# US 7,609,735 B2 · Providing a suitable output current to a laser diode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,735 B2 - Document ID: US7609735B2 - Status: Granted - Kind: B2 - Application number: 12/013,548 - Filed: 2008-01-14 - Published: 2008-10-23 - Granted: 2009-10-27 - Earliest claimed: 2004-03-03 - Assignees: Ricoh Company, Ltd. - Inventors: Shinichi Kubota - Web page: https://patentgrep.com/patent/US7609735B2 ## CPC - H01S 5/042: Electrical excitation {; Circuits therefor (monolithically integrated laser drive components H01S5/0261)} - H01S 5/06808: {by monitoring the electrical laser parameters, e.g. voltage or current} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract A laser diode driving circuit capable of providing a suitable output current to a laser diode is disclosed. The laser diode driving circuit includes a current supply, a first pseudo laser diode, a second pseudo laser diode, and an output current mirror circuit. An input current provided by the current supply is output through the output current mirror circuit to the laser diode. By making the characteristic of each of the first and second pseudo laser diodes substantially equal to the characteristic of the laser diode, the non-linearity between the input current and the output current is compensated. ## Claims ### Claim 1 A light emitting system comprising: a laser diode having a predetermined characteristic, said laser diode being configured to generate a light according to an output current; a controller configured to generate a control signal; and a laser diode driving circuit configured to supply said output current to the laser diode in accordance with the control signal, and comprising a current supply configured to supply a predetermined current; a first pseudo laser diode configured to receive a first current being substantially equal or proportional to the predetermined current; a second pseudo laser diode configured to receive a second current substantially equal to the first current; and an output circuit configured to provide said output current, with the output current being substantially equal or proportional to at least one of the first current and the second current, wherein each of said first pseudo laser diode and said second pseudo laser diode has a characteristic substantially the same as the predetermined characteristic of the laser diode. ### Claim 2 A laser diode driving circuit for driving a laser diode, comprising: a current supply configured to supply a predetermined current; a first pseudo laser diode configured to receive a first current being substantially equal or proportional to the predetermined current; a second pseudo laser diode configured to receive a second current substantially equal to the first current; and an output circuit configured to provide an output current to the laser diode, with the output current being substantially equal or proportional to at least one of the first current and the second current. ### Claim 3 (depends on 2) The laser diode driving circuit of claim 2, wherein each of said first pseudo laser diode and said second pseudo laser diode has a characteristic substantially the same as the predetermined characteristic of the laser diode. ### Claim 4 (depends on 2) The laser diode driving circuit of claim 2, wherein each of said first pseudo laser diode and said second pseudo laser diode has substantially similar characteristics as the other. ### Claim 5 (depends on 2) The laser diode driving circuit of claim 2, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode comprising an adjustable voltage supply configured to receive a control signal and output a supply voltage in accordance with the control signal, and a resistor circuit serially connected to the voltage supply, and wherein the output voltage of the voltage supply is controlled based on the control signal to correspond to a forward voltage of the laser diode. ### Claim 6 (depends on 2) The laser diode driving circuit of claim 2, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode configured to receive a control signal, and a forward voltage of the pseudo laser diode is controlled based on the control signal to match a forward voltage of the laser diode. ### Claim 7 (depends on 2) The laser diode driving circuit of claim 2, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode configured to receive a control signal and comprising a voltage supply configured to output a supply voltage and a resistor circuit serially connected to die voltage supply and having an adjustable resistance, and wherein the resistance of the resistor circuit is controlled based on the control signal to correspond to a resistance of the laser diode. ### Claim 8 (depends on 2) The laser diode driving circuit of claim 2, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode configured to receive a control signal, and wherein the pseudo laser diode is controlled based on the control signal to have a characteristic similar to that of the laser diode. ### Claim 9 (depends on 1) The light emitting system of claim 1, wherein each of said first pseudo laser diode and said second pseudo laser diode has substantially similar characteristics as the other. ### Claim 10 (depends on 1) The light emitting system of claim 1, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode comprising an adjustable voltage supply configured to receive the control signal from the controller and output a supply voltage in accordance with the control signal, and a resistor circuit serially connected to the voltage supply, and wherein the output voltage of the voltage supply is controlled based on the control signal to correspond to a forward voltage of the laser diode. ### Claim 11 (depends on 1) The light emitting system of claim 1, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode configured to receive the control signal from the controller, and a forward voltage of the pseudo laser diode is controlled based on the control signal to match a forward voltage of the laser diode. ### Claim 12 (depends on 1) The light emitting system of claim 1, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode comprising a voltage supply configured to output a supply voltage and a resistor circuit serially connected to the voltage supply and having an adjustable resistance, and wherein the resistance of the resistor circuit is controlled based on the control signal front the controller to correspond to a resistance of the laser diode. ### Claim 13 (depends on 1) The light emitting system of claim 1, wherein at least one of said first and second pseudo laser diodes is constituted by a pseudo laser diode configured to receive the control signal from the controller, and the pseudo laser diode is controlled based on the control signal to have a characteristic similar to that of the laser diode.