JP6333007B2 - Virtual image display device - Google Patents

Description

  The present invention relates to a virtual image display device that allows an observer to visually recognize a virtual image.

  There is known a vehicle head-up display that is mounted on a vehicle and allows a driver to visually recognize a virtual image. Patent Document 1 discloses a light source, a scanning unit that scans light from the light source two-dimensionally, a screen that forms an image of the scanning light, and a projection that projects an image on the screen in order to make the display distance of a virtual image variable. A vehicle head-up display device comprising means and a movable mechanism for changing the position of the screen is described. Patent Document 1 discloses a spherical concave mirror, an aspherical concave mirror, a free-form curved mirror, and a front shield as projection means, and further discloses that the scanning means is arranged near the focal position of the projection means.

JP 2009-150947 A

  In Patent Document 1, as described in Paragraph 0042, when the display distance from the driver to the virtual image is changed by changing the position of the screen, the size of the virtual image is constant. However, since the virtual image size is constant, when the display distance from the driver's eyes to the virtual image becomes long, the apparent virtual image size visually recognized by the driver becomes small. Further, when an image projected at the center of the screen and an image projected at a position away from the center are visually recognized as virtual images, the brightness of the two is different, that is, so-called brightness unevenness occurs. There's a problem.

  The present invention has been made in order to solve the above-described problems, and a virtual image display device in which a virtual image does not appear small even when a display distance from a driver's eyes to a virtual image becomes long and luminance unevenness is small. The main purpose is to provide

The invention described in claim is a virtual image display device that allows an observer to visually recognize a virtual image, a scanning unit that scans light from a light source, a screen on which scanning light scanned by the scanning unit is incident, and the screen Reflecting means for reflecting while condensing the light constituting the upper image, and first driving means for moving the screen between the scanning means and the reflecting means, the screen comprising the screen The intensity of the transmitted light is maximized in the direction of the transmission angle that is opposite to the incident angle of the light incident surface and the normal to the incident surface and is the same angle as the incident angle. It has a characteristic of transmitting the light and gradually decreasing the intensity of the transmitted light as it moves away from the direction of the transmission angle .

1 shows a configuration of a virtual image display device according to a first embodiment. It is a figure which shows the characteristic of a screen typically. The example of a display in case a virtual image distance differs is shown. The structure of the virtual image display apparatus which concerns on 2nd Example is shown.

  In a preferred embodiment of the present invention, a virtual image display device that allows an observer to visually recognize a virtual image includes a scanning unit that scans light from a light source, a screen on which scanning light scanned by the scanning unit is incident, And reflecting means for collecting and reflecting the light constituting the image, and first driving means for moving the screen between the scanning means and the reflecting means, and the scanning means includes the scanning The means and the position of the eyes of the observer are arranged at a position where the optically conjugate relationship is established.

  In the virtual image display device described above, an image is formed on the screen by scanning light from the light source. The scanning light corresponding to the image on the screen is reflected by the reflecting means and reaches the eyes of the observer. Thereby, the observer visually recognizes a virtual image corresponding to the image on the screen. By moving the screen between the scanning means and the reflecting means, the position of the virtual image visually recognized by the observer changes. Since the scanning means and the position of the observer's eyes are optically conjugate, there is no occurrence of luminance unevenness in the virtual image. Further, since the angle of view of the virtual image does not change even if the position of the virtual image is changed by moving the screen, the content of the virtual image does not become difficult to see even when the virtual image is displayed far away.

  Preferably, the screen is opposite to the incident angle of light to the incident surface of the screen with respect to the normal to the incident surface, and in the direction of the transmission angle that is the same angle as the incident angle. The light is transmitted so that the intensity of the transmitted light is maximized, and the intensity of the transmitted light is gradually decreased as the distance from the direction of the transmission angle is increased.

  In the virtual image display device, when the distance to the virtual image visually recognized by the observer is increased, the first driving unit sets the distance between the screen and the scanning unit from the first distance to the first distance. What is necessary is just to move to a short 2nd distance.

  In the virtual image display device, the angle of view of the virtual image visually recognized by the observer is constant regardless of the distance between the screen and the scanning unit.

