JP2018151457A - Projector and calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely perform automatic calibration regardless of the brightness of external light and entering of illumination light.SOLUTION: A projector includes a projection lens including a zoom lens and projecting an image onto a projection surface and an image sensor capturing the image on the projection surface. When performing calibration for projecting a test pattern including a plurality of calibration points, to establish a correlation between a captured image captured by the image sensor and the image on the projection surface, the test pattern is projected by using the position of the zoom lens as a second position to which a smaller image is projected with respect to a first position where actual projection is performed and the coordinate values of the respective calibration points acquired from the image obtained by the image sensor at that time are corrected from the first position and the second position.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an electronic blackboard system, and more particularly to a projector for an electronic blackboard and a calibration method performed by the projector.

  As an electronic blackboard system for a projector as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-126225), the current mainstream uses an electronic pen having a pen tip that emits infrared light when pressed down. In this method, light is acquired by an infrared imaging camera such as a CMOS image sensor, and the pressed coordinates are determined.

  FIG. 1A is a perspective view showing an appearance of a projector used in the electronic blackboard system. The projector 101 is provided with a projection lens 102 and a camera unit 103 that performs infrared imaging. FIG. 1B is a diagram showing a projection range 105 in which an image is projected by the projection lens 102 on the screen 104 and an imaging range 106 by the camera unit 103. As shown in FIG. 1B, the imaging range 106 is set wider than the projection range 105.

  It is necessary to establish a correlation between the image projected from the projection lens 202 and the image captured by the camera unit 103, and it is necessary to perform calibration.

  Calibration is often performed by displaying a test pattern on a projection plane with a projector and acquiring the position of the test pattern on the projection plane with a camera unit.

  FIG. 2 is a diagram showing a test pattern for calibration displayed by the projector 101 shown in FIG. The test pattern 201 is projected by the projection lens 102 in the camera capture area 202 by the camera unit 103. The camera capture area 202 corresponds to the imaging range 106, and the test pattern 201 corresponds to the projection range 105. The test pattern 201 is also an area where an electronic pen (not shown) is used when operating as an electronic blackboard system.

  As the test pattern 201, the test pattern 201 of only the point A is displayed and photographed by the camera unit 103, the display position is acquired, and then the test pattern 201 of only the point B is displayed and photographed by the camera unit 103. Calibration is performed by establishing the correlation between the projection screen and the imaging screen by capturing the display position of each point with the camera unit 103, such as acquiring the display position, and acquiring the display position.

  In automatic calibration without human intervention, the test pattern projected from the projection lens 102 of the projector 101 is captured by the camera unit 103, and thus visible light is processed. On the other hand, since manual calibration is performed by pressing each point with the pen using an electronic pen, infrared light is processed. Moreover, since the electronic pen is used when the electronic blackboard function is used, infrared light is processed.

JP 2011-126225 A

  Since automatic calibration captures visible light, it causes a problem of operation failure depending on the implementation environment. Specifically, the contrast of the test pattern captured by the camera is reduced due to the influence of external light, and the test pattern cannot be identified.

  When the outside light is bright, the screen 104 itself shown in FIG. 1 becomes bright, the contrast of the test pattern 201 with respect to the camera capture area 202 shown in FIG. 2 is lowered, and the test pattern 201 is difficult to identify.

  Another problem is that other light sources that enter the camera capture area 201 cannot be identified from the test pattern 201.

  As shown in FIG. 3, when illumination light 301 such as a fluorescent lamp provided around or reflected light 302 reflected by the screen 104 enters, it becomes impossible to distinguish between the light and the test pattern 102, resulting in malfunction. Occur.

  In order to process infrared light during manual calibration or when using the electronic pen function, a visible light cut filter, etc. is installed in front of the lens of the camera unit 103 to eliminate the influence of external light and other light sources. However, when automatic calibration is performed, visible light is processed, so that the influence cannot be excluded.

By increasing the brightness of the test pattern projected from the projector, the contrast to external light or an external light source can be increased and the test pattern can be identified reliably, but the test pattern is simply increased by increasing the light output of the projection light from the projector. If the brightness of the device is increased, there is a concern that the size of the device may increase, the power consumption may increase, or the like.

The present invention provides a projector for an electronic blackboard system capable of reliably performing automatic calibration regardless of the brightness of external light or the entry of illumination light without causing an increase in the size of the apparatus or an increase in power consumption. A calibration method performed by a projector is realized.

A projector according to the present invention is a projector constituting an electronic blackboard system,
A projection lens that includes a zoom lens and projects an image on a projection surface;
A zoom mechanism for changing the position of the zoom lens;
An image sensor that captures the image on the projection surface;
A control unit that controls the position of the zoom lens via the zoom mechanism,
The control unit is configured to perform zooming during calibration for projecting a test pattern including a plurality of calibration points in order to establish a correlation between a captured image captured by the image sensor and the image on the projection plane. The test pattern is projected as a second position where a smaller image is projected with respect to the first position where the actual projection is performed via the mechanism, and at that time, by the image sensor The coordinate value of each calibration point acquired from the obtained image is corrected from the first position and the second position.

