Display controller, display device and display control method

Abstract

To restrain visual recognition and perception of variation in size from becoming difficult due to the virtual object displayed remotely getting too small at view from a visible person on a vehicle and to restrain size in virtual object from getting too big when displaying the virtual object nearby as a vehicle travels.SOLUTION: A control unit 701 of a display controller 700 executes size adjustment processing which enlarges size of a virtual object VOB maintained in a prescribed actual spatial position gradually until the size changes from a first size to a second size in response to the approach to the prescribed actual spatial position of a vehicle 1, and adjusts so that the rate of change in the size relative to perception distance of the virtual object VOB is smaller than the rate of change in the size of an actual object when it is assumed that the virtual object VOB is an actual object that exists in actual space, in at least a part of a size adjustment period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display control device, a display device, a display control method, etc., that are mounted on a vehicle such as an automobile. [Background technology]

[0002] Patent Document 1 (see Figure 3,

[0017] to

[0019] ) discloses a technology in which a virtual image for the left viewpoint and a virtual image for the right viewpoint having parallax are displayed at a first display position in front of the vehicle, causing the viewer to perceive as if a three-dimensional virtual object is present at a second display position that is farther away than the first display position.

[0003] Patent document 2 (see Figure 17,

[0165] ) shows an example of display control in which a first route guidance content that guides a vehicle is moved, and then a fourth route guidance content that indicates a change point in the vehicle's direction of travel (a change of direction point) is displayed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-194709 [Patent Document 2] Japanese Patent Publication No. 2020-64047 Summary of the Invention [Problem to be solved by the invention]

[0005] Through investigations by the present inventors, the following problems have become apparent. (1) In the display example shown in FIG. 17 of Patent Document 2, a first arrow mark, which is a virtual object that guides the vehicle along its travel route, moves along a road. When the first arrow mark reaches a right-turn point, which is a turning point, a second arrow mark, which is a virtual object that guides the vehicle to turn right, is displayed superimposed on the right-turn road. Here, by displaying the first arrow mark so that its size decreases as the distance from the viewer increases, the first arrow mark as a virtual object can be given a natural sense of perspective similar to that of a real object existing in real space. In this case, the size of the second mark (virtual object) that guides the driver to turn right is also adjusted so that the same perspective as the first arrow mark is created. Here, if the right turn point is quite far away from the viewer, the size of the second arrow mark (virtual object) guiding the viewer to turn right will be significantly small, which may make it difficult for the viewer to see. Furthermore, as the vehicle travels, it gradually approaches the right turn point over time, but the visual sensitivity of the human eye is quite low for distant objects. Therefore, when reproducing the same perspective as for real objects in the real world for the second mark (virtual object) in the distant area, it is possible that the viewer will have difficulty perceiving the increase in size of the second arrow mark (virtual object) as the vehicle approaches, and will perceive its size as barely changing. In this case, it becomes difficult for the viewer to get a sense that the vehicle is approaching a right turn point. (2) To alleviate the problem in (1) above, it is conceivable to enlarge the size of the second arrow mark (virtual object) at the right turn point compared to the size of the real object to make it easier to see, thereby improving the viewer's visibility of the second arrow mark (virtual object). However, in this case, if we assume that the vehicle is quite close to the right turn point, the visual sensitivity of the human eye is sufficiently high for objects that are close by, so the second arrow mark (virtual object) will rapidly expand as the vehicle approaches, which may make it too large compared to the size of the real object, causing a sense of incongruity. This new problem has been identified by the present inventors. Such problems are not mentioned in the above Patent Documents 1 and 2, and no countermeasures are mentioned.

[0006] One of the objects of the present invention is to prevent a virtual object displayed at a distance from being too small for a viewer in a vehicle, making it difficult to see the object or perceive changes in its size, and to prevent the size of the virtual object from becoming too large when the virtual object is displayed close by as the vehicle moves.

[0007] Other objects of the present invention will become apparent to those skilled in the art by referring to the following exemplary aspects and best modes, as well as the accompanying drawings. [Means for solving the problem]

[0008] In order to facilitate an understanding of the outline of the present invention, the following examples are given of embodiments according to the present invention.

[0009] In a first aspect, there is provided a display control device that is mounted on a vehicle and that performs display control when a virtual object is displayed so as to be visible to a viewer aboard the vehicle, wherein the control unit displays the virtual object of a first size so as to be perceived by the viewer as if the virtual object were present at a predetermined real-space position in front of the vehicle, and performs a size adjustment process in which, in response to the vehicle approaching the predetermined real-space position, the size of the virtual object maintained at the predetermined real-space position is gradually increased until the size of the virtual object reaches a second size, and where a distance from a viewpoint position of the viewer to the predetermined real-space position is defined as a perceived distance, during the size adjustment process, the control unit adjusts the size of the virtual object so that, for at least a portion of a period during which the size of the virtual object changes from the first size to the second size, a rate of change in size of the virtual object with respect to the perceived distance is smaller than a rate of change in size of the real object when it is assumed that the virtual object is a real object existing in real space.

[0010] In the first mode, a size adjustment process is performed to adjust the size of a virtual object while the vehicle is approaching a predetermined real space position.

[0011] Even if a predetermined real space position is located quite far away from the viewer, it is possible to adjust the size of the virtual object appropriately and display it at a relatively large, easy-to-view size.

[0012] However, if a virtual object displayed at a size that is easy to see in the distant area is adjusted in size as the vehicle moves at the same size change rate as that of a real object in real space (size change rate relative to perceived distance), the size of the virtual object may become too large in the near area, causing a sense of discomfort.

[0013] Therefore, in this embodiment, a size adjustment process is performed, and during at least a portion of the period during which the vehicle is approaching a predetermined real-space position, the rate of change in size of the virtual object, in other words, the degree of change in size relative to the distance (perceived distance) between the viewer and the real-space position when the size of the virtual object gradually increases, is set to be smaller than the rate of change in size of the real object (sometimes referred to as the real-world size change rate). This makes it possible to prevent the size of a virtual object in the near area from becoming too large when viewed from the viewer. Therefore, the size of the virtual object can be controlled to an appropriate size from the far area to the near area, improving visibility and reducing the sense of discomfort.

