Distance Measuring Apparatus with Diode Clamping and Gain Switching
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Solution Overview
Problem
Existing distance measuring apparatus using the Time of Flight method faces challenges in achieving high precision distance compensation due to variations in reflected light intensity, leading to errors in distance calculation, especially when the amplifying circuit becomes supersaturated, and requires expensive circuit configurations to handle dynamic ranges of reflected light.
Innovation Solution
A distance measuring apparatus with a photodiode connected in series to a diode for clamping light current, an amplifying circuit for stable output, and an integration processor to calculate total electric charge, allowing for accurate distance compensation without saturation and reducing the need for multiple amplifying circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain of the amplifying circuit is increased to accurately detect weak reflected light, then the detection sensitivity is improved, but the amplifying circuit becomes supersaturated when the reflected light intensity is great, causing waveform distortion and measurement error
Solution Approach 1:
The light receiver is divided into two separate paths: one path uses an amplifying circuit with high gain for detecting weak reflected light, while the other path uses an amplifying circuit with low gain for detecting strong reflected light. This segmentation allows each path to operate within its optimal range without saturation, resolving the contradiction between detection sensitivity and circuit saturation.
2Adaptability or versatility
If the gain of the amplifying circuit is increased to detect weak reflected light, then the detection range is enlarged, but the circuit becomes supersaturated for great reflected light intensity, requiring multiple amplifying circuits which increases device complexity and cost
Solution Approach 1:
A gain switching mechanism is implemented that dynamically selects between high gain and low gain modes based on the intensity of the reflected light. When weak reflected light is detected, the high gain mode is activated; when strong reflected light is detected, the low gain mode is activated. This dynamic adaptation enlarges the detection range while maintaining relatively simple circuit configuration by using a single amplifying circuit with switchable gain states.
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 solution provides stable and accurate distance measurement across varying reflected light intensities without circuit saturation, maintaining precision and reducing costs by eliminating the need for separate amplifying circuits for charge measurement.
Implementation Method 1
a photodiode for photo-electrically converting the reflected light
Data Source
AI summary
A distance measuring apparatus, which can attain a distance compensation of a high precision and can be stably operated by using a cheap circuit, without any arrival at a supersaturated state for a great reflected light intensity, while a gain of an amplifying circuit is made higher, in order to accurately detect even a weak reflected light. The apparatus comprises: a light source for outputting a pulsed measurement light towards a measurement target object; a light receiver for detecting the reflected light from the measurement target object; and a calculator for calculating the distance from the measurement target object on the basis of the delay time between the output timing of the measurement light and the detected timing of the reflected light by the light receiver, and a light receiver 5 is composed of a photodiode PD for photo-electrically converting the reflected light, a diode D that is connected in series to the photodiode PD and clamps the light current generated in the photodiode PD, and an amplifying circuit 50 for amplifying the output of the photodiode PD, and it contains an integration processor for integrating the output of the amplifying circuit 50 and a distance compensator for compensating the distance in accordance with the output of the integration processor.