Light emitting device
AssigneeTopcon Corporation
InventorsYoshikatsu Tokuda, Yoshiaki Goto
Life of this patent
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Abstract
Light with a short pulse width is emitted using a simple structure. A light source 101, a differentiation circuit 102, and a switch 103 are connected in series. When the switch 103 is switched on, inrush current flows in a capacitor 102b forming the differentiation circuit 102, and accordingly the light source 101 is supplied with electric current and thereby emits light. When the capacitor 102b is charged, electric current flows in a resistor 102a, and voltage drops at the resistor 102a. Then, the voltage applied to the light source 101 is decreased, whereby the light source 101 stops emitting light. By using the inrush current at the capacitor 102b, light with a short pulse width can be generated.
Claims11
A light emitting device comprising:
- a light source that generates a relaxation oscillation immediately after an electric current is applied thereto for driving light emission;
- a capacitive reactance circuit that exhibits low impedance immediately after the electric current is applied thereto and which is chargeable with electrical charge;
- a resistance circuit that discharges electrical charge charged in the capacitive reactance circuit after a predetermined time passes after the electric current is applied;
- a differentiation circuit formed of the capacitive reactance circuit and the resistance circuit, which are connected in parallel;
- and
- a switching element,
- wherein the light source and the differentiation circuit are connected in series, the switching element is configured to switch on or off for application of voltage to the light source and the differentiation circuit, the capacitive reactance circuit and the resistance circuit are made to have characteristics so that initial oscillation of the relaxation oscillation is generated and that generation of other oscillations is suppressed, the initial oscillation is generated by inrush current at the capacitive reactance circuit, and the generation of the other oscillations is suppressed by making electric current flow to the resistance circuit after the capacitive reactance circuit is charged by the inrush current.
Dependencies are inferred from the claim text.