as shown in fig1 and designated by the noted general reference ( 10 ), a dental x - ray unit according to the invention is a cephalometric type of device . this device allows cephalometric images or shots to be produced of the head of a human being . the device includes a fixed frame ( 12 ), for example a vertical bracket aligned along the axis z , on which an x - ray unit ( 14 ) is assembled which will now be described . this unit includes a structure ( 16 ) comprising a horizontal beam ( 16 a ) which forms a support that comprises , on one end , a vertical arm ( 16 b ) dropping from the horizontal beam , and , at the opposite remote end , an arm ( 16 c ) that is both horizontal and vertical . a source or generator of x - rays ( 18 ) is fix mounted on the arm ( 16 b ), while an x - ray sensor ( 20 ) is mounted on the remote arm ( 16 c ) which allows the sensor to be positioned at a good distance from the generator , for example at 4 m from it . the generator ( 18 ) and the sensor ( 20 ) are thus placed facing each other and are placed in a fixed geometric relation with respect to each other . the structure ( 16 ) that acts as a support for the generator ( 18 ) and the sensor ( 20 ) constitutes the core of the x - ray unit ( 14 ). the x - ray device ( 10 ) also comprises a positioning device ( 21 ) fixed upon the arm ( 16 c ) in front of the sensor ( 20 ) and which makes it possible to immobilize the head of the patient while the x - ray films are taken , during the operation of the equipment . the head is placed between the generator ( 18 ) and the sensor ( 20 ). more specifically , the device ( 21 ) comprises one part , a vertical descending positioner ( 21 a ) the two branches of which have free ends which are opposite each other , and designed to be positioned in the ears of the patient and , another part , a descending vertical beams ( 21 b ), designed to come into contact with the forehead of the patient in order to prevent back and forth movement of the head . the x - ray generator is equipped with a support ( 22 ), placed against the face of the generator that is opposite the sensor ( 20 ) and within which an opening for the output of x - rays from the generator is arranged . the support is positioned in from of this x - ray output opening and comprises the means of collimation that will be described in reference to fig2 a and 2 b . the collimated x - ray beam has a cone form ( 23 ) that was truncated by its passage through the slot opposite the rectangular section . this beam is positioned on its base ( in a section parallel to the plane of the slot ), along a direction that corresponds to the direction in which the slot is laid out . the sensor ( 20 ) fastened to the arm ( 16 c ) is positioned opposite the generator ( 18 ). it is capable , on the one hand , to receive the x - ray coming from the generator and having irradiated the object ( patient &# 39 ; s head ) placed between the generator and the sensor and , on the other hand , to convert this x - ray which has been attenuated by its passage through the object into an electrical signal representative of an x - ray image of this object . it should be noted that the sensor consists of a pixel matrix which is arranged in correspondence with the beam emitted from the collimation slot . this sensor is , for example , a form of a phosphor scintillator including the active surface pixel matrix and its dimensions are for example , 30 cm ( height )× 30 cm ( width ). the pixel matrix have for example a size of 150 pm and thus form a matrix of 2000 × 2000 pixels . alternately , the sensor is constituted of a pixel matrix with a ccd - type charge - transfer with a size of , for example , 5 cm × 5 cm and which is provided with an optical focus with an optical zoom of 6 . the design includes an electronic control and power supply located behind it . fig2 a and 2 b show the means of collimation ( 30 ) which enables the collimation slot to be geometrically variable . the means for adjustment is set up so that it is able to change , on command , the geometry of the slot and , in particular , its length along two directions which are perpendicular to each other , for example , horizontal and vertical . more specifically , the adjustment means adapted to change the length of the slot along one direction is independent of those adapted to change the length in the other direction , offering thusly greater flexibility in the adjustment . in the example illustrated , the x - ray equipment comprises four independent means of adjustment ( 50 , 52 , 54 , 56 ) to independently change the position of each of the four edges ( 58 , 60 , 62 , 64 ) defining the collimation slot . on the support positioned in front of the output window of fig1 , are successively superimposed the arrangement ( 30 a ) of fig2 a , then that ( 30 b ) of fig2 b . these arrangements are not shown in a superimposed fashion for reasons of clarity . more specifically , the arrangement ( 30 a ) of fig2 a comprises two edges ( 58 , 60 ) of two plates ( 66 . 