JP2005243283A - Projector and vehicular night-vision device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular night-vision device capable of clearly carrying out photographing from a distant location. <P>SOLUTION: Light emitted from a light source 10 is spectrally diffracted by a prism 11, and visible light and infrared light emitted from the prism 11 are entered into reflecting mirrors 12 and 16 different from each other, respectively. The infrared light entered into the reflecting mirror 16 is reflected/converged by the reflecting mirror 16 and entered into the next reflecting mirror 17. Then, the infrared light 20 reflected on the reflecting mirror 17 is projected upward relative to the visible light by a wave light lens 18 so as to be radiated to a further location than the visible light. As a result, the smaller the wavelength of the luminous flux of the infrared light 20 becomes, the more upper side it is directed to. Luminous flux 20a in the smallest wavelength region of the infrared light 20 corresponds to a high-sensitivity wavelength region of an infrared camera, and the luminous flux 20a is radiated to the furthest location, whereby a distant photographed image is made clearer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projector and a night vision device for a vehicle.

  2. Description of the Related Art Conventionally, night vision devices using an infrared camera are known as devices that improve the visibility of distant objects that are difficult to see with a headlight. When photographing darkness with an infrared camera, an infrared projector that illuminates the front of the vehicle with infrared light is required. Therefore, an infrared projector is mounted on the vehicle, or a headlamp having an infrared projector function is mounted (for example, see Patent Document 1).

JP 2000-235803 A

  However, even with a night vision device using an infrared camera, the amount of reflected infrared light decreases with increasing distance to the viewing range, so that there is a problem in that the contrast between the light and darkness decreases and the visibility decreases as the landscape is distant. .

In the projector according to the present invention, the infrared light emitted from the light source is separated into light of the first region having a short wavelength and light of the other second region using an infrared light separating unit. The infrared light projecting unit projects the infrared light so that the light in the first region is emitted farther than the light in the second region.
Alternatively, the light in the high sensitivity wavelength region of the imaging means may be separated from the emitted light and irradiated with the light far away.

  According to the present invention, light in the high-sensitivity wavelength region of the imaging unit included in the light source light and light having a short wavelength in the infrared light included in the light source light are projected far away. Therefore, when the reflected light from the object irradiated by the projector is photographed by an imaging means such as an infrared camera, the light in the high-sensitivity wavelength region of the imaging means, for example, the light in the short wavelength region of infrared light is projected far away. As a result, the far distance is clearly imaged and visibility is improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a night vision device for a vehicle according to the present invention. As shown in FIG. 1, the night vision device for a vehicle includes light projecting devices 1 </ b> R and 1 </ b> L, an infrared camera 2, an electronic control unit 3, and a head-up display 4.

  The light projectors 1R and 1L have both a conventional headlamp and an infrared projector, and separate light emitted from a headlamp light source into visible light and infrared light as will be described later. The light is projected in different directions. The infrared camera 2 is disposed near the front window shield above the vehicle interior, and receives infrared light from the front of the vehicle to photograph the front of the vehicle. Infrared rays are invisible to the human eye, but a night vision device using an infrared camera can shoot infrared images, so it can be used as a visual field assist device for recognizing distant places where headlamp light is difficult to reach at night It is used.

  There are two types of infrared cameras: a far-infrared type (light with a wavelength of 5600 nm to 25000 nm) that senses the heat source, and a near-infrared type (light with a wavelength of 780 nm to 1500 nm) that can obtain almost the same image as a normal monochrome camera. . Usually, a near-infrared type infrared camera is used for the night vision apparatus for vehicles, and the infrared camera 2 in FIG. 1 is also a near-infrared type camera. In the case of the near-infrared type infrared camera 2, the light reflected by the object is received in the same manner as a normal camera, so that it is necessary to project near-infrared light in front of the vehicle by the light projecting devices 1R and 1L at night. There is.

  The video signal output from the infrared camera 2 that has received near-infrared light is input to the electronic control unit 3 provided in the engine room, where image processing is performed. The captured video is displayed on the head-up display 4. The head-up display 4 is provided at a position where the driver on the front window shield is easy to see.

  For the infrared camera 2, for example, a solid-state image sensor such as a CCD image sensor is used. FIG. 2 is a diagram showing the relationship between the wavelength and sensitivity of a general CCD image sensor. In FIG. 2, the horizontal axis represents the wavelength of light, and the vertical axis represents the specific sensitivity of the image sensor. Specific sensitivity is expressed with reference to a peak value in the vicinity of a wavelength of 600 nm.