[0014] In a second aspect dependent on the first aspect, the control unit may display a virtual image for a left viewpoint and a virtual image for a right viewpoint having parallax on a virtual first display surface set in front of the vehicle, thereby causing the viewer to perceive the virtual object as being present on a virtual second display surface set farther away than the first display surface.

[0015] In the second aspect, for example, a parallax stereoscopic image display device (such as a parallax 3D HD device) can display a virtual object on a second display surface that is located farther from the viewer than the first display surface on which the virtual image is displayed. During this display, for example, the size of the virtual object perceived by the viewer can be variably controlled by appropriately adjusting the size of the virtual images for the left and right viewpoints displayed on the first display surface.

[0016] In a third aspect dependent on the first or second aspect, where Ds is the perceived distance, L is the size of the virtual object at the predetermined real space position, Atan is the arctangent that is the inverse trigonometric function of tangent, degrees is a function that converts an angle in radians to an angle in degrees, θ is degrees(Atan(L / 2Ds)), 2θ is 2*degrees(Atan(L / 2Ds)), and 2θ is a visual angle, the control unit may use the visual angle 2θ as an index that indicates an apparent size of the virtual object perceived by the viewer, and may specify the visual angle 2θ that corresponds to the perceived distance based on a function that indicates a relationship between the perceived distance and the visual angle 2θ, and variably control the size of the virtual object based on the specified visual angle 2θ.

[0017] In the third aspect, the size of a virtual object, the appearance of which changes depending on the sensitivity of the human (viewer's) eyes, can be objectively determined by the viewing angle (=2θ). For example, a function (characteristic line) relating the distance between the viewer and a predetermined position in real space to the visual angle 2θ can be prepared in advance, and the visual angle 2θ corresponding to the distance can be quickly calculated using that function.The apparent size of the virtual object can be variably controlled based on that visual angle 2θ, thereby enabling high-speed size adjustment processing.

[0018] In a fourth aspect dependent on any one of the first to third aspects, when a period during which the size of the virtual object changes from the first size to the second size is divided into a far period during which the vehicle is located relatively far from the predetermined real space position and a near period during which the vehicle is located relatively close to the predetermined real space position, the control unit may set a rate of change of the size of the virtual object to be the same as a rate of change of the size of the real object during the near period.

[0019] In the fourth aspect, by making the rate of change in size of the virtual object the same as the rate of change in size of the real object in the near area as seen by the viewer, it is possible to create a natural perspective for the virtual object similar to that of the real object in real space, which contributes to reducing the sense of discomfort.

[0020] In a fifth aspect dependent on any one of the first to fourth aspects, when a period during which the size of the virtual object changes from the first size to the second size is divided into a far period during which the vehicle is located relatively far from the predetermined real space position and a near period during which the vehicle is located relatively close to the predetermined real space position, the control unit may make a rate of change of the size of the virtual object larger than a rate of change of the size of the real object during the far period.

[0021] In the fifth aspect, the rate of change in size of a virtual object relative to distance in the far zone is made larger than the rate of change in size of a real object relative to distance, emphasizing the change, making it easier to grasp the sense of perspective. In other words, it becomes easier for the viewer to perceive the approach of a virtual object even in the far zone. In the far-away region, the rate of change in size of a real object in real space relative to a change in distance is significantly small, and therefore the virtual object may be perceived as if it is not even approaching a predetermined position in real space. According to this aspect, even in a distant area, the viewer can easily perceive a change in size of the virtual object (i.e., a change in perspective) that accompanies the movement of the vehicle. In other words, the viewer can intuitively recognize, for example, that the vehicle is approaching a turning point.

[0022] In a sixth aspect dependent on any one of the first to fifth aspects, prior to the size adjustment process, the control unit may move a virtual object for forward guidance, which guides the vehicle's forward travel, from a position close to the vehicle to the predetermined real space position far away, and during the movement, adjust the size of the virtual object for forward guidance at a rate of change in size of a real object when the virtual object for forward guidance is assumed to be a real object.

[0023] In the sixth aspect, prior to the size adjustment process, a virtual object for forward guidance is moved from a near area to a predetermined distant real space position as viewed by the viewer, thereby providing guidance on the vehicle's driving route, etc. At this time, the rate of change in size of the virtual object for forward guidance relative to the perceived distance (the distance from the viewer to a predetermined position in real space) can be adjusted to be the same as the rate of change in size of the real object in real space. Note that this display processing is sometimes referred to as "initial processing." This initial processing allows the viewer to roughly perceive the distance to a predetermined position in real space (for example, a vehicle turning position), providing a sense of security. Furthermore, when the virtual object for forward guidance reaches a predetermined position in real space, even if its size is too small to be easily seen, the visibility can be improved by displaying the virtual object for turning guidance at an easy-to-see size, for example. Furthermore, as the vehicle approaches a predetermined position in real space, the size adjustment process described above is performed to adjust the size appropriately, thereby giving an appropriate sense of perspective to virtual objects used for turning directions, etc., thereby reducing the sense of incongruity. Therefore, it is possible to display a guide image (navigation image) that is easy to see and does not cause discomfort.

[0024] In a seventh aspect dependent on the sixth aspect, the virtual object that is the target of the size adjustment process may be a virtual object for turning guidance that provides guidance for turning the vehicle.

[0025] In the seventh aspect, the virtual object that is the target of the size adjustment process can be, for example, a guide mark for turning directions (for example, turning left or right) that guides a vehicle in turning directions (for example, turning left or right). This allows the viewer to reliably recognize the direction change position (left or right turn position) by using a guide mark of an appropriate size.

[0026] In an eighth aspect, the display device has an image generation unit that generates an image, a display unit that displays the image, and a display control device of any one of the first to seventh aspects, and allows the viewer to perceive the virtual object by projecting display light of the image onto a projection member provided in the vehicle.

[0027] According to the eighth aspect, it is possible to realize a display device (preferably a projection display device such as a HUD device) that can prevent a virtual object displayed in the distance from being too small for a viewer in a vehicle, making it difficult to see the virtual object or perceive changes in its size, and that can prevent the size of the virtual object from becoming too large when the virtual object is displayed in the vicinity as the vehicle moves.

