GB/T 43596-2023
The calibration method of the grayscale standard display function for image (English Version)

Standard No.

GB/T 43596-2023

Language

Chinese, Available in English version

Release Date

2023

Published By

General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China

Latest

GB/T 43596-2023

Introduction

Analysis of the core content of the standard

This standard systematically specifies the grayscale calibration system of medical imaging display equipment for the first time, and establishes the grayscale standard display function (GSDF) based on the Barten human eye vision model to achieve accurate mapping of input level and output brightness/optical density. The main innovations include:

1. Dual media coverage: Applicable to both electronic display media (display/projector) and printed media (film/reflective sheet)
2. Physiological adaptation: Ensure that the grayscale steps meet the just noticeable difference (JND) of the human eye through the visual model in Appendix A
3. Dynamic adaptation: Supports device calibration in the luminance range of 10^-4~10³ cd/m²

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Comparison of calibration technology frameworks

Dimensions	Electronic display media	Printed display media
Measurement parameters	Brightness (cd/m²)	Optical Density (OD)
Core Formula	Lj+1=Lj(1+Sj)/(1-Sj)	D(φ)=-log10[(L[Dm(φ)]-La)/L0]
Standard Function	Appendix B Brightness Lookup Table	Appendix C/D Density Lookup Table
Equipment Requirements	First-Class Brightness Meter (JJG 211)	Standard densitometer (JJG 452)

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Key technologies of Barten vision model

The model integrates 8 physiological characteristic parameters of human eye:

1. Nervous system noise threshold
2. Retinal photoreceptor cell discreteness
3. Pupil diameter dynamic adjustment (Formula A.6)
4. Photon quantum efficiency (357×3600 photos/td sec deg²)
5. 0.1s time integration characteristics
6. Spatial frequency response (0.2-50 c/deg)
7. Optical modulation transfer function (Formula A.1)
8. Directional sensitivity difference

The contrast sensitivity S(L) calculated by formula A.7 ensures that each grayscale step corresponds to 1 JND unit.

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Implementation Suggestions

Electronic Display Calibration Process:

• Under <0.05 cd/m² darkroom environment
• Use a 2° field of view luminance meter to measure 256 levels of grayscale
• Generate LUT by interpolation according to Appendix B
• Verify u(L_D)<0.0015

Medical Film

Calibration Key Points:

• The transmission type needs to control the L₀=2000 cd/m² viewing light
• The reflection type standard observation surface brightness is 1300 cd/m²
• The density meter needs to meet the error of ±0.02 when D≤2.0

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Uncertainty Analysis

Synthetic uncertainty model (Formula 13):

u(D_output)=√[u(L_m)²+u(L_D)²]

Where u(L_D) is calculated by the RMS of the brightness difference of 255 calibration points (Formula 14), the typical value should be <0.0015.