The present invention relates to the field of "interactive screens", sometimes referred to as "interactive whiteboards" (TBI) or "interactive digital table" (TNI). An interactive whiteboard typically includes a computer, a video projector (projecting an image provided by the computer), a projection screen (receiving the image from the video projector), and a system allowing the operator to control the position the computer mouse acting directly on the projection screen, it behaves similarly to a touch screen. The operator can thus directly control the computer by acting at the level of the projected image. These devices are widely used in the fields of education where they tend to replace the traditional white or black boards that equip schools. These interactive whiteboards are also used in business, where they help to make presentations more professional, by allowing the user to act directly on the images projected on the screen. Several technologies are conventionally used to transform a projection screen interactive touch screen or pseudo-touch. A first category uses technologies implanted at the level of the projection screen, this being replaced by a real touch screen (of the resistive, electromagnetic, or capacitive type), or else being provided with peripheral sensors (ultrasonic detectors , optical detectors ...). These touch screens can locate the position (X, Y) of the user's finger or a specific pointer that comes into contact with or near the screen. A second category is based on optical technologies using a camera-type position sensor which observes the projection screen, a light spot (generally derived from an infrared light diode fixed on a designation pointer) being displaced by the light. operator on the projection screen, its position on this screen being located by means of the camera, and then transformed by calculation in order to provide the computer with the XY position of the cursor of the computer (cf. FIGS. 1-2) . A projection screen is thus transformed into a computer screen, the operator being able to act directly on the projection screen in order, for example, to move the cursor of the computer on the projected image as he pleases.
These various interactive video projection devices, however, pose a problem of use, related to the need to "calibrate" the device. Indeed, it is necessary that, on the projection screen, the cursor generated by the computer is located exactly at the point pointed by the operator.
For this, it is necessary to pinpoint the position of the projected image with respect to the position sensors connected to the computer. To set the device, it is necessary for the operator to manually point on the screen several cue points generated by the computer and projected by the video projector. In general, nine or more landmarks are distributed over the surface of the image (see Figures 4). In the case where a detection technology related to the screen is used, this calibration operation must be renewed as soon as the projector moves very little compared to the screen (see FIGS. 6A-6B). In the case where an optical technology is used with a camera that is observing the projection screen, the calibration defect is less important if the projector is moved relative to the screen, provided that the camera is attached to the camera. projector. But, in this case, a calibration defect remains, the camera and the projector not seeing the projection screen at the same angle (parallax). This parallax is proportional to the angle formed by the camera and the projector when they are aimed at the same point of the screen. Thus, for a projector of very short focal length secured to a projection screen, it is necessary to calibrate the device again when the projector is subjected to a small displacement. On the other hand, and irrespective of the focal length of the headlamp, it is hitherto impossible to use a light mobile device composed solely of a mechanically secured projector and a camera of observation, capable of be placed in front of any projection screen, without necessarily performing a calibration not only at the beginning of each sequence of use of the device but also as soon as it is changed. A mobile and lightweight TNI type device, usable in front of any screen, not requiring recalibration, would be highly appreciated by the users and would allow the market of these devices to be rapidly extended. Remedies have been proposed to solve this problem by simplifying the process of calibrating TNIs using camera sensing technology. In particular, one of the possible solutions is to ensure that the camera automatically detects the position of a predefined set of cue points generated by the computer and projected by the video projector, during the calibration phase. The use of this method, however, faces several difficulties making it difficult to implement. First, the automatic detection by the camera of landmarks generated the video projector is only possible when the video projector and the detection camera operate in the spectral range of the visible. But in this case, the detection of landmarks by the camera may be disturbed by the stray light likely to hit the screen. In order to avoid the problem of stray light, some video-projection devices use a camera observing the screen in the infrared spectrum which makes it possible to clearly distinguish the spot emitted by an infrared pointer operated by the user and without being disturbed by the image provided by the video projector in the visible spectrum. However, in this case, the infrared camera does not automatically detect landmarks in the visible image generated by the video projector. The user must then repoint the reference points at each calibration procedure. In this case, the calibration can not be automatic. There is therefore no video projection device comprising robust automatic calibration means vis-à-vis the movements of the video-projection device with respect to the screen as well as vis-à-vis the stray light . The object of the present invention is to overcome these drawbacks and more particularly concerns an autocalibrated interactive video projection device comprising a video projector comprising a projection optical system having a projection pupil, said video projector being able to transmit a illumination beam according to an illumination optical path for forming an image on a projection screen and a video detection system comprising a detector and an optical detection system having a detection pupil, said video detection system being adapted to receive a detection beam