Research On The Evaluation Methodology And Experiment Of Office Light Environment Based On Eeg And Micro-Expression Recognition

Office space is one of the main places for people’s daily activities.Improving the quality of the office environment has an important significance in promoting the physical and mental health of office population as well as boosting employee work efficiency.However,the current evaluation indicators of the office light environment are mostly based on physical parameters,and there is still no clear and unified definition of light comfort.How to build a user-centered light environment evaluation system and create an office light environment that satisfies the physiological and psychological needs of workers has received more and more attention from researchers.For exploring a more objective and efficient method of office light environment evaluation as well as analyzing the light environment needs of office workers in different behavioral states,the paper uses EEG as an objective physiological parameter,combined with subjective evaluation and cognitive task performance,in order to analyze the effects of office light environment on workers’ physiological and psychological states and study the neural response mechanism of light comfort.Meanwhile,a non-contact method is explored for tracking the human light comfort level,which is to use facial microexpression recognition technology to evaluate the comfort level of personnel when in a light environment.The paper analyzes the physiological basis of EEG and facial microexpressions respectively from the theory,explores the feasibility of applying both to office light environment evaluation,and introduces the data processing and analysis methods systematically.On the basis of theoretical analysis,the paper designs experiments to explore.The illuminance of the working surface is the independent variable in the experiment.The illuminance levels of 75 lux,300lux,500 lux,750lux and 1200 lux are designed.Considering the difference in the illuminance needs of office workers during sitting rest and mental load,each illuminance level is subdivided into a rest stage and a task stage.The subjects are tested with spontaneous EEG,subjective evaluation,cognitive task performance,and facial micro-expressions,respectively.The study explores the effect of illuminance on the psychological and physiological patterns of office workers during sitting rest.Firstly,the subjective evaluation results of the rest stage under different working conditions are analyzed,and the best subjective evaluation of the 500 lux illuminance environment is observed.Secondly,the fast Fourier transform is used to calculate the EEG power in the rest stage.The differences and change patterns of the total EEG power and the EEG power of each channel and each frequency band under five illuminance levels are analyzed.It is observed that the total EEG power and the power of the δ-band and β-band of some channels in the parietal area differ significantly under different working conditions.The total EEG power and the power of the δ-band and β-band of some channels in the parietal region are revealed to be significantly different under different working conditions.On this basis,the relationship between the subjective evaluation results of light comfort and EEG power was continued to be studied.The total EEG power and the power of the δ-band at the Cz channel were revealed to be most strongly correlated with light comfort,which can be used as the EEG characteristic values to characterize light comfort.Finally,the comfort intelligent evaluation system is used to process the facial micro-expression data of the people in the rest stage,and the results show that the highest percentage of people are comfortable in the 500 lux illuminance environment.After validation,the results obtained by the comfort intelligent evaluation system in judging people’s light comfort are reliable.Taking into account,in order to satisfy the physiological and psychological needs of the office employees in a resting state,the illuminance level of the task area is recommended to be set to 500 lux when the office workers are sitting rest.Meanwhile,the study explores the pattern of illuminance effects on office workers’ performance and physiology during mental load.Firstly,the cognitive task performance of the task stage under different working conditions is analyzed.The highest performance indicator is observed in the 500～750lux illuminance range.Secondly,the fast Fourier transform is used to calculate the EEG power in the task stage.The differences and change patterns of the total EEG power and the EEG power of each channel and each frequency band under five illuminance levels are analyzed.No statistically significant differences of total EEG power are observed at different illuminance levels.The frequency bands of power significantly affected by illuminance level are δ-band and β-band,and the responding channels are distributed in the parietal,frontal and temporal regions.Thirdly,the relationship between cognitive task performance indicator and EEG power is studied,and it is pointed out that the power of β-band at FT10 channel is significantly correlated with the performance indicator of the cognitive task,which can be used as the EEG characteristic value reflecting the cognitive task performance under different illuminance levels.Finally,the comfort intelligent evaluation system is used to process the facial micro-expression data of the people in the task stage,and the results show that the highest percentage of people are comfortable in the 750 lux illuminance environment.After comprehensive analysis,it is recommended that the illuminance level of the task area during mental load is set to 750 lux,considering to ensure the work performance and physiological needs of office workers.The continuous optimization and improvement of office light environment evaluation methods,which ultimately aims to improve the quality of the office light environment to indicate the direction,and more targeted adjustments.It is the key to protect the physical and mental health of employees and improve productivity by designing the office light environment approximately and satisfying the needs of the office population for healthy light.The research methods applied in this paper and the conclusions obtained are believed to provide a new way of thinking for the creation of the office light environment and the in-depth study of light comfort,which is of reference significance.