Embodiments of this application disclose a laser diode drive circuit and a LiDAR. The laser diode drive circuit includes a laser diode and a charging and discharging circuit. A cathode of the laser diode is grounded. The charging and discharging circuit is in a one-to-one correspondence with the laser diode, and includes an energy storage element, a first switch element, and a second switch element. The energy storage element is connected to an anode of the laser diode via the first switch element, and the energy storage element is grounded via the first switch element and the second switch element in sequence.

A photodiode current comparison circuit has a first current source coupled to a circuit node configurable to operate in a first mode, a second current source coupled to the circuit node configurable to operate in a second mode opposite the first mode, and a third current source switchable to route a current to the circuit node in response to a data signal using a transistor coupled between the circuit node and the third current source. A photodiode is coupled to the circuit node. In a first configuration, an anode of the photodiode is coupled to the circuit node and a cathode of the photodiode is coupled to a power supply terminal. In a second configuration, a cathode of the photodiode is coupled to the circuit node and an anode of the photodiode is coupled to a power supply terminal. An amplifier provides an error signal of the photodiode.

A laser device includes: a light source including laser diodes; a processor that holds: a maximum current value of a driving current applied to the laser diodes, and a maximum power value of a power of light emitted from the light source; and a memory, coupled to the processor, that stores a relationship between a magnitude of the driving current, a magnitude of the power of the light, and a degree of deterioration of the light source. The processor further refers to the memory and estimates the degree of deterioration from the maximum current value and the maximum power value.

Multi-section laser systems are configured with a gain/modulation section and a pre-bias section. Both sections are electrically connected to a diode laser resonator and both sections are independently controllable via laser driver circuitry. The multi-section laser can be used to provide pulsing optimizations that include reducing the turn-on delay of the laser while also ensuring that the resulting laser light's spectral linewidth satisfies a threshold linewidth requirement. During use, a pre-bias current is applied to the pre-bias section. This current causes some photons to be spontaneously emitted. During this time, a gain current is refrained from being applied to the gain section until the resonator is seeded with a spectrum of photons from the pre-bias section. Once the resonator is sufficiently seeded, the gain current is applied to the gain section, thereby producing a seeded pulse of laser light having a desired spectral linewidth.

A method for correcting a wavelength and a tuning range of a laser spectrometer in which the light from a wavelength-tunable laser diode, after being radiating through a gas, is detected and evaluated, wherein the laser diode is periodically driven with a current ramp, such that a time-resolved absorption spectrum of the gas is obtained upon the detection of the light, where in order to correct the wavelength and the tuning range of the laser spectrometer, a first step involves readjusting the central wavelength of the laser diode via the temperature thereof and based on the position of one of two different selected absorption lines in the detected absorption spectrum, and a second step involves correcting the tuning range of the laser diode via the gradient of the current ramp such that the spacing of the two absorption lines in the detected absorption spectrum remains constant.

The present invention provides a method for estimating a condition parameter of a laser diode having an associated photodiode, to an apparatus for monitoring the operation of such a laser diode, and to a particle sensor apparatus. The photodiode (PD) is operable together with the laser diode (LD), wherein it detects the light (LS) of the laser diode (LD) and converts it into an electrical current, and is thermally coupled to the laser diode (LD). The at least one condition parameter is estimated during the operation of the laser diode (LD) and the estimation is based on current measurements and/or voltage measurements at the laser diode (LD) and/or at the photodiode (PD).

The present invention provides methods and an apparatus for monitoring the optical output power of a laser diode (LD) having an associated photodiode (PD), and a particle sensor apparatus. The photodiode (PD) is operable together with the laser diode (LD), wherein it detects the light (LS) of the laser diode (LD) and converts it into an electrical current, and is thermally coupled to the laser diode (LD). Monitoring of the optical output power P is effected during the operation of the laser diode (LD) and is based on current measurements and/or voltage measurements at the laser diode (LD) and at the photodiode (PD).

The disclosure provides a light source device and an image display device. The light source device includes a laser light source configured to emit laser light having a wavelength in a range from 635 nm to 645 nm inclusive, a temperature sensor configured to detect temperature around the light source device, and a laser control circuit configured to control the laser light source. The laser control circuit approximates, with use of a quartic expression, change in threshold current of the laser light source relative to temperature, and approximates, with use of a quadratic expression, change in slope efficiency of the laser light source relative to temperature, to obtain threshold current and slope efficiency of the laser light source corresponding to detection temperature of the temperature sensor, and controls the laser light source in accordance with the threshold current and the slope efficiency thus obtained.

The present invention comprises: a light-emitting element group configured from columns of serially connected light-emitting elements, one of the ends from each of the columns of the light-emitting elements being collectively connected to a power source; current control elements, provided to correspond to the columns, and being connected to each of the columns of the light-emitting elements at the other end thereof, for controlling the current flowing through the light-emitting elements; a forward voltage monitoring circuit for monitoring, for each of the columns, the total forward voltage across the light-emitting elements; and a control circuit for controlling the current control elements, on the basis of the total forward voltage across the light-emitting elements from each of the columns detected by the forward voltage monitoring circuit, in such a manner that the variations in the total forward voltage across the columns of the light-emitting elements reach a threshold value or lower.

A control device, which controls a laser scanning display device, includes a laser device, a first current source that generates a first driving current supplied to the laser device, a second current source that generates a second driving current supplied to the laser device, and a controller. The controller controls the first current source to generate the first driving current having a first set current value that is 1/n times a threshold current value at a time when oscillation of the laser device starts, when scanning a non-display area in which no image is displayed, where n is a number greater than 1. The controller controls the second current source to generate the second driving current having a second set current value that is zero or greater and less than 11/n times the threshold current value, when scanning the non-display area.