A calibration method according to the present invention includes a zoom lens, and a projection lens that projects an image on a projection surface;
A zoom mechanism for changing the position of the zoom lens;
A calibration method performed by a projector constituting an electronic blackboard system having an image sensor that captures the image on the projection plane,
In order to establish a correlation between the captured image captured by the image sensor and the image on the projection plane, the calibration mechanism that projects a test pattern including a plurality of calibration points is used to perform the above-described zoom mechanism. The test pattern is projected with the position of the zoom lens as a second position where a smaller image is projected relative to the first position where actual projection is performed, and from the image obtained by the image sensor at that time The coordinate value of each acquired calibration point is corrected from the first position and the second position.

In the present invention configured as described above, automatic calibration is reliably performed regardless of the brightness of external light or the entrance of illumination light.

(A) is a perspective view showing an external appearance of a projector used in the electronic blackboard system, and (b) is a diagram showing a projection range 105 in which an image is projected by the projection lens 102 on the screen 104 and an imaging range 106 by the camera unit 103. It is. It is a figure which shows the test pattern for a calibration displayed with the projector 101 shown in FIG. It is a figure which shows the disturbance light which entered into the camera taking-in area. It is a figure which shows the projection area at the time of the automatic calibration performed by this invention. It is a figure which shows the projection area at the time of the automatic calibration performed by this invention. It is a block diagram which shows the principal part structure of one Embodiment of the projector by this invention. It is a flowchart which shows the control operation of the control part 604 at the time of performing automatic calibration in embodiment of this invention. It is a figure for demonstrating the coordinate correction method performed by step S710 of FIG.

  Next, embodiments of the present invention will be described with reference to the drawings. 4 and 5 are diagrams showing a projection area at the time of automatic calibration performed in the present invention, and FIG. 6 is a block diagram showing a main configuration of an embodiment of the projector according to the present invention.

  In the present invention, when the test pattern is projected and captured by the camera unit, the test pattern is brightened by changing the zoom ratio of the projection lens and projecting the test pattern to make the test pattern brighter and contrast with the external light. To increase. For example, the screen brightness of the test pattern 401 having a zoom ratio of 1/2 as shown in FIG. 4 is four times that of the test pattern 201 so far, and the contrast can be made four times.

  In the present invention, since the projection area of the test pattern 201 that actually uses the electronic pen function is different from the projection area of the test pattern 401 that performs calibration, the correlation between the projection screen and the imaging screen is shifted. Therefore, the correlation is established by automatically detecting the zoom ratio and correcting the shift as shown in FIG.

  Next, the configuration of the projector according to the present embodiment that performs projection and correction of the test pattern will be described with reference to FIG.

  The projector according to this embodiment includes an image sensor 601, a motor 602, a motor drive circuit 603, a control unit 604, a test turn generation circuit 605, a display device 606, a zoom drive circuit 607, a projection lens 608, A position sensor 609.

  In addition to the configuration shown in FIG. 6, the projector is provided with an external video signal receiving unit, a display device driving circuit for driving the display device 606 in accordance with the video signal, and the like. Since it is a simple structure and is not particularly involved in the operation of the present invention, illustration and description thereof are omitted.

  The image sensor 601 constitutes the camera unit 103 shown in FIG. 1, images a projection screen using visible light or infrared light from an electronic pen, and outputs the result to the control unit 604.

  The control unit 604 causes the test pattern generation circuit 605 to generate a test pattern. The test pattern generated by the test pattern generation circuit 605 is supplied to a display device 606 which is an optical device for image generation such as an LCD (Liquid Crystal Device), DMD (Digital Micromirror Device), etc., and becomes an image light. The image is enlarged and projected by (corresponding to the projection lens 102 shown in FIG. 1).

  The projection lens 608 includes a plurality of lenses including a movable zoom lens, and the projection magnification is variable as the zoom lens moves in the projection direction. The zoom position is determined by the control of the zoom drive unit 607. The position of the zoom lens of the projection lens 608 (hereinafter referred to as the zoom position) is detected by the position sensor 609 and sent to the control unit 604.

  The motor 602, the motor drive unit 603, and the zoom drive unit 607 constitute a zoom mechanism, and the control unit 604 drives the motor 602 that determines the operation of the zoom drive unit 607 via the motor drive circuit 603. A zoom drive unit 607 controls the zoom state of the projection lens 608. Further, it has a function of storing the projection magnification of the projection lens 608, the acquired value of the image sensor 601 corresponding thereto, and the value calculated from these.

  FIG. 7 is a flowchart showing the control operation of the control unit 604 when performing automatic calibration in the present embodiment.

  When automatic calibration is started (step S701), the control unit 604 is a test that is also an area where the electronic pen is used when operating as the electronic blackboard system before displaying the test pattern 401 for calibration. The current zoom position “A” of the projection lens 608 that projects the pattern 201 is acquired (step S702).

