JP2005070412A - Image projector and its focus adjustment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult for the ranging light reflected by a screen to enter a photodetecting section in the diagonal projection when the projection optical axis to the screen is not perpendicular. <P>SOLUTION: The projector 1 has a light emitting element within a light emitting section 61 which emits the ranging light Lm, a movable reflection mirror 63 which causes plane scanning of the ranging light on the screen 100 by changing the optical axis of the ranging light Lm, and a photodetecting position sensor 71 which receives the reflected light generated by reflection of the ranging light Lm on the screen 100 at the time of plane scanning. The projector 1 measures the relative positional relation between a projection optical system 5 and the screen 100 from the information on the change of the exit optical axis of the movable reflection mirror 63 when the photodetecting position sensor 71 receives the reflected light and determines the amount of the focus adjustment of the projection optical system 5 so as to match the focus on the screen 100 on the basis of the measured reult. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image projection apparatus such as a projector capable of measuring a relative position between a projection optical system and a projection surface (for example, a screen) outside the apparatus and focusing a projected image based on the measurement result. And the focus adjustment method.

In a projection-type image display device such as a projector (hereinafter referred to as an image projection device), the method of correcting the blur of the image projected on the screen is to manually adjust the focal length of the projection optical system and view the screen. However, it is common to adjust the focus.
Although it is a method that is not so popular, a small camera with a CCD image sensor is used to capture the image projected on the screen and measure the screen size and the distance between the projection optical system and the screen from the video signal. Therefore, a method used for focusing calculation is known. Furthermore, a method is known in which light from an infrared LED is applied to a screen, reflected light (reflected light) is received, and focus calculation is performed based on the result.

As an image projection apparatus that performs focusing control using infrared LED light, a liquid crystal projector including an optical axis adjustment mechanism that changes the angle of the optical axis of LED light using a prism is known (for example, Patent Document 1).
The liquid crystal projector described in Patent Document 1 has prisms on the light emitting side and the light receiving side of the infrared LED, respectively, which adjust the optical axis at the time of light emission and light reception and measure the distance at the center of the screen. belongs to. That is, this measurement is based on the arrangement when the liquid crystal projector is placed almost in front of the screen.

By the way, recent image projection apparatuses such as liquid crystal projectors include functions such as trapezoidal distortion correction, which are premised on the use of oblique projection in which the optical axis of the projection optical system is not perpendicular to the screen surface.
In the case of such oblique projection, in the liquid crystal projector described in Patent Document 1, reflected light often does not enter the light receiving unit. In particular, when the vertical angle and horizontal angle of the optical axis of the projection optical system with respect to the screen surface change from the case of front projection, the reflected light hardly enters the light receiving unit. In such a case, it is necessary to find the angle at which the reflected light enters the light receiving unit by changing the direction of the liquid crystal projector. However, if the orientation of the projector is changed, the distance from the screen changes, and it becomes impossible to accurately measure the focal length in the actual use state.
Japanese Patent Application Laid-Open No. 11-264963 (page 3, etc.)

  The problem to be solved is that it is difficult for the reflected light to enter the light receiving part during oblique projection in which the projection optical axis is not perpendicular to the projection surface such as a screen, and therefore the distance between the image projection device and the projection surface, etc. The information of is not obtained cleverly.

  An image projection apparatus according to the present invention is an image projection apparatus that has a projection optical system capable of adjusting a focal position and projects an image on a projection surface outside the apparatus by projection light emitted from the projection optical system. A light emitting element that emits distance measuring light, a scanning mechanism that changes an angle of an optical axis of the distance measuring light and performs surface scanning of the distance measuring light on the projection surface, and the projection during the surface scanning. A light receiving unit that receives reflected light generated by reflection of the distance measuring light on a surface, and an angle of an optical axis of the distance measuring light emitted from the scanning mechanism when the light receiving unit receives the reflected light. Based on the change information, the relative positional relationship between the projection optical system and the projection surface is measured, and the adjustment amount of the focal position of the projection optical system is adjusted based on the result of the measurement so that the focal point is focused on the projection surface. An adjustment amount calculation unit to calculate.

