JPH0247666Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field of the invention> This invention relates to an imaging device that can be used, for example, as a device for monitoring the rear of a car, and in particular an imaging device that can display images of a wide area without distortion. This is what we are trying to provide.

<Prior Art> Conventionally, a rear view monitoring device for an automobile has a structure in which a convex mirror is installed at the rear of the vehicle, and the image reflected on the convex mirror is viewed from the driver's seat.

With this structure, since it is a convex mirror, it can capture an image of a wide area, but the visible image has a distortion in that the ground side is magnified, making it impossible to visually recognize an appropriate sense of distance. The reason for this is that since the surface of the convex mirror is mounted vertically, the ground becomes the closest subject.

Another rear monitoring device is a television camera installed at the rear of the bus, as seen on large buses.
Some models have a structure in which the image captured by this television camera is projected onto a cathode ray tube installed in the driver's seat.

With this structure, a wide-angle lens or a fisheye lens must be attached to the television camera in order to project an image over a wide area. A wide-angle lens or a fisheye lens is generally expensive, and an image captured through a wide-angle lens or a fisheye lens is subject to distortion in which the top, bottom, left, and right sides are compressed. To eliminate this distortion, a standard lens is used, and a television camera equipped with a standard lens is mounted on the roof of the bus to image the subject from a distance and project a wide area without distortion.

For vehicles with high roofs, such as large buses, this method allows images of a wide area to be projected without distortion. However, small vehicles, particularly sedan-type vehicles, have the disadvantage that they cannot capture a wide range of images with standard lenses because of their low vehicle height.

<Purpose of the invention> This invention aims to provide an imaging device that can image a wide range of images without using an expensive wide-angle lens, and which does not distort the image.

<Structure of the device> This device has a structure in which a vertically asymmetrical concave mirror is used to magnify the upper side of the subject to capture the subject, the image of this concave mirror is reflected by a plane mirror, and the reflected image is incident on an image sensor to capture an image. .

According to the structure of this invention, a wide area can be captured by the concave mirror. Additionally, the vertically asymmetrical concave mirror allows you to capture a wide range of objects on the upper side, or in the periphery. By reflecting this image with a plane mirror provided at an angle and projecting it onto an image sensor, a normal image can be displayed on a cathode ray tube.

<Example of the invention> Fig. 1 shows an example of the invention. 1 in the figure indicates a case. For example, as shown in FIG. 2, this case 1 has a curved front surface 1a so that it can be incorporated into the rear corner of a vehicle 2.
A is made of a transparent resin material, glass, or the like.

A concave mirror 3, a plane mirror 4, and an image sensor 5 are mounted inside the case 1. For example, a semiconductor image sensor called CCD can be used as the image sensor 5.

The concave mirror 3 has a concave shape with an asymmetrical top and bottom as shown in FIG. In other words, the radius of curvature R ₁ of the lower side and the radius of curvature R ₂ of the upper side are selected to satisfy the relationship R ₁ > R ₂ , and the length of the arc of the lower side L ₁ and the length of the arc of the upper side L ₂
Select L ₁ > L ₂ .

This concave mirror 3 is attached to the innermost part of the case 1 so that the long side is on the bottom side and the short side is on the top side. With this concave mirror 3, an inverted image can be obtained as shown in FIG. This inverted image is photographed with the top side facing the ground side due to the difference in the radius of curvature between the bottom and top sides.

The inverted image obtained by the concave mirror 3 is reflected by the plane mirror 4 and incident on the image sensor 5. Plane mirror 4 is concave mirror 3
5, and arranged as shown in FIG. That is, the distance between the lower side of the concave mirror 3 and the lower side of the plane mirror 4 is selected to be larger than the distance between the upper sides.

By arranging the plane mirror 4 at an angle and projecting the image onto the image sensor 5, the inverted image obtained by the concave mirror 3 is reduced in size on the lower side because the distance on the lower side is larger than the distance on the upper side. image sensor 5
projected on. Therefore, an image that has been corrected to a normal state in which distortion between the sky and the ground has been removed is incident on the image sensor 5, and this image is projected onto the cathode ray tube 6, thereby providing an undistorted rear view in the driver's seat. can be confirmed.

In this embodiment, as shown in FIG. 2, an image pickup device is provided on both sides of the rear of the vehicle. When two imaging devices are installed in this way, the cathode ray tube 6
As shown in Figure 6, there are two screens 7 and 8 at the top and bottom.
or, as shown in FIG. 7, two screens 7 and 8 on the left and right can be combined and displayed.

<Operations and Effects of the Invention> As explained above, according to this invention, by using the concave mirror 3 which is asymmetrical in the vertical direction, it is possible to image the top side with a wide field of view. Further, by arranging the plane mirror 4 so as to be inclined with respect to the concave mirror 3, image distortion can be corrected. Therefore, a normal image without distortion can be obtained.

Moreover, since the concave mirror 3 can be formed from a resin material, the curvature can be arbitrarily selected and it can be manufactured at low cost. Therefore, an imaging device that can obtain images without distortion can be manufactured at low cost.

Furthermore, according to this invention, since a concave mirror is used, a wide field of view can be obtained even if the mounting position is low.
Therefore, an image of a wide area can be projected on the cathode ray tube 6 even if the vehicle height is low, such as in a sedan type vehicle.

<Modified embodiment of the invention> In the above description, a case has been described in which the plane mirror 4 is tilted to return the image of the concave mirror 3 to a normal image. It is also possible to display the image on the monitor 6 by reducing the size of the top side compared to the bottom side.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing an embodiment of this invention, Figure 2 is a plan view illustrating the state in which the imaging device of this invention is installed in a vehicle, and Figure 3 is the shape of the concave mirror used in this invention. A perspective view for explaining the fourth
The figure is a front view for explaining the image obtained by the concave mirror, Figure 5 is a layout diagram for explaining the arrangement relationship between the concave mirror and the plane mirror, and Figures 6 and 7 are for the imaging device of this invention. FIG. 3 is a front view illustrating a state in which the obtained image is displayed on a monitor. 1: case, 1a: front of case, 2: vehicle,
3: concave mirror, 4: plane mirror, 5: image sensor, 6: monitor.

Claims (1)

[Claims for Utility Model Registration] A. A concave mirror whose lower side has a radius of curvature larger than that of its upper side. B. A plane mirror that reflects an image obtained by this concave mirror. C. A plane mirror that receives an image reflected by this plane mirror. An imaging device comprising: an imaging element;