JP2021081232A - Superimposed image display device and computer program - Google Patents

Abstract

To provide a superimposed image display device and a computer program with which it is possible to cause the content of a guidance object to be recognized by occupants and a correspondence relation between the guidance object and a guidance target point to be intuitively grasped.SOLUTION: When a guidance target point that is a guidance target exists ahead of a vehicle in its travel direction, a guidance object for guiding to the guidance target point is displayed, and when displaying the guidance object, the distance from the vehicle to a position where the guidance object is superimposed is made to be shorter than the distance from the vehicle to the guidance target point, the distance from the vehicle to the position where the guidance object is superimposed being gradually shortened in correspondence to a decrease in the distance from the vehicle to the guidance target point due to the traveling of the vehicle, whereby the guidance object is displayed.SELECTED DRAWING: Figure 10

Description

The present invention relates to a superimposed image display device and a computer program that support the traveling of a vehicle.

Conventionally, various means have been used as information providing means for providing various information for providing various information for providing vehicle running support such as route guidance and obstacle warning to vehicle occupants. For example, a display on a liquid crystal display installed in a vehicle, a sound output from a speaker, or the like. In recent years, as one of such information providing means, there is a device that provides information by displaying an image superimposed on the surrounding environment (landscape, actual scenery) of the occupant. For example, in addition to a head-up display and a window shield display, a method of superimposing an image on a captured image of the surroundings of a vehicle displayed on a liquid crystal display and displaying the image is applicable.

For example, Japanese Patent Application Laid-Open No. 2009-236843 superimposes on a landscape when there is a sign to be guided to a vehicle occupant (for example, a sign of an intersection name installed at a guidance intersection) in front of the vehicle in the traveling direction. Then, while displaying the 3D sign at the position where the sign exists, the technique of displaying the enlarged 2D sign near the user and displaying them so as to associate them is disclosed.

JP-A-2009-236843 (pages 8-9, FIG. 8)

The technique described in Patent Document 1 superimposes and displays two guide objects, a 3D sign and a 2D sign, on a landscape. Here, since the 3D sign is superimposed on the position where the sign is actually installed (for example, the guide intersection), the size of the 3D sign becomes very small when the distance to the guide intersection is long, and the 3D sign from the occupant. There is a problem that cannot be recognized. On the other hand, since the 2D sign is always displayed in a certain size that can be seen by the occupants regardless of the distance to the guide intersection, it is possible to grasp the contents of the sign even when the distance to the guide intersection is long. However, there is a problem that it is difficult to intuitively grasp what the sign is for. Furthermore, displaying two signs with the same content at different positions at different positions at the same time causes confusion for the occupants of the vehicle and widens the area covered by the signs, resulting in deterioration of visibility to the landscape. There is also.

The present invention has been made to solve the above-mentioned conventional problems, and the contents of the guidance object can be clearly recognized by the occupant even when the distance from the vehicle to the guidance target point is long. Moreover, it is an object of the present invention to provide a superposed image display device and a computer program capable of intuitively grasping the correspondence relationship between a guide object and a guide target point.

In order to achieve the above object, the superimposed image display device according to the present invention is a superimposed image display device mounted on a vehicle and superimposing and visually recognizing a guide object for guiding information to the occupants of the vehicle on the scenery around the vehicle. Therefore, when there is a guidance target point to be guided in front of the traveling direction of the vehicle, the object display means for displaying the guidance object for guiding the guidance target point is provided, and the object display means is The first distance from the vehicle to the position where the guide object is superimposed is set to be shorter than the second distance from the vehicle to the guide target point, and the second distance becomes shorter as the vehicle travels. The guide object is displayed by gradually shortening the first distance accordingly.
The "landscape" includes, in addition to the scenery (actual scenery) actually seen from the vehicle, an image obtained by capturing the scenery, an image reproducing the scenery, and the like.

Further, the computer program according to the present invention is a program for supporting the traveling of a vehicle. Specifically, a superposed image display device mounted on the vehicle to superimpose and visually recognize a guidance object that guides information to the occupants of the vehicle on the scenery around the vehicle is to be guided in front of the vehicle in the traveling direction. This is a computer program for functioning as an object display means for displaying the guidance object for guiding the guidance target point when there is a guidance target point. Further, the object display means sets the first distance from the vehicle to the position where the guide object is superimposed to be shorter than the second distance from the vehicle to the guide target point, and the vehicle travels. As the second distance becomes shorter, the first distance is gradually shortened to display the guide object.

According to the superimposed image display device and the computer program according to the present invention having the above configuration, since the guide object is superimposed on the position closer to the guide target point and visually recognized by the occupant, the distance from the vehicle to the guide target point is increased. Even in the state, it is possible to make the occupant clearly recognize the contents of the guide object. On the other hand, as the vehicle approaches the guidance target point, the guidance object gradually approaches and is visually recognized by the occupants, so that the correspondence between the guidance object and the guidance target point can be intuitively grasped. Is possible.

It is a block diagram which showed the navigation device which concerns on 1st Embodiment. It is a flowchart of the driving support processing program which concerns on 1st Embodiment. It is a figure which showed an example of the traveling guidance screen displayed on the liquid crystal display. It is a flowchart of the sub-processing program of the guide object display position determination processing. It is a figure which showed the relationship between the distance from a vehicle to a guide target point, and the distance from a vehicle to a guide object. It is a figure which showed the arrangement example (horizontal direction) of a guide object. It is a figure which showed the arrangement example (vertical direction) of a guide object. It is a figure which showed the transition of the arrangement mode of the guide object with the traveling of a vehicle. It is a figure which showed an example of the visual recognition image which visually recognized the guide object arranged in the three-dimensional space. It is a figure which showed the traveling guidance screen which is displayed on the liquid crystal display as the vehicle travels. It is a schematic block diagram of the superimposition image display device which concerns on 2nd Embodiment. It is a figure which showed the display example of the guide object in the superimposition image display apparatus which concerns on 2nd Embodiment.

Hereinafter, the first embodiment and the second embodiment in which the superimposed image display device according to the present invention is embodied in a navigation device will be described in detail with reference to the drawings.

[First Embodiment]
First, the schematic configuration of the navigation device 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a navigation device 1 according to the first embodiment.