according to an optical detection path from the projection screen and to detect an image of said projection screen. According to the invention, said interactive video-projection device comprises optical separation means disposed at an intersection between said optical illumination path and said optical detection path, said separation optical means being capable of being oriented from whereby said optical illumination and detection paths are superimposed between said optical separation means and the projection screen. According to a preferred embodiment of the invention, the video projector and the video-detection system are arranged in such a way that the projection pupil and the detection pupil are optically conjugated through said optical separation means. According to a preferred embodiment, the interactive video projection device comprises an optical pointer capable of forming on the projection screen a light spot in a spectral emission band located in the infrared or the near infra-red, said video-detection system being able to detect a signal in said emission spectral band of the optical pointer, said video projector being able to generate an image in the spectral range of the visible, and said optical separation means comprise a dichroic filter capable of spatially separating a beam in the visible spectral range and a beam in said spectral transmission band of the pointer. According to a first embodiment of the invention, said dichroic filter is transparent in the visible range and reflecting in said spectral transmission band of the pointer. According to a second embodiment of the invention, said dichroic filter is reflective in the visible and transparent domain in said spectral emission band of the pointer. According to various particular aspects of the invention: said optical separation means comprise a separating plate or a splitter cube; said optical separation means comprise a plate with plane and parallel faces, said plate being inclined with respect to the optical axis of the video projector and with respect to the optical axis of the video-detection system; said optical separation means comprise a substrate having at least one curved surface so as to correct the optical aberrations of the image on the projection screen and / or on the detector; Said device further comprises means for attenuating the stray light produced by the video projector and directed by said separation optics towards the video-detection system; said device comprises means for fixing the video projector, detection means and separation means in solidarity with each other; said device comprises displacement means able to position said interactive video-projection device facing a surface or a projection screen. The present invention also relates to the features which will emerge in the course of the description which follows and which will have to be considered individually or in all their technically possible combinations. This description is given by way of nonlimiting example and will better understand how the invention can be made with reference to the accompanying drawings in which: - Figure 1 shows schematically a video projector and a camera attached to the projector observing the screen projection according to the prior art; FIG. 2 illustrates the various elements and the operation of an interactive whiteboard with optical pointer according to the prior art; FIG. 3 illustrates the appearance of the projected image seen by the observation camera according to the prior art; FIG. 4 illustrates the position of the reference points in the projected image, making it possible to calibrate the system according to the prior art; FIG. 5 illustrates the image of these landmarks seen by the observation camera according to the prior art; FIGS. 6A and 6B illustrate the modification of the image of the reference points seen by the camera following a variation of the relative positions of the camera projector assembly with respect to the projection screen in a device of the art prior; FIG. 7 represents the optical diagram of a device according to the prior art, and illustrates the calibration problems that occur when the position of the projection screen varies with respect to the projector camera assembly; FIG. 8 illustrates a first embodiment of the invention, the camera observing the screen after reflection on a separating mirror disposed in the field of the video projector; FIG. 9 represents the relative position of the optical elements seen in the optical space of the projection screen, according to the first embodiment of the invention; FIG. 10 represents an assembly that solidifies the various elements of the device according to the first embodiment of the invention; FIG. 11 illustrates a variant of a mobile device made using the invention; FIG. 12 illustrates a second embodiment of the invention, the camera observing the screen through a splitter mirror which reflects the light beam coming from the video projector. Figures 1 to 7 commented below illustrate the principle of operation of TNI-type devices based on observation camera according to the prior art. FIG. 1 schematically shows a TNI according to a conventional configuration based on a video projector (1) which projects an image (3) onto a projection screen (14) and a detection camera (2) which observes the projection screen (14). The camera (2) is generally mounted integrally with the projector (1). The projector (1) camera assembly (2) is located at the distance (d) of the screen (14). The camera (2) observes the image (3). There is a parallax gap (angle a) between the objectives of the projector (1) and the camera (2). Figure 2 shows the various components of an interactive display based on optical technology using a detection camera. The image to be projected is generated by a computer (35), this image being transmitted to the projector (1). This projector generates an image (3) on a projection screen (14), this image including a cursor (13). A camera (2) observes a light spot emitted by a pointer (18), the field of view of this camera being larger than the surface of the projected image (3). The image (15) captured by the camera (2) includes the image (25) of the light spot emitted by the pointer (18). This image (15) is processed by a subset (30) which transforms the coordinates (Xcam Ycam) of the point (25) in the plane of the camera into coordinates (Xpc Ypc) in the plane of the screen memory. from the computer. The computer can then position the cursor so that the image of the cursor (13) is located at the end of the pointer (18).
