Encoder, robot, and printer

A robot comprising:

• a first member;
• a second member rotatably connected to the first member, a plurality of marks being provided on a surface of the second member, the plurality of marks including a first mark;
• a decelerator configured to deliver drive force to the second member from the first member;
• an image sensor disposed in the first member, the image sensor being configured to capture the plurality of marks on the surface of the second member;
• a memory configured to store a program and a first reference image corresponding to the first mark;
• and
• a processor configured to execute the program so as to:
• continuously cause the image sensor to capture images of the plurality of marks by comparing each of the captured images with the first reference image when the second member rotates relative to the first member;
• identify a first location of the first mark in the plurality of marks when the captured image matches with the first reference image at a first time;
• continuously cause the image sensor to capture images of the plurality of marks by comparing each of the captured images with the first reference image when the second member rotates relative to the first member by 360° after the identification of the first location of the first mark;
• identify a first location of the first mark in the plurality of marks when the captured image matches with the first reference image at a first time;
• count a number of pixels in the captured images that are located at positions between the first location of the first mark and the second location of the first mark;
• determine a physical quantity amount corresponding to the counted number of pixels;
• and
• perform calibration of the robot in response to the determined physical quantity amount and the rotation angle of 360°.

A printer comprising:

• a platen configured to transfer a printing medium;
• a head configured to record an image on the printing medium;
• and
• an optical device having:
• a light source configured to emit light toward the printing medium;
• a first member;
• a second member, the second member rotating relative to the first member, a plurality of marks being provided on a surface of the second member, the plurality of marks including a first mark and a second mark;
• a decelerator configured to deliver drive force to the second member from the first member;
• an image sensor disposed in the first member, the image sensor being configured to capture the plurality of marks on the surface of the second member;
• a memory configured to store a program and first and second reference images corresponding to the first mark and the second mark, respectively;
• and
• a processor configured to execute the program so as to:
• continuously cause the image sensor to capture images of the plurality of marks by comparing each of the captured images with the first reference image when the second member rotates relative to the first member;
• identify a first location of the first mark in the plurality of marks when the captured image matches with the first reference image:
• continuously cause the image sensor to capture images of the plurality of marks by comparing each of the captured images with the second reference image when the second member rotates relative to the first member;
• identify a second location of the second mark in the plurality of marks when the captured image matches with the second reference image;
• count a number of pixels in the captured images that are located at positions between the first location of the first mark and the second location of the second mark;
• determine a physical quantity amount corresponding to the counted number of pixels;
• and
• perform calibration of the optical device in response to the determined physical quantity amount.