Optical device and method for detection target substance analysis

An analysis device, comprising:

• an optical pickup configured to irradiate, with an irradiation light, a sample analysis disc having a surface to which detection target substances and particles bound to the detection target substances are fixed, and receive a reflection light of the irradiation light from the sample analysis disc to generate a light reception level signal;
• and
• a controller configured to detect a fall when a signal intensity of the light reception level signal is a first predetermined threshold or smaller,
• wherein the controller is further configured to measure a first decreasing time that the signal intensity of the light reception level signal takes to decrease from the first predetermined threshold to a first extreme value point at which the signal intensity shifts from a fall to a rise,
• wherein the controller is further configured to measure a first increasing time that the signal intensity of the light reception level signal takes to increase from the first extreme value point to a third extreme value point at which the signal intensity shifts from a rise to a fall,
• wherein the controller is further configured to measure a second decreasing time that the signal intensity of the light reception level signal takes to decrease from the third extreme value point to a second extreme value point at which the signal intensity shifts from a fall to a rise,
• wherein the controller is further configured to measure a second increasing time that the signal intensity of the light reception level signal takes to increase from the second extreme value point to the first predetermined threshold,
• wherein the controller is further configured to determine whether the first increasing time and the second decreasing time conform to each other such that the first increasing time has a value within a predefined range of a value of the second decreasing time, and the first decreasing time and the second increasing time conform to each other such that the first decreasing time has a value within a predefined range of a value of the second increasing time, and
• wherein the controller is further configured to count a pulse derived from the particles as plural particles when the controller determines the first increasing time and the second decreasing time, and the first decreasing time and the second increasing time, conform to each other, the controller not counting the pulse derived from the particles as plural particles when the controller determines that the first increasing time and the second decreasing time, and the first decreasing time and the second increasing time, do not conform to each other.