68 ) placed opposite of each other ( for example rectangular in shape ) and which are each attached respectively to another plate ( 70 , 72 ) positioned perpendicularly . each pair of plates ( 66 , 70 and 68 , 72 ) form in this way an l or an l turned 180 °. the second plate ( 70 , 72 ) of each pair is supplied , on one of its edges which is opposite to the one against which the first plate is fixed , with a longitudinal row of teeth ( 74 , 76 ). a means of moving the edge ( 58 ) ( respectively 60 ) comprising a motor ( 50 ) ( respectively 52 ) equipped with a toothed sprocket ( 78 ) on the output shaft ( respectively 80 ). this sprocket works with the teeth ( 76 ) ( respectively 74 ) to cause the movement of plates ( 72 and 68 ) in the direction d 1 in either direction depending on the direction of rotation of the sprocket . a light guide ( 82 ) ( respectively 84 ) is provided for on the second plate ( 72 ) ( respectively 70 ) and two guide pins ( 86 , 88 ) ( respectively 90 , 92 ) interdependent with the aforementioned support are positioned in this groove to guide the movement longitudinally of the corresponding plate and therefore the corresponding edge . this arrangement allows , by adjusting the space between the opposing edges ( 58 and 60 ) in direction d 1 , adjusting one of the dimensions of the slot and thus its length in one direction . in the identical manner , the arrangement shown in 30 b in fig2 b allows , by adjusting the space between the opposing edges ( 62 and 64 ) in direction d 2 , adjusting one of the dimensions of the slot in the other direction . thus , by bringing the edges ( 62 and 64 ) closer and by moving the edges ( 58 and 60 ) apart of the slot in a lengthwise fashion along direction d 1 . a slot that follows along axis z shown in fig2 c is obtained in this manner . to the contrary , if the edges ( 62 and 64 ) are moved apart and edges ( 58 and 60 ) are brought together , the lengthwise shape of the slot is carried out along direction d 2 . one thus obtains an elongated slot following an axis perpendicular to axis z . we can also adjust the spacing of opposite edges ( 58 , 60 ) and ( 62 , 64 ) in order to obtain a slot in the form of a square or close to such a form . the different elements shown in fig2 b , i . e ., the first and second plates ( 100 , 102 ) ( respectively 104 , 106 ), the grooves ( 108 ) ( respectively 110 ), the motor ( 54 ) ( respectively 56 ) and its toothed sprocket ( 116 ) ( respectively 118 ), as well as the guide pins ( 120 , 122 ) ( respectively 124 , 126 ) in the guide light ( 128 ) ( respectively 130 ) are identical to their corresponding parts in fig2 a but that are only shifted 90 °. the equipment of fig1 also comprises , as shown in fig3 a ( front view of the arm 16 b ), the means of acquisition ( 132 ) of at least one photographic image of the object placed between the x - ray generator and the sensor , i . e ., the patient &# 39 ; s head . in fig3 a , on the lower part of the arm ( 16 b ), the support ( 22 ) placed in front of the generator ( 18 ), is also shown , as well as the means collimation ( 30 ) shown with a dotted line and a collimation slot ( 133 ) placed before the x - ray output slot . the acquisition means ( 132 ) which take , for example , the form of a digital image capture device ( such as a photographic camera fitted with a lens ( 134 )) are positioned as close as possible to the x - ray emission chamber . in the example of fig3 a , the means ( 132 ) are placed above the generator and are shifted laterally with respect to the latter . nevertheless , other layouts are possible , based on the constraints of the environment . these means ( 132 ) are also represented in fig3 b by letter a , while the emission chamber is represented by the letter f . the distance between these means of photographic image acquisition and the generator chamber is small in comparison with the distance l between the chamber and the sensor ( 20 ). as an example , distance d is equal to 5 cm and distance l is equal to 170 mm . thus , by positioning the means of image acquisition as close as possible to the generator chamber , in light of the available space around the means of collimation placed in front of the of x - ray emission slot , we ensure that the angle under which the photographic image ( s ) of the head of the patient are taken is very close to the angle at which the cone x - ray beam is emitted viewed from the sensor . as an example , a shift of less than 5 degrees will give good results . correspondingly , the photographic image of the patient &# 39 ; s head , and the cephalometric image are superimposable . as diagrammatically illustrated in fig3 b , the photographic and cephalometric images are provided respectively by the means of acquisition ( a ) and by the sensor ( 20 ) to a data processing unit ( 136 ) including a means for storing the images . a screen ( 140 ) to display the images acquired individually and superimposed is also connected to the processing unit . the processing unit ( 136 ) and the display means ( 140 ) make part of the x - ray equipment illustrated in fig1 . the processing unit ( 136 ) ensures control of the operation of the equipment ( 10 ). it should be noted that the dimensions of the pixel matrix of the sensor ( 20 ) encompass the dimensions of the x - ray beam projection that irradiated the head ( p ) of the patient . fig4 represents an algorithm outlining the main stages of a method according of the invention and that may be implemented for example , by the equipment ( 10 ). this algorithm is for example , is stored in a memory area of the processing unit ( 136 ) and is run on command . to implement the method according of the invention , the patient should be placed between the x - ray generator and the sensor illustrated in fig1 and that his / her head should be immobilized close to the sensor , in other words , at a good distance from the generator , for example , around 150 cm . when the practitioner starts the equipment , for example from a keyboard and a pointing interface such as a mouse , which are not shown in the figures but that interact with the processing unit ( 136 ) and the screen ( 140 ) of fig3 b , a mode of acquisition of one or more photographic images of the patient &# 39 ; s head ( face view or profile view ) is started during a first stage ( s 1 ). through the second stage ( s 2 ), processing of an image is provided for in order to preserve only the outline of the patient &# 39 ; s head . in fact , these outlines are sufficient to supply the necessary information to the equipment user . this processing is performed by the processing unit ( 136 ) which determines the dimensions of the outline of the head , among other things . the algorithm comprises a third stage ( s 3 ) controlling the means of collimation with respect to the photographic image ( s ) acquired in stage s 1 and , in particular , the dimensions of the patient &# 39 ; s head obtained in stage s 2 . this ensures that the dimensions of the x - ray beam emitted by the chamber ( f ) and collimated by the means of collimation are adjusted to the dimensions of the outline of the patient &# 39 ; s head . thus , the cephalometric image ( s ) that one wishes to carry out using the equipment will be perfectly adapted to the dimensions of the patient &# 39 ; s head . correspondingly , the patient &# 39 ; s head will not be truncated on the image ( s ) and the patient will not receive useless doses of radiation as was the case in the past . from the practical point of view , control of the means of collimation consists of setting the dimensions of the x - ray beam so that it is adapted to the dimensions of the outline of the patient &# 39 ; s head . this setting includes , more in particular , the adjustment of the length of the collimation slot of the means 30 a and 30 b illustrated in fig2 a and 2 b , in a perpendicular direction between them . this setting is controlled by the processing unit ( 136 ) of fig3 b from the dimensions of the outline of the head calculated in stage s 2 . optionally , the algorithm may include a stage s 3 a of display on the screen ( 140 ) of the edges of the collimation slot projected once it is set to the dimensions of the outline of the patient &# 39 ; s head , and that are superimposed upon the outline of the head . this stage of display makes it possible to ensure that the automatic control of the collimator at the patient &# 39 ; s head is correct and may be validated during stage s 3 b . under the hypothesis where the edges of the collimation slot shift , it will not be adapted to the dimensions of the outline of the patient &# 39 ; s head , or perhaps that this shift will be too great or too small with respect to the head , stage s 3 b also provides for the modification of the setting of the collimation slot in order to obtain an adjustment with respect to the outline of the patient &# 39 ; s head . alternatively , stage s 3 b makes it possible to return to the collimation slots pre - programmed by default . stage s 3 b is then followed by the display stage s 3 a so that the user of the device may see the new setting which has been carried out . then , stage s 3 b is performed again so the user can validate the setting . the algorithm then comprises an s 4 stage of the emission of the cone x - ray beam , this beam being collimated by the collimation slot the setting of which was obtained and validated in stage s 3 . thus , the collimated beam is perfectly adapted to the dimensions of the outline of the patient &# 39 ; s head . fig5 a shows the display on the screen of the patient &# 39 ; s head ( p ) and of the cone projection of the edges of the slot when the automatic control according to the invention has not been performed . fig5 b shows the position corresponding to the edges of the slot , of the head , and of the sensor in the layout shown in fig3 b . fig5 c shows the display on the screen of the head ( p ) of the cone projection of the edges of the slot after the automatic control with respect to the photographic image has been previously performed . the means of collimation is represented in fig5 d in an adjusted position obtained through the automatic control . the configuration of the x - ray beam is thus adapted to the patient &# 39 ; s head and the latter receives an optimal dose of radiation . the x - ray projection of the beam which irradiated the head is recorded on the active surface of the sensor ( 20 ). stage s 5 provides for the acquisition of one or more cephalometric images of the patient &# 39 ; s head . this or these images are acquired instantaneously so that the patient has no opportunity to move , thus avoiding distortions . it should be noted that a shot will be taken , for example , in ½ s . in the embodiment described , the photographic and cephalometric