Preferably, the light receiving unit includes a light receiving lens mechanism and a light receiving position sensor that measures a position of a light receiving point within a light receiving surface through which an optical axis of the light receiving lens mechanism passes.
Preferably, the adjustment amount calculation unit includes a reference setting unit that sets a reference position of the scanning mechanism in advance, and the light receiving position sensor that is generated at the time of projection in which the optical axis of the projection light forms an arbitrary angle with the projection surface. The light receiving point position of the reflected light is input from the light receiving position sensor, and when the light receiving point position is obtained, the magnitude and direction of the control amount changed from the reference position by the control of the scanning mechanism are calculated. And a calculation unit for obtaining an adjustment amount of the focal position of the projection optical system based on the calculated magnitude and direction of the control amount change and the input light receiving point position.
Preferably, the light receiving lens mechanism has a lens exchange function or a magnification adjustment function for changing a range of the projection surface corresponding to the light receiving surface.

  An image projection apparatus focus adjustment method according to the present invention includes a projection optical system capable of adjusting a focus position, and projects an image onto a projection surface outside the apparatus by projection light emitted from the projection optical system. A focus adjustment method for a projection apparatus, wherein a scanning step of changing the angle of an optical axis of distance measuring light by a scanning mechanism and surface-scanning the distance measuring light on the projection surface, and the projection surface during the surface scanning From the light receiving step of receiving the reflected light generated by reflecting the distance measuring light above, and the change information of the angle of the optical axis of the distance measuring light emitted from the scanning mechanism when the reflected light is received, A relative relationship measuring step for measuring a relative positional relationship between the projection optical system and the projection surface, and an adjustment amount of the focal position of the projection optical system that is focused on the projection surface based on the measurement result of the distance. Calculation of adjustment amount required And a step.

  Preferably, the adjustment amount calculating step further includes a reference setting step of setting a reference position of the scanning mechanism in advance, and the reflected light generated at the time of projection in which the optical axis of the projection light forms an arbitrary angle with the projection surface. When the light receiving point position is input, the magnitude and direction of the control amount changed from the reference position by the control of the scanning mechanism when the light receiving point position is obtained are calculated, the magnitude of the calculated control amount change and A calculation step of calculating an adjustment amount of the focal position of the projection optical system based on the direction and the input light receiving point position.

Hereinafter, the operation will be described taking the case of the image projection apparatus as an example.
The image projection apparatus of the present invention has reference setting means in the adjustment amount calculation unit. This reference setting means uses the scanning control point of the scanning mechanism when the optical axis of the projection optical system is parallel to the optical axis of the distance measuring light reaching the projection surface as a reference for measuring the angle change of the optical axis of the distance measuring light. Set to position (origin). Thereafter, when the angle of the optical axis of the distance measuring light changes, the amount of change from this reference position can be obtained.
Now, it is assumed that the image projection device is arranged at an arbitrary position with respect to the projection surface outside the device, and ranging light is projected from the light emitting element toward the projection surface. At this time, the distance measuring light is reflected on the projection surface, and the reflected light at that time returns to the image projection apparatus side. However, when the optical axis of the distance measuring light is largely deviated from the vertical with respect to the projection surface, the reflected light may not enter the light receiving unit. In this case, the scanning mechanism is scanned to change the angle of the optical axis of the distance measuring light, and the distance measuring light is scanned on the projection surface. Here, the “surface scanning” is a scanning method in which, for example, the distance measuring light is scanned in one direction, then the distance measuring light is shifted to the other, the distance measuring light is scanned again in one direction, and this reciprocating motion is repeated. It is. The amount to be shifted to the other side is not required if there is no projection surface area that cannot be detected by the light receiving unit. For example, a surface scan in which all areas of the detection target surface (in this case, the projection surface) can be detected by the light receiving surface of the light receiving unit in this way is referred to as “surface scanning”.
When reflected light is detected by the light receiving unit by surface scanning, information on the light receiving point position is output from the light receiving position sensor and sent to the calculation unit. The calculation unit calculates the magnitude and direction of the controlled variable that has changed from the reference position in the control of the scanning mechanism when the light receiving point position information is obtained. Furthermore, the magnitude and direction of the controlled variable change and the input are input. A focus adjustment amount of the projection optical system is calculated based on the information on the light receiving point position.