  As shown in the characteristic diagram of FIG. 2, the CCD imaging device has a sensitivity peak in the visible light region, and in the near infrared light region (wavelength 780 nm to 1500 nm), the sensitivity decreases as the wavelength increases. And in the region where the wavelength exceeds 1000 nm, the sensitivity is almost zero. In the infrared camera 2 using the image pickup device having such characteristics, a filter that cuts visible light (light having a wavelength of 380 nm to 780 nm) is arranged immediately before the image pickup device, and the light that cuts the visible light region by the filter is used as the image pickup device. The light is received and imaged.

  On the other hand, light having characteristics as shown by a curve L1 in FIG. 3 is emitted from the light sources of the light projecting apparatuses 1R and 1L, that is, the conventional headlamp light source. FIG. 3 shows the power ratio between the visible light region and the near-infrared light region of the light emitted from the light source, the horizontal axis represents the wavelength of the light, and the vertical axis represents the power ratio of the emitted light. ing. As shown in FIG. 3, the light emitted from the light source includes not only visible light but also near infrared light having a longer wavelength, and the power ratio is higher in the near infrared light region than in the visible light region. Is getting bigger.

  Therefore, in the present embodiment, the light from the light source is split into visible light and infrared light, visible light is used as headlamp projection light, and infrared light is used as night vision device projection light. I have to. 4 is a diagram showing a schematic configuration of the light projecting device 1L shown in FIG. 1, and shows a cross section of the light projecting device 1L as viewed from the side of the vehicle. The projector 1R has the same configuration as the projector 1L.

  Light emitted from the light source 10 in the right direction (rear side of the vehicle) enters the prism 11 which is a spectroscopic optical element. The refractive index of the prism 11 varies depending on the wavelength of light, and the light is emitted in the emission direction corresponding to each wavelength, and is continuously dispersed according to the wavelength. The light emitted from the prism 11 has a larger refraction angle as the wavelength is shorter. Infrared light including near-infrared light is emitted in the angle α1 direction on the upper side in the figure, and near-infrared in the angle α2 direction on the lower side in the figure. Visible light or ultraviolet light having a shorter wavelength than light is emitted.

  In this embodiment, light emitted in the direction of the angle range α1 (hereinafter referred to as light in the direction of the angle α1) is used for a night vision device, and light emitted in the direction of angle range α2 (hereinafter referred to as the angle α2). Directional light) is used as illumination light for headlamps. As described above, the light emitted from the prism 11 in the direction of the angle α1 includes not only near infrared light but also infrared light having a longer wavelength. Since near-infrared light is used for imaging by the infrared camera 2, the light emitted in the direction of the angle α1 will be described below centering on near-infrared light.

  On the other hand, the light emitted from the prism 11 in the direction of the angle α2 includes ultraviolet light having a wavelength shorter than that of visible light. However, visible light is used as headlamp light that illuminates the front of the vehicle brightly. Therefore, hereinafter, the light emitted in the direction of the angle α2 will be referred to as visible light.

  Visible light emitted from the prism 11 in the angle α2 direction is incident on the reflecting mirror 12 disposed in the lower right direction of the prism 11 in the figure. The visible light incident on the reflecting mirror 12 is reflected and converged by the concave reflecting mirror 12. The visible light reflected by the reflecting mirror 12 is further reflected by the reflecting mirror 13 to change its direction, and from the projection device 1L through the diffusion optical member 14 and the light distribution lens 15 for diffusing light, such as a diffusion plate, to a predetermined position in front of the vehicle. Emitted in the direction. Visible light emitted from the reflecting mirror 13 is divided into various kinds of light depending on the wavelength due to the effect of the prism 11, so that it is once diffused by the diffusing optical member 14 to be white light and then projected.

  On the other hand, the infrared light 20 emitted from the prism 11 in the direction of the angle α1 enters the reflecting mirror 16 disposed so as to be in contact with the reflecting mirror 12 above. Since the light emitted from the prism 11 has a smaller refraction angle as the wavelength is longer, the infrared light 20 in the region A in FIG. 4 is divided for each wavelength region as shown in FIG.

