Photoelectric sensor

A photoelectric sensor, comprising:

• a housing including a first upright portion, a second upright portion, and a base portion, wherein the first upright portion and the second upright portion are connected to the base portion, the first upright portion has a first concave structure and a first opening, the first concave structure includes a first side wall and a first outer wall that surrounds the first side wall, and the second upright portion has a second concave structure and a second opening, the second concave structure includes a second side wall and a second outer wall that surrounds the second side wall;
• a light-emitting module including a first circuit board and a light-emitting element, wherein the light-emitting module is embedded in the first concave structure, and the light-emitting element corresponds to the first opening;
• a light-receiving module including a second circuit board and a light-receiving element, wherein the light-receiving module is embedded in the second concave structure, and the light-receiving element corresponds to the second opening;
• and
• two adhesive members being respectively provided on side walls of the first concave structure and the second concave structure, so as to respectively bond the light-emitting module into the first concave structure and the light-receiving module into the second concave structure;
• wherein a top of the first outer wall and a top of the second outer wall are separated by a first distance, a bottom of the first outer wall and a bottom of the second outer wall are separated by a second distance, and a difference between the second distance and the first distance is less than 28% of the second distance.