images correspond to views of the profile of the patient &# 39 ; s head . in stage s 6 , after acquiring a cephalometric image ( 150 ), the superimposition of the cephalometric image ( 150 ) and the photographic image ( 160 ) is provided for as shown in fig6 . the photographic image ( 160 ) makes the soft tissue of the patient &# 39 ; s head ( nose , lips , chin . . . ) appear , while the cephalometric image ( 150 ) reveals the hard tissue ( bone , teeth . . . ). it should be noted that the superimposition of images is carried out in a particularly reliable and accurate manner due to positioning the means of acquisition of the photographic image at a very short distance from the x - ray emission chamber . it should be noted that superimposing the photographic image onto the cephalometric image needs to apply a geometric conversion based on recognition of the profile and target point in order to get a perfect match . for example , we can use the device &# 39 ; s ( 21 ) patient support arms in fig1 for this purpose . as already mentioned , views from the sensor ( 20 ) illustrated in fig3 b , the two photographic and cephalometric images may be considered to have been taken at the same camera angle . an almost perfect line up between the two images makes it possible to correctly position within the same view ( fig6 ) both the soft tissue and the hard tissue in relation to each other . this superimposition of images is followed by step s 7 of viewing the images thus superimposed which is shown in the aforementioned fig6 . this display takes place , for example , on the screen ( 140 ) of fig3 b . the image thus obtained on the display screen allows the practitioner , for example , an orthodontist , to establish a diagnosis by identifying certain defects needing to be corrected , for example , in the patient &# 39 ; s jaw . he may thus determine the corrections that will be provided to the jaw as well as the appropriate treatment . in the example shown in fig6 , and shown as a magnified view in fig7 , the implantation of the incisor ( 170 ) in the jaw of the patient is such that the latter is particularly inclined from the vertical toward the front of the patient &# 39 ; s mouth , which causes a deformation of the upper lip ( 172 ). in the same way , the tooth ( 174 ) is implanted in the lower jaw in such a way that it is strongly tilted towards the vertical direction in the front of the mouth , which also causes a deformation of the lower lip ( 176 ). on the basis of this report , the practitioner will take measures and possibly scans in order to determine the corrections to be made to the jaw of the patient , as well as the appropriate treatment ( for example , installation of an appliance in order to correct the position of the teeth ( 170 and 174 )). the following stage s 9 makes it possible to display , as a preview , the effects through time of the treatment recommended by the practitioner for the patient &# 39 ; s jaw . the reshaping of the hard tissue in the cephalometric image is obtained by calculation , from the data selected by the practitioner when he determines the corrections to be made and the appropriate treatment , this stage is performed by the processing unit ( 136 ) and corresponds to running an algorithm of a known type and available on the market . for example software marketed by the company practice works would work . the effects thus simulated on the hard tissue of the cephalometric image are illustrated in fig8 . similarly , the manner in which the soft tissues ( the lips in particular ) are distorted correspondingly over time is obtained through a morphing algorithm , of a known type , which is also implemented by the processing unit ( 136 ). the display of the effects thus simulated on the soft tissues of the patient is also illustrated in fig8 corresponding to the superimposition of the two images , after reshaping each of them . it should be noted that the reshaping of the hard tissue in the cephalometric image and the reshaping of the soft tissues of the photographic image are performed independently from each other insofar as , in the image of fig6 , the superimposition of the two images is shown , each of them correspond to a set of separate data and thus it is possible to process them separately . due to the display of this simulation , the practitioner , as well as the patient , are both able to appreciate the impact of the treatment recommended by the practitioner , in a particularly realistic manner .
a dental x - ray unit comprising : an x - ray generator adapted to generate an x - ray beam in the direction of a patient &# 39 ; s head , means of collimation adapted to confer given dimensions to the generated x - ray beam ; a sensor placed facing the generator , receiving the radiologic projection of the collimated beam having irradiated the patient &# 39 ; s head and supplying a cephalometric image of the patient &# 39 ; s head , characterized in that the device includes : the means to acquire at least one photographic image of the patient &# 39 ; s head , the means of automatic control for the means of collimation according to the at least one photographic image so that the dimensions of the collimated x - ray beam are adjusted to the dimensions of the patient &# 39 ; s head .