  FIG. 5 is an enlarged view schematically showing the spectral state in the region A of FIG. 4, and in order to simplify the explanation, five light beams 20a corresponding to the wavelength region of near infrared light in the wavelength region 780 nm to 1030 nm are shown. (Wavelength 780 nm to 830 nm), light beam 20 b (wavelength 830 nm to 880 nm), light beam 20 c (wavelength 880 nm to 930 nm), light beam 20 d (wavelength 930 nm to 9800 nm), and light beam 20 e (wavelength 980 nm to 1030 nm). The light beams 20a having the largest refraction angle are arranged in the upward direction in the figure. There is a visible light region below the light beam 20a.

  The spectrally separated infrared light 20 is reflected by the reflecting mirror 16 as described above, and further reflected by the second reflecting mirror 17. Then, the light is emitted upward from the visible light so as to be emitted from the projection device 1L through the light distribution lens 18 in a predetermined direction in front of the vehicle, that is, farther than the visible light. As shown in FIG. 6, the two light beams B1 and B2 that are emitted from the prism 11 (not shown) and are arranged in the upper and lower directions in the figure enter the reflecting mirror 16 from the left in the drawing, and are sequentially reflected by the reflecting mirror 16 and the reflecting mirror 17. Thus, the direction in which the light travels is changed to the left in the figure. At this time, the vertical positional relationship between the light beams B1 and B2 incident on the reflecting mirror 16 and the vertical positional relationship between the light beams B1 and B2 emitted from the reflecting mirror 17 are reversed.

  Therefore, as shown in FIG. 5, the infrared light 20 that is split from the lower side of the figure in the order of the light beams 20 a, 20 b, 20 c, 20 d, and 20 e and emitted from the prism 11 is arranged in the arrangement order after being reflected by the reflecting mirror 17. Will be turned upside down. And the infrared light 20 projected on the front side of the vehicle by the light distribution lens 18 is dispersed in the order of light beams 20a, 20b, 20c, 20d, and 20e from the top. The light distribution lens 18 is adjusted so that the optical axis of the infrared light 20 is directed higher than the optical axis of the visible light so that the infrared light 20 is projected farther than the visible light.

  FIG. 7 is a view for explaining the irradiation range of visible light and infrared light 20, wherein (a) is a view seen from the side of the vehicle, and (b) is a plan view seen from above the vehicle. The night vision device is a device that assists the driver so that a pedestrian or an obstacle ahead can be visually recognized even if the headlamp is a low beam, and the visible light in FIG. 7 indicates a low beam state.

  As shown in FIG. 7A, since the infrared light 20 is projected at an angle higher than the visible light, the infrared light 20 is irradiated forward (left side in the drawing) from the range irradiated with the visible light. FIG. 7B shows an example of the irradiation range, and visible light in a low beam state is irradiated up to 50 m ahead of the vehicle.

  On the other hand, with respect to the infrared light 20, the visible light side luminous flux 20 e in FIG. Then, light beams 20d, 20c, 20b, and 20a are irradiated in the direction away from the vehicle. The light beam 20e is irradiated to a distance of 50m to 80m, the light beam 20d is irradiated to a distance of 80m to 110m, the light beam 20c is irradiated to a distance of 110m to 140m, the light beam 20b is irradiated to a distance of 140m to 170m, and the light beam 20a is irradiated to a distance of 170m to 200m. The

  As described above, when the configuration is such that the near-infrared light having a shorter wavelength irradiates the farther region, the following advantages are obtained. As shown in FIG. 2, the sensitivity of the image sensor mounted on the infrared camera 2 decreases as the wavelength increases in the near-infrared light region. Therefore, even when near-infrared light having the same amount of light is received, a clear image with higher contrast can be taken with a shorter wavelength. Therefore, in this embodiment, near-infrared light in the low wavelength region where the sensitivity of the image sensor is high is irradiated in the distance, and near infrared light in the long wavelength region where the sensitivity of the image sensor is low is irradiated in a region close to the vehicle. By doing so, it has become possible to photograph distant objects with higher accuracy.

  On the other hand, in the conventional projector described above, light in the near-infrared light region separated by the dichroic mirror from the light of the headlamp as indicated by the characteristic L1 is projected forward of the vehicle without distinguishing the wavelength. For this reason, the near-infrared light irradiated in the distance includes near-infrared light in a wavelength range with low sensitivity in the image sensor, so that only the light beam 20a having a short wavelength is separated and irradiated as in the present embodiment. As compared with the case of doing so, the lack of clarity and the accuracy of the drop are reduced.

