Image brightness correction module and optical inspection apparatus including the same

An optical inspection apparatus comprising:

• a light source unit configured to emit light;
• an optical unit configured to guide the light from the light source unit to a device under inspection;
• an image capturing unit configured to obtain a captured image of the device under inspection by using light reflected from the device under inspection;
• a controller configured to control operations of the light source unit and the image capturing unit;
• and
• a processor configured to generate a histogram of the captured image obtained by the image capturing unit, detect an extreme point, at which a slope changes in the histogram, to set the extreme point as a representative brightness value, and, based on a difference between the representative brightness value and a preset reference brightness value, correct brightness of the captured image,
• wherein the representative brightness value represents a grayscale level value at the extreme point in the histogram of the captured image.

An optical inspection apparatus comprising:

• a light source unit configured to emit light;
• an optical unit configured to guide the light from the light source unit to a device under inspection;
• a stage configured to support the device under inspection;
• an image capturing unit configured to obtain a captured image of the device under inspection by using light reflected from the device under inspection;
• a controller configured to control operations of the light source unit, the stage, and the image capturing unit;
• and
• a processor configured to process the captured image obtained by the image capturing unit,
• wherein the processor comprises:
• a histogram generator configured to generate a histogram from the captured image;
• a noise eliminator configured to eliminate noise from the histogram;
• a derivative calculator configured to calculate a derivative for the histogram from which the noise has been eliminated;
• a representative brightness value-setting unit configured to set, as a representative brightness value, one of x values for which y values are zero in a graph for the derivative;
• a comparator configured to compare the representative brightness value to a reference brightness value;
• a final brightness value-setting unit configured to set the representative brightness value as a final brightness value when a difference between the representative brightness value and the reference brightness value is within a certain range;
• a corrected brightness value-setting unit configured to set a corrected brightness value when the difference between the representative brightness value and the reference brightness value is outside of the certain range, wherein the corrected brightness value is obtained by adding a certain brightness value to the representative brightness value;
• and
• a corrected image generator configured to form a corrected image having the final brightness value or the corrected brightness value, wherein a brightness value of the captured image is set to the final brightness value or the corrected brightness value,
• wherein the representative brightness value represents a grayscale level value at an extreme point in the histogram of the captured image, and
• wherein in the histogram, an x-axis represents a grayscale level value of the captured image and a y-axis represents a number of pixels corresponding to the grayscale level value of the captured image.