As shown in FIG. 1, the navigation device 1 according to the first embodiment includes a current position detection unit 11 that detects the current position of a vehicle on which the navigation device 1 is mounted, and a data recording unit 12 in which various data are recorded. , A navigation ECU 13 that performs various arithmetic processes based on the input information, an operation unit 14 that accepts operations from the user, and a liquid crystal display 15 that displays an actual scene image of the front in the traveling direction for the user. Communication is performed between the speaker 16 that outputs voice guidance regarding route guidance, the DVD drive 17 that reads DVD as a storage medium, and an information center such as a probe center or a VICS (registered trademark: Vehicle Information and Communication System) center. It has a communication module 18. Further, the navigation device 1 is connected to a front camera 19 and various sensors installed on the vehicle on which the navigation device 1 is mounted via an in-vehicle network such as CAN.

Hereinafter, each component of the navigation device 1 will be described in order.
The current position detection unit 11 includes a GPS 21, a vehicle speed sensor 22, a steering sensor 23, a gyro sensor 24, and the like, and can detect the current position and direction of the vehicle, the traveling speed of the vehicle, the current time, and the like. .. Here, in particular, the vehicle speed sensor 22 is a sensor for detecting the moving distance and the vehicle speed of the vehicle, generates a pulse according to the rotation of the driving wheel of the vehicle, and outputs the pulse signal to the navigation ECU 13. Then, the navigation ECU 13 calculates the rotation speed and the moving distance of the drive wheels by counting the generated pulses. It is not necessary for the navigation device 1 to include all of the above four types of sensors, and the navigation device 1 may include only one or a plurality of of these sensors.

Further, the data recording unit 12 is a driver for reading a hard disk (not shown) as an external storage device and a recording medium, a map information DB 31 recorded on the hard disk, a predetermined program, and the like, and writing predetermined data on the hard disk. It is equipped with a recording head (not shown). The data recording unit 12 may be configured by a flash memory, a memory card, or an optical disk such as a CD or DVD instead of the hard disk. Further, the map information DB 31 may be stored in an external server and acquired by the navigation device 1 by communication.

Here, the map information DB 31 is, for example, link data 32 related to a road (link), node data 33 related to a node point, branch point data 34 related to a branch point, point data related to a point such as a facility, and a map display for displaying a map. It is a storage means in which data, search data for searching a route, search data for searching a point, and the like are stored.

Further, the link data 32 includes the width of the road to which the link belongs, the width of the road, the cant, the bank, the condition of the road surface, the number of lanes of the road, the place where the number of lanes decreases, and the width of each link constituting the road. Data representing narrowed points, crossings, etc. are data representing corners such as radius of curvature, intersections, T-shaped roads, corner entrances and exits, and data representing road attributes such as downhill roads and uphill roads are roads. Data representing highways and general roads (national roads, prefectural roads, narrow streets, etc.) are recorded for each type.

Further, as the node data 33, the coordinates (positions) of the actual road branch points (including intersections, T-shaped roads, etc.) and the node points set for each predetermined distance according to the radius of curvature of each road, etc. A node attribute that indicates whether a node is a node corresponding to an intersection, a connection link number list that is a list of link numbers of links that connect to a node, and an adjacency that is a list of node numbers of nodes that are adjacent to a node via a link. Data related to the node number list, the height (altitude) of each node point, etc. are recorded.

Further, the branch point data 34 includes the intersection name of the branch point, the corresponding node information for specifying the node forming the branch point, the connection link information for specifying the link connected to the branch point, and the link connected to the branch point. The corresponding direction name, information for specifying the shape of the branch point, etc. are stored. In addition, the structure that can be a mark when performing right / left turn guidance at the branch point is also memorized.

On the other hand, the navigation ECU (electronic control unit) 13 is an electronic control unit that controls the entire navigation device 1, and is a computing device, a CPU 41 as a control device, and a working memory when the CPU 41 performs various arithmetic processes. In addition to being used as a RAM 42 for storing route data and the like when a route is searched, a control program, and a ROM 43 and a ROM 43 in which a travel support processing program (FIG. 2) described later is recorded are read. It is provided with an internal storage device such as a flash memory 44 for storing a program. The navigation ECU 13 has various means as a processing algorithm. For example, the object display means displays a guidance object for guiding to a guidance target point when there is a guidance target point to be guided ahead in the traveling direction of the vehicle.

The operation unit 14 is operated when inputting a starting point as a traveling start point and a destination as a traveling end point, and has a plurality of operation switches (not shown) such as various keys and buttons. Then, the navigation ECU 13 controls to execute various corresponding operations based on the switch signals output by pressing each switch or the like. The operation unit 14 may have a touch panel provided on the front surface of the liquid crystal display 15. Further, the configuration may include a microphone and a voice recognition device.

Further, on the liquid crystal display 15, map images including roads, traffic information, operation guidance, operation menus, key guidance, guidance routes from the departure point to the destination, guidance information along the guidance routes, news, weather forecasts, etc. The time, mail, TV program, etc. are displayed. Further, particularly in the first embodiment, the liquid crystal display 15 displays an image captured by the front camera 19, that is, a landscape (actual view image) around the vehicle at the present time (particularly in front of the vehicle) during normal driving, which is further necessary. The guide object is superimposed and displayed on the landscape according to the above.

Here, as the guide object displayed superimposed on the landscape, there are various information used for supporting the driving of the occupant and the information about the vehicle. For example, a warning to an object (another vehicle, a pedestrian, a guide sign) to be warned to an occupant, a guide route set by the navigation device 1, and guidance information based on the guide route (arrow indicating the right / left turn direction, guidance branch). Icon indicating a dot mark, distance to a guide branch point, etc.), warning displayed on the road surface (crash caution, speed limit, etc.), lane marking line where the vehicle is traveling, current vehicle speed, shift position, remaining energy, advertisement There are images, facility information, information signs, map images, traffic information, news, weather forecasts, times, screens of connected smartphones, etc. In the first embodiment described below, the guide object is the guide information for guiding at the guide branch point ahead in the traveling direction of the vehicle, and more specifically, the exit of the guide branch point along the guide route. It shall be a (guidance) sign indicating the direction.

Further, the speaker 16 outputs voice guidance for guiding the traveling along the guidance route and traffic information guidance based on the instruction from the navigation ECU 13.

The DVD drive 17 is a drive capable of reading data recorded on a recording medium such as a DVD or a CD. Then, based on the read data, music and video are reproduced, the map information DB 31 is updated, and the like. A card slot for reading and writing a memory card may be provided instead of the DVD drive 17.

