Fluorescence information reading device and fluorescence information reading method
Sensitivity is increased by enhancing the fluorescence collection efficiency while suppressing the increase in size of an objective lens. An objective lens 17 is structured to have a convex lens part 26 in a center portion and to have a truncated conical cylindrical body 27 around the convex lens part 26 . Therefore, a fluorescence component b having too wide an emission angle to fit in the convex lens part 26 , of fluorescence emitted from a sample 16 , can be collected by total reflection on an outer peripheral surface 27 b of the cylindrical body 27 . Thus, even light having too wide an emission angle to be collected by a normal convex lens can be collected. As a result, it is possible to suppress the increase in size of the objective lens, to enhance the fluorescence collection efficiency, and to prevent the S/N ratio from being decreased by the existence of undetected fluorescence that is blocked by a prism 20 . This can realize a fluorescence information reading device having high sensitivity.
1. A fluorescence information reading device, comprising:
a light source that irradiates a reading object with excitation light for exciting fluorescence;
an objective lens element that transmits the excitation light from the light source and collects the fluorescence emitted from the reading object by the irradiation with the excitation light;
a lens that converts the fluorescence collected by the objective lens element into substantially parallel fluorescence;
a wavelength filter on which the substantially parallel fluorescence from the lens is incident, the wavelength filter reducing a light component having a wavelength equal to a wavelength of the excitation light; and
a photodetection element that detects the fluorescence from the filter; wherein
the objective lens element is a single monolithic member that includes a center portion that collects light by refraction, the center portion including an upper convex surface and a lower convex surface that spherically projects along an optical axis, the lower convex surface projecting towards the photodetection element, and a peripheral portion located around the center portion to collect light by total reflection, the peripheral portion projects farther towards the photodetection element than the lower convex surface;
at least a portion of the center portion serves as an excitation-light transmitting portion that transmits the excitation light;
the peripheral portion includes a truncated conical body opening downward towards the photodetection element, the truncated conical body including an upper end surface, an outer peripheral surface, and a lower end surface, wherein the fluorescence enters the truncated conical body from the upper end surface and is deflected towards the optical axis on the outer peripheral surface and emitted from the lower end surface, and
a portion of the upper convex surface is on a same plane as a portion of the upper end surface.
2. A fluorescence information reading method, comprising:
emitting, from a light source, excitation light that excites fluorescence;
applying the excitation light from the light source onto a reading object through an excitation-light transmitting portion in a center portion of an objective lens element, the objective lens element is a single monolithic member having the center portion that collects light by refraction and a peripheral portion located around the center portion to collect light by total reflection;
collecting fluorescence emitted from the reading object by the application of the excitation light on the center portion and the peripheral portion of the objective lens element;
converting the fluorescence collected by the objective lens element into substantially parallel fluorescence by a lens;
reducing a light component having a wavelength equal to a wavelength of the excitation light by a wavelength filter from the substantially parallel fluorescence converted by the lens; and
detecting the fluorescence from the wavelength filter by a photodetection element; wherein
the center portion includes an upper convex surface and a lower convex surface that spherically project along an optical axis, the lower convex surface projecting towards the photodetection element;
the peripheral portion projects farther towards the photodetection element than the lower convex surface;
the peripheral portion includes a truncated conical body opening downward towards the photodetection element, the truncated conical body including an upper end surface, an outer peripheral surface, and a lower end surface, wherein the fluorescence enters the truncated conical body from the upper end surface and is deflected towards the optical axis on the outer peripheral surface and emitted from the lower end surface, and
a portion of the upper convex surface is on a same plane as a portion of the upper end surface.