Thread Shape Measurement with Dual Illumination and Focus Adjustment
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Solution Overview
Problem
Existing methods for measuring the shape dimensions of flank surfaces on threaded pipes with overhanging flank surfaces, such as those used in oil well pipes, result in inaccurate measurements due to positional deviations of one flank surface, leading to errors in calculated thread dimensions like thread ridge width and thread root width.
Innovation Solution
A thread shape dimension measuring device and method that employs two illumination directions and adjusts the focusing position of the imaging unit to accurately measure both flank surfaces by calculating the shape dimension of one flank surface directly and the other flank surface after adjusting the focusing position to match its true position on the pipe axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the light projection method is used to measure thread shape dimension, then automatic measurement is achieved, but measurement precision deteriorates when both flank surfaces are formed in an overhanging manner due to positional deviations
Solution Approach 1:
The imaging unit dynamically adjusts its focusing position along the optical axis based on the thread lead angle. By calculating the lead angle from the threaded portion specifications and adjusting the focal distance accordingly, the system maintains accurate focus on both overhanging flank surfaces during automatic measurement, resolving the precision issue while preserving automation.
Solution Approach 2:
The system changes the focusing position parameter of the imaging unit based on the thread lead angle. By calculating the lead angle from thread specifications and using it to adjust the focal distance, the measurement system adapts to different thread geometries, ensuring accurate measurement of both overhanging flank surfaces without positional deviations.
2Ease of operation
If the focusing position is fixed for measuring one flank surface, then the measurement process is simplified, but the other flank surface cannot be accurately measured due to positional deviation
Solution Approach 1:
The system automatically adjusts the focusing position parameter based on the thread lead angle to accurately capture both overhanging flank surfaces. This dynamic parameter adjustment maintains measurement precision while the control unit automates the process, preserving ease of operation.
Solution Approach 2:
The system uses the calculated lead angle as feedback to determine the appropriate focusing position. By continuously adjusting the focal distance based on the thread geometry parameters, the system ensures accurate measurement of both flank surfaces while maintaining an automated, user-friendly operation process.
3Device complexity
If the imaging unit position is fixed, then device complexity is reduced, but measurement precision deteriorates for overhanging flank surfaces
Solution Approach 1:
The imaging unit incorporates a movable positioning mechanism that adjusts the focusing position along the optical axis based on the thread lead angle. This dynamic adjustment capability enables accurate measurement of both overhanging flank surfaces while maintaining relatively simple device architecture through automated control.
Solution Approach 2:
The system replaces complex mechanical positioning with an automated control system that calculates the lead angle from thread specifications and electronically adjusts the focusing position. This substitution of mechanical complexity with computational control achieves high measurement precision for both flank surfaces while keeping the physical device structure relatively simple.
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
Accurately measures the shape dimensions of both flank surfaces without positional deviation, ensuring precise calculation of thread dimensions like thread ridge width and thread root width.
Implementation Method 1
an illumination unit illuminating the end portion by emitting parallel light in a first illumination direction inclined in a direction forming an angle larger than a lead angle of the threaded portion with respect to a direction orthogonal to the cross section including the pipe axis or a second illumination direction inclined to a side opposite to the lead angle of the threaded portion with respect to a direction orthogonal to the cross section including the pipe axis
Implementation Method 2
an imaging unit disposed to face the illumination unit with the end portion of the threaded pipe interposed therebetween and configured to generate a first captured image of the end portion by imaging light that has passed between the thread ridges from the parallel light emitted in the first illumination direction
Implementation Method 3
an adjustment unit adjusting a focusing position of the imaging unit... calculates a shape dimension of the second flank surface on the basis of the second captured image generated in a second state in which the focusing position of the imaging unit is brought closer to the pipe axis by a predetermined distance than that in the first state
Data Source
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AI summary
This thread shape dimension measuring device includes an illumination unit, an imaging unit, a focal distance adjustment unit, a calibration value setting unit, and a control unit. The illumination unit selectively emits parallel light in two directions including a first illumination direction and a second illumination direction. The imaging unit selectively performs capturing of a first captured image and capturing of a second captured image. The focal distance adjustment unit adjusts a focusing position of the imaging unit by receiving an adjustment instruction from the control unit. The calibration value setting unit has a difference value between a focal distance of the second captured image from a focusing position to the imaging unit before the focusing position adjustment and a focal distance of the first captured image from a focusing position to the imaging unit. The control unit acquires the difference value from the calibration value setting unit, gives the adjustment instruction to bring the focusing position closer to the illumination unit by the difference value to the focal distance adjustment unit when the second captured image is captured, and calculates the thread shape dimension on the basis of the captured first captured image and the second captured image.