According to the image projection apparatus and the focus adjustment method thereof according to the present invention, the focus adjustment can be performed without using an image pickup apparatus such as a camera that is expensive. In addition, even when the image projection apparatus is arranged at an arbitrary position with respect to the projection surface outside the apparatus, and the oblique projection in which the optical axis of the projection light is not perpendicular to the projection surface outside the apparatus, the distance measurement light can be easily and reliably The reflected light can be detected. For this reason, it is possible to focus the image on the projection surface smartly and easily.
As described above, it is possible to provide a small and low-priced projection type image display device (image projection device) to which an automatic focusing device is added.

  The present invention includes an image display device such as an LCD (liquid crystal display), DMD (digital micro-mirror device), or CRT (cathode ray tube), and projects an image displayed on the device to project outside the apparatus. The present invention can be widely applied to a projection-type image display device (hereinafter referred to as a projector) that projects and displays on a screen, for example, a screen.

[First Embodiment]
FIG. 1 is a view of a projector and a screen according to the present embodiment as viewed from above when they are arranged obliquely. FIG. 2 shows a front view of the projector.
In FIG. 1, when an unillustrated person who views the screen 100 from the rear side of the projector 1 is an observer, the projector 1 is positioned on the lower left side of the screen as viewed from the observer. In other words, both are arranged so that the optical axis (hereinafter referred to as the projection optical axis or Lp axis) 5A of the projection lens of the projector 1 faces the screen 100 obliquely upward to the right.
In the present embodiment, it is assumed that the projector 1 and the screen 100 are arranged in an arbitrary positional relationship. Since the projector 1 of the present embodiment can easily adjust the focus even in the case of a projection that is oblique in both the vertical and horizontal directions (hereinafter simply referred to as oblique projection), here the light is directed to the screen diagonally upward to the right. Although the oblique projection which goes to is given as an example, the relative position of both is not limited to the case of illustration.

  The front surface of the projector shown in FIG. 2 refers to a surface on the image projection side, that is, a screen side surface. As shown in FIG. 2, the projector 1 has a projection optical system window 2 in front of the projector 1, a light emitting element window 3 that emits ranging light at the time of focus adjustment at a substantially upper position thereof, and a lateral direction thereof. And a light receiving window 4 for receiving the reflected light returned by the distance measuring light reflected by the screen. As shown in FIG. 1, a projection optical system 5 including an image display device such as an LCD panel, a light source, and an optical component such as a projection lens (hereinafter referred to as a projection lens mechanism) is disposed inside the projector 1. Although not particularly illustrated, the projection optical system 5 is configured such that its focal length can be changed by, for example, an operation ring for focusing. A ranging light projection unit 6 is disposed above the projection optical system 5 at a position in the projector corresponding to the window 3 (FIG. 2) of the light emitting element. In addition, a light receiving unit 7 is disposed at a projector internal position corresponding to the light receiving window 4 (FIG. 2) that is laterally separated from the distance measuring light projecting unit 6.

As shown in FIG. 1, a light emitting unit 61 incorporating a light emitting element such as an infrared LED, a lens 62, and a movable reflecting mirror 63 are arranged in the distance measuring light projection unit 6.
In the arrangement example of each part of the distance measuring light projection unit 6 of this example, the mirror 63 is tilted to the center of two independent rotation axes provided on one movable reflecting mirror 63, and the distance measuring light is all areas on the screen. The angle of the optical axis of the distance measuring light after being reflected by the mirror 63 (hereinafter also referred to as “the direction of the outgoing optical axis”) can be freely changed within a range sufficient to hit this.

  The light receiving unit 7 includes a light receiving position sensor 71 that can determine the position of a light receiving surface such as a PSD (position sensitive detector) based on an output signal, and a light receiving lens mechanism 72 that guides light to the light receiving surface of the light receiving position sensor 71. The light receiving lens mechanism 72 includes a lens zoom mechanism that can replace the lens. As a result, initially, a high magnification is ensured so that the light receiving point is likely to be present on the light receiving surface of the light receiving position sensor 71, and when the light receiving point is captured, the movement of the light receiving point within the light receiving surface is increased as a low magnification. Thus, the position detection of the light receiving point can be made highly sensitive.

