Patent Publication Number: US-2002012043-A1

Title: Stereoscopic camera fitted with means to facilitate the adjustment of its opto-mechanical parameters

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a stereoscopic camera comprising means to facilitate the adjustment of its optomechanical parameters by an operator.  
       [0003] 2. Description of the Prior Art  
       [0004] A stereoscopic camera simultaneously films two views of the same scene, a left view and a right view, so as to obtain relief images of the scene. To this end, it generally comprises two cameras, called 2D cameras, each delivering images in two dimensions corresponding respectively to a left view and a right view of the scene filmed. The adjustment of a stereoscopic camera consists in adjusting the optomechanical parameters of each of the 2D cameras and the parameters fixing the position of the 2D cameras one with respect to the other. This consists, for example, in adjusting the distance separating the two 2D cameras, the angle between the axes of the two 2D cameras, (commonly called the convergence angle), the focal length and the focus of the two 2D cameras.  
       [0005] The parameters are adjusted one after the other. Adjustment of a parameter consists in altering the value of the parameter in question until obtaining the best result. The adjustment is carried out roughly by the operator depending on his needs. Since the adjustment of each parameter affects the other parameters, the adjustment operation is often very lengthy. In addition, it is often very difficult to go backwards, when, after modifying several parameters, the operator considers that the earlier adjustments would be more suitable.  
       SUMMARY OF THE INVENTION  
       [0006] The aim of the invention is to facilitate the adjustment of the optomechanical parameters of a stereoscopic camera.  
       [0007] To this end, the invention is a stereoscopic camera comprising first and second cameras intended to generate first and second sequences of images, respectively, each image of the said first sequence being associated with an image of the said second sequence, means to display a sequence of stereoscopic images from the said first and second sequences of images, first storage means in order to store respectively at least one image of the said first sequence of images and the associated image of the said second sequence of images, and first selection means placed upstream of the display means in order to selectively supply to the said display means either the said at least one stored image of the said first sequence of images and the associated stored image of the said second sequence of images, or the said first and second sequences of images coming from the said first and second cameras.  
       [0008] With this stereoscopic camera, it is then possible to store at least one stereoscopic image and to be able to display either the current stereoscopic image or the stored stereoscopic image. The aim of this form of embodiment is to facilitate comparison between the two images. In this way, before each operation of adjusting the parameters of the stereoscopic camera, a stereoscopic image is stored in the first and second storage means. Then, after altering at least one of the adjustment parameters, the adjustment thus obtained can be evaluated by comparing the current stereoscopic image with the stored stereoscopic image.  
       [0009] According to a variant, the stereoscopic camera also makes it possible to assess the connection between a current stereoscopic image and a stored stereoscopic image corresponding, for example, to a previous scene. In order to do this, the stereoscopic camera may also comprise first and second inputs in order to receive respectively third and fourth sequences of images coming from a piece of equipment external to the said stereoscopic camera, and second selection means in order to selectively supply to the said first storage means either the said first and second sequences of images coming from the said first and second cameras, or the said third and fourth sequences of images coming from the said external piece of equipment.  
       [0010] In order to facilitate the return to previous adjustments, it is possible to store values representative of the adjustment parameters of the first and second cameras. To this end, the stereoscopic camera may comprise a second storage means.  
     
    
    
     BRIEF DESCRIPTION OF THE SOLE FIGURE  
     [0011] The characteristics of the invention mentioned above will appear clearer on reading the following description, made in relation to the single FIGURE which represents a form of embodiment of a stereoscopic camera according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012] In the single FIGURE, a stereoscopic camera comprising two 2D cameras, referenced  10  and  11 , is considered. They generate respectively first and second digital image sequences in two dimensions. The camera  10  films, for example, a left view of the scene to be filmed and the camera  11 , a right view. Two control signals, denoted C 1  and C 2 , are provided in order to control these two cameras. The control signals are delivered by a control circuit referenced  19 . The stereoscopic camera also comprises two inputs, referenced  12  and  13 , in order to receive respectively the third and fourth sequences of images delivered by an external piece of equipment  30 , for example a video recorder or a hard disk. The images of the said third and fourth sequences relate, for example, to a scene filmed previously by the cameras  10  and  11 , respectively. A selection means, referenced  15 , is used in order to select either the first and second sequences of images, or the third and fourth sequences of images. This selection means is controlled by a control signal denoted C 3  supplied by the control circuit  19 . Normally, the two sequences selected are then transmitted to a stereoscopic display means, referenced  14 , which then generates a sequence of stereoscopic images from these two sequences. The display means  14  is, for example, a pair of glasses with an LCD screen.  
     [0013] According to the preferred embodiment, two storage circuits, denoted  16  and  17 , are provided in order for each one to store at least one digital image coming from the selection means  15 . In the example illustrated, the storage circuit  16  is provided in order to store a digital image of the sequence coming either from the camera  10 , or from the input  12  and the storage circuit  17  is itself placed in order to store either an image of the sequence coming from the camera  11 , or from the input  13 . The memory space needed to store a stereoscopic digital image is about 1.6 Mb for a single definition standard (PAL standard, for example). A control signal C 4  is provided in order to simultaneously control the storage circuits  16  and  17 . Finally, a second selection means  18  is provided in order to select the digital images to supply to the stereoscopic display means  14 . This selection means is controlled by a control signal C 5 . This selection means outputs either the images coming from the storage circuits  16  and  17 , or the images selected by the selection means  15 .  
     [0014] With such a stereoscopic camera, it is thus possible to store images coming either from cameras  10  and  11 , or from the external piece of equipment  30 .  
     [0015] At the time of filming a scene, the operator can display the current scene filmed by the cameras  10  and  11 , and compare it with a scene stored previously in the storage circuits  16  and  17 . The selection means  18  is then used to switch between the two scenes. The operator can then compare the two scenes and act on the controls of the stereoscopic camera in order to adjust the parameters of the camera according to his needs. Note that, in order that the comparison of two images is conclusive, it is necessary that the images compared are of the same quality. It is therefore preferable that the images stored in the circuits  16  and  17  are not compressed.  
     [0016] Of course, the means of the invention can be used in a camera with multiple views comprising n 2D cameras. In this case, the camera then comprises n storage circuits.  
     [0017] Advantageously, the stereoscopic camera also comprises an additional storage circuit  20  in order to store values of control signals C 1  and C 2  of cameras  10  and  11 , the stored signals C 1  and C 2  corresponding to a given adjustment of the stereoscopic camera. Thus, before altering the optomechanical parameters of the camera, the operator stores the control signals corresponding to a starting adjustment. He may then alter the value of these parameters in order to try to improve the adjustment. If he considers that the new adjustment is less beneficial than the starting adjustment, the operator can then recover the stored signals C′ 1  and C′ 2  which correspond to the starting adjustment. Advantageously, the storage circuit  20  stores all the signals sent to the cameras  10  and  11  which may correspond to the values of many parameters such as the distance between the cameras  10  and  11 , the angle between the axes of the cameras  10  and  11 , the focal length, the focus and the gain or the aperture of the iris of cameras  10  and  11 .