Further, the communication module 18 is a communication device for receiving traffic information including various information such as traffic jam information, regulation information, and traffic accident information transmitted from a traffic information center, for example, a VICS center or a probe center. For example, mobile phones and DCM.

Further, the front camera 19 is an image pickup device having a camera using a solid-state image pickup element such as a CCD, and is installed with the optical axis direction facing forward in the traveling direction of the vehicle. Then, the captured image captured by the front camera 19 is displayed on the liquid crystal display 15 as a landscape (actual scene image) around the vehicle (particularly in front of the vehicle) as described above.

Subsequently, a travel support processing program executed by the navigation ECU 13 in the navigation device 1 having the above configuration will be described with reference to FIG. FIG. 2 is a flowchart of the traveling support processing program according to the first embodiment. Here, the travel support processing program is executed after the ACC power supply (accessory power supply) of the vehicle is turned on, and the vehicle travels by visually recognizing the guidance object superimposed on the scenery around the vehicle displayed on the liquid crystal display 15. It is a program that provides support. The programs shown in the flowcharts of FIGS. 2 and 4 below are stored in the RAM 42 and ROM 43 included in the navigation device 1 and are executed by the CPU 41.

In the following description, as a vehicle traveling support using the guidance object, an example of providing vehicle traveling guidance along the guidance route set by the navigation device 1 will be described. In addition, the guidance object to be displayed is the guidance information for guiding at the guidance branch point ahead in the traveling direction of the vehicle, and in particular, the processing when displaying the sign indicating the exit direction of the guidance branch point as the guidance object is performed. Let's take an example. However, the navigation device 1 can also provide guidance and information other than the above-mentioned traveling support by using the guidance object. Further, the guide object to be displayed can be information other than the above arrows. For example, warnings to occupants as guidance objects (other vehicles, pedestrians, guidance signs), warnings to be displayed on the road surface (rear-end collision caution, speed limit, etc.), lane markings in which the vehicle travels It is also possible to display the current vehicle speed, shift position, remaining energy, advertising image, facility information, guide sign, map image, traffic information, news, weather forecast, time, screen of connected smartphone, and the like.

First, in the travel support processing program, in step 1 (hereinafter abbreviated as S) 1, the CPU 41 specifies the current position of the vehicle based on the detection result of the current position detection unit 11 and the map information. When specifying the current position of the vehicle, a map matching process for matching the current position of the vehicle with the map information is also performed. After that, the guide route set by the navigation device 1 is read out, and the distance from the current position of the specified vehicle to the next guide branch point along the guide route is calculated. The guide branch point is a branch point (intersection) to which guidance such as a right / left turn instruction is given when the navigation device 1 guides the traveling according to the guidance route set in the navigation device 1.

Next, in S2, the CPU 41 determines whether or not the distance to the next guidance branch point calculated in S1 is equal to or less than the predetermined guidance start distance. The guidance start distance is determined by the road type of the road on which the vehicle travels. For example, the expressway is set to 1000 m. On the other hand, if there is another branch point on a general road within 500 m, which is shorter than the expressway, or 500 m on the front side of the guide branch point, the distance from the guide branch point to the other branch point is set.

Then, when it is determined that the distance to the next guidance branch point calculated in S1 is equal to or less than the guidance start distance (S2: YES), the process proceeds to S3. On the other hand, when it is determined that the distance to the next guidance branch point calculated in S1 is not less than or equal to the guidance start distance (S2: NO), the process returns to S1.

In S3, the CPU 41 acquires the coordinates of the point to be guided by the guide object, that is, the point where the guide object should be superimposed (arranged) (hereinafter referred to as the guide target point). In the first embodiment, since the guidance object is used to guide the exit direction at the guidance branch point, the guidance branch point corresponds to the guidance target point. Therefore, the coordinates of the guidance target point are the coordinates X of the guidance branch point. Corresponds to. The coordinates X of the guidance branch point are specified from the map information possessed by the navigation device 1, but may be specified by performing image recognition processing on the image captured by the front camera 19. In that case, for example, on an expressway, the coordinates X of the branch approach point (start point at which the branch starts) are set as shown in FIGS. 6 and 8.

Next, in S4, the CPU 41 performs a guide object display position determination process (FIG. 4) described later. The guide object display position determination process is based on the current position of the vehicle and the coordinates of the guide target point acquired in S3, and the shape of the guide object to be displayed on the liquid crystal display 15 and the position (range) at which the guide object is displayed. Is a process for specifically determining. The shape of the guide object and the position where the guide object is displayed, which are determined in S4, are conditions for superimposing the guide object on the guide target point in the landscape and making the occupant visually recognize the guide object. However, in the first embodiment, as will be described later, the guide object is superimposed on the guide target point in the landscape and visually recognized.

Subsequently, in S5, the CPU 41 transmits a control signal to the liquid crystal display 15, and displays an image of the guide object having the shape determined in S4 on the liquid crystal display 15 at the position (range) determined in S4. Display against. The liquid crystal display 15 displays an image captured by the front camera 19 in advance, that is, a landscape (actual view image) around the vehicle (particularly in front of the vehicle) at the present time. As a result, it becomes possible for the occupants of the vehicle to visually recognize the guide object superimposed on the landscape.

FIG. 3 is a diagram showing an example of a traveling guide screen 51 displayed on the liquid crystal display 15 in S5. As shown in FIG. 3, the liquid crystal display 15 displays the current scenery 52 in front of the vehicle captured by the front camera 19. Then, the image 53 of the guide object is displayed so as to be superimposed on the landscape 52 in front of the vehicle. The image 53 of the guidance object is displayed superimposed on a predetermined point in the landscape 52 (for example, a point in front of a predetermined distance of the vehicle), and includes an arrow indicating the exit direction of the guidance branch point of the vehicle and a sign including the direction name of the exit direction. Has the shape of. Therefore, when the occupant of the vehicle visually recognizes the traveling guidance screen 51, the position of the guidance branch point to be turned left or right and the exit direction at the guidance branch point can be accurately grasped.

In addition to the above-mentioned sign indicating the exit direction of the guidance branch point of the vehicle as a guidance object, an arrow indicating the exit direction of the guidance branch point and an image indicating the distance to the guidance branch point are also displayed superimposed on the landscape. You can do it. For example, the position where the arrow indicating the exit direction of the guide branch point is superimposed is the position of the guide branch point, and is displayed while the distance from the vehicle to the guide branch point is within a predetermined distance section (for example, within 300 m). Further, the position where the image showing the distance to the guide branch point is superimposed is set on the road surface closest to the front of the vehicle, and is displayed while the distance from the vehicle to the guide branch point is within a predetermined distance section (for example, 1000 m to 150 m). To do.