  Furthermore, in this embodiment, the light from the same light source is separated into visible light and near-infrared light, and visible light is used as headlamp illumination light and near-infrared light is used as night-light illumination light. Thus, the light projecting devices 1L and 1R serve as both a headlamp and a night vision projector. As a result, the light from the light source 10 can be used effectively, and it is not necessary to add a new infrared projector, and an increase in cost and installation space can be reduced as much as possible. In addition, since the infrared light is split using the prism 11, the spectroscopic mechanism can be configured simply and an increase in space can be suppressed.

  In the above-described embodiment, since all the wavelengths of light emitted from the light source 10 are split by the prism 11, visible light is also split. Therefore, the light is diffused by the diffusing optical element 14 and then projected forward of the vehicle. Therefore, in another embodiment shown in FIG. 8, infrared light transmitted through the dichroic mirror 30 is split by a prism and projected to the front of the vehicle.

  The dichroic mirror 30 is composed of, for example, a multilayer mirror in which a large number of dielectric thin films are stacked. The thickness and refractive index of the film constituting the multilayer film are high for infrared light and low for visible light, and conversely, low for infrared light. For visible light, the reflectance is set to be high. Therefore, infrared light contained in the light from the light source 10 is transmitted through the dichroic mirror 30, and visible light is reflected by the dichroic mirror 30.

  The infrared light transmitted through the dichroic mirror 30 is split by the prism 11 as described above. In the case of FIG. 8, since the direction of the prism 11 is upside down from that of FIG. 3, the upper side of the infrared light 20 emitted from the prism 11 becomes a light beam 20a on the short wavelength side with a large refraction angle. The lower side of the figure 20 is a long wavelength light beam 20e having a small refraction angle. The infrared light 20 emitted from the prism 11 is projected forward of the vehicle by the light distribution lens 18.

  On the other hand, the visible light reflected by the dichroic mirror 30 is reflected by the reflecting mirror 31 and then projected forward of the vehicle via the light distribution lens 15. The projection angles of visible light and infrared light are the same as those in FIG. 3, and their irradiation areas are the same as those shown in FIG. In the apparatus shown in FIG. 8, since the visible light is not split by the prism 11, the diffusion optical member 14 shown in FIG. 3 is not required.

  The present invention can be applied not only to the projector having both the headlamp and the night vision device projector described above, but also to the infrared projector 40 dedicated to the night vision device as shown in FIG. In FIG. 9, reference numeral 41 denotes a light source used in the near-infrared projector, and for example, a halogen lamp is used. The light emitted from the light source 41 is split by the prism 11. Also in the case of the projector 40 shown in FIG. 9, the prism 11 is arranged so that the light on the short wavelength side included in the emitted light is on the upper side in the drawing.

  The light (dispersed light) emitted from the prism 11 enters the visible cut filter 42. The visible cut filter 42 cuts the visible light included in the incident light, and only the infrared light 20 passes through the visible cut filter 42 and is projected to the left side of the figure (front of the vehicle). As described above, since the light emitted from the prism 11 has a long wavelength side on the lower side in the figure, the infrared light 20 that has passed through the visible cut filter 42 has a light beam 20e, a light beam 20d, a light beam 20c, The light beam 20b and the light beam 20a are arranged in this order. Therefore, the shorter wavelength infrared light is projected farther, and when the front of the vehicle is photographed with an infrared camera, the far field can be photographed brighter and clearer than before.

  In the embodiment shown in FIGS. 8 and 9, for example, instead of the prism 11, a dichroic mirror having a characteristic of transmitting a wavelength region of 900 nm or more and reflecting a wavelength region smaller than 900 nm may be used. The long-wavelength infrared light transmitted through the dichroic mirror is projected at a downward angle through the lens 18 (or the visible cut filter 42), and the short-wavelength infrared light reflected by the dichroic mirror is reflected by a mirror or the like. The light is deflected upward by the deflecting member, and is projected farther than the long-wavelength infrared light through the lens 18 (or the visible cut filter 42). Even with such a configuration, it is possible to take an image of a distant area brighter and clearer than in the prior art, and there is an effect that the weight is reduced because no prism is used. Of course, a dichroic mirror having a characteristic of reflecting a wavelength region of 900 nm or more and transmitting a wavelength region smaller than 900 nm may be used.

  Further, a first state of projecting near-infrared rays far away by disposing the diffusing plate in front of the lens 18 in FIG. 4 and driving the diffusing plate with an electric motor or the like by a driver's operation; You may make it switch to the 2nd state which projects the whole infrared light in the wide range as usual. Thus, for example, in a traveling environment where distant objects are too exaggerated and it becomes difficult to recognize nearby objects, the mode can be changed to the conventional mode. Similarly, in the embodiment shown in FIGS. 8 and 9, the prism 11 may be detachably disposed on the optical path, and the prism may be driven by an electric motor or the like by the driver's operation.