[0028] In a ninth aspect, a display control method displays a virtual object of a first size so that it is perceived by a viewer aboard the vehicle as if the virtual object were present at a predetermined real-space position in front of the vehicle, the display control method including: performing a size adjustment process in which, in response to the vehicle approaching the predetermined real-space position, the size of the virtual object maintained at the predetermined real-space position is gradually increased until the size of the virtual object reaches a second size; and, where a distance from a viewpoint position of the viewer to the predetermined real-space position is defined as a perceived distance, adjusting, during the size adjustment process, a rate of change of the size of the virtual object with respect to the perceived distance, for at least a portion of a period during which the size of the virtual object changes from the first size to the second size, so that it is smaller than a rate of change of the size of the real object when it is assumed that the virtual object is a real object present in real space.

[0029] According to the ninth aspect, a display control method can be realized that can prevent a virtual object displayed in the distance from being too small for a viewer in a vehicle, making it difficult to see the object or perceive changes in its size, and that can prevent the size of the virtual object from becoming too large when the virtual object is displayed in the close vicinity as the vehicle travels.

[0030] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1A is a diagram showing an example of the configuration of an in-vehicle system including a parallax 3D HUD device, and FIG. 1B is a diagram showing a suitable example of the configuration of a control unit. [Figure 2] 2(A) to 2(D) are diagrams showing display examples using a virtual object for forward guidance and a virtual object for turning guidance. [Figure 3]FIG. 3 is a diagram showing a display example in which a virtual object located far away is adjusted to a size that is easy to see when the virtual object is too small. [Figure 4] FIG. 4 is a diagram illustrating a problem that occurs when the size of a virtual object is changed at the same rate as that of a real object after the display example of FIG. [Figure 5] FIG. 5 is a diagram showing a display example based on the size adjustment process of the virtual object. [Figure 6] 6A and 6B are diagrams showing that the apparent size of a virtual object can be determined using the viewing angle 2θ. [Figure 7] FIG. 7 is a diagram showing an example of control when the size of a virtual object is controlled using a function that relates the visual angle 2θ to the distance (perceived distance) from the viewer to a predetermined position in real space, and an example of change in the size of the virtual object when this control is implemented. [Figure 8] FIG. 8 is a diagram showing another example of control when the size of a virtual object is controlled using a function that relates the visual angle 2θ to the distance from the viewer to a predetermined position in real space (perceived distance), and another example of change in the size of the virtual object when that control is implemented. [Figure 9] FIG. 9 is a diagram showing yet another example of control when the size of a virtual object is controlled using a function that relates the visual angle 2θ to the distance from the viewer to a predetermined position in real space (perceived distance), and yet another example of change in the size of the virtual object when that control is implemented. [Figure 10] FIG. 10 is a diagram showing an example of control in which the size of a virtual object is adjusted by variably controlling the distance (perceived distance) from the viewer to a predetermined position in real space, and an example of a change in the size of the virtual object when this control is implemented. [Figure 11] FIG. 11 is a diagram showing an example of control when initial processing is performed, and an example of a change in size of a virtual object (for example, a guide mark for guiding ahead) when the control is performed. [Figure 12] FIG. 12 is a flowchart illustrating an example of a procedure for controlling the display of a virtual object. DETAILED DESCRIPTION OF THE INVENTION

[0032] The best mode described below is used to facilitate understanding of the present invention, and therefore, those skilled in the art should be aware that the present invention is not unduly limited by the embodiments described below.

[0033] (First embodiment) Please refer to Fig. 1. Fig. 1(A) is a diagram showing an example of the configuration of an in-vehicle system including a parallax 3D HUD device, and Fig. 1(B) is a diagram showing a suitable example of the configuration of a control unit.

[0034] 1(A) and 1(B), the direction along the line segment connecting the viewer's left and right eyes E1 and E2 (in other words, the width direction of the vehicle 1) is defined as the left-right direction (or lateral direction: X direction), the direction along the line segment that is perpendicular to the left-right direction and perpendicular to the ground or a surface equivalent to the ground (here, road surface 6) is defined as the up-down direction (or height direction: Y direction), and the direction along the line segment that is perpendicular to both the left-right direction and the up-down direction (directions indicating the forward and backward directions of the vehicle 1) is defined as the front-rear direction (Z direction). The positive Z direction is defined as the forward direction, and the negative Z direction is defined as the backward direction. This is also true for the other drawings.

[0035] The in-vehicle system 3 in Figure 1 (A) provided in a vehicle (own vehicle) 1 has an pupil (or face) detection camera 43 for detecting the pupil (or face) that detects the gaze direction and position of the left eye EL and right eye ER of a viewer (a passenger, driver, etc. in the vehicle 1) 4, a front (broadly speaking, surroundings) imaging camera (e.g., a stereo camera) 45, an image processing unit 46 (including a distance measurement unit 47 and an object type / size detection unit 48), a HUD device 100, a communication unit (having functions such as GPS communication and vehicle-to-vehicle communication) 123, and an ECU 120 that can collect various information related to the vehicle 1 (e.g., lighting on / off information, vehicle speed information, information related to the engine, etc.).

[0036] If necessary, a radar unit 125 or the like may further be provided as a distance measuring means. The distance measuring means can be used, for example, to measure the distance from the vehicle 1 to a vehicle ahead (ahead object). Based on the measurement result, display control can be performed, such as performing a parallax 3D display in an area where there is no head object.

[0037] In addition, the distance measurement unit 47 included in the image processing unit 46 may, for example, refer to a pair of left and right original images captured by a stereo camera as the imaging camera 45, detect the parallax to the same object (the target object in front) by, for example, stereo matching that searches for corresponding points in each image, and measure the distance to the target object in front using the principle of triangulation based on this parallax.

[0038] Furthermore, the radar unit 125 may measure the distance and direction to the target (target ahead) by emitting radio waves toward the target (target ahead) and measuring the reflected waves.

[0039] The information acquisition unit 119 of the HUD device 100 acquires the measured distance information and the like as needed, and supplies it to the control unit 701 of the stereoscopic display device 111 .

[0040] The HUD device 100 is installed, for example, in a dashboard (not shown) of the vehicle 1. The HUD device 100 includes a stereoscopic display device 111, an optical system 116, a light exit window 118, and an information acquisition unit 119.

[0041] The information acquisition unit 119 can acquire various pieces of information from the communication unit 127, the ECU 120, the radar unit 125, the image processing unit 46, and the like.

