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JJF 1951-2021Calibration Specification for Optical 3D Measuring Systems Based on Structured Light Scanning (English PDF)

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Issued by

State Administration for Market Regulation Administrative organization

Level / Type

National · Mandatory

Issue date

December 28, 2021

Implementation date

June 28, 2022

Scope

JJF 1951-2021 (Calibration Specification for Optical 3D Measuring Systems Based on Structured Light Scanning) is available as an English-translated PDF.

JJF 1951-2021 is the Chinese standard "Calibration Specification for Optical 3D Measuring Systems Based on Structured Light Scanning". Its scope clause reads: This calibration specification applies to the calibration of optical 3D measuring systems based on structured light scanning (hereinafter referred to as structured light measuring systems).

Its clauses include terms and definitions; overview; metrological characteristics; calibration conditions; calibration items and methods; processing of calibration results; recalibration interval.

It was issued by the State Administration for Market Regulation Administrative organization on 2021-12-28 and took effect on 2022-06-28.

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Document preview — JJF 1951-2021

National Standard of the People's Republic of China

Issued by: State Administration for Market Regulation Administrative organization

Introduction...5
1 Scope...6
2 Terms and definitions...6
3 Overview...7
4 Metrological characteristics...8
5 Calibration conditions...9
5.1 Operation modes and environmental conditions...9
5.2 Calibration software...9
5.3 Etalons for calibration...9
6 Calibration items and methods...10
6.1 spherical form probe error PF, size probe error PS...10
6.2 Flat form probe error F...12
6.3 Sphere-spacing error, SD...13
7 Processing of calibration results...14
8 Recalibration interval...14
Annex A Examples for assessment of sphere-spacing error uncertainty...15
Annex B Format for inside page of calibration certificate...18

1 Scope

This calibration specification applies to the calibration of optical 3D measuring systems based on structured light scanning (hereinafter referred to as structured light measuring systems).

2 Terms and definitions

The following terms and definitions apply to this Specification.

2.1 point cloud [data]

A set of spatial coordinate points that are obtained by measurement to characterize contour features and are associated with each other.

2.2 ball bar, dumb bell

An etalon consisting of two spherical targets of the same diameter connected by a rigid structure.

2.3 ball plate

A standard measuring tool consisting of a series of standard balls with different diameters and a fixed bottom plate.

2.8 sphere-spacing error; SD

The difference between the measured value and the reference value of the center distance between two balls.

3 Overview

The structured light measuring system is a non-contact measurement device. By projecting the structured light onto the surface of the measured object, and by collecting the point cloud of the structured light pattern on the surface of the measured object, the surface contour features of the measured object are calculated and obtained.

4 Metrological characteristics

The metrological characteristics are shown in Table 1.

5 Calibration conditions

5.1 Operation modes and environmental conditions

Before calibration, the operation mode needs to be set, including the type and brightness of lighting, the measurement range, the type, quantity and distribution of sensors used in the system.

5.2 Calibration software

5.3 Etalons for calibration

Etalons for calibration shall be made of ceramic, steel, aluminum or other rigid material.

It shall have a diffuse surface (non-volumetric scattering). The etalons used to calibrate different metrological characteristics are shown in Table 1.

6 Calibration items and methods

6.1 spherical form probe error PF, size probe error PS

Select the appropriate diameter standard ball according to Table 1.

Standard balls shall be fixed in an appropriate way. Avoid introducing measurement errors due to instability.

6.1.2 Multi-view system

The standard ball shall be located in at least n=3 positions within the measurement range. The standard ball shall be measured from no less than 5 different directions at each position, see Figure 3, so that the point cloud shall cover the surface of the standard ball as completely as possible.

Figure 3 -- Schematic diagram of 5 measuring directions

6.2 Flat form probe error F

Select a standard plane of appropriate size according to Table 1.

6.3 Sphere-spacing error, SD

6.3.1 Single-view system

Choose the appropriate length ball bar according to Table 1.

The sphere-spacing error SD shall be measured at 7 different positions in the entire measurement range. It is recommended to arrange and measure the etalon as shown in

Figure 5.

7 Processing of calibration results

Calibration certificate is issued to the calibrated structured light measuring system. The calibration certificate shall meet the requirements of 5.12 in JJF 1071-2010.Calibration results and their uncertainties list the calibration items and data.

8 Recalibration interval

The user decides the recalibration interval according to the actual usage. It is recommended that the interval between recalibration shall not exceed 1 year.

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 18 pages — is available in the English PDF.

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