## 1 Introduction  
With the acceleration of digitalization, students and most office workers involved in desk work spend a significant amount of their day on completing computer work. When using a computer, it is important to maintain a good posture while performing tasks. Good posture refers to a position where the natural curves of the spine, including the forward, backward, and sideways curves, are maintained without any deviation as shown in Figure 1a[1]. However, prolonged computer use can cause the head's center of gravity to gradually shift forward due to focusing on the computer monitor, resulting in a posture where the neck bends forward as shown in Figure 1b. Prolonged sitting in front of a desk while maintaining such a poor posture can cause pain in the back of the neck, shoulders, waist, and other areas. Furthermore, if this poor posture is continued, the arrangement of the vertebrae in the neck can become abnormally straightened, leading to text neck syndrome. This leads to the weight of the head being directly transmitted to the neck and shoulders, without being evenly distributed, which can cause problems such as neck disc, headaches, and numbness in the hands, as well as structural changes in the cervical and thoracic spine [2; 3; 4]. And as the distance between the head and the monitor decreases, eye fatigue increases, and vision can significantly deteriorate. When using a computer, people often assume the L-posture, where they sit with their buttocks positioned towards the front of the chair and lean their shoulders against the backrest as shown in Figure 1c. This posture puts pressure on the lower back and causes the neck to bend, as the buttocks and shoulders bear the weight of the upper body, and it has a negative impact on the neck and waist. In addition, the text neck posture and L-posture cause tension in the cervical and spinal areas, leading to discomfort and, in severe cases, can cause herniated discs in the neck or waist. Moreover, since this incorrect posture habit can have detrimental effects on body development, it is especially important to prevent adolescents during their growth years from adopting such postures [5]. However, until recently, most of the published studies have focused on theories and methodologies for preventing the text neck posture, and there have been few studies with high accuracy that classify both text neck and L-posture together [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. Furthermore, since most sensor equipment is attached to the body or clothing, it can be heavy and uncomfortable, and there is the limitation of the cost of posture-correction chairs that are commercially available with attached sensors.  
In this paper, we propose a study to classify good posture, text neck posture, and L-posture when working in front of a desktop computer, the latter two of which are common postures that have a negative impact on the cervical and lumbar spine. In this study, we classified postures including the L-posture and the text neck posture, which can have a negative impact on the cervical and spinal areas and are not often classified together in previous research. In addition, since the user's side posture is captured with a camera and the angle of a specific part is measured to classify the posture, it can be measured anywhere as long as there is space available on the side. Furthermore, it has the advantage of being cost-effective as it can be utilized not only with CCD cameras, but also with images captured by smartphones. The structure of this paper is as follows. In Section 2, we introduce previous studies on posture correction. In Section 3, we describe the posture classification algorithm proposed in this paper, and in Section 4, we verify and analyze the experimental results of the proposed algorithm. Finally, we draw conclusions on this paper.