Research On Techniques Of Geometric Correction And Luminance Correction In Projective Systems

With the development of virtual reality technology,the corresponding display technology has been further improved.At present,the main display technologies are head-mounted display(HMD)and large-screen projection display.The large-screen projection display is still widely used in interactive cinema,industrial design,assembly and other areas,due to its characteristics of wide viewing range,low dizziness and simple implementation.However,most of the current large-screen projections systems support single-view rendering.Even if there are multiple users in the same physical space,scenes can be rendered only according to the position and perspective of one of them,which will cause confusion of perspectives and affect the sense of co-located collaborative experience.Compared with the flat projection screen,the virtual reality environment based on the curved projection screen enables users to have a wider field of vision and move more naturally,thus enhancing their sense of immersion and realism.However,due to the geometric characteristics of the surface,geometric deformation,luminance and color distortion appear in the projected image of the projector,which affects the user's perception of shape and color.The attention of this paper is the large-screen projection display system.It focuses on the display and interaction problems of multi-user co-located collaboration.At the same time,considering the influence of the geometric shape on the superimposed projection of multiple projectors,this paper proposes a geometric correction method based on flat screen in order to eliminate the distortion caused by the superimposed projection of three projectors.Besides,it studies the difference of users' perception of luminance when viewing at the same screen position along with moving,due to the geometric shape of the surface.And then it makes corrections so that users can perceive the same luminance at the fixed position on the screen.Therefore,this paper proposes a multi-user co-located collaborative working environment based on large-screen stereoscopic projection.And with the background of fire drill,we design and implement virtual fire drill system supporting co-located collaboration.At the same time,it studies the geometric correction of multi-projector superimposed projection on the flat screen,which can be applied to complete the pre-correction of multi-view stereoscopic projection display.In addition,it proposes a method of luminance correction based on position of viewer on curved screen.Thus,the viewer in different position can perceive the same luminance when watching the same position on the screen,which enhances the user immersive and realistic.The main contributions of this paper are as follows:1.In this paper,we propose a multi-user co-located collaborative working environment based on large-screen stereoscopic projection.And with the background of fire drill,we design and implement virtual fire drill system supporting co-located collaboration.It allows three users independently control the roaming path and watch the exclusive stereoscopic video.Also,users can hold the simulated firefighting water-gun to carry out the task of collaborative firefighting,which enhances the sense of co-located collaborative experience.At the same time,it allows another remote user to view the real-time state of the scene through two display ways,and adjust the layout of the virtual scene through a variety of interactive ways,which enhances the flexibility of the system.2.In this paper,we propose a method of geometric correction of multi-projector superimposed projection on flat screen.In order to meet better visual effects,for example,in the multi-view stereoscopic projection display system,multiple projectors need to be projected on the same projection screen to realize co-located collaboration.In this paper,a camera-projector system based on square checkerboard template is used to realize the geometric correction of three projectors superimposed on a flat screen.To verify the method,we also developed another application system which called virtual tennis training system.3.This paper proposes a method of luminance correction based on position of viewer on curved screen.In this system,due to the fact that moving users can perceive different luminance on the same screen position,this paper proposes a real-time method of luminance correction.Firstly,select several reference positions in the moving region of the observer,and the appropriate position is selected as benchmark to make sure the target luminance image.Secondly,the corresponding relationship between the corresponding camera image and the projected image pixel is obtained by using the stripe pattern projection,and the measured luminance of every pixel on the projected image is obtained,and compared with the measured brightness of the reference position to determine the correction parameters.Finally,capture the position of the observer in real time and based on the relative position relation with reference position,calculate the real-time luminance correction matrix according to interpolating of the correction matrix at the reference position.So,it adjusts luminance of the projection image by this real-time luminance correction matrix in real time,which makes the moving viewer perceive the same luminance on the same screen position.