Figure 3 shows the image plane (15) of the camera (2) with the area of the projected image (16) acquired by the camera (2). FIG. 4 represents the image (3) projected by the projector (1) on the screen (14), with 9 markers (17) of graphic type which are successively pointed by the operator using the pointer (18) to to calibrate the device. FIG. 5 shows the image plane (15) of the camera (2) with the detection zone (16) including the projected image (3) by the projector (1) on the screen (14) with the images (19). ) of the nine projected landmarks (17). Fig. 6A is similar to Fig. 5. Fig. 6B shows the picture plane of the camera after a change in the relative position of the screen with respect to the projector-camera assembly. It is observed that the position of the image (16) has moved with respect to the image plane (15) of the camera (2), as a result of the parallax between the projector (1) and the camera (2). It is then necessary to calibrate the device again, identically to the method of FIG. 4, to obtain again the superposition on the projection screen (14) of the image of the cursor (13) generated by the computer and the end of the pointer (18). FIG. 7 represents the optical diagram of a device according to the prior art. The observation camera is provided with a lens (6) having a pupil (8) and a focal plane (26). The projector is provided with a lens (5) with a pupil (7) and a focal plane (28). When the device is properly calibrated, the projection screen (14) is located at a distance (d) from the projector. If the stylus (18) is pointed at the point (29) of the projected image (3), the focal plane (26) of the camera will receive a luminous point (25), and the system will generate a slider (27) in the focal plane (28) of the projector, so that the image (30) of this cursor exactly points on the screen (14) the point (29) of the projected image (3). Suppose that the position of the screen (14) is varied by moving it back to the distance (d ') of the projector, and that the stylus (18) is pointed at the point (31) of the screen. projection, this point (31) having an image located at the same location on the focal plane (26) of the camera as that of the point (29) pointed earlier. The system will again generate a cursor (27) on the focal plane (28) at the same location as before. But the image of the cursor will now point the point (32) in the projection plane to the distance of, and not the point (31) initial. The distance between the points (31) and (32) illustrates the calibration defect induced by the modification of the relative position between the projection screen and the video projector and camera assembly. In order to be able to use the device of FIG. 7 interactively, it is therefore necessary to recalibrate the device for the new relative position of the screen with respect to the video projection and detection assembly. We will now describe a device which makes it possible to solve the problem of recalibration. A statement forming part of the invention is that ideally, so that the points (32) and (31) remain merged regardless of the distance (d ') and whatever the position pointed by the stylet (18), it The pupils (8) is and (7) objectives (6) and (5) must be combined in the screen space. In the previous devices, this condition is not physically possible to achieve for reasons of space. The implementation of this condition, however, is a particular aspect of the present invention. The interactive video projection device of the invention comprises an optical component which optically couples the exit pupils of the video detection camera and the video projector. This conjugation makes it possible to confuse in the optical space of the screen, the positions of the objective of the video projector and the objective of the camera, thus eliminating the effect of parallax between these two subsets. This optical device also directs the luminous flux coming from the video projector in the visible range towards the projection screen, and directs the luminous flux, coming from the spot actuated by the operator and diffused by the projection screen. towards the camera. This optical device fulfills both the superposition function of the optical paths (towards the screen) and the separation of the optical paths respectively towards the video projector and towards the camera. More precisely, the optical device makes it possible to superimpose the optical paths of the video projector and the video-detection system between the screen and the optical device. The optical separation device is positioned at the intersection of the projection field of the video projector and the field of view of the camera. The pupil of the objective (5) which emits the light and the objective (6) which receives it being optically confused, a point emitting light in the focal plane of the projector will have an image always situated at the same place in the focal plane of the camera irrespective of the position of the projection screen (14), provided that the camera observes a field at least equal to the size of the projected image, and that the objectives of the video projector and the camera are in focus at the same distance. Preferably, the interactive video-projection device comprises a video projector capable of receiving a video image from a computer and projecting an image on a screen, a light spot generator (for example in the infra-red field) actuated by the operator and a video detection system attached to the video projector. The video detection system includes a camera capable of acquiring an image of the screen and the light spot. The video detection system is coupled to a processing system capable of analyzing the video detection image and interacting on the computer. In addition, the interactive video projection device comprises an optical device for correcting the parallax defect between the video projector and the camera. A video projector having a source of diode type or laser diode of small extent and high brightness is preferably used. Such a video projector makes it possible to form a sharp image on a very large depth of field. As a result, the image formed on the screen remains clear, even if the distance between the video projector and the screen varies. It is therefore not necessary to redefine the objective of the video projector after a variation in distance between the video projector and the screen. Furthermore, the camera (2) is arranged to be able to observe a field greater than or equal to the size of the projected image (3). The objective (6) of the camera (2) is preferably chosen so as not to require refocusing of the image on the detector when the distance between the screen and the detector varies. The video projector and the detection system are preferably manufactured so that both lenses can form sharp images of and on the projection screen regardless of the distance between the screen and the display device. Interactive video projection without the need to focus lenses. Several embodiments can be implemented to implement this device depending on the type of objective of the video projector, the lens of the camera, the optical device conjugating the pupils of these two lenses, and according to the arrangement. relative of these different components. Figures 8 to 12 commented below illustrate particular embodiments of the invention. In a first embodiment, the luminous flux from the projector is directed directly to the projection screen, the camera observing the screen after reflection by a separating optical device located in the projection field of the video projector. FIG. 8 represents a first embodiment of the invention, the camera (2) observing the zone of the screen containing the projected image (3) after reflection on a separating mirror (4) arranged in the field of the video projector (1). In FIG. 8, the separating mirror (4) is plane and the pupils of the lenses (5) and (6) are situated symmetrically with respect to this mirror (4). On the other side of the mirror (4) relative to the camera (2) is placed a black screen (9) absorbing stray light (10) from the projector (1) possibly reflected by the mirror (4). The axis of the camera (2) aims at the center of the projected image (3) after reflection on the mirror (4). The separating mirror is processed in such a way that it transmits the visible spectrum emitted (luminous flux emitted by the video projector) and that it reflects at least partially the infrared spectrum corresponding to the diode fixed on the end of the stylus (18). ) that the manipulator uses to designate points on the projector screen. Preferably, the separator mirror (4) reflects at least 5% of the infrared spectrum in the transmission band of the optical pointer (18). Fig. 9 shows the optical scheme of this first embodiment in the optical space of the projection screen (14). The pupil (7) is that of the objective (5) of the projector (1). The pupil (8) is that of the lens (6) of the camera (2). The center (11) of the pupil (7) of the objective (5) of the video projector (1) is symmetrical with the center (12) of the pupil (8) of the lens (6) of the camera ( 2) relative to the plane of the separating mirror (4). It may be noted that the separating mirror (4) is preferentially anti-reflective on the side facing the video projector and that the overall transmission coefficient of the separating mirror (4) in the visible range must be as close to 1 as possible. It may also be noted that this separator mirror (4) is preferably made using a sufficiently thin support, in order to limit the optical aberrations induced on the projected image (3). The surface (9) is matt black in order to better absorb the stray light coming from the projector and reflected by the mirror (4). It can be seen that under these conditions, and whatever the relative position of the camera projector assembly (1 and 2) with respect to the screen (14), the light rays can be confused in the optical space of the