Device for detecting passing of object and device for measuring velocity of passed object

A device for measuring a velocity of a passed object by using a time difference detected by two devices for detecting a passing object as the passing object traverses a light path between a light source and a light reflecting means that reflects light emitted from the light source, said two devices being disposed along a passing path of the passing object, each of said devices comprising:

• said light source;
• said light reflecting means;
• a light receiving sensor that receives light reflected by said light reflecting means;
• and
• an optical member that transmits a portion of light and reflects a portion of light,
• wherein, in each of said devices for detecting the passing object:
• said light source and said light receiving sensor are disposed on a side opposite to the light reflecting means with respect to the passing path of the passing object;
• a light path of light reflected by said light reflecting means and a light path of light incident on said light reflecting means are aligned each other;
• said optical member is disposed on the light path between said light source and said light reflecting means;
• and
• said light receiving sensor is disposed in a location so that said light receiving sensor receives light that is reflected by said light reflecting means and that is reflected or transmitted by said optical member.