The purpose of this study is to propose a method for detecting a blink and the facial expression changes from changes in DCT (Discrete Cosine Transform) signs and determining whether the subject is a real person or a photograph. Face detection was performed on two frames taken continuously with the camera, and DCT signs were used to determine whether or not changes in expression occurred in the detected facial images. First, we check whether there are any large changes such as changes in direction or tilting between the two frames of facial images. Next, we check for the presence of changes in expression using only the center portion of the facial image. If a change in expression occurs, the image taken with the camera is determined to be a real person. As a result, we were able to detect blinking or changes in expression from changes in DCT signs. We conclude that it is possible to determine whether a photographed subject is a photograph or a real person using the proposed method, and that this could be used to prevent impersonation in face detection system. The purpose of this study is to propose a method for detecting a blink and the facial expression changes from changes in DCT (Discrete Cosine Transform) signs and determining whether the subject is a real person or a photograph. Face detection was performed on two frames taken continuously with the camera, and DCT signs were used to determine whether or not changes in expression occurred in the detected facial images. First, we check whether there are any large changes such as changes in direction or tilting between the two frames of facial images. Next, we check for the presence of changes in expression using only the center portion of the facial image. If a change in expression occurs, the image taken with the camera is determined to be a real person. As a result, we were able to detect blinking or changes in expression from changes in DCT signs. We conclude that it is possible to determine whether a photographed subject is a photograph or a real person using the proposed method, and that this could be used to prevent impersonation in face detection system.The purpose of this study is to propose a method for detecting a blink and the facial expression changes from changes in DCT (Discrete Cosine Transform) signs and determining whether the subject is a real person or a photograph. Face detection was performed on two frames taken continuously with the camera, and DCT signs were used to determine whether or not changes in expression occurred in the detected facial images. First, we check whether there are any large changes such as changes in direction or tilting between the two frames of facial images. Next, we check for the presence of changes in expression using only the center portion of the facial image. If a change in expression occurs, the image taken with the camera is determined to be a real person. As a result, we were able to detect blinking or changes in expression from changes in DCT signs. We conclude that it is possible to determine whether a photographed subject is a photograph or a real person using the proposed method, and that this could be used to prevent impersonation in face detection system.