  According to one aspect of the virtual image display device, a detection unit that detects a position of the eyes of the observer, and the scanning unit according to the position of the eyes detected by the detection unit, the scanning unit and the observer Second driving means for moving to a position where the position of the eye is optically conjugate. In this aspect, since the scanning unit is automatically moved according to the position of the driver's eyes, the scanning unit can always be maintained at an appropriate position.

  In another aspect of the virtual image display device, the second driving unit drives a projection unit including the scanning unit, the screen, and the first driving unit. In this aspect, since the entire projection unit including the scanning unit is moved, the distance between the screen and the scanning unit does not change. Therefore, the influence on the angle of view of the virtual image visually recognized by the observer can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 shows a configuration of a virtual image display apparatus according to the first embodiment. The virtual image display device 10 is a device that allows an observer to visually recognize a virtual image, and includes a light source 1, a MEMS (Micro Electro Mechanical System) mirror 2, a screen 3, an actuator 4, and a concave mirror combiner 5.

  The light source 1 is a laser light source or the like, and emits light L1 that constitutes an image visually recognized by an observer. The MEMS mirror 2 scans the light L1 emitted from the light source 1 and projects a two-dimensional image (hereinafter also referred to as “intermediate image”) onto the screen 3. Scanning light L2 emitted from the MEMS mirror 2 passes through the screen 3 and enters the concave mirror combiner 5. The concave mirror combiner 5 is a half mirror formed in a concave shape, and is disposed in front of the observer. The concave mirror combiner 5 reflects a part of the scanning light L2 constituting the intermediate image projected on the screen 3, and reaches the observer's eye position EP as reflected light L3. Thereby, the observer visually recognizes the virtual image VI behind the concave mirror combiner 5 (on the side opposite to the observer). The virtual image VI is obtained by enlarging the intermediate image drawn on the screen 3 at a magnification according to the curvature of the concave mirror combiner 5.

  FIG. 2 schematically shows the transmission characteristics of the screen 3. The screen 3 basically has a characteristic of diffusing incident light Li. In addition to this, the screen 3 has a characteristic that the intensity of the transmitted light Lt becomes maximum in the direction in which the incident light Li travels straight, and the intensity of the transmitted light Lt gradually decreases as it deviates from the rectilinear direction. Here, if the incident light Li and the transmitted light Lt are respectively made with respect to the normal 9 of the screen 3 as the incident angle θi and the transmission angle θt, the incident angle θi and the transmission angle θt of the screen 3 are equal (θi = Θt) characteristic. That is, the screen 3 is opposite to the incident angle θi of the incident light Li on the incident surface of the screen 3 with respect to the normal line 9 with respect to the incident surface, and is the same transmission angle as the incident angle θi. The incident light Li is transmitted in the direction of θt so that the intensity of the transmitted light Lt is maximized, and the intensity of the transmitted light Lt is gradually reduced as the distance from the direction of the transmission angle θt increases.

  The actuator 4 moves the screen 3 between the MEMS mirror 2 and the concave mirror combiner 5 along the optical axis of the light L2, that is, in the direction of the arrow 7 in FIG. Thereby, the position of the virtual image VI, that is, the distance between the observer's eye position EP and the virtual image VI (hereinafter referred to as “virtual image distance”) changes. Specifically, when the screen 3 is moved in the direction of the MEMS mirror 2 by the operation of the actuator 4, the virtual image distance becomes longer and the virtual image VI moves in a direction away from the observer. On the other hand, when the screen 3 is moved in the direction opposite to the MEMS mirror 2, that is, in the direction of the concave mirror combiner 5, the virtual image distance is shortened and the virtual image VI is moved in a direction approaching the observer. Thus, by operating the actuator 4 and changing the position of the screen 3, the position of the virtual image VI visually recognized by the observer can be changed.

  In the above configuration, the MEMS mirror 2 is an example of the scanning unit of the present invention, the concave mirror combiner 5 is an example of the reflecting unit of the present invention, and the actuator 4 is an example of the first driving unit of the present invention.

