# US 9,753,139 B2 · Electro-optical distance measuring device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,753,139 B2 - Document ID: US9753139B2 - Status: Granted - Kind: B2 - Application number: 14/135,414 - Filed: 2013-12-19 - Published: 2014-07-24 - Granted: 2017-09-05 - Earliest claimed: 2011-09-06 - Assignees: Leica Geosystems AG - Applicants: Leica Geosystems AG - Inventors: Kurt Giger; Reto Metzler; Bernhard Fiegl - Web page: https://patentgrep.com/patent/US9753139B2 ## CPC - G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) - G01B 11/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) - H01S 5/0014: {Measuring characteristics or properties thereof (measuring techniques per se G01J, G01K, G01N, G01R)} - H01S 5/0428: {for applying pulses to the laser} - H01S 5/06825: {Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation} - H03K 3/57: the switching device being a semiconductor device - G01S 7/484: Transmitters - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - 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 - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract An electro-optical distance measuring device includes a laser driver for a laser diode for emitting laser light pulses. The measuring device further includes a laser diode voltage supply having a cascade of at least two voltage regulators, each of which provides an output voltage at a level below a laser threshold voltage of the laser diode. By changing from a first to a second switching position of an electronic switching element of the measuring device, one of the laser light pulses can be emitted and, in the steady-state first and the steady-state second switching positions, no laser light is emitted. ## Claims ### Claim 1 An electro-optical distance measuring device including a laser driver for a laser diode for emitting laser light pulses, comprising: a laser diode voltage supply having a cascade of at least two voltage regulators, each of which provides an output voltage below its input voltage and at a level below a laser threshold voltage of the laser diode; an inductive component in a supply path of the laser diode, and an electronic switching element which is arranged interactively in such a way that: in a first switching position of the switching element, a current flow through the inductive component can be produced; and in a second switching position of the switching element, the current flow can be conducted through the laser diode, wherein: by changing from the first to the second switching position, one of the laser light pulses can be emitted and, in the steady-state first and the steady-state second switching positions, no laser light can be emitted. ### Claim 2 (depends on 1) The electro-optical distance measuring device according to claim 1, wherein a first voltage regulator of the at least two voltage regulators provides a first output voltage below the laser threshold voltage and a subsequent second voltage regulator of the at least two voltage regulators provides a second output voltage below the first output voltage. ### Claim 3 (depends on 2) The electro-optical distance measuring device according to claim 2, wherein at least one of the first voltage regulator and the second voltage regulator is embodied as a linear voltage regulator. ### Claim 4 (depends on 2) The electro-optical distance measuring device according to claim 2, wherein at least one of the first output voltage and the second output voltage is monitored to be below the laser threshold voltage by a voltage monitoring circuitry at said at least one of the first output and the second output voltage. ### Claim 5 (depends on 2) The electro-optical distance measuring device according to claim 2, wherein said at least one of the first output voltage and the second output voltage is clamped by a suppressor diode a shunt regulator, an avalanche diode or a Zener diode, or a varistor, a Metal-Oxide varistor, with a rated voltage below the laser threshold voltage and above the respective output voltage. ### Claim 6 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, further comprising: a voltage monitoring circuit of the laser diode voltage supply for detecting a value of the voltage which is above a predetermined limit. ### Claim 7 (depends on 6) The electro-optical distance measuring device as claimed in claim 6, wherein the predetermined limit is the laser threshold voltage. ### Claim 8 (depends on 6) The electro-optical distance measuring device as claimed in claim 6, wherein detecting the value of the voltage which is above the predetermined limit is done by a voltage comparator. ### Claim 9 (depends on 6) The electro-optical distance measuring device as claimed in claim 6, wherein: the voltage monitoring circuit is effected by a short-circuit detection circuit of a voltage regulator. ### Claim 10 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, further comprising: a further switching element for isolating the supply path of the laser diode or the entire