A projection and measurement system comprising: a projection unit configured to project light onto a body part of a user; a tracking unit configured to detect an image of the body part of the user; and a control unit configured to: control the projection unit to project illuminating light onto the body part of the user during detection of the image of the body part of the user; determine a position and an orientation of the body part of the user based on the image of the body part of the user; determine a feature of the body part of the user based on the image of the body part of the user; generate an optical guide to be projected onto the body part of the user based on the determined feature; and control the projection unit to project the optical guide such that the position and the orientation of the optical guide correspond to a current position and orientation of the body part of the user, characterized in that the control unit is further configured to perform at least one of controlling the projection unit to project the optical guide onto the body part of the user in an asynchronous manner with respect to the detection of the image of the body part such that when the illumination light is being projected by the projection unit the tracking unit does not perform any image detection operations, and generating a modulated form of at least one of the optical guide and the illuminating light by including an identification pattern and controlling the projection unit to project the modulated form onto the body part of the user such that the projection of the modulated form of the illumination light onto the body part of the user and the detection of the image of the body part are be performed in an alternating manner wherein the projection of the illumination light by the projection unit is performed between instances of detection of images of the body part of the user by the tracking unit. a projection unit configured to project light onto a body part of a user; a tracking unit configured to detect an image of the body part of the user; and a control unit configured to: control the projection unit to project illuminating light onto the body part of the user during detection of the image of the body part of the user; determine a position and an orientation of the body part of the user based on the image of the body part of the user; determine a feature of the body part of the user based on the image of the body part of the user; generate an optical guide to be projected onto the body part of the user based on the determined feature; and control the projection unit to project the optical guide such that the position and the orientation of the optical guide correspond to a current position and orientation of the body part of the user, characterized in that the control unit is further configured to perform at least one of controlling the projection unit to project the optical guide onto the body part of the user in an asynchronous manner with respect to the detection of the image of the body part such that when the illumination light is being projected by the projection unit the tracking unit does not perform any image detection operations, and generating a modulated form of at least one of the optical guide and the illuminating light by including an identification pattern and controlling the projection unit to project the modulated form onto the body part of the user such that the projection of the modulated form of the illumination light onto the body part of the user and the detection of the image of the body part are be performed in an alternating manner wherein the projection of the illumination light by the projection unit is performed between instances of detection of images of the body part of the user by the tracking unit. control the projection unit to project illuminating light onto the body part of the user during detection of the image of the body part of the user; determine a position and an orientation of the body part of the user based on the image of the body part of the user; determine a feature of the body part of the user based on the image of the body part of the user; generate an optical guide to be projected onto the body part of the user based on the determined feature; and control the projection unit to project the optical guide such that the position and the orientation of the optical guide correspond to a current position and orientation of the body part of the user, characterized in that the control unit is further configured to perform at least one of controlling the projection unit to project the optical guide onto the body part of the user in an asynchronous manner with respect to the detection of the image of the body part such that when the illumination light is being projected by the projection unit the tracking unit does not perform any image detection operations, and generating a modulated form of at least one of the optical guide and the illuminating light by including an identification pattern and controlling the projection unit to project the modulated form onto the body part of the user such that the projection of the modulated form of the illumination light onto the body part of the user and the detection of the image of the body part are be performed in an alternating manner wherein the projection of the illumination light by the projection unit is performed between instances of detection of images of the body part of the user by the tracking unit.