  In this embodiment, the concave mirror combiner 5 is characterized in that the MEMS mirror 2 and the position EP of the observer's eyes are arranged in a position that is optically conjugate. Specifically, as shown in FIG. 1, the distance between the concave mirror combiner 5 and the screen 3 is “a”, the distance between the concave mirror combiner 5 and the virtual image VI is “b”, and the distance between the MEMS mirror 2 and the screen 3 is “C”, where the distance between the observer's eye position EP and the concave mirror combiner 5 is “d” and the focal length of the concave mirror combiner 5 is “f”, each element is arranged so that The

  In this way, when the MEMS mirror 2 and the position EP of the observer's eye are in an optically conjugate relationship, no luminance unevenness occurs in the virtual image VI. Furthermore, even if the screen 3 is moved to change the virtual image distance b, the MEMS mirror 2 and the concave mirror 5 are fixed, and (a + c) is constant. Therefore, even if the screen 3 is moved, the conjugate relationship is maintained, the luminance remains constant, and luminance unevenness does not occur.

  Further, since the MEMS mirror 2 and the position EP of the observer's eye are optically conjugate, the angle of view of the virtual image VI is constant regardless of the virtual image distance b. This will be described below. In the equation (1), when a + c = k is established, the equation (2) is obtained.

  When the constant (angle constant) depending on the scanning angle of the MEMS mirror 2 is “A”, the size (height) H of the intermediate image on the screen 3 can be obtained by Expression (3).

  On the other hand, when the magnification of the concave mirror combiner 5 is “M”, the size (height) H ′ of the virtual image VI can be obtained by Expression (4).

  From the relationship between the intermediate image and the virtual image, Equation (5) is established for a, b, and f.

  The angle of view F of the virtual image viewed from the observer is expressed by Equation (6).

  Here, Expression (7) is obtained from Expressions (2) to (5).

  Therefore, from the formulas (6) to (7), the angle of view F of the virtual image VI is obtained by the formula (8).

  In equation (8), A, k, and f are all constants, so the angle of view F is constant. That is, even if the screen 3 is moved, the angle of view F of the virtual image VI visually recognized by the observer is constant.

  For this reason, when displaying the virtual image of the same design by changing the virtual image distance, an appropriate virtual image size can be maintained without performing any special processing other than moving the screen 3.

  FIG. 3 is a diagram illustrating how the virtual image looks when the virtual image distance is changed. FIG. 3A shows the case where the virtual image distance is D1, and FIG. 3B shows the case where the virtual image distance is D2 (<D1). In FIG. 3, the virtual image distance is set so as to correspond to the distance to the vehicle ahead so that the observer can easily see. As can be understood from FIG. 3, even if the screen 3 is moved to change the position of the virtual image VI, the angle of view F of the virtual image VI does not change, so the virtual image VI is displayed far away by increasing the virtual image distance. However, there is no problem that the virtual image VI becomes small and information cannot be read. Furthermore, the resolution does not change between when the virtual image distance is long and short, that is, when the virtual image VI is far and near.

  As described above, in this embodiment, each element is arranged so that the MEMS mirror 2 and the position EP of the observer's eye have an optically conjugate relationship. Therefore, luminance unevenness does not occur in the virtual image VI. In addition, even if the virtual image distance is changed by moving the screen 3, the angle of view F of the virtual image VI does not change, so that the display content does not become difficult to see when the virtual image VI is displayed far away.

  Although the MEMS mirror 2 is used in the above embodiment, a galvanometer mirror may be used instead. The concave mirror combiner 5 may be a concave mirror having a spherical or aspherical concave surface, or may be a magnifier combining a Fresnel lens and a mirror.

[Second Embodiment]
FIG. 4 shows a configuration of a virtual image display apparatus according to the second embodiment of the present invention. In this embodiment, the virtual image display device is applied to a head-up display (HUD) 50 for a vehicle. In FIG. 4, the vehicle has a roof 41, a windshield (wind shield) 42, and a dashboard 43. The HUD 50 makes the observer visually recognize the virtual image VI by using the windshield 42 of the vehicle.

