Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
  • H04N13/30—Image reproducers
  • H04N13/363—Image reproducers using image projection screens
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
  • H04N13/30—Image reproducers
  • H04N13/327—Calibration thereof
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/12—Picture reproducers
  • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
  • H04N9/3141—Constructional details thereof
  • H04N9/3147—Multi-projection systems

Definitions

• the present invention relates to a technique of aligning a second projection means on a first projection means.
• Such an alignment is implemented to increase the level of light on large screens, or for a simultaneous stereoscopic projection "left eye-right eye” in which the images for each eye are assigned to different projectors.
• Alignment can also be used for correct overlay of red, green, and blue images for a given projector.
• the high-end three-component electronic projectors allow adjustment of the superposition of the three primary (or convergence) by adjusting the orientation of the three imaging systems.
• the collimation of the three primaries also requires the alignment of the three projected primary images. This adjustment is not motorized in the current state of the art.
• Aligning two projectors is usually a tedious task that requires the assistance of two people: the projectionist and a person in the room near the screen. This adjustment is currently done manually, as follows: the projectionist projects the same pattern on the two projectors, while the person in the room observes the gap on the screen between the two projected images, and communicates by signs the correction to bring. The projectionist uses this information to modify the position of the second projector (the first one used as a position reference), until an alignment appears satisfactory to the observer. If the projector has a remote control that includes moving the projected image horizontally and vertically, the projectionist can be placed near the screen and manually control the operation.
• identifying centers of respective circles projections and transmit control commands of the second projection means to align the center of the circle of the image projected by the second means with the center of the circle of the image projected by the first means.
• the method comprises a determination of respective positions of said centers of circles, comprising, for each circle, the steps implemented by the analysis device:
• the circle of the projected images is specifically black (or at least dark) on a uniform colored background, and a minimum in light intensity is sought in each of the aforementioned profiles.
• the aforementioned uniform colored background may be of green primary color, because this color, which has the greatest brightness, serves as a geometric reference in the trichromatic systems.
• the two images of the two projection means can be projected simultaneously, in particular if the two circles of the respective projections can be identified by, for example, different colors.
• the method alternatively, rather comprises the steps:
• extremums in each zone gave much more precise results.
• One possible embodiment for this purpose consists in obtaining the luminous intensity profiles respectively by Radon projections, followed for example by Lagrange interpolations to obtain an extremum point for each profile (as detailed below with reference to FIG. 5).
• the zones of the first pair are situated at the left and right ends of the circle and the sum divided by two of the abscissas of the respective precise points of the zones of the first pair gives the abscissa of the center of the circle in a chosen reference point, and
• the zones of the second pair are situated at the lower and upper ends of the circle and the sum divided by two of the ordinates of the respective specific points of the zones of the second pair gives the ordinate of the center of the circle in the chosen reference point.
• the reference chosen is the same for the two images respectively projected by the first and the second projection means (for example a pixel (0,0) of lower left edge of the captured image which encompasses the entire projected pattern, the means of shooting remaining fixed between the two acquisitions of projected images).
• the luminous intensities of pixels of each zone are averaged to construct the profile associated with the zone.
• the luminous intensities of pixels of each zone are summed to build the profile associated with the zone (without necessarily having to calculate an average of these intensities, in the case of rectangular areas).
• the first and second projection means may be two projectors in stereoscopic cinematography.
• the method of the invention may be implemented for collimation of projections by said first and second projection means.
• the method may comprise the alignment of at least a third projection means (or more) on the first and / or second projection means, with a reiteration of the steps of the method to do this.
• four projection means used for stereoscopic cinematography can be considered, with two projection means aligned with each other for each eye, and the pairs of projection means for each eye. being further aligned with each other for stereoscopic vision.
• the present invention also relates to a system for adjusting a second projection means to be aligned on a first projection means, comprising, for the implementation of the method according to the invention:
• an analyzing device connected to the sensor for determining the position of the center of the circle in the projected image and comparing this position with a determined circle position on an image projected by the first projection means, for delivering adjustment controls in alignment second means according to said comparison.
• the present invention also relates to the analysis device executing the precise determination of the center of the circle according to the invention.
• the present invention also relates to a computer program (and / or a readable memory medium comprising the instruction data of such a program), this program including in particular instructions for the implementation of the method, when this program is executed by a processor (for example from the above-mentioned analysis device).
• a processor for example from the above-mentioned analysis device.
• FIG. 1 illustrates an exemplary system according to the invention capable of aligning two projectors PI and P2;
• FIG. 2 illustrates the main steps of an exemplary method within the meaning of the invention
• Fig. 3 illustrates an example of a projected pattern having a circle
• FIG. 4 illustrates the aforementioned areas each including an arc
• FIG. 5 illustrates the light intensity profiles associated with the zones and each having an extremum.
• a specific projection screen is used, associated with an elaborate procedure for very accurately locating the geometric alignment of the projected image.
• the registration element (a circle according to a preferred option), constituting the projected image, is associated with a determined position in a digital image taken by a sensor, with a precision better than the tenth of a pixel of this sensor, and thanks to the procedure elaborated above.