After that, in S6, the CPU 41 calculates the distance from the current position of the vehicle to the next guide branch point along the guide path in the same manner as in S1, and the calculated distance to the next guide branch point is a predetermined guide. Determine if it is less than or equal to the end distance. The guidance end distance is determined by the road type of the road on which the vehicle travels. For example, the expressway is 50 m, and the general road is 10 m, which is shorter than the expressway.

Then, when it is determined that the distance to the next guidance branch point is equal to or less than the guidance end distance (S6: YES), the process proceeds to S7. On the other hand, when it is determined that the distance to the next guidance branch point is not less than or equal to the guidance end distance (S6: NO), the process returns to S4 and the guidance object is continuously displayed.

Subsequently, in S7, the CPU 41 transmits a control signal to the liquid crystal display 15, and gradually changes the transmittance of the image of the guide object displayed on the liquid crystal display 15 according to the distance to the guide branch point. Raise it. Specifically, the transmittance is increased so that the transmittance becomes 100% at the timing when the vehicle reaches the guide branch point. The transmittance of the guide object image is set to, for example, 20% instead of 0% at the start of display so that the vehicle occupants can grasp the scenery hidden behind the guide object image (however,). , The transmittance at the start of display may be 0%). Therefore, the image of the guide object is displayed with a transmittance of 20% until the distance from the vehicle to the guide branch point is less than or equal to the guide end distance, and then 20% → 30% → 40% as it approaches the guide branch point. The transmittance gradually increases as → ..., and the transmittance finally reaches 100% when the vehicle finally reaches the guide branch point.

After that, in S8, the CPU 41 determines whether or not the vehicle has passed the guide branch point. For example, the determination is made based on the current position of the vehicle detected by the current position detection unit 11 and the map information.

Then, when it is determined that the vehicle has passed the guidance branch point (S8: YES), a control signal is transmitted to the liquid crystal display 15 to hide the guidance object displayed on the liquid crystal display 15. (S9). The captured image captured by the front camera 19, that is, the landscape (actual view image) around the vehicle at the present time (particularly in front of the vehicle) is continuously displayed. However, the landscape image may also be hidden and the display screen of the liquid crystal display 15 may be switched to a map image display or the like. The guide object may be hidden at a timing before the vehicle passes the guide branch point (for example, 30 m before the guide branch point) instead of the timing when the vehicle passes the guide branch point.

On the other hand, when it is determined that the vehicle has not passed the guide branch point (S8: NO), the vehicle returns to S4 and the guide object is continuously displayed.

Next, a sub-process of the guide object display position determination process executed in S4 will be described with reference to FIG. FIG. 4 is a flowchart of a sub-processing program for guiding object display position determination processing.

First, in S11, the CPU 41 identifies the current position of the vehicle based on the detection result of the current position detection unit 11 and the map information. When specifying the current position of the vehicle, a map matching process for matching the current position of the vehicle with the map information is also performed. After that, the distance from the current position of the specified vehicle to the coordinates of the guidance target point (that is, the guidance branch point) acquired in 3 above is calculated.

Next, in S12, the CPU 41 determines whether or not the distance to the coordinates of the guidance target point calculated in S11 is less than a predetermined threshold value. The timing at which the distance to the coordinates of the guidance target point becomes the threshold value is the content of the guidance object arranged on the liquid crystal display 15 one distance ahead of the current position of the vehicle as in S15 described later. The timing is set so that the occupant can surely see it (that is, the timing when the display size of the guide object becomes sufficiently large for easy recognition). For example, the threshold value is set to 300 m.

Then, when it is determined that the distance to the guidance target point calculated in S11 is less than the threshold value (S12: YES), the process proceeds to S16. On the other hand, when it is determined that the distance to the guidance target point calculated in S11 is equal to or greater than the threshold value (S12: NO), the process proceeds to S13.

In S13, the CPU 41 acquires the proportionality coefficient. Here, in the first embodiment, when the distance from the current position of the vehicle to the guidance target point is equal to or greater than the threshold value, the distance from the current position of the vehicle to the guidance target point as the vehicle travels (hereinafter referred to as the second). As the distance) becomes shorter, the distance from the current position of the vehicle to the position on which the guide object is superimposed (hereinafter referred to as the first distance) is gradually shortened to display the guide object. Then, when the first distance is shortened according to the second distance, the ratio of the decrease value of the first distance to the decrease value of the second distance is a constant, and in S13, the constant is acquired as a proportional coefficient.

For example, as shown in FIG. 5, if the second distance is 300 m, the first distance is 50 m, and the second distance is 1000 m, the first distance is 150 m. The constant N, which is the ratio (inclination) of the decrease value of the first distance to the decrease value, is 1/7. Therefore, 1/7 is acquired as the proportional coefficient. The proportional coefficient is not necessarily 1/7 and can be set as appropriate.

Subsequently, in S14, the CPU 41 determines the current state of the vehicle corresponding to the present time based on the proportional coefficient acquired in S13 and the distance from the current position of the vehicle to the guidance target point calculated in S11 (that is, the second distance). The distance from the position to the guide object (that is, the first distance) is calculated. For example, in the case of the conditions shown in FIG. 5, the first distance is calculated by the following equation (1).
1st distance [m] = (2nd distance [m] +50) / 7 ... (1)

After that, in S15, the CPU 41 sets the "position where the guide object is superimposed on the landscape" at a position where the guide object is superimposed and visually recognized in front of the first distance calculated in S14 from the current position of the vehicle. .. Specifically, the position one distance ahead of the current position of the vehicle is set as the superimposition (arrangement) position of the guide object.

On the other hand, in S16, the CPU 41 sets the "position where the guide object is superimposed on the landscape" at a position where the guide object is superimposed and visually recognized while the relative position with respect to the current position of the vehicle is fixed. Specifically, the position in front of the first distance, which is a fixed value with respect to the current position of the vehicle, is set as the overlapping (arrangement) position of the guide object. The first distance set in S16 is the first distance calculated when the second distance is set as the threshold value of the determination condition of S12 in the above formula (1) (for example, the threshold value is 300 m and the proportional coefficient is 1). If it is / 7, it shall be 50 m). As a result, when the second distance crosses the threshold value (the timing when S12 changes from NO to YES), the superposed position of the guide object does not change significantly, so that the occupant of the vehicle does not feel uncomfortable.