[0042] Here, the stereoscopic display device 111 is a parallax 3D display device. The stereoscopic display device (parallax 3D display device) 111 includes an image generation unit 112, an image display unit (such as a liquid crystal display device having an image display surface for displaying an image) 113, a light beam separation unit 114 having a lenticular lens, a parallax barrier (parallax barrier), or the like, which separates light emitted from the image display surface into light beams for the left and right eyes, and a display control device 700.

[0043] The display control device 700 includes a control unit 701. The control unit 701 includes a virtual object size adjustment unit 703.

[0044] The control unit 701 can, for example, control the operation of the image generation unit (specifically, image rendering) 112 and the image display unit 113, and can also switch between 2D display and 3D display, and can also control the visibility of content images as a countermeasure against crosstalk.

[0045] The optical system 116 has a curved mirror (concave mirror or the like) 117 that reflects the light from the light beam separation unit 114 and projects the image display lights K1 and K2 onto the windshield (projection target member) 2. However, the optical system 116 may further have other optical members (lenses, auxiliary reflecting mirrors, etc.).

[0046] 1(A), viewpoint images having parallax for each of the left and right eyes (sometimes referred to as "parallax images") are displayed by the stereoscopic display device 111 of the HUD device 100. As shown in FIG. 1(A), the parallax images are displayed as virtual images 25L and 25R on a virtual image display surface (imaging surface or adjustment surface) PS serving as a first display surface.

[0047] A stereoscopic image (stereoscopic image, 3D image) 27 having a sense of depth is displayed as a virtual object VOB on a convergence surface (stereoscopic image display surface) VS, which serves as a second display surface located further back from the viewer 4 than the first display surface PS.

[0048] In the following description, the position of the first display surface PS may be referred to as the "adjustment position." Furthermore, based on a reference point set on the viewer 4 side (here, the viewer's viewpoint position), the distance to the first display surface PS may be referred to as the "adjustment distance," and the distance to the second display surface VS may be referred to as the "perceived distance (or convergence distance)," which is the distance at which the stereoscopic image is perceived by the viewer 4.

[0049] The distance from the first display surface PS to the second display surface VS may be referred to as the “virtual distance (or depth distance).” The “perceptual distance” can also be said to be the distance obtained by adding the “virtual distance” to the “adjusted distance.”

[0050] When 2D display control is executed instead of 3D display control, a planar virtual image is displayed on the first display surface PS.

[0051] 1(B), the virtual object size adjustment unit 703 included in the control unit 701 has a perceptual distance calculation unit 705 and a visual angle 2θ determination unit 707 that determines the visual angle 2θ corresponding to the calculated perceptual distance.

[0052] Here, the viewing angle 2θ is used as an index for specifying the apparent size of the virtual object VOB as seen by the viewer 4. This point will be described later with reference to FIGS. 6(A) and 6(B).

[0053] Please refer to Fig. 2. Fig. 2(A) to (D) are diagrams showing display examples using a virtual object for forward guidance and a virtual object for turning guidance.

[0054] In FIG. 2(A), a vehicle speed display (displaying "60 km / h") SP and an arrow shape (guidance arrow mark) FU1 are displayed as a virtual object VOB1 for forward guidance that moves along the road surface 6.

[0055] The arrow graphic FU1 is a type of navigation display that guides the vehicle 1 along the road surface 6. The arrow graphic FU1 can also be considered an augmented reality (AR) element of a moving object that moves along the road surface 6, either overlapping the road surface 6 or moving away from the road surface, changing its position as needed. In addition, in FIGS. 7(A) to 7(C), the movement path of the arrow graphic FU1 is indicated by a dashed arrow.

[0056] In FIG. 2(B), the arrow graphic FU1 changes its direction of travel, thereby prompting the vehicle 1 to change route.

[0057] In FIG. 2(C), the arrow FU1 approaches the right turn road 7.

[0058] In Figure 2(D), a direction change (direction change guidance) arrow graphic FU2 indicating a direction change point is displayed as virtual object VOB2. Specifically, the direction change arrow graphic FU2 is an arrow element for right turn guidance, encouraging a right turn. The transition from Figure 2(C) to Figure 2(D) results in a switch from virtual object VOB1 to VOB2.

[0059] In the example of FIG. 2(D), the graphic FU2 of the arrow for turning can be said to be displayed at a size that can be seen by the viewer 4.

[0060] Next, reference is made to Fig. 3. Fig. 3 is a diagram showing a display example in which a virtual object located far away is adjusted to an easily viewable size when it is too small.

[0061] In A-1 of Fig. 3, it is assumed that the turning point (here, left turn road 9) is located further away than the right turn point shown in Fig. 2(D). In this case, the turning guide arrow graphic FU3, which is the virtual object VOB3 indicating the left turn point (left turn road 9), is located far away, so its size becomes quite small and it is difficult for the viewer 4 to see.

[0062] In such a case, as shown in A-2 of FIG. 3, the visibility can be improved by adjusting the size of the arrow graphic FU3 for turning guidance to a size that is easy to see.

[0063] Next, reference is made to Fig. 4. Fig. 4 is a diagram showing a problem that arises when, after the display example of Fig. 3, the size of the virtual object is changed at the same rate as that of the real object.

[0064] A-1 in FIG. 4 shows a graphic FU3 of an arrow for guiding a turn as a virtual object VOB3 in A-2 in FIG.

[0065] It is assumed that the size of the arrow graphic FU3 for maneuver guidance, which is the virtual object VOB3, is then changed at the same rate of change as the real object.

[0066] In A-2 of FIG. 4, as the vehicle 1 travels forward, the perceived distance becomes shorter and the size of the arrow graphic FU3 for maneuver guidance gradually increases.

[0067] In A-3 of FIG. 4, the sensitivity of the human eye is sufficiently high in the near range, so the size of the arrow graphic FU3 for maneuver guidance as the virtual object VOB3 suddenly appears large, which can cause discomfort.

[0068] Next, reference will be made to Fig. 5. Fig. 5 is a diagram showing a display example based on the size adjustment process of a virtual object.

[0069] A-1 and A-2 in FIG. 5 are the same as A-1 and A-2 in FIG.

[0070] In A-3 of Figure 5, the size of the arrow graphic FU3 for maneuver guidance, which is the virtual object VOB3 in the near area, is adjusted to an appropriate size that is easy to see by performing a virtual object size adjustment process. This reduces the sense of incongruity and achieves a natural sense of perspective.