  In the embodiment described above, the case where the imaging device used in the infrared camera 2 has sensitivity characteristics as shown in FIG. 2 has been described as an example. It was configured to project infrared light far away. However, the present invention can be similarly applied to an image sensor having characteristics different from those in FIG. 2, and the image sensor may be configured to project infrared light in a highly sensitive wavelength region far away. Furthermore, the projector and night-vision device according to the present invention can be used without being limited to vehicles. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

  In the correspondence between the embodiment described above and the elements of the claims, the light beam 20a is the light in the first region, the light beams 20b to 20e are the light in the second region, the prism 11 is the infrared light separating means and the spectroscopic device. The reflecting mirrors 16 and 17 and the light distribution lens 18 are infrared light projecting means, the reflecting mirrors 12 and 13, the diffusion optical member 14 and the light distribution lens 15 are visible light projecting means, and the light projecting devices 1L and 1R are In the projector according to claim 5, the infrared camera 2 constitutes an imaging means, and the head-up display 4 constitutes a display means.

1 is a schematic configuration diagram showing an embodiment of a night vision device for a vehicle according to the present invention. It is a figure which shows the relationship between the wavelength and sensitivity in a CCD image pick-up element. It is a figure which shows the power ratio of the visible light area | region of the light radiate | emitted from the light source 10, and a near-infrared-light area | region. It is sectional drawing which looked at 1L of light projection apparatuses from the vehicle side. FIG. 5 is an enlarged view schematically showing a spectral state in a region A in FIG. 4. It is a figure explaining reflection of the light by the reflective mirrors 16 and 17. FIG. It is a figure explaining the irradiation range of visible light and the infrared light 20, (a) is the figure seen from the vehicle side, (b) is the top view seen from the vehicle upper direction. It is a figure which shows other embodiment of a light projector. It is a figure which shows the infrared projector 40 only for a night vision apparatus.

Explanation of symbols

1L, 1R Projecting device 2 Infrared camera 3 Electronic control unit 4 Head-up display 10, 41 Light source 11 Prism 12, 13, 16, 17 Reflector 14 Diffusing optical member 15, 18 Light distribution lens 20 Infrared light 20a-20e, B1, B2 Luminous flux 30 Dichroic mirror 40 Infrared projector 42 Visible cut filter

Claims (8)

A light source;
Infrared light separating means for separating the infrared light emitted from the light source into light of a first region having a short wavelength and light of another second region;
The projector according to claim 1, further comprising: an infrared light projecting unit configured to project the infrared light so that the light in the first region is irradiated farther than the light in the second region. The projector according to claim 1,
The infrared light separating means continuously separates infrared light emitted from the light source according to wavelength,
The projector for projecting infrared light, wherein the infrared light projecting unit projects the infrared light so that light having a shorter wavelength is irradiated more distantly. The projector according to claim 1 or 2,
The projector according to claim 1, wherein the infrared light separating means includes a prism that separates light according to a wavelength. In a projector that projects light from an object with an imaging unit and displays an image captured by the imaging unit with a display unit, and projects infrared light onto the object.
Infrared light separating means for separating infrared light emitted from the projector into light in a high sensitivity wavelength region of the imaging means and light in other wavelength regions;
The projector according to claim 1, further comprising: an infrared light projecting unit that projects the infrared light so that the light in the high sensitivity wavelength region is irradiated farther than the light in the other wavelength regions. In the light projector in any one of Claims 1-4,
The light source also emits visible light,
A projector that includes visible light projection means for separating visible light from light emitted from the light source and projecting the separated visible light in a downward direction with respect to a projection direction of the infrared light. The projector according to claim 1,
The infrared light separating means includes a dichroic mirror that separates infrared light emitted from the light source into light of the first region and light of the second region. In the light projector in any one of Claims 1-6,
The infrared light separating means includes a first state that separates the light of the first region and the light of the second region, and a second that does not separate the light of the first region and the light of the second region. It is possible to switch between the state of the projector. The projector according to any one of claims 1 to 7,
Imaging means for imaging the region irradiated with the infrared light;
A vehicle night vision apparatus comprising: display means for displaying an image picked up by the image pickup means.

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