Thickness-distribution measurement device and thickness-distribution measurement method

A thickness-distribution measurement device comprising:

• a conveyor configured to convey an object including a first surface and a second surface in a conveying direction along the first surface and the second surface, the second surface facing opposite to the first surface;
• a light source that is disposed at a position facing the second surface of the object, and that is configured to irradiate a region of the object being conveyed with light, the region extending in a width direction intersecting the conveying direction;
• a light detector that is disposed at a position facing the first surface of the object, and that is configured to detect emitted light that has transmitted through the object irradiated with the light;
• and
• an arithmetic processor configured to obtain information on a distribution of a relative thickness of the region of the object in the width direction based on a detection result in the light detector, wherein
• the light detector includes an image sensor that includes a pixel unit including a plurality of pixels arranged at least in the conveying direction, and that is configured to detect an intensity of the emitted light for each pixel to output image data, and a lens unit that includes a plurality of lenses having an equal magnification and arranged along the width direction, and that is configured to collect the emitted light and forms an image of the emitted light on the pixel unit of the image sensor,
• the image sensor is configured to be able to switch a gain value for amplifying signals output from the plurality of pixels, and
• the thickness-distribution measurement device further comprising:
• another light source that is disposed at a position facing the first surface, and that is configured to irradiate the region or another region of the object being conveyed with light, the another region extending in the width direction,
• wherein the light detector is configured to detect emitted light emitted from the object irradiated with the light by the another light source, and
• the gain value of the image sensor when irradiation with the light from the another light source is performed is different from the gain value of the image sensor when irradiation with the light from the light source is performed.