Flash Ladar Camera Automatic Range Correction
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Solution Overview
Problem
Conventional laser radar systems face challenges in achieving accurate 3-D imaging due to unpredictable laser pulse startup delay, modal stability, and thermal stability issues, which affect range accuracy and pulse shape repeatability.
Innovation Solution
A flash ladar camera system with an optimized laser transmitter that improves pulse shape and repeatability, incorporates digital signal processing for reliability and thermal stability, and uses Automatic Range Correction (ARC) techniques to mitigate timing jitter and enhance range accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If solid state laser with Neodymium-YAG or Erbium glass rod and saturable Q-switch is used, then high peak power requirement is met, but unpredictable laser pulse startup delay and modal stability issues occur
Solution Approach 1:
The patent applies preliminary action by pre-saturating the Q-switch material before the actual laser pulse is generated. This is achieved by using a pump pulse that提前 excites the gain medium and saturates the Q-switch, ensuring that when the main pulse is triggered, the laser cavity is already in the optimal state for predictable pulse generation. This preliminary preparation eliminates the unpredictable startup delay while maintaining high peak power.
2Power
If solid state laser materials are used, then high energy pulse generation is enabled, but thermal stability issues arise
Solution Approach 1:
The patent extracts the thermal management function from the laser rod itself by implementing separate active cooling systems. The laser cavity is designed with independent thermal control mechanisms that can actively remove heat generated during high energy pulse generation, thereby maintaining thermal stability without compromising the energy output capability of the solid state laser materials.
3Measurement precision
If conventional focal plane array detector with readout integrated circuit is used, then object detection and range determination are enabled, but time delay varies with input signal amplitude
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual time delay variations in the readout integrated circuit and using this information to dynamically adjust the ranging calculations. A reference channel measures the timing characteristics under different signal conditions, and this measured data is fed back to correct the range determination algorithm, compensating for the amplitude-dependent time delay variations and maintaining consistent measurement precision.
4Power
If laser pulse shape varies, then high power transmission is achieved, but pulse shape repeatability deteriorates
Solution Approach 1:
The patent applies dynamics by implementing adaptive pulse shaping control that can dynamically adjust laser cavity parameters during operation. Based on real-time monitoring of pulse characteristics, the system dynamically modifies mirror coatings, Q-switch timing, or gain medium conditions to maintain consistent pulse shape while preserving high power transmission capability. This dynamic adaptation ensures repeatability without sacrificing power.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves improved range accuracy and reliability by stabilizing the laser pulse shape and timing, enabling true 3-D imaging with high spatial and range resolution using a single laser pulse.
Implementation Method 1
The wavelength of choice for the laser radar is typically 1570 nanometers... there are laser system components commercially available at this wavelength which enable the design and production of a laser capable of producing the high energy pulse required
Implementation Method 2
The detector material is a binary compound of Indum Phosphide (InP), or a more exotic quaternary compound such as Indium Gallium Arsenide Phosphide (InGaAsP)... The detector in this case must respond to wavelengths outside the visible range, in the near infrared spectrum
Implementation Method 3
An optical sample of the transmitted laser pulse is fed back through a sacrificial pixel in the infrared focal plane array and through the accompanying input amplifier in the readout integrated circuit, producing a stable, amplitude adjusted zero time reference
Data Source
AI summary
A three dimensional imaging camera comprises a system controller, pulsed laser transmitter, receiving optics, an infrared focal plane array light detector, and an image processor. The described invention is capable of developing a complete 3-D scene from a single point of view. The 3-D imaging camera utilizes a pulsed laser transmitter capable of illuminating an entire scene with a single high power flash of light. The 3-D imaging camera employs a system controller to trigger a pulse of high intensity light from the pulsed laser transmitter, and counts the time from the start of the transmitter light pulse. The light reflected from the illuminated scene impinges on a receiving optics and is detected by a focal plane array optical detector. An image processor applies image enhancing algorithms to improve the image quality and develop object data for subjects in the field of view of the flash ladar imaging camera.