[0071] By performing the size adjustment process in this manner, it is possible to prevent a virtual object displayed in the distance from being too small for the viewer 4 in the vehicle 1, making it difficult to see the object or perceive changes in its size (see A-2 in Figure 3), while on the other hand, when a virtual object is displayed in the vicinity as the vehicle 1 moves, it is possible to effectively prevent the size of the virtual object from becoming too large (see A-3 in Figure 5).

[0072] Next, let us refer to Figure 6. Figures 6(A) and (B) are diagrams showing that the apparent size of a virtual object can be determined using the viewing angle 2θ. In Figure 6, parts that are common to Figure 1(A) are assigned the same reference numerals.

[0073] In Figures 6(A) and (B), the perceived distance, which is the distance from the viewpoint of the viewer 4 to a specified real space position, is denoted as Ds, the size of the virtual object VOB at the specified real space position is denoted as L, the arctangent, which is the inverse trigonometric function of tangent, is denoted as Atan, the function that converts an angle in radians to an angle in degrees is denoted as degrees, θ is denoted as degrees(Atan(L / 2Ds)), 2θ is denoted as 2*degrees(Atan(L / 2Ds)), and 2θ is the visual angle.

[0074] In Figures 6(A) and (B), Dp is the adjustment distance, which is the distance from the viewer 4's viewpoint to the first display surface (virtual image display surface) VS, VL and VR are virtual images with parallax for each of the left and right viewpoints displayed on the first display surface VS, and PS is the second display surface (convergence surface) on which the virtual object VOB is displayed.

[0075] Furthermore, the perceived distance Ds varies, for example, within a range of 4 m to 50 m. However, this is just an example and is not limited to this example. The range of perceived distances from 35 m to 50 m is generally referred to as far, and any range below this is referred to as near. However, this is just an example, and the terms far (far range) and near (near range) should be interpreted flexibly in consideration of various conditions.

[0076] For example, in the examples of FIGS. 6A and 6B, the size L of the virtual object VOB is set to, for example, 0.5 m, and there is no difference in actual size.

[0077] However, since the perceptual distance Ds is shorter in FIG. 6(B) than in FIG. 6(A), the apparent size of the virtual object VOB perceived by the viewer 4 is larger in FIG. 6(B).

[0078] As can be seen from FIGS. 6A and 6B, the visual angle 2θ corresponds to the size L of the virtual object VOB, and the shorter the perceptual distance Ds, the greater the visual angle 2θ. The degree of change (rate of change) of this visual angle 2θ with respect to the perceived distance is similar (similar) to the rate of change indicated by the characteristic line Q1 (Q2, Q3) in A-1 of FIG.

[0079] Therefore, the viewing angle 2θ can be used as an index indicating the apparent size of the virtual object VOB perceived by the viewer 4.

[0080] Therefore, based on a function (characteristic line) showing the relationship between the perceptual distance Ds and the visual angle 2θ, the visual angle 2θ corresponding to the perceptual distance Ds can be identified, and the size of the virtual object VOB can be variably controlled based on the identified visual angle 2θ.

[0081] For example, by appropriately changing the size (and display position) of the virtual images VL and VR on the first display surface (virtual image display surface) VS, the size and position of the virtual object VOB can be changed.

[0082] First, the perceptual distance calculation unit 705 of the control unit 701 shown in Figure 1(B) calculates the perceptual distance Ds, and the visual angle 2θ determination unit 707 determines (calculates, etc.) the visual angle 2θ corresponding to the calculated perceptual distance Ds, and supplies the obtained information on the visual angle 2θ to the image generation unit 112, thereby enabling the above display processing to be realized at high speed.

[0083] Next, reference is made to Fig. 7. Fig. 7 is a diagram showing an example of control when the size of a virtual object is controlled using a function that relates the visual angle 2θ to the distance from the viewer to a predetermined position in real space (perceived distance), and an example of change in the size of the virtual object when this control is implemented.

[0084] A-1 of FIG. 7 shows four characteristic lines (functions) Q1 to Q4.

[0085] The characteristic line Q1 indicated by the two-dot chain line is a characteristic line (characteristic line for the case of size "small") that indicates the size change rate (real-world size change rate) corresponding to a real object existing in real space when the size L (see Figures 6(A) and (B)) of the virtual object VOB is set to "0.05 [m]" as an example.

[0086] The characteristic line Q2 indicated by the dashed line is a characteristic line (characteristic line for a "medium" size) that indicates the size change rate (real-world size change rate) corresponding to a real object existing in real space when the size L (see Figures 6(A) and (B)) of the virtual object VOB is set to "0.07 [m]", for example.

[0087] The dashed characteristic line Q3 is a characteristic line (characteristic line for "large" size) that indicates the size change rate (real-world size change rate) corresponding to a real object existing in real space when the size L (see FIGS. 6A and 6B) of the virtual object VOB is set to "0.1 [m]" as an example.

[0088] A characteristic line Q4 indicated by a solid line is a characteristic line (adjusted characteristic line) used in the size adjustment process.

[0089] Also, in A-1 of Figure 7, for example, D10 indicates the perceived distance when the distance between the viewer 4 and the specified real space position is the farthest (when the specified real space position is the farthest), and D0 indicates the perceived distance when the distance is the shortest (when the viewer 4 is closest to the specified real space position).

[0090] The sensitivity of the human eye is low in the far range and sufficiently high in the near range, so for example, for characteristic lines Q1 to Q3, when the perceived distance is in the range of D10 to D4, the rate of change of the visual angle 2θ with respect to the perceived distance Ds is small (the change is gradual), but when the perceived distance is in the range of D4 to D0, the rate of change suddenly becomes large (the change is sudden).

[0091] As shown in the lower right of Figure 7, at perceptual distance D10, when the apparent size of the virtual object VOB is VM1, it is too small and difficult to see, so the size of the virtual object VOB is adjusted so that the apparent size becomes VM2, which is relatively easy to see.

[0092] If the apparent size of the virtual object VOB is set to VM2 at a perceptual distance D10, this apparent size VM2 corresponds to the apparent size at the perceptual distance D10 on the characteristic line Q3 for the "large" size indicated by the dashed line.

[0093] Therefore, if the size of the virtual object VOB is to be changed at the same rate as the real object, characteristic line Q3 will be selected.