screen. passing through the center (11) of the pupil (7) of the objective (5) of the projector (1) with the light rays passing through the center (12) of the pupil (8) of the lens (6) of the camera (2). The relative positions of the objects projected on the screen by the projector (1) and their image captured by the camera (2) io will then remain fixed, regardless of the position of the screen (14). This property makes it unnecessary to calibrate the device again when the screen (14) is moved relative to the camera projector assembly (1 and 2). Figure 10 schematically shows a mechanical device for securing the projector (1), the camera (2) and the separating mirror is (4) with a plate (33). By acting on the wheel (34), it is possible to vary the height of the projected image without disturbing the calibration. Figure 11 schematically shows a Mobile Interactive Digital Table, mounted on wheels (20), being positionable in front of any projection screen without having to calibrate the device. In a second embodiment, the camera observes the screen directly through a splitter optical device that reflects the luminous flux from the projector. Figure 12 schematically shows an interactive video projection device according to a second embodiment of the invention. The Interactive Digital Table comprises an ultra-short-throw projector (21) provided with a splitter mirror (23) integrally mounted with an observation camera (2). The fixing bracket (24) of the projector-camera assembly is fixed for example to a wall which also supports the projection screen (14). Here the separating mirror (23) reflects on the front face the visible spectrum and at least partially transmits the infrared spectrum. The camera (2) is also positioned in such a way that the pupil of its lens is located at the same place as the pupil of the objective of the projector (21) in the optical space of the projected image (3). Generally, this type of ultra-short-throw projector (21) is used with a mirror (23) which is not flat but aspherical, of generally complex shape, and provided with a reflective treatment on the front face, which contributes to the dioptric function of the projector. In the context of the invention, the shape of the front face of this mirror remains unchanged from the state of the art, the rear face of the mirror being substantially parallel to the front face, in order to limit the optical aberrations for the observation camera (2). According to various variants, the optical separator system can be achieved by using a mirror, or a cube or equivalent system for superimposing the pupils of the objectives of the projector and the camera, the camera observing the entire projected image. The choice between these two embodiments and the configuration of the optical separation device depends essentially on the type of video projector used. It will be preferred to use the first embodiment, with a separator device composed of a flat separating plate, transmitting the visible radiation and at least partially reflecting the infra red radiation ("hot" mirror) in the case where a video projector is used. long focal length (a distance of about 1.5 m or more separating the long throw projector from the screen, for a projected image of 1 m base). It will be preferred to use the second embodiment when employing an ultra short-throw video projector (a distance of about 0.3 m or less between the ultra-short throw projector and the screen for a projected image of 1 m base), with an aspherical mirror reflecting visible radiation and at least partially transmitting infrared radiation (mirror "cold"). The invention makes it possible to produce interactive devices whose calibration does not vary as a function of the relative position of the projector and the projection screen. The invention makes it possible to improve the interactive projection devices using an optical detection camera, eliminating the need to calibrate the device when the video projector moves relative to the screen. It is thus possible to produce foolproof and mobile projectors. By construction, the device of the invention remains calibrated. In addition, the device of the invention makes it possible to eliminate the parallax between the video projector and the camera, this paralaxe being responsible for deformations in the detected images.
The device of the invention is very easy to use, compatible with projectors already used for interactive screens, and induces a limited cost over previous devices. The invention makes it possible to have an optical interactive projection device that can be mobile and does not require calibration when it is moved relative to the projection screen. The video projector is advantageously based on a system that does not require focusing operation during a variation in distance between the screen and the video projector. The device of the invention is also robust vis-à-vis the stray light from not only the video projector but also the environment of use. 5 i0