# A Regional Brightness Control Method for a Beam Projector to Avoid Human Glare
## 5 Conclusions  
The hardware technology associated with beam projectors is continuously evolving. As higher-performance light sources for beam projectors are developed and applied, the negative effects on human glare are also increasing. This study proposes a regional brightness control method for beam projector systems to protect the eyesight of people who perform activities such as delivering lectures in front of a beam projector.  
The proposed system detects the human body area on the screen and regionally reduces the light intensity in the detected area. To achieve these functions, the proposed system first generates two profiles for geometric and color transformations to eliminate the differences between the original source image and the projected image sampled by the camera. After applying transformations with those two profiles, the SSIM is used to generate a SSIM-MAP for the corresponding locations in the compared two images. Areas with lower SSIM values would indicate people or unintended objects in front of the screen. Then, those areas are segmented to extract only the actual human body. Finally, the system works by controlling the area's output brightness to reduce human glare.  
One of the important features or implications of our study is that we have applied SSIM-MAP to the segmentation model so that the proposed system can identify the human body area with a method based on image differences. It enables the proposed system to escape confusion between human figures in the projected image and the real human body. The most important contribution of this research is proposing a new way to utilize the SSIM for beam projectors. The SSIM was developed as a metric to evaluate the quality of an image, but by reducing the window size for calculation, it can be used to identify where the changes have occurred.  
Another point is that we have proposed and implemented blurring and color conversion methods to increase the similarity between the original image and the projected image captured by a camera. Though blurring is a common method to degrade image quality by reproducing the effect of light smearing [8], it is quite suitable for the proposed system to simulate image degradation due to projection and capture with a camera. Color conversion also achieved additional similarity improvements by correcting color values based on the position of each pixel. Since the two methods have different causes of the phenomenon they solve, we propose that applying both methods to this problem is an appropriate way to improve the similarity.  
Figure 16: FP rates of the proposed system: (**a**) Selfie model case; (**b**) DeepLab-v3 model case.  
For future work, more experiments with various scenarios and configurations would be carried out to enhance the proposed system's performance and energy efficiency. To perform this, additional segmentation models need to be applied or newly trained to optimize our purpose. Some image quality assessment methods, such as PSNR and MSE, can be considered in comparison with SSIM. For real-time processing, you need to consider process optimization, dynamic brightness control, and energy efficiency to improve performance. During the installation process, some additional preprocessing tasks, such as brightness equalization and camera calibration, may considerably affect the system's performance. Finally, referring to user experience would improve the ease of use of your proposed system.  
Conceptualization, H.-G.J. and K.-H.L.; formal analysis, H.-G.J.; investigation, H.-G.J.; methodology, H.-G.J. and K.-H.L.; writing--original draft, H.-G.J.; writing--review and editing, K.-H.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported by Innovative Human Resource Development for Local Intellectualization program through the Institute of Information & Communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (IITP-2024-RS-2022-00156334).  
Not applicable.