[0094] However, if the size of the virtual object VOB is changed in accordance with characteristic line Q3, as shown in the upper left of A-1 in Figure 7, when the perceptual distance is D0, the apparent size of the virtual object VOB becomes VM4, which is too large and causes an uncomfortable feeling.

[0095] Therefore, in A-1 of FIG. 7, the size adjustment process is carried out using the adjusted characteristic line (function) Q4 shown by the solid line, and the size of the virtual object VOB is variably controlled while being adjusted to an appropriate size.

[0096] In other words, in the example of FIG. 7, a "size adjustment process" is carried out to adjust the size of the virtual object VOB while the vehicle 1 is approaching a predetermined real space position.

[0097] In the "size adjustment process," the rate of change of the size of the virtual object VOB with respect to the perceived distance, in other words, the degree of change in size with respect to the distance (perceived distance) between the viewer 4 and the real space position when the size of the virtual object gradually increases, is set to be smaller than the rate of change of the size of the real object during at least a part of the period when the vehicle 1 is approaching a predetermined real space position. This makes it possible to prevent the size of the virtual object VOB in the near area from becoming too large as seen by the viewer.

[0098] In the example of A-1 in Figure 7, size adjustment processing is performed using the adjusted characteristic line Q4 shown by the solid line, and when the perceptual distance is near D0, the apparent size of the virtual object VOB becomes VM3, which is not too large and is easy to see.

[0099] In this way, in the example of FIG. 7, the size of the virtual object VOB can be controlled to an appropriate size from the far area to the near area, thereby improving visibility and reducing the sense of incongruity.

[0100] Next, we will explain the main features of the adjusted characteristic line Q4 of A-1 in Fig. 7. The adjusted characteristic line Q4 shown by the solid line has a size change rate that is smaller than the size change rate of the characteristic line Q3 shown by the dashed line in the range of perceptual distances D10 to D4. This size restriction makes it possible to make the apparent size of the virtual object VOB near the perceptual distance D0 a size VM3 that is not too large.

[0101] Furthermore, in the adjusted characteristic line Q4, the rate of change of size in the range of perceptual distances D4 to D0 is set to be approximately the same as (the same as) the rate of change of the characteristic line Q3 or the characteristic line Q2.

[0102] In other words, if the period during which the apparent size of the virtual object VOB changes from the first apparent size VM2 at perceptual distance D0 to the second apparent size VM3 at perceptual distance D0 (the period from time t1 to t6 in A-2 of Figure 7) is divided, for convenience, into a far period during which the vehicle 1 is located relatively far from a predetermined real space position, and a near period during which the vehicle 1 is located relatively close, the control unit 701 sets the rate of change of the size of the virtual object VOB to be approximately the same as (the rate of change of) the size of the real object during the near period (from around time t4 to around time t6 in A-2 of Figure 7).

[0103] In the near area seen by the viewer 4, the rate of change in size of the virtual object VOB is set to be the same as the rate of change in size of the real object, thereby creating a natural perspective for the virtual object VOB similar to that of a real object in real space, which contributes to reducing the sense of incongruity.

[0104] See A-2 in Fig. 7. A-2 in Fig. 7 shows an example of a change in the distance (perceived distance) between the position of the vehicle 1 and the position of the virtual object when the apparent size of the virtual object VOB is gradually enlarged over time in a case where the size of the virtual object VOB is adjusted based on the adjusted characteristic line Q4 in A-1 in Fig. 7.

[0105] 7, the apparent size of the virtual object VOB changes at each of times t1 to t6 according to the visual angle 2θ (=Q4(Ds)) on characteristic line Q4, which corresponds to the perceptual distance Ds. In other words, with Q4(Ds) as a function on characteristic line Q4, the apparent size of the virtual object VOB changes at each of times t1 to t6 as follows: Q4(Ds(t1))=Q4(D10), Q4(Ds(t2)), Q4(Ds(t3)), Q4(Ds(t4)), Q4(Ds(t5))=Q4(D2), Q4(Ds(t6))=Q4(D0). Time t1 corresponds to the perceptual distance D10, time t5 corresponds to the perceptual distance D2, and time t6 corresponds to the perceptual distance D0. Furthermore, at each of times t1 to t6, the size of the virtual object VOB changes as the value of time t, from L(t1), L(t2), L(t3), L(t4), L(t5), L(t6), in other words, approximately as large size, large size, medium size' (medium size' > medium size), medium size, medium size, medium size. In this way, in the example of FIG. 7, the size of the virtual object VOB can be controlled to an appropriate size from the far area to the near area, thereby improving visibility and reducing the sense of incongruity.

[0106] (Second embodiment) Please refer to A-1 in Fig. 8. In the example of A-1 in Fig. 8, the size adjustment process is performed using the adjusted characteristic line (function) Q5.

[0107] In the example of A-1 in Figure 8, for convenience, the section from perceptual distance D10 to D4 (the period from time t11 to t15 in A-2 in Figure 8) is defined as the far zone, and the section from perceptual distance D4 to D0 (the period from time t15 to t19 in A-2 in Figure 8) is defined as the near zone.

[0108] 8, the rate of change in size of the virtual object VOB with respect to distance (perceived distance) in the far area (the range of perceive distances D10 to D4) is made larger than the rate of change in size of the real object with respect to distance (characteristic line Q3), emphasizing the change, making it easier to grasp the sense of perspective. In other words, even in the far area, it becomes easier for the viewer 4 to perceive the approach of the virtual object VOB.

[0109] In the distant region, the rate at which real objects in real space change in size relative to changes in distance is quite small. Therefore, if size control is performed to match the real object, it may be perceived as if the virtual object VOB is not even approaching its designated position in real space.

[0110] 8, even in the distant area, the viewer 4 can easily perceive a change in size of the virtual object VOB (in other words, a change in perspective) that accompanies the travel of the vehicle 1. In other words, the viewer 4 can easily intuitively recognize, for example, that the vehicle 1 is approaching a turning point or the like.