  Inside the dashboard 43, the projection unit 20, the concave mirror 25, the actuator 26, and the control unit 28 are accommodated. The projection unit 20 includes a light source 21, a MEMS mirror 22, a screen 23, and an actuator 24. Each element in the projection unit 20 is basically the same as in the first embodiment. That is, the screen 23 can be moved in the direction of the arrow 31 by the actuator 24. Furthermore, in the present embodiment, the entire projection unit 20 can be moved in the direction of the arrow 32 by the actuator 26. A camera 27 is attached to the roof 41 of the vehicle. A captured image from the camera 27 is input to the control unit 28.

  The light emitted from the projection unit 20 is reflected by the concave mirror 25 and further reflected by the windshield 42 to reach the eye position EP of the observer. Thereby, the observer visually recognizes the virtual image VI behind the windshield 42. Similar to the first embodiment, the virtual image distance is changed by moving the screen 23, and the position of the virtual image VI visually recognized by the observer is changed. Each element is arranged so that the MEMS mirror 22 and the position of the observer's eyes are in an optically conjugate relationship.

  In the above configuration, the MEMS mirror 22 is an example of the scanning unit of the present invention, the actuator 24 is an example of the first driving unit of the present invention, the concave mirror 25 is an example of the reflecting unit of the present invention, and the actuator 26 is It is an example of the 2nd drive means of this invention, and the camera 27 is an example of the detection means of this invention.

  In this embodiment, the camera 27 is used to detect the position EP of the observer's eyes, and the position of the MEMS mirror 22 is automatically adjusted according to the detected position, so that the MEMS mirror 22 and the observer's eyes can be adjusted. The position EP is always maintained in a conjugate relationship. Specifically, the camera 27 captures an image of the observer's face and supplies the captured image to the control unit 28. The control unit 28 detects the position of the observer's eyes based on the captured image using a known technique. Then, the control unit 28 moves the position of the MEMS mirror 22 based on the position of the observer's eyes.

  Preferably, the control unit 28 controls the actuator 26 to move the entire projection unit 20 in the direction of the arrow 32. As a result, the control unit 28 moves the projection unit 20 so that the MEMS mirror 22 comes to a position having a conjugate relationship with the detected position of the observer's eyes. When the entire projection unit 20 is moved when moving the MEMS mirror 22 in this way, the distance between the screen 23 and the MEMS mirror 22 does not change, so the size of the intermediate image on the screen 23 does not change, and observation is performed. The influence on the angle of view F of the virtual image VI visually recognized by the person can be reduced.

  In the present embodiment, automatic adjustment is possible so that the MEMS mirror 22 and the position EP of the observer's eye have a conjugate relationship regardless of the difference in the observer's physique.

1, 21 Light source 2, 22 MEMS mirror 3, 23 Screen 4, 24, 26 Actuator 5 Concave mirror combiner 25 Concave mirror 27 Camera 28 Control unit

Claims (6)

A virtual image display device that allows an observer to visually recognize a virtual image,
Scanning means for scanning light from the light source;
A screen on which scanning light scanned by the scanning means is incident;
Reflecting means for reflecting while condensing the light constituting the image on the screen;
First driving means for moving the screen between the scanning means and the reflecting means;
With
The screen has an intensity of transmitted light in the direction of the transmission angle that is opposite to the incident angle of the light to the incident surface of the screen with respect to the normal to the incident surface and is the same angle as the incident angle. The virtual image display device has a characteristic of transmitting the light so as to be maximized and gradually decreasing the intensity of the transmitted light as the distance from the direction of the transmission angle increases . The virtual image display device according to claim 1, wherein the scanning unit is arranged at a position where the scanning unit and the position of the eyes of the observer are in an optically conjugate relationship .   The first driving means moves the distance between the screen and the scanning means from the first distance to a second distance shorter than the first distance when extending the distance to the virtual image visually recognized by the observer. The virtual image display device according to claim 1, wherein:   4. The virtual image display device according to claim 1, wherein an angle of view of the virtual image visually recognized by the observer is constant regardless of a distance between the screen and the scanning unit. 5. Detecting means for detecting the position of the eyes of the observer;
A second driving unit configured to move the scanning unit to a position where the scanning unit and the position of the observer's eye are in an optically conjugate relationship according to the position of the eye detected by the detection unit;
The virtual image display device according to claim 1, comprising:   The virtual image display device according to claim 5, wherein the second driving unit drives a projection unit including the scanning unit, the screen, and the first driving unit.