Next, in S17, the CPU 41 creates a three-dimensional space corresponding to the vicinity of the current position of the vehicle (particularly in front of the vehicle in the traveling direction). In addition to roads, buildings, road signs, and the like may be modeled in the three-dimensional space, or only roads may be modeled. Alternatively, the road may be simply a blank three-dimensional space with only the ground that is not modeled. Further, the three-dimensional space may be stored in the map information DB 31 as three-dimensional map information in advance, and in S17, the three-dimensional map information around the position of the own vehicle may be read out from the map information DB 31. Further, a three-dimensional space may be generated based on the image captured by the front camera 19. For example, by performing point cloud matching on the captured image captured by the front camera 19, it is possible to detect a road or a structure around the road and generate a three-dimensional space.

Further, in S17, the CPU 41 also specifies the current position and orientation of the own vehicle in the generated three-dimensional space based on the parameters detected by the current position detection unit 11. In particular, the position of the front camera 19 installed in the vehicle is set as the current position of the own vehicle, and the optical axis direction of the front camera 19 is set as the direction of the own vehicle. The position of the front camera 19 corresponds to the position of the occupant of the vehicle, and the optical axis direction of the front camera 19 also corresponds to the line-of-sight direction of the occupant of the vehicle.

Subsequently, in S18, the CPU 41 generates a guide object to be displayed on the liquid crystal display 15. In the first embodiment, the guide object is a sign indicating the exit direction of the guide branch point ahead of the vehicle in the traveling direction, and in particular, as shown in FIGS. 6 to 8, an arrow indicating the exit direction of the vehicle guide branch point and exit. Generate a sign 61 that includes a direction name for the direction. If the guide route is a route that turns right at a guide branch point ahead in the traveling direction, the sign includes an arrow indicating the right direction. If the guide route is a route that turns left at a guide branch point ahead in the direction of travel, the sign includes an arrow indicating the left direction. Further, the guide object is a two-dimensional polygon, and basically there is no thickness. However, it may be a three-dimensional polygon having a thickness. Further, the shape of the guide object generated in S18 can be changed as appropriate, and any sign that can indicate the exit direction at the guide branch point may be used. For example, the sign may omit the direction name.

Subsequently, in S19, the CPU 41 arranges the guide object generated in S18 with respect to the three-dimensional space generated in S17. The position where the guide object is arranged in the three-dimensional space is determined based on the "position where the guide object is superimposed on the landscape" set in S15 or S16.

As described above, the "position where the guide object is superimposed on the landscape" is set to the position one distance ahead of the current position of the vehicle. Therefore, as shown in FIG. 6, the current position of the vehicle 64 in the three-dimensional space is set. The sign 61, which is a guide object, is placed at a position one distance ahead of the position. Here, FIG. 6 is a diagram showing an example of arrangement of guide objects when a guide route for exiting the guide branch point 60 of the expressway to the left is set as an example. Specifically, as shown in FIG. 6, the vehicle 64 is arranged at the left edge of the road in the traveling direction at a position separated by the first distance from the current position of the vehicle 64. Here, the sign 61 has a rectangular shape and is arranged so as to be parallel to the direction intersecting the traveling direction (that is, to face the vehicle side). On the other hand, in the vertical direction, as shown in FIG. 7, the lower end of the sign 61 is arranged at a position separated from the road surface by a predetermined distance (for example, 1 m).

Further, as described above, the calculation standard for the first distance differs depending on whether the second distance, which is the distance from the current position of the vehicle to the guidance target point, is equal to or more than the threshold value and is less than the threshold value. Specifically, when the second distance is equal to or greater than the threshold value, the first distance is gradually shortened as the second distance becomes shorter as the vehicle travels. On the other hand, when the second distance is less than the threshold value, the first distance becomes a fixed value regardless of the second distance. Therefore, as shown in FIG. 8, the position where the sign 61 is arranged in the three-dimensional space is such that the sign 61 also refers to the vehicle 64 as the vehicle 64 approaches the guide branch point when the vehicle 64 is away from the guide branch point. It is arranged so that it gradually approaches. However, after the sign 61 approaches the vehicle 64 to a certain distance (for example, 50 m), the distance from the vehicle 64 to the sign 61 is maintained at a constant distance.

Next, in S20, the CPU 41 first visually recognizes the three-dimensional space in which the guide object is arranged from the position of the vehicle (corresponding to the viewpoint) specified in S17 in the traveling direction of the vehicle (hereinafter referred to as a visual image). ) To get. For example, FIG. 9 is a diagram showing a visual image 66 acquired when a vehicle and a guide object are arranged in the manner shown in FIG. In particular, since the position of the vehicle is the position of the front camera 19, the acquired visual image 66 is an image that can be visually recognized when the guide object arranged in the three-dimensional space is visually recognized from the viewpoint of the front camera 19 in the traveling direction of the vehicle. However, it also corresponds to the visibility of the occupants of the vehicle.

After that, the CPU 41 stores the shape of the guide object and the position of the guide object included in the visual image 66 as the shape of the guide object to be displayed by the liquid crystal display 15 and the position of the guide object. Here, the shape of the guide object stored in S20 is the shape of the guide object that can be visually recognized when the guide object arranged in the three-dimensional space is visually recognized from the viewpoint of the vehicle (more accurately, the front camera 19). .. Further, the position of the guide object stored in S20 is the position of the guide object that can be visually recognized when the guide object arranged in the three-dimensional space is visually recognized from the viewpoint of the vehicle (more accurately, the front camera 19).

After that, in S21, the CPU 41 determines the range in which the guide object is displayed on the liquid crystal display 15 based on the shape of the guide object and the position of the guide object stored in S20. The display range of the guide object is a range in which the guide object having the shape stored in S20 is displayed at the same position as the guide object arranged in the three-dimensional space. After that, the process proceeds to S5, a control signal is transmitted to the liquid crystal display 15 as described above, and an image of the guide object having the shape stored in S20 is determined in S21 to the liquid crystal display 15. Display in the display range.