[0111] 8, at each of times t11 to t19, the apparent size of the virtual object VOB changes according to the visual angle 2θ on the characteristic line Q5 corresponding to the perceived distance, in other words, Q5(Ds(t11)) = Q5(D10), Q5(Ds(t12)), Q5(Ds(t13)), Q5(Ds(t14)), Q5(Ds(t15)) = Q5(D4), Q5(Ds(t16)), Q5(Ds(t17)), Q5(Ds(t18)), Q5(Ds(t19)) = Q5(D0). Time t11 corresponds to the perceived distance D10, time t15 corresponds to the perceived distance D4, and time t19 corresponds to the perceived distance D0. Furthermore, at each of times t11 to t19, the size of the virtual object VOB changes as follows: L(t11), L(t12), L(t13), L(t14), L(t15), L(t16), L(t17), L(t18), L(t19), in other words, approximately: large size, large size', large size'' (large size'' > large size' > large size), large size', medium size'' (medium size'' > medium size' > medium size), medium size', medium size, medium size, medium size. In this way, in the example of Figure 8, the size of the virtual object VOB can be controlled to an appropriate size from the far area to the near area, and visibility in the far area in particular is improved, making it possible to improve visibility and reduce the sense of discomfort.

[0112] (Third embodiment) Please refer to Fig. 9. In the example of Fig. 9, the size adjustment process is performed using the adjusted characteristic line (function) Q6 or Q7. In this embodiment, the change in size of the virtual object in the distant area is emphasized, as in the previously described example of Fig. 8. However, the example of Fig. 9 has an even higher degree of emphasis than the example of Fig. 8.

[0113] In FIG. 9, the portion of characteristic line Q6 from point A to point B corresponds to the far range, and the portion from point B to point C corresponds to the near range.

[0114] Moreover, the portion of characteristic line Q7 from point A to point D corresponds to the far range, and the portion from point D to point C corresponds to the near range.

[0115] In the example of Figure 9, the rate of change in size of a virtual object VOB in the distant area relative to distance (perceived distance) is made greater than the rate of change in size of a real object relative to distance (characteristic line Q3), thereby emphasizing the change and making it easier to grasp the sense of perspective. In other words, the viewer 4 can more easily perceive the approach of the virtual object VOB even in the far distance area.

[0116] (Fourth embodiment) Please refer to Fig. 10. Fig. 10 is a diagram showing an example of control in which the size of a virtual object is adjusted by variably controlling the distance (perceived distance) from the viewer to a predetermined position in real space, and an example of a change in the apparent size of the virtual object when this control is implemented.

[0117] A-1 in Figure 10 is the same as A-1 in Figure 8 described above. Also, the change in size of the virtual object VOB corresponding to times t11 to t19 in A-2 in Figure 10 is the same as A-2 in Figure 8, and at each of times t11 to t19, the size of the virtual object VOB changes as follows: L(t11), L(t12), L(t13), L(t14), L(t15), L(t16), L(t17), L(t18), L(t19), in other words, roughly as follows: large size, large' size, large'' size (large size'' > large' size > large), large' size, medium'' size (medium size'' > medium' size > medium), medium' size, medium size, medium, medium size.

[0118] However, in A-2 of Fig. 10, this is achieved by variably controlling the distance (perceived distance) from the viewer 4 to a predetermined position in real space from time t12 to t14. As in A-2 of Fig. 10, by changing the position at which the virtual object VOB is displayed, the apparent size of the virtual object VOB changes to Q5 (Ds(t12) after change), Q5 (Ds(t13) after change), and Q5 (Ds(t14) after change) at each of times t12 to t14, and the same effect as in the example of Fig. 8 is obtained.

[0119] (Fifth embodiment) Please refer to Fig. 11. Fig. 11 is a diagram showing an example of control when initial processing is performed, and an example of a change in size of a virtual object (for example, a guide mark for guiding ahead) when the control is performed.

[0120] A-1 in Fig. 11 is the same as A-1 in Fig. 7, which was previously explained. The changes in size of the virtual object VOB from time t1 to time t6 in A-2 in Fig. 11 and the changes in the apparent size of the virtual object VOB are also the same as A-2 in Fig. 7.

[0121] However, in A-2 of FIG. 11, the initial process is carried out in the period from time ts to time tw, before time t1.

[0122] In the initial processing at A-2 in FIG. 11, prior to the size adjustment processing, a virtual object VOB for forward guidance (for example, the arrow shape FU1 shown in FIG. 2) is moved from the near area to a predetermined distant real space position as seen by the viewer 4, thereby providing guidance on the driving route of the vehicle 1, etc.

[0123] At this time, the rate of change in size of the virtual object VOB for forward guidance relative to the perceived distance (the distance from the viewer 4 to a predetermined position in real space) can be adjusted to be the same as the rate of change in size of the real object VOB in real space. This type of display processing is called "initial processing."

[0124] From time ts to time tu, the size of the virtual object VOB for forward guidance changes from medium size to small size' to small size, or alternatively, may be fixed at small size from time ts to time tu.

[0125] This initial processing allows the viewer 4 to roughly perceive the distance to a predetermined position in real space (for example, a vehicle turning position), and gives a sense of security.

[0126] When the virtual object VOB for forward guidance reaches a predetermined position in real space, even if its size is too small to be easily seen, as explained above, for example, the virtual object VOB for turning guidance can be displayed in an easily visible size through size adjustment processing, thereby improving visibility.

[0127] Furthermore, as the vehicle 1 approaches a predetermined position in real space, the size adjustment process described above is performed to adjust the size appropriately, thereby giving the virtual object VOB for turning directions an appropriate sense of perspective and reducing the sense of incongruity. Therefore, it is possible to display a guide image (navigation image) that is easy to see and does not cause discomfort.

[0128] (Sixth embodiment) Next, reference will be made to Fig. 12. Fig. 12 is a flowchart showing an example of a procedure for controlling the display of a virtual object.

[0129] In step S1, it is determined whether or not the apparent size of the virtual object needs to be adjusted based on a rate of change different from the real-world size rate of change. The "real world size change rate" is the rate of change in size of a real object relative to distance, assuming that the virtual object is a real object in real space. If the answer is Y in step S1, the process proceeds to step S2, and if the answer is N, the process proceeds to step S7.

[0130] In step S2, a characteristic line (function) that determines the relationship between distance (perceptual distance) and size (visual angle) is selected.

[0131] In step S3, the virtual object is displayed at a size corresponding to the distance (perceptual distance) determined by the selected characteristic line (function).

[0132] In step S4, it is determined whether the distance (perceptual distance) has been changed. If the result is Y, the process proceeds to step S5, and if the result is N, the process returns to step S3.

[0133] In step S5, the distance (perceptual distance) is updated.