• the obtaining of precise positions of the projection makes it possible to automatically control each additional projector to make the projected images coincide as well as possible.
• a device MIR for projecting projection control the projectors, and in particular the first projector PI for projecting onto a ECR screen a specific reference pattern, for example a black circle on a green background.
• the MIR device activates the reference projector, or "first projector" PI, the other projectors being extinguished.
• the sensor CAP acquires an image corresponding to that of FIG. 3 and transmits the digital data of the projected image (arrow DAT) to a processor PROC of a device DIS within the meaning of the invention which calculates the precise position of the center of the circle. This position is then stored in the MEM memory of the device.
• the CAP sensor is for example a digital camera, a digital camera or other.
• the projector PI (shown in dotted lines) is off, and the MIR control device controls the additional projector P2 to align ("second projector" above shown in solid lines) to project on the ECR screen the same image (circle black on a green background).
• the projectors are not aligned at the beginning, the new position of the center of the circle is different. These differences are received and interpreted by the processor PROC of the analysis device DIS to deliver, for example in the form of signals addressed to a processing unit of the projector P2, control commands moving the projector P2 (arrow COM).
• Step by step it is done again the acquisition of a translated image as well as the geometric calculation of position of the center of the circle until that the distance between the obtained position and the reference position of the center of the circle of the image projected by the PI reference projector coincide at a tolerance threshold close (typically one pixel).
• the calculation of the circle centers then gives the geometric positions of the respective centers of the three circles.
• the green used as a reference because it has the greatest brightness, the operator is shown a square representing the center of the green circle and red and blue squares representing the respective positions of the centers of the red and blue circles on a considerably enlarged scale .
• the operator makes the necessary adjustments to match the three primary images. More sophisticated imaging system settings can be proposed to approach good convergence at several locations in the image. For example, it is possible to project circles in the center and at the four corners of the screen, and possibly at the position of the subtitles. that is, in the middle of the bottom of the screen.
• the method within the meaning of the invention then proposes a calculation and a display of the best conditions for each of the five positions.
• the sensor CAP can be rotated little perceptible, in which case a horizontal and a vertical image do not translate obliques detected on the sensor,
• the shape of the circle has been retained because it can be detected very robustly, especially in image processing by a Hough transform.
• step S2 after acquisition of the image by the sensor CAP in step S1, a rough processing of identification of the circle is implemented in step S2. Missing points, because of value too close to the light background, do not disturb the detection of the form. The approximate knowledge of the radius of the circle further facilitates its detection.
• step S2 after Hough transform, a first position (xa, ya) of the center of the circle whose accuracy depends on the parameters of the algorithm but first of all on the pixel size of the sensor is then obtained. This position is retained as an integer address of one pixel on the sensor. The accuracy of the detection is then improved as follows.
• zones Z1, Z2, Z3 and Z4 are deduced at step S3, corresponding to the (almost) vertical left and right zones of the circle, as well as to the (quasi) horizontal zones of the top and the bottom, as represented in FIG. 4.
• the luminous intensity values in each zone are accumulated, by vertical projection for ZI and Z2, or horizontal for Z3 and Z4 (Radon transform), in step S4.
• a profile modeled by a curve (in dashed lines in FIG. 5) obtained by Lagrange interpolation in particular at the values of the pixels having the lowest intensity sums (dotted line curves of FIG. 5) is obtained.
• the sum SL of the light intensities / pixels along a column is calculated for the left zone ZI of length L (large dimension of the rectangle formed by zone ZI), and for each column until reaching the width of the zone ZI (small dimension of the rectangle ZI), along the axis x of FIG.
• x corresponds to a pixel abscissa and takes an integer value (like pixel addresses in general).
• step S5 the position of the lowest point of each dotted line curve of FIG. 5, rounded to the nearest tenth of a pixel, is sought.
• the middle of the two optimum points for the right and left areas gives a more accurate value xc of the abscissa of the center of the circle.
• the medium is used because each side calculated on an arc area does not give a precise position of the edge of the circle.
• the term "circle” used above generally encompasses any concave closed curve whose center is to be determined. It may be a square (as indicated above, even if the measurement accuracy of the center is less efficient), or an ellipse or an oval whose center is to be determined.
• zones have been described above as a possible embodiment. Nevertheless, the zones may have other shapes (for example elliptical or circular), in which case it is appropriate to average (and not just sum) the luminous intensities of pixels in directions perpendicular to the radial direction (because the number of pixels varies from one average calculation to another).
• the method being characterized in that it comprises a determination of respective positions of said centers of circles, comprising, for each circle, the steps implemented by the analysis device:

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Projection Apparatus (AREA)
• Transforming Electric Information Into Light Information (AREA)
• Video Image Reproduction Devices For Color Tv Systems (AREA)
• Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
• Controls And Circuits For Display Device (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=50336344

Family Applications (1)

Country Status (7)

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• 2014
  • 2014-02-13 WO PCT/FR2014/050294 patent/WO2015121542A1/fr active Application Filing
  • 2014-02-13 EP EP14711288.2A patent/EP3105925A1/fr not_active Withdrawn
  • 2014-02-13 KR KR1020167024762A patent/KR20160145545A/ko not_active Application Discontinuation
  • 2014-02-13 US US15/118,150 patent/US9992486B2/en not_active Expired - Fee Related
  • 2014-02-13 CN CN201480076119.5A patent/CN106416242A/zh active Pending
  • 2014-02-13 CA CA2939474A patent/CA2939474A1/fr not_active Abandoned
  • 2014-02-13 JP JP2016551814A patent/JP2017511038A/ja active Pending

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