As a result, the travel guidance screen 51 displayed on the liquid crystal display 15 as the vehicle travels becomes a screen as shown in FIG. First, when the distance from the vehicle to the guidance branch point is equal to or less than the guidance start distance (for example, 1000 m), the image 53 of the guidance object is superimposed on the landscape 52 in front of the vehicle in the traveling direction captured by the front camera 19. Will be done. The position where the image 53 of the guide object is first superimposed is a position on the front side (for example, 300 m ahead) of the guide branch point which is the guide target point. After that, the distance from the vehicle to the position where the image 53 of the guide object is superimposed is gradually shortened as the vehicle approaches the guide branch point as the vehicle travels. Since the relative distance to the vehicle is gradually shortened, the display size of the displayed guide object image 53 is gradually increased.

After that, when the vehicle approaches the guide branch point to a threshold value (for example, 300 m), the image 53 of the guide object is displayed superimposed on the current position of the vehicle in a fixed state. Since the relative position with respect to the vehicle is fixed, the display size of the displayed guide object image 53 is also fixed thereafter. Further, when the distance from the vehicle to the guide branch point becomes less than or equal to the guide end distance (for example, 50 m), the transmittance of the image 53 of the guide object gradually increases (S7), and the timing when the vehicle passes the guide branch point. The image 53 of the guide object disappears from the liquid crystal display 15 (S9). After the relative position between the vehicle and the image 53 of the guide object is fixed, the color of the image 53 of the guide object is changed or the shape of the image 53 of the guide object is changed in order to show that to the occupants. You may.

As a result, when the occupant of the vehicle visually recognizes the traveling guidance screen 51, the image 53 of the guidance object indicating the exit direction of the guidance branch point can be clearly visually recognized even when the vehicle is far from the guidance branch point. , You can accurately grasp the exit direction of the guidance branch point. Further, as the vehicle approaches the guide branch point, the image 53 of the guide object is gradually approached and visually recognized by the occupants, so that the correspondence between the guide object and the guide branch point can be intuitively grasped. It becomes possible to make it. After that, after the vehicle approaches the guide branch point to some extent and the image 53 of the guide object can be reliably seen by the occupants of the vehicle, the relative position between the vehicle and the guide object is fixed, so that the guide object It is possible to keep the guide object visible to the occupants of the vehicle in a state where it is easy to see without enlarging the display size of the above.

As described in detail above, according to the navigation device 1 and the computer program executed by the navigation device 1 according to the first embodiment, when there is a guidance target point to be guided ahead in the traveling direction of the vehicle, the guidance target is to be guided. The guidance object for guiding the point is displayed (S5). On the other hand, when the guidance object is displayed, the distance from the vehicle to the position where the guidance object is superimposed is shorter than the distance from the vehicle to the guidance target point. In addition to setting the distance, the distance from the vehicle to the position where the guidance object is superimposed is gradually shortened as the distance from the vehicle to the guidance target point becomes shorter as the vehicle travels, and the guidance object is displayed (S12). Since ~ S15), it is possible to make the occupant clearly recognize the contents of the guidance object even when the distance from the vehicle to the guidance target point is long. On the other hand, as the vehicle approaches the guidance target point, the guidance object gradually approaches and is visually recognized by the occupants, so that the correspondence between the guidance object and the guidance target point can be intuitively grasped. Is possible.

[Second Embodiment]
Next, the superimposed image display device according to the second embodiment will be described with reference to FIGS. 11 and 12. In the following description, the same reference numerals as the configuration of the superimposed image display device according to the first embodiment of FIGS. 1 to 10 are the same as or corresponding to the configuration of the superimposed image display device or the like according to the first embodiment. It shows.

The schematic configuration of the superimposed image display device according to the second embodiment is almost the same as that of the superimposed image display device according to the first embodiment. Further, various control processes are also substantially the same as the superimposed image display device according to the first embodiment.
However, the superimposed image display device according to the first embodiment displays the captured image captured by the front camera 19 on the liquid crystal display 15 of the navigation device 1, and further displays the guide object on the liquid crystal display 15. , While the guide object is superimposed and displayed on the landscape around the vehicle, the superimposed image display device according to the second embodiment uses a head-up display system as a means for displaying the image superimposed on the landscape around the vehicle. Is different.

The schematic configuration of the superimposed image display device according to the second embodiment will be described below with reference to FIG. FIG. 11 is a schematic configuration diagram of the superimposed image display device 101 according to the second embodiment.
As shown in FIG. 11, the superimposed image display device 101 basically includes a navigation device 103 mounted on the vehicle 102 and a front display 104 mounted on the vehicle 102 and connected to the navigation device 103. The front display 104 functions as a head-up display together with the windshield 105 of the vehicle 102, and serves as an information providing means for providing various information to the occupant 106 of the vehicle 102.

Here, the front display 104 is a liquid crystal display installed inside the dashboard 107 of the vehicle 102 and having a function of displaying an image on an image display surface provided on the front surface. As the backlight, for example, CCFL (cold cathode fluorescent lamp) or white LED is used. As the front display 104, a combination of an organic EL display or a liquid crystal projector and a screen may be used in addition to the liquid crystal display.

Then, the front display 104 functions as a head-up display together with the windshield 105 of the vehicle 102, and the image output from the front display 104 is reflected on the windshield 105 in front of the driver's seat to be visually recognized by the occupant 106 of the vehicle 102. It is configured as follows. A guide object is displayed on the front display 104 as needed. In the second embodiment described below, the guide object is the guide information for guiding at the guide branch point ahead in the traveling direction of the vehicle as in the first embodiment, and more specifically, the guide branch point. An arrow or the like indicating the exit direction of.

Further, when the occupant 106 visually recognizes the image displayed on the front display 104 by reflecting the windshield 105, the occupant 106 does not have the position of the windshield 105 but the front display at a position far beyond the windshield 105. The image displayed on the 104 is configured to be visually recognized as a virtual image 110. Further, the virtual image 110 is displayed superimposed on the surrounding environment (landscape, actual scenery) in front of the vehicle, and is superimposed on, for example, an arbitrary object (road surface, building, object to be warned, etc.) located in front of the vehicle. It is also possible to display it.

Here, the position where the virtual image 110 is generated, more specifically, the distance L from the occupant 106 to the virtual image 110 (hereinafter, referred to as an imaging distance) L is determined by the position of the front display 104. For example, the image formation distance L is determined by the distance (optical path length) along the optical path from the position where the image is displayed on the front display 104 to the windshield 105. For example, the optical path length is set so that the imaging distance L is 1.5 m.

