Ando Electric Company

Takuya Hosoda

Takashi Tamura

Shoji Adachi

Mitsuhiro Morishita

Atsushi Kudo

Yasuo Nihira

An apparatus for generating a pulse-like constant current with a variable pulse width for use in evaluating thermal characteristics of a laser diode. The apparatus comprises a first constant current (or voltage) circuit constituted by a high-speed amplifer, a second constant (or voltage) circuit constituted by a low-speed amplifier and connected in parallel with the first constant current circuit, a bias circuit for increasing higher the output voltage of the second constant current circuit than that of the first constant current circuit, a switching circuit for turning on and off the first and second constant current circuits in response to first and second timing signals, respectively, in such a manner that the first timing signal and the second timing signal are simultaneously turned on while the second timing signal is turned off only after the first timing signal has been turned off, and a regulator for changing the width of the output current pulse by varying the on/off durations of the first and second timing signals. For evaluating the thermal characteristics of the laser diode, the pulse-like constant current is applied for excitation and the pulse width of the current is varied to change the light emission characteristics of the diodes, which are measured and compared for making evaluation.

Apparatus for generating pulse-like constant current having variable

An apparatus for measuring a radiation characteristic of a laser diode. An AC signal and a step-like DC voltage are applied to the laser diode and the radiant power output thereof is received by a photodiode having an output to which a first amplifier, a transformer, a capacitor and an AC amplifier for extracting the AC signal. The apparatus further comprises a first switch connected between the input of the first amplifier and the capacitor, and a second switch connected between both ends of the transformer. Every time the step-like voltage is stepped up, the first and second switches are closed for a short time as compared with the duration of a step period to protect the measurement from the influence of the change in the DC voltage.

Radiation characteristic measuring apparatus for laser diode

An electrostatic voltmeter for measuring the surface potential of a charged body, includes a detecting electrode locatable adjacent to the charged body, and a vibrating element having a pair of parallel spaced legs between which the detecting electrode is disposed in spaced relation. The vibrating element is vibratable such that the legs move toward and away from the charged body. The vibrating element may extend transversely or parallel to a line connecting the charged body and the detecting electrode.

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Tokyo, Japan

Takuya Hosoda