values respective pixels of the image belong;
• d) defining, on a basis of the determination of the memorized values, a first reference lightness of the first surface portion in accordance with lightness of all the pixels of the image corresponding with the first surface portion and defining, on a basis of the determination of the memorized values, a second reference lightness of the second surface portion in accordance with lightness of all the pixels of the image corresponding with the second surface portion;
• e) calculating a difference between the first reference lightness and each lightness of the pixels of the image corresponding with the first surface portion and a difference between the second reference lightness and each lightness of the pixels of the image corresponding with the second surface portion;
• and
• f) inspecting lightness of the surface of said object on a basis of the calculated differences.