Further, the front camera 111 is installed above the front bumper of the vehicle, behind the rearview mirror, and the like. The front camera 111 is an image pickup device having a camera using a solid-state image sensor such as a CCD, and is installed with the optical axis direction facing forward in the traveling direction of the vehicle. Then, by performing image processing on the captured image captured by the front camera 111, the situation of the front environment (that is, the environment in which the virtual image 110 is superimposed) visually recognized by the occupant 106 through the front glass is detected. To. A sensor such as a millimeter wave radar may be used instead of the front camera 111.

In addition, an in-vehicle camera 112 is installed on the upper surface of the instrument panel of the vehicle. The in-vehicle camera 112 is an image pickup device having a camera using a solid-state image sensor such as a CCD, and is installed with the optical axis direction facing the driver's seat. The range in which the face of the occupant is generally expected to be located in the vehicle is set as the detection range (the imaging range of the in-vehicle camera 112), and the face of the occupant 106 sitting in the driver's seat is imaged. Then, image processing is performed on the captured image captured by the in-vehicle camera 112 to detect the eye position (line-of-sight start point) and the line-of-sight direction of the occupant 106.

Then, the superimposed image display device according to the second embodiment displays the image 120 of the guide object on the front display 104 as shown in FIG. 12 in S5 of the traveling support processing program (FIG. 2) described above. As a result, as shown in FIG. 12, when the vehicle occupant visually recognizes the image 120 of the guide object displayed on the front display 104, the virtual image 121 of the image 120 of the guide object is superimposed on the landscape through the windshield 105. It is visually recognized.

As a result, similarly to the superimposed image display device according to the first embodiment, the position of the guide branch point to be turned left or right and the exit direction at the proposed branch point can be accurately grasped. In the superimposed image display device according to the second embodiment, in the guide object display position determination process of S4, the shape of the guide object to be displayed on the front display 104 and the position (range) where the guide object is displayed are determined. .. Further, it is desirable that the current position and orientation of the own vehicle specified in the three-dimensional space in S17 are the position of the occupant of the vehicle and the line-of-sight direction of the occupant detected by using the in-vehicle camera 112.

It should be noted that the present invention is not limited to the above embodiment, and it goes without saying that various improvements and modifications can be made without departing from the gist of the present invention.
For example, as a means for displaying an image superimposed on the scenery around the vehicle, the liquid crystal display 15 on which the actual scene image is displayed is used in the first embodiment, and the head-up display system is used in the second embodiment, but the windshield is used. On the other hand, a window shield display (WSD) that displays an image may be used. In WSD, the windshield may be used as a screen to display an image from the projector, or the windshield may be used as a transmissive liquid crystal display. The image displayed on the windshield by the WSD is an image superimposed on the scenery around the vehicle.

Further, in the first and second embodiments, the guide object is an image of a sign indicating the exit direction and the exit direction of the vehicle at the guide branch point, but other images may be used. For example, an image of an arrow indicating the direction of travel of a vehicle, an image of a warning for an object (for example, another vehicle, a pedestrian, a guide sign) to be warned to a occupant of the vehicle, an image of a lane marking in which the vehicle is traveling, etc. good.

Further, in the first and second embodiments, the guide object is used to guide the guide branch point, but the point to be guided by the guide object is not limited to the guide branch point, for example, a lane reduction point or the like. It may be another point that calls attention to the occupants of the vehicle such as a confluence section. In addition, it is desirable to change the content of the guidance object to be displayed depending on the type of guidance target point.

Further, in the first and second embodiments, the traveling support using the guide object is performed both when traveling on the expressway and when traveling on the general road, but only when traveling on the expressway or when traveling on the general road. You may do it only at the time.

Further, in the first and second embodiments, as shown in FIG. 5, the current position of the vehicle becomes shorter as the distance from the current position of the vehicle to the guidance target point (second distance) becomes shorter as the vehicle travels. When the distance from the position to the position where the guide object is superimposed (first distance) is gradually shortened and the first distance is shortened according to the second distance, the decrease of the first distance with respect to the decrease value of the second distance. The ratio of the values is a constant, but if the first distance is gradually shortened as the second distance is shortened, the ratio of the decrease value of the first distance to the decrease value of the second distance is not a constant. You may. For example, when the second distance is in the range of 1000 m to 800 m, the first distance may be set to 300 m, and when the second distance is in the range of 800 m to 600 m, the first distance may be set to 200 m.

Further, in the first and second embodiments, when the distance (second distance) from the current position of the vehicle to the guidance target point is less than the threshold value (for example, 300 m), the first distance is set as a fixed value. Even when the distance (second distance) from the current position to the guidance target point is less than the threshold value (for example, 300 m), the first distance is increased as the second distance becomes shorter as in the case where the distance is greater than or equal to the threshold value. The distance may be gradually shortened.

Further, in the first embodiment, the actual scene image and the guidance object captured by the front camera 19 are displayed on the liquid crystal display 15 of the navigation device 1, but the display for displaying the actual scene image and the guidance object is in the vehicle. As long as it is an arranged display, it may be a display other than the liquid crystal display 15.

Further, in the second embodiment, the front display 104 is configured to generate a virtual image in front of the windshield 105 of the vehicle 102, but a configuration in which a virtual image is generated in front of a window other than the windshield 105 may be used. Further, the target for reflecting the image by the front display 104 may be a visor (combiner) installed around the windshield 105 instead of the windshield 105 itself.

Further, in the first and second embodiments, the navigation ECU 13 of the navigation device 1 executes the processing of the driving support processing program (FIG. 2), but the execution subject can be changed as appropriate. For example, it may be configured to be executed by the control unit of the liquid crystal display 15, the vehicle control ECU, or other in-vehicle device.

Further, although the embodiment in which the superimposed image display device according to the present invention is embodied has been described above, the superimposed image display device can also have the following configuration, and in that case, the following effects are obtained.