[0134] In step S6, it is determined whether or not to end the display. If the answer is Y, the display ends, and if the answer is N, the process returns to step S3.

[0135] In step S7, the display (3D display) based on the real world change rate is continued.

[0136] In step S8, it is determined whether or not to end the display. If the answer is Y, the display is ended, and if the answer is N, the process returns to step S7.

[0137] As described above, according to the present invention, it is possible to prevent a virtual object displayed at a distance from being too small for a viewer in a vehicle, making it difficult to see the object or perceive changes in its size, and it is also possible to prevent the size of the virtual object from becoming too large when the virtual object is displayed at a closer distance as the vehicle travels.

[0138] The present invention is not limited to the above-described embodiment and can be modified in various ways. For example, although the above-described embodiment has been described using parallax 3D as an example, the present invention can also be applied to a case where images for the left and right viewpoints are displayed as the same image without parallax in 2D.

[0139] In this specification, the term "vehicle" can be broadly interpreted as a vehicle. Furthermore, navigation-related terms (e.g., signs, etc.) are also broadly interpreted, taking into consideration the perspective of broad navigation information useful for vehicle operation. Furthermore, HUD devices and display devices (and display devices in the broad sense) are also intended to include devices used as simulators (e.g., aircraft simulators, simulators as game devices, etc.).

[0140] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art will be able to easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0141] 1···Vehicle (host vehicle), 2···Windshield (projected member), 3···Display system, 4···Viewer (passenger, driver), 6···Road surface, 43···Pupil imaging camera, 45···Surrounding imaging camera, 46···Image processing unit, 47···Distance measurement unit, 48···Object type / size detection unit, 100···HUD device, 111···Stereoscopic display device, 112···Image generation unit, 113···Display unit (display panel, etc.), 114···Light beam separation unit (lenticular lens, parallax barrier, etc.), 116···Optical unit, 117···Curved mirror (concave mirror, etc.), 118···Light exit window, 119···Information acquisition unit, 120···ECU, 121···Navigation unit, 123···Communication unit, 125···Radar unit, 700···Display control unit device (processor, etc.), 701···Control unit, 703···Virtual object size adjustment unit, 705···Perceptual distance calculation unit, 707···Visual angle 2θ determination unit, K1, K2···Display light, PS···First display surface (virtual image display surface), VS···Second display surface (convergence surface), 2θ···Visual angle.

Claims

1. A display control device including a control unit that is mounted on a vehicle and performs display control when a virtual object is displayed so as to be visible to a viewer riding in the vehicle, The control unit displaying the virtual object of a first size so that the viewer perceives the virtual object as if it were present at a predetermined real-space position in front of the vehicle; performing a size adjustment process of gradually increasing a size of the virtual object maintained at the predetermined real space position in response to the approach of the vehicle to the predetermined real space position until the size of the virtual object reaches a second size; When the distance from the viewpoint position of the viewer to the predetermined real space position is defined as the perceived distance, During the size adjustment process, adjusting a rate of change in size of the virtual object with respect to the perceived distance so that the rate of change in size of the virtual object with respect to the perceived distance is smaller than a rate of change in size of the real object when it is assumed that the virtual object is a real object existing in a real space, during at least a part of a period during which the size of the virtual object changes from the first size to the second size; Display control device.

2. The control unit a virtual image for a left viewpoint and a virtual image for a right viewpoint having parallax displayed on a virtual first display surface set in front of the vehicle; causing the viewer to perceive the virtual object as if it were present on a virtual second display screen that is set farther away than the first display screen; The display control device according to claim 1 .

3. The perceptual distance is Ds, the size of the virtual object at the predetermined real space position is L, The inverse trigonometric function of tangent, the arctangent, is written as Atan. The function that converts an angle in radians to an angle in degrees is denoted as degrees, Let θ be degrees (A tan (L / 2Ds)), 2θ is 2*degrees (A tan (L / 2Ds)), When 2θ is the visual angle, The control unit The visual angle 2θ is an index indicating the apparent size of the virtual object perceived by the viewer, specifying the visual angle 2θ corresponding to the perceived distance based on a function indicating the relationship between the perceived distance and the visual angle 2θ, and variably controlling the size of the virtual object based on the specified visual angle 2θ. The display control device according to claim 1 .

4. a period during which the size of the virtual object changes from the first size to the second size is divided into a far period during which the vehicle is located relatively far from the predetermined real space position and a near period during which the vehicle is located relatively close to the predetermined real space position, The control unit During the near period, the rate of change in size of the virtual object is set to be the same as the rate of change in size of the real object. The display control device according to claim 1 .

5. a period during which the size of the virtual object changes from the first size to the second size is divided into a far period during which the vehicle is located relatively far from the predetermined real space position and a near period during which the vehicle is located relatively close to the predetermined real space position, The control unit During the distant period, the rate of change in size of the virtual object is made larger than the rate of change in size of the real object. The display control device according to claim 1 .

6. The control unit Prior to the size adjustment process, a virtual object for forward guidance, which guides the vehicle in traveling forward, is moved from a position close to the vehicle to the predetermined real space position far away from the vehicle; During the movement, the size of the virtual object for front guidance is adjusted at a rate of change of the size of a real object when the virtual object for front guidance is assumed to be a real object. The display control device according to claim 1 .

7. the virtual object that is the target of the size adjustment process is a virtual object for turning guidance that guides the vehicle when turning, The display control device according to claim 6 .

8. an image generation unit that generates an image; a display unit that displays the image; A display control device according to any one of claims 1 to 7; and projecting display light of the image onto a projection target member provided in the vehicle, thereby allowing the viewer to perceive the virtual object; Display device.

9. 1. A display control method for displaying a virtual object of a first size so that the virtual object is perceived by a viewer riding in a vehicle as if the virtual object exists at a predetermined real space position in front of the vehicle, comprising: performing a size adjustment process in which, in response to the vehicle approaching the predetermined real space position, the size of the virtual object maintained at the predetermined real space position is gradually increased until the size of the virtual object reaches a second size, and in a case where a distance from a viewpoint position of the viewer to the predetermined real space position is a perceived distance, during the size adjustment process, adjusting a rate of change in size of the virtual object with respect to the perceived distance to be smaller than a rate of change in size of the real object when it is assumed that the virtual object is a real object existing in real space, during at least a part of a period during which the size of the virtual object changes from the first size to the second size; Display control method.

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