The details of the ranging light projection unit 6 are schematically shown in FIG. Further, the connection relationship between the ranging light projection unit and the light receiving unit is shown in the block diagram of FIG.
As shown in FIG. 3, the movable reflection mirror 63 has a rotation axis AXh during horizontal scanning and a rotation axis AXv during vertical scanning. These rotary shafts AXh and AXv are connected to drive means 64h and 64v for rotationally driving them, respectively, and a control circuit (indicated as “Cont.” In the drawing) 65 for controlling these drive means 64h and 64v is provided. ing.
Ranging light (for example, infrared light) Lm emitted from the light emitting element 61A in the light emitting unit 61 is appropriately focused by the lens 62, then reflected by the movable reflecting mirror 63, and emitted to the screen side. At this time, the driving means 64h and 64v are operated under the control of the control circuit 65, and the direction of the outgoing optical axis of the distance measuring light Lm changes.

  The surface scanning with respect to the screen 100 is possible by controlling the direction of the outgoing optical axis of the distance measuring light. Here, the “surface scanning”, for example, scans the distance measuring light in the horizontal direction, then shifts the distance measuring light in one vertical direction, scans the distance measuring light in the horizontal direction again, and repeats this reciprocating motion. Such a scanning method. The amount of shifting in the vertical direction may be such that an area of the screen surface that cannot be detected by the light receiving position sensor 71 does not occur. For example, a surface scan in which all areas of the screen surface can be detected by the light receiving surface of the light receiving position sensor 71 in this way is referred to as “surface scanning”.

  In this example, as shown in FIG. 4, the control circuit 65 includes a reference setting unit 65A and a calculation unit 65B. As shown in FIG. 1, the reference setting means 65A of the present example includes, for example, an optical axis (Lm axis) 6A of the distance measuring light Lm after being reflected by the movable reflecting mirror 63, and an optical projection axis (Lp axis) 5A of the image. The control amount of the scanning mechanism that is parallel to each other, that is, the control amount of the driving means is set as the reference position. If the scanning mechanism is reset to return to the reference position, the resetting means corresponds to the reference setting means 65A. Alternatively, in the case of having a memory for storing the reference position, this memory and a means for controlling the memory correspond to the reference setting means 65A. In any case, this reference position can be input to the calculation unit 65B. In the case shown in FIG. 4, the control circuit 65 incorporating the reference setting means 65A corresponds to one embodiment of the “adjustment amount calculation unit” of the present invention. When the reference setting means 65A is outside the control circuit 65, the reference setting means 65A and the control circuit 65 correspond to one embodiment of the “adjustment amount calculation unit” of the present invention.

  FIG. 4 shows a case where a light receiving point is captured on the light receiving surface of the light receiving position sensor 71 by surface scanning. A signal obtained by converting the light receiving point position at this time into a physical quantity, for example, a current quantity, is input to the arithmetic unit 65B. Based on the sensor output at the reference position, the computing unit 65B obtains the relative positional relationship between the projector and the screen, for example, the distance and inclination between the projector and the screen, based on the sensor output after the surface scanning.

FIG. 5 shows the relative positional relationship between the projector and the screen when a light receiving point is captured on the light receiving surface by surface scanning.
At this time, the reflected light generated when the distance measuring light Lm is reflected by the screen 100 is Lmb, the angle of the distance measuring light Lm with respect to the normal of the screen 100 is θ1, and the angle of the reflected light Lmb with respect to the vertical of the screen 100 is θ2. . These angles are a composite angle of a vertical angle and a horizontal angle. Assuming that the point corresponding to the reference position on the light receiving surface of the light receiving position sensor 71 is controlled as the center point, when the light receiving point overlaps the center point, the two angles θ1 and θ2 have the same value. Usually, the light receiving point is often shifted from the center point, and in this case, the angles θ1 and θ2 are slightly shifted. The calculation unit 65B can calculate the angle between the screen and the projector based on the output of the light receiving position sensor 71 representing the amount of deviation and the direction and magnitude of the control amount obtained from the driving means 64h and 64v at that time. In addition, the absolute values of the angles θ1 and θ2 vary depending on the distance between the screen and the projector, that is, the absolute value of the angle decreases when they are separated from each other, and increases when they are reversed. The calculation unit 65B can measure the distance between the absolute value of the angle obtained from the output of the light receiving position sensor 71 and the direction and magnitude of the control amount obtained from the driving units 64h and 64v. Note that the calculation unit 65B can determine the distance with reference to a table of angles and distances (not shown) as necessary.