For example, the first configuration is as follows.
A superposed image display device (1) that superimposes and visually recognizes a guidance object (61) mounted on a vehicle and guiding information to the occupants of the vehicle on the scenery around the vehicle, and guides the vehicle forward in the traveling direction of the vehicle. When there is a target guidance target point (60), the object display means (41) for displaying the guidance object for guiding the guidance target point is provided, and the object display means is the guidance from the vehicle. The first distance to the position where the objects are superimposed is set to be shorter than the second distance from the vehicle to the guidance target point, and the second distance becomes shorter as the vehicle travels. The guide object is displayed by gradually shortening one distance.
According to the superimposed image display device having the above configuration, since the guide object is superimposed on the position closer to the guide target point and visually recognized by the occupant, the contents of the guide object even when the distance from the vehicle to the guide target point is long. Can be clearly recognized by the occupants. On the other hand, as the vehicle approaches the guidance target point, the guidance object gradually approaches and is visually recognized by the occupants, so that the correspondence between the guidance object and the guidance target point can be intuitively grasped. Is possible.

The second configuration is as follows.
When the first distance is shortened according to the second distance, the ratio of the decrease value of the first distance to the decrease value of the second distance is a constant.
According to the superimposed image display device having the above configuration, it is possible to intuitively grasp the correspondence relationship between the guide object and the guide target point.

The third configuration is as follows.
When the second distance is equal to or greater than the threshold value, the object display means (41) gradually shortens the first distance in accordance with the shortening of the second distance as the vehicle travels, to guide the object. Display the object.
According to the superimposed image display device having the above configuration, the guidance object is superimposed on the position closer to the guidance target point and visually recognized by the occupant, especially when the distance from the vehicle to the guidance target point is large. It is possible to make the occupants clearly recognize the contents of. On the other hand, as the vehicle approaches the guidance target point, the guidance object gradually approaches and is visually recognized by the occupants, so that the correspondence between the guidance object and the guidance target point can be intuitively grasped. Is possible.

The fourth configuration is as follows.
When the second distance is less than the threshold value, the object display means (41) fixes the first distance.
According to the superimposed image display device having the above configuration, after the vehicle approaches the guidance target point to a certain distance, the guidance object is superimposed and displayed in a state of being relatively fixed with respect to the current position of the vehicle. The object. As a result, it is possible to continuously visually recognize the guide object while maintaining a state in which it is easy for the occupants of the vehicle to visually recognize the guide object without enlarging the display size of the guide object more than necessary.

The fifth configuration is as follows.
When the second distance is equal to or greater than the threshold value, the object display means (41) gradually increases the display size of the guide object as the second distance becomes shorter as the vehicle travels. If the second distance is less than the threshold value, the display size of the guide object is fixed.
According to the superimposed image display device having the above configuration, especially when the distance from the vehicle to the guidance target point is large, the guidance object gradually from the occupant as the vehicle approaches the guidance target point. Is enlarged and visually recognized, it is possible to intuitively grasp the correspondence relationship between the guide object and the guide target point. In addition, after the display size of the guide object has reached a size that can be reliably seen by the occupants of the vehicle, the guide object can be visually recognized by the occupants of the vehicle without enlarging the display size of the guide object more than necessary. It is possible to keep the state easy to visually recognize continuously.

The sixth configuration is as follows.
When the second distance is less than the threshold value, the object display means (41) displays the guide object by gradually increasing the transmittance according to the second distance.
According to the superimposed image display device having the above configuration, the transmittance of the guide object is gradually increased as the vehicle approaches the guide target point, so that the guide object reduces the visibility of the occupants of the vehicle. To prevent. In addition, it is possible to visually recognize the vehicle as passing through the guide object.

The seventh configuration is as follows.
The guide target point (60) is a guide branch point to be guided, and the guide object (61) is a sign indicating the exit direction of the vehicle at the guide branch point.
According to the superimposed image display device having the above configuration, since the guide object is superimposed on the position closer to the guide branch point and visually recognized by the occupant, the guide branch point is located even when the distance from the vehicle to the guide branch point is large. It is possible to make the occupants clearly recognize the exit direction of the vehicle. On the other hand, as the vehicle approaches the guide branch point, the guide object gradually approaches and is visually recognized by the occupants, so that the correspondence between the guide object and the guide branch point can be intuitively grasped. Is possible.

1 Navigation device 15 Liquid crystal display 19 Front camera 41 CPU
42 RAM
43 ROM
51 Driving guidance screen 52 Scenery 53 Image of guidance object 60 Guidance branch point 61 Sign (example of guidance object)
64 vehicles

Claims (8)

A superimposed image display device that superimposes and visually recognizes a guide object mounted on a vehicle and guiding information to the occupants of the vehicle on the scenery around the vehicle.
It has an object display means for displaying the guidance object for guiding to the guidance target point when there is a guidance target point to be guided ahead in the traveling direction of the vehicle.
The object display means sets the first distance from the vehicle to the position where the guide object is superimposed to be shorter than the second distance from the vehicle to the guide target point, and the second distance as the vehicle travels. A superimposed image display device that displays the guide object by gradually shortening the first distance as the distance becomes shorter. The superimposed image display device according to claim 1, wherein the ratio of the decrease value of the first distance to the decrease value of the second distance is a constant when the first distance is shortened according to the second distance. When the second distance is equal to or greater than the threshold value, the object display means displays the guide object by gradually shortening the first distance as the second distance becomes shorter as the vehicle travels. The superimposed image display device according to claim 1 or 2. The superimposed image display device according to claim 3, wherein the object display means fixes the first distance when the second distance is less than a threshold value. The object display means is
When the second distance is equal to or greater than the threshold value, the display size of the guide object is gradually enlarged and displayed as the second distance becomes shorter as the vehicle travels.
The superimposed image display device according to any one of claims 1 to 4, wherein when the second distance is less than the threshold value, the display size of the guide object is fixed. The object display means is
The superimposed image display according to any one of claims 1 to 5, wherein when the second distance is less than the threshold value, the transmittance of the guide object is gradually increased according to the second distance and displayed. apparatus. The guidance target point is a guidance branch point to be guided.
The superimposed image display device according to any one of claims 1 to 6, wherein the guide object is a sign indicating the exit direction of the vehicle at the guide branch point. A superposed image display device that is mounted on a vehicle and superimposes and visually recognizes a guidance object that guides information to the occupants of the vehicle on the scenery around the vehicle.
It is a computer program for functioning as an object display means for displaying the guidance object for guiding the guidance target point when there is a guidance target point to be guided ahead in the traveling direction of the vehicle.
The object display means sets the first distance from the vehicle to the position where the guide object is superimposed to be shorter than the second distance from the vehicle to the guide target point, and the second distance as the vehicle travels. A computer program that displays the guide object by gradually shortening the first distance as the distance becomes shorter.

Images