Patent ID: 8619827

Claim:
A correction circuit apparatus, comprising: a surface-emitting semiconductor laser; a current source operative for driving the surface-emitting semiconductor laser in a pulsed manner and having a current source output terminal for outputting a rectangular current pulse; and a correction circuit having a correction circuit output terminal connected to the current source output terminal and including a RC time constant circuit operative for outputting an assist current pulse having an initial peak value that attenuates over time, wherein the correction circuit in conjunction with the RC time constant circuit is operative to correct a waveform of the rectangular current pulse outputted from the current source output terminal of the current source by adding the assist current pulse thereto to form a resultant corrected current pulse so that a pulse waveform of light output of the semiconductor laser is approximately a rectangle, wherein both the rectangular current pulse and the assist current pulse commence at least substantially simultaneously at a time T 1 and terminate at least substantially simultaneously at a later time T 2 , wherein the waveform of the rectangular current pulse is corrected so that a resultant initial peak value of the resultant corrected current pulse is attenuated with time in accordance with an RC time constant of the RC time constant circuit, the time being a period of time equal to time T 2 minus time T 1 , wherein the RC time constant circuit includes a plurality of first time constant circuits attenuating the initial peak value of the current pulse with time, the first time constant circuits have RC time constants different from one another, at least one second time constant circuit of the plurality of first time constant circuits has an RC time constant having a value within a range of 20 nsec to 50 nsec both inclusive, and one or multiple third time constant circuits other than the second time constant circuit of the plurality of first time constant circuits have an RC time constant having a value of more than 50 nsec, wherein the semiconductor laser has a vertical resonator structure including an active layer sandwiched by a pair of multilayer reflectors and wherein the correction circuit corrects the waveform of the rectangular current pulse so that the initial peak value of the rectangular current pulse varies in correspondence to variation in temperature of the active layer.