  Based on the information on the relative positional relationship calculated by the calculation unit 65B, the calculation amount of the focus adjustment is further calculated by the calculation unit 65B, and this is sent to the projection lens mechanism of the projection optical system to automatically focus. Done. The calculation of the control amount for focus adjustment may be executed by other means. In this case, the “adjustment amount calculation unit” of the present invention is configured including other means.

Next, the automatic focusing procedure will be described with reference to the flowchart of FIG.
A reference position is set (step ST1), and then surface scanning is executed by the method described above (step ST2).
When the light receiving surface of the light receiving position sensor 71 captures the reflected light Lmb during the surface scanning process (light reception: step ST3), in the next step ST4, the calculation unit 65B calculates the relative position (tilt and distance) by the method described above. calculate. The ideal value of the optimum screen size is determined from the relative position obtained in this way and the magnification at that time (usually predetermined in the order of 1 to 1.2 times). If the user is not satisfied with the screen size, the user needs to start again from step ST1 after performing re-installation by moving the projector away from or closer to the screen.

  When the screen size is determined, the appropriate zoom magnification is finely adjusted taking into account the screen size, the relative position information of the screen, and the lens information (step ST6), and an appropriate focal length is obtained by calculation (step ST7). Finally, the projection optical system is adjusted to the obtained focal length to automatically adjust the focus of the image (automatic focusing: step ST8).

In the above example, one reflection mirror that can rotate biaxially is used, but the same function can be realized by using two or more uniaxial movable reflection mirrors. These reflection mirrors can be realized by combining one, two, or more so-called galvanometer mirrors. Furthermore, a so-called polygon mirror may be used. The polygon mirror is composed of a plurality of polygon-arranged mirrors that rotate around one axis. If you want to add a movable axis to the polygon mirror, you can place the polygon mirror on a tilting table that is movable in one or two axes. realizable. In any case, if the LED light is scanned over the entire screen, the relative position can be measured.
Needless to say, the present invention can calculate in-focus even when the projection optical axis Lp is perpendicular to the screen surface or when the projection optical axis Lp is at the center of the screen. Further, the deviation d (FIGS. 1 and 2) between the projection optical axis Lp and the distance measuring optical axis Lm may be zero.
In addition, the reference position setting unit 65A and the calculation unit 65B shown in FIG. 4 and the functions of the entire control circuit 65 including these may be realized on a soft wafer as a description of a program that can be executed by a CPU or microcomputer. it can.

[Second Embodiment]
In the first embodiment, the distance measuring light Lm from the light emitting unit 61 is controlled to change the path of the optical axis by a scanning mechanism including a reflection mirror. However, as in the present embodiment, the light emitting unit 61 is controlled. It can have a scanning mechanism.

FIG. 7 is a diagram showing the operation of the scanning mechanism of the light emitting unit in polar coordinates. FIG. 8 is a diagram illustrating a case where the light receiving point of the reflected light is captured by the light receiving position sensor by the surface scanning.
In this example, it is assumed that the infrared LED 61A is positioned at the center of a virtual sphere, and the point where the spherical surface and the infrared ray (ranging light Lm) intersect is represented by polar coordinates (r, θ, Φ). Here, r is a radius of a virtual sphere, θ is an angle formed by the optical axis of the distance measuring light Lm and the z axis, and Φ is an angle formed by the optical axis of the distance measuring light Lm and the y axis. The infrared LEDs 61A and the lens 62A are integrated and moved so that the angles θ and Φ change and the light scans on the hemisphere facing the screen side.
Accordingly, the movable reflecting mirror 63 and the fixed lens 62 shown in FIG. 1 are not necessary. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.
The relative position information measurement and focus adjustment methods are basically the same as those in the first embodiment.

  In FIG. 8, a front projection type projector is depicted, but this scanning mechanism can be applied particularly to a projection type projector of the whole sky.

  The present invention can be applied to the use of an image projection apparatus such as a so-called front projector or an all-around projection type projector.