  Next, the zoom position of the projection lens 608 is moved to the position (Tele end) where the projection image is minimum (step S703), and the zoom position “B” at that time is acquired (step S704).

  Next, the zoom magnification C (= A / B) is calculated from the zoom position “A” where the electronic pen function is used and the position (Tele end) “B” where the projected image is minimum (step S705).

  Next, the test pattern 401 is displayed (step S706), and an image of the displayed calibration point is acquired (step S707). Since the test pattern 401 used in the present embodiment includes nine calibration points, the test pattern display and imaging of each point are repeated in order, and the display of the test pattern is terminated when the nine points are completed (step S708). ), Move to next process.

  Next, the coordinates (x, y) of each calibration point are calculated from the image acquired in step S707 (step S709).

  Next, the coordinates (x, y) of each calibration point calculated in step S709 are corrected and calculated from the zoom magnification C obtained in step S705 at the zoom position where the electronic pen function is used. (Step S710) and store (step S711).

  Next, the zoom position of the projection lens 608 is set to the zoom position “A” using the electronic pen function (step S712), and the calibration is finished (S713).

  FIG. 8 is a diagram for explaining the coordinate correction method performed in step S710 of FIG. 7, and is a diagram illustrating a test pattern when the zoom magnification is “2 ×” as an example.

  When the reference coordinate (0, 0) of the coordinate is “E”, correction is performed by applying a zoom magnification “2” to each coordinate of the calibration point.

Position “A”: calibration position coordinates “−x, + y” = correction coordinates “X, Y” = “− 2x, + 2y”
Position “B”: Calibration position coordinate “0, + y” ⇒ Correction coordinate “X, Y” = “0, + 2y”
Position “C”: Calibration position coordinates “+ x, + y” ⇒ Correction coordinates “X, Y” = “+ 2x, + 2y”
Position “D”: Calibration position coordinate “+ x, 0” ⇒ Correction coordinate “X, Y” = “+ 2x, 0”
Position “E”: Calibration position coordinate “0, 0” ⇒ Correction coordinate “X, Y” = “0, 0”
Position “F”: Calibration position coordinate “−x, 0” ⇒ Correction coordinate “X, Y” = “− 2x, 0”
Position “G”: Calibration position coordinates “−x, −y” ⇒ Correction coordinates “X, Y” = “− 2x, −2y”
Position “H”: Calibration position coordinates “0, −y” ⇒ Correction coordinates “X, Y” = “0, −2y”
Position “I”: Calibration position coordinates “+ x, −y” ⇒ Correction coordinates “X, Y” = “+ 2x, −2y”
In order to simplify the explanation in this description, it is assumed that the launch angle of the projection screen is “0 °”, the screen and the projector are orthogonal, and the screen is not distorted. Correction is possible even when the screen is distorted due to oblique projection or the like. In this case, a calculation formula is calculated and corrected based on the launch angle, magnification, and the relationship between the screen and the projection axis.

  In the above-described embodiment, the zoom position of the projection lens 608 has been described as being moved to the position where the projection image is minimum (Tele end) during automatic calibration. However, the present invention is not limited to this. If it is a position where an image smaller than the position where actual projection is performed is projected, the brightness of the test pattern can be made brighter than during actual projection, and the effect of the present invention is realized.

Claims (4)

A projector constituting an electronic blackboard system,
A projection lens that includes a zoom lens and projects an image on a projection surface;
A zoom mechanism for changing the position of the zoom lens;
An image sensor that captures the image on the projection surface;
A control unit that controls the position of the zoom lens via the zoom mechanism,
The control unit is configured to perform zooming during calibration for projecting a test pattern including a plurality of calibration points in order to establish a correlation between a captured image captured by the image sensor and the image on the projection plane. The test pattern is projected as a second position where a smaller image is projected with respect to the first position where the actual projection is performed via the mechanism, and at that time, by the image sensor A projector that corrects the coordinate value of each calibration point acquired from the obtained image from the first position and the second position. The projector according to claim 1, wherein
A projector comprising a position sensor for detecting a position of the zoom lens, wherein the control unit detects a position of the zoom lens based on an output of the position sensor. In the projector according to claim 1 or 2,
The projector, wherein the control unit sets a position where an image projected as the second position is a minimum. A projection lens that includes a zoom lens and projects an image on a projection surface;
A zoom mechanism for changing the position of the zoom lens;
A calibration method performed by a projector constituting an electronic blackboard system having an image sensor that captures the image on the projection plane,
In order to establish a correlation between the captured image captured by the image sensor and the image on the projection plane, the calibration mechanism that projects a test pattern including a plurality of calibration points is used to perform the above-described zoom mechanism. The test pattern is projected with the position of the zoom lens as a second position where a smaller image is projected relative to the first position where actual projection is performed, and from the image obtained by the image sensor at that time A calibration method for correcting coordinate values of each acquired calibration point from the first position and the second position.

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