laser driver or for short-circuiting the laser diode such that no laser light can be emitted. ### Claim 11 (depends on 10) The electro-optical distance measuring device as claimed in claim 10, wherein the further switching element is actuated on the basis of the detection of the voltage monitoring circuit. ### Claim 12 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, further wherein: the inductive component is in the form of a pulse-shaping network for shaping the emitted laser light pulses. ### Claim 13 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, wherein: the switching element for laser pulse emission is actuated by a configurable pulse-width modulation unit, wherein the energy of the laser light pulse and/or an intensity profile of the laser light pulse can be configured by the pulse width modulation. ### Claim 14 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, wherein: the laser driver, with the exception of the laser diode and the inductive component, is embodied as an ASIC. ### Claim 15 (depends on 1) The electro-optical distance measuring device as claimed in claim 1, further comprising: a transmission unit for emitting the laser light pulses with the laser driver and the laser diode; a reception unit for receiving a rejected component of the laser light pulses with a photosensitive electronic component; and an evaluation unit for determining a distance from a target object on the basis of a propagation time of the laser light pulses from the distance measuring device to the target object and back again. ### Claim 16 (depends on 15) The electro-optical distance measuring device as claimed in claim 15, wherein the laser light pulses are emitted as burst-like laser pulse packets. ### Claim 17 (depends on 1) The electro-optical distance measuring device according to claim 1, wherein the inductive component is connected to the laser diode in the circuit between the voltage supply. ### Claim 18 (depends on 1) The electro-optical distance measuring device according to claim 1, wherein the laser diode and the electronic switching element is in parallel with the laser diode. ### Claim 19 (depends on 1) The electro-optical distance measuring device according to claim 1, wherein the voltage regulator is embodies as: a low dropout linear voltage regulator, a step-down converter, a low-dropout series regulator, or a step-down fixed voltage regulator. ### Claim 20 A method for generating a laser pulse using a laser diode in an electro-optical distance measuring device, comprising: supplying a first voltage, which is below a laser threshold voltage of the laser diode to an input of a second voltage regulator, which second voltage regulator has a second output voltage, which is below the first voltage at its input; supplying the second output voltage to the laser diode via an inductive component, building up a current through the inductive component by closing a switching element arranged in parallel with the laser diode; and decreasing the current across the laser diode while emitting the laser pulse by opening the switching element. ### Claim 21 (depends on 20) The method according to claim 20, further comprising: detecting a fault case by monitoring the supply voltage to ascertain whether a predetermined voltage limit has been reached or exceeded; and isolating or short-circuiting the laser diode by means of a further switching element in the event of a fault. ### Claim 22 (depends on 21) The method as claimed in claim 21, wherein: the monitoring is performed by short-circuit detection at a circuit which reduces the supply voltage. ### Claim 23 (depends on 20) A method for pulsed operation of a laser diode of an electro-optical distance measuring device using a supply voltage which is below the laser threshold voltage according to claim 20, wherein: the inductive component is arranged in series with the laser diode; and the laser diode can be short-circuited by the switching element arranged in parallel with the laser diode. ### Claim 24 (depends on 21) A method for pulsed operation of a laser diode of an electro-optical distance measuring device using a supply voltage which is below the laser threshold voltage according to claim 21, wherein: the inductive component is arranged in series with the laser diode; and the laser diode can be short-circuited by the switching element arranged in parallel with the laser diode. ### Claim 25 (depends on 22) A method for pulsed operation of a laser diode of an electro-optical distance measuring device using a supply voltage which is below the laser threshold voltage according to claim 22, wherein: the inductive component is arranged in series with the laser diode; and the laser diode can be short-circuited by the switching element arranged in parallel with the laser diode. ### Claim 26 (depends on 20) A method for ensuring single-fault failsafety without the use of monitor diodes in a laser diode driver in an electro-optical distance measuring device by means of the method according to claim 20.