The figure which looked at both from the upper direction, when the projector and screen which concern on the 1st Embodiment of this invention are arrange | positioned diagonally Front view of projector The figure which shows the details of the ranging light projection part typically Block diagram showing the connection between the ranging light projection unit and the light receiving unit Top view showing the relative positional relationship between the projector and the screen when a light receiving point is captured on the light receiving surface by surface scanning Flow chart showing the autofocus procedure The figure showing operation | movement of the scanning mechanism of the light emission part in the polar coordinate in the 2nd Embodiment of this invention. The top view which shows the relative positional relationship of a projector and a screen when a light-receiving point is caught by the light-receiving surface by surface scanning in 2nd Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector (image projection apparatus), 2 ... Projection optical system window, 3 ... Issuing element window, 4 ... Light receiving window, 5 ... Projection optical system, 5A ... Projection optical axis (Lp axis), 6 ... Ranging light Projection unit, 6A ... optical axis of distance measuring light (Lm axis), 61 ... light emitting unit, 61A ... light emitting element, 62, 62A ... lens, 63 ... movable reflecting mirror, 64h, 64v ... driving means, 65 ... control circuit ( Adjustment amount calculation unit), 65A: reference setting means in the adjustment amount calculation unit, 65B ... calculation unit, 7 ... light receiving unit, 71 ... light receiving position sensor, AXh, AXv, AXθ, AXΦ ... rotation axis

Claims (7)

An image projection apparatus having a projection optical system capable of adjusting a focal position and projecting an image on a projection surface outside the apparatus by projection light emitted from the projection optical system,
A light emitting element that emits distance measuring light;
A scanning mechanism that changes the angle of the optical axis of the distance measuring light and scans the distance measuring light on the projection surface;
A light receiving unit that receives reflected light generated by reflecting the distance measuring light on the projection surface during the surface scanning;
The relative positional relationship between the projection optical system and the projection surface is measured from the change information of the angle of the optical axis of the ranging light emitted from the scanning mechanism when the light receiving unit receives the reflected light, and the measurement is performed. An adjustment amount calculation unit that calculates an adjustment amount of the focal position of the projection optical system so that the focal point is in focus on the projection surface,
An image projection apparatus. The scanning mechanism has one or more reflecting mirrors,
The image projection apparatus according to claim 1, wherein the entire scanning mechanism includes a plurality of axes that independently change the inclination of a reflection surface that reflects the distance measuring light of the reflection mirror. The light receiving unit is
A light receiving lens mechanism;
A light receiving position sensor for measuring the position of the light receiving point within the light receiving surface through which the optical axis of the light receiving lens mechanism passes,
The image projection device according to claim 1, comprising: The adjustment amount calculator is
Reference setting means for setting a reference position of the scanning mechanism in advance;
The light receiving point position of the reflected light in the light receiving position sensor generated during the projection in which the optical axis of the projection light forms an arbitrary angle with the projection surface is input from the light receiving position sensor, and the light receiving point position is obtained. Sometimes the magnitude and direction of the control amount changed from the reference position by the control of the scanning mechanism is calculated, and based on the magnitude and direction of the calculated control amount change and the input light receiving point position, A calculation unit for obtaining an adjustment amount of the focal position of the projection optical system;
The image projection apparatus according to claim 3, comprising: The image projection apparatus according to claim 3, wherein the light receiving lens mechanism has a lens replacement function or a magnification adjustment function for changing a range of the projection surface corresponding to the light receiving surface. A projection optical system capable of adjusting a focal position, and a focus adjustment method for an image projection apparatus that projects an image on a projection surface outside the apparatus by projection light emitted from the projection optical system,
A scanning step in which the angle of the optical axis of the distance measuring light is changed by a scanning mechanism to scan the surface of the distance measuring light on the projection surface;
A light receiving step for receiving reflected light generated by reflecting the distance measuring light on the projection surface during the surface scanning;
A relative relationship measuring step for measuring a relative positional relationship between the projection optical system and the projection surface, based on change information of the angle of the optical axis of the ranging light emitted from the scanning mechanism when the reflected light is received;
An adjustment amount calculating step for obtaining an adjustment amount of the focal position of the projection optical system that is focused on the projection surface based on the measurement result of the distance;
Adjustment method for an image projection apparatus including The adjustment amount calculating step further includes:
A reference setting step for setting a reference position of the scanning mechanism in advance;
The light receiving point position of the reflected light generated at the time of projection in which the optical axis of the projection light forms an arbitrary angle with the projection surface is input, and when the light receiving point position is obtained, it is controlled from the reference position by controlling the scanning mechanism. The magnitude and direction of the changed control amount are calculated, and the adjustment amount of the focal position of the projection optical system is calculated by calculation based on the calculated magnitude and direction of the control amount change and the input light receiving point position. A calculation step to be obtained;
The focus adjustment method according to claim 6 including:

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