Mirror for camera system and camera system

Abstract

To provide a mirror for a camera system and a camera system that suppress unevenness in picture quality.SOLUTION: A mirror 100 for a camera system comprise a substrate 101, a mirror layer 102, a fluorescent layer 103, and an excitation window layer 104. The substrate 101 is provided at a position facing the objective lens of an infrared camera and transmits visible light and infrared light. The mirror layer 102 is provided in the principal plane of the substrate 101 on the side facing the infrared camera, reflects visible light, and transmits infrared light. The fluorescent layer 103 is provided in at least a portion of the surface of the mirror layer 102 and emits at least infrared light upon receiving prescribed excitation light. The excitation window layer 104 is provided in such a way as to cover the fluorescent layer 103, transmits excitation light, and reflects at least infrared light.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a mirror for a camera system and a camera system. [Background technology]

[0002] Camera systems have been developed that have infrared cameras built into the back of the mirror.

[0003] For example, Patent Document 1 discloses a technique related to an in-vehicle imaging device. The in-vehicle imaging device detects the angle of the mirror surface of the rearview mirror relative to the vehicle, and estimates the position of the passenger's head in the vehicle cabin based on the detection result of the angle sensor. Then, based on the estimation result, the in-vehicle imaging device changes the imaging direction of the camera relative to the mirror surface so that the passenger's head is positioned on the optical axis of the camera.

[0004] For example, Patent Document 2 discloses a technology relating to a camera-integrated mirror device in which an infrared camera, an infrared light emitting device, and a shutter-synchronized light emission drive device are arranged inside a mirror case on the back side of a cold mirror. In the camera-integrated mirror device, the infrared light emitting device performs intermittent light emission operation in synchronization with the shutter operation of the infrared camera by the shutter-synchronized light emission drive device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-290545 A [Patent Document 2] JP 2002-316580 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the infrared light emitting elements used as light sources in the above-mentioned technology are susceptible to changes in the wavelength of light emitted by the elements due to changes in the environmental temperature, which may result in unstable quality of images captured by the infrared camera.

[0007] The present invention has been made to solve such problems, and provides a mirror for a camera system and a camera system that suppresses variations in image quality. [Means for solving the problem]

[0008] The mirror for a camera system according to the present invention has a substrate, a mirror layer, a fluorescent layer, and an excitation window layer. The substrate is provided at a position facing the objective lens of an infrared camera and transmits visible light and infrared light. The mirror layer is provided on the main surface side of the substrate that faces the infrared camera and reflects substrate visible light and transmits infrared light. The fluorescent layer is provided on at least a portion of the surface of the mirror layer and emits at least infrared light when exposed to predetermined excitation light. The excitation window layer is provided so as to cover the fluorescent layer and transmits the excitation light and reflects at least the infrared light. Effect of the Invention

[0009] According to the present invention, it is possible to provide a mirror for a camera system and a camera system that suppresses variations in image quality. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a moving object equipped with a camera system according to an embodiment. [Diagram 2] 1 is a cross-sectional view of an infrared camera system according to an embodiment. [Diagram 3] FIG. 2 is a view of the camera system mirror as seen from inside the vehicle interior. [Figure 4] FIG. 2 is a cross-sectional view showing the state of light rays in the camera system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described below through the embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. In addition, not all of the configurations described in the embodiments are necessarily essential as means for solving the problems. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0012] <Embodiment Mode> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram of a moving object equipped with a camera system according to the embodiment. Fig. 1 shows an automobile 90 as one embodiment of the moving object. The automobile 90 has a camera system 10 and an ECU 80 (Electronic Control Unit).

[0013] The camera system 10 is provided on the interior side of the windshield of an automobile 90, and functions as an inner mirror. The inner mirror may also be called a rearview mirror or a rear-view mirror.

[0014] Furthermore, the camera system 10 captures an image of the interior of the automobile 90 from the installed position. More specifically, in the camera system 10, a light-emitting unit that emits infrared light having a predetermined wavelength illuminates the interior of the automobile 90, and an infrared camera captures an image of the interior of the automobile 90.

[0015] Furthermore, the camera system 10 is communicably connected to the ECU 80 and can realize a predetermined function by cooperating with the ECU 80. For example, when the camera system 10 receives a signal from the ECU 80 instructing the camera system 10 to capture an image, the camera system 10 captures an image of the interior of the vehicle in response to the received signal and supplies the image data generated by capturing the image to the ECU 80.

[0016] The ECU 80 is a control device provided in the automobile 90, and has an electronic circuit board including a calculation device such as a CPU (Central Processing Unit). The ECU 80 is communicatively connected to the camera system 10, and supplies signals that instruct the camera system 10. The ECU 80 also acquires image data related to images captured by the camera system 10. In other words, the ECU 80 can operate the camera system 10.

[0017] The ECU 80 may also be connected to other devices of the automobile 90 so as to be able to communicate with them. For example, the ECU 80 may be connected to a display device and may supply image data received from the camera system 10 to the display device. The ECU 80 may have a wireless communication function. In this case, the ECU 80 may operate the camera system 10 in cooperation with an external device through the wireless communication function. The camera system 10 and the ECU 80 described above may be collectively referred to as the camera system 10.

[0018] Next, the camera system 10 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view of the camera system according to the embodiment. Fig. 2 shows the cross section II-II shown in Fig. 1. The camera system 10 mainly includes a camera system mirror 100, an enclosure 110, an infrared camera 120, and a light source block 130.

[0019] The camera system mirror 100 is a plate-like member, and is fitted into the enclosure 110 so as to close the opening 111 of the enclosure 110. The camera system mirror 100 is provided at a position facing the infrared camera 120 and the light emitting unit 131. The camera system mirror 100 receives excitation light emitted by the light emitting unit 131 housed in the enclosure 110 and emits infrared light to the outside. The camera system mirror 100 transmits infrared light in a predetermined area. The infrared light transmitted by the camera system mirror 100 allows the infrared camera 120 housed in the enclosure 110 to capture an image of the outside. The camera system mirror 100 mainly includes a substrate 101, a mirror layer 102, a fluorescent layer 103, and an excitation window layer 104.

[0020] The substrate 101 is provided at a position facing the infrared camera 120. The substrate 101 is a transparent plate-like structure that transmits at least visible light and infrared light. The substrate 101 may be made of, for example, transparent glass, acrylic, or polycarbonate.

[0021] The mirror layer 102 is provided on the main surface of the substrate 101 facing the infrared camera 120, and reflects visible light and transmits infrared light. In other words, the mirror layer 102 is provided on the main surface side of the substrate 101 facing the infrared camera 120, and reflects visible light and transmits infrared light. That is, a so-called cold mirror can be adopted as the mirror layer 102.

[0022] The mirror layer 102 is provided on the main surface of the camera system mirror 100 facing the infrared camera 120, and reflects visible light and transmits infrared light.

[0023] The fluorescent layer 103 is provided on at least a part of the surface of the mirror layer 102, and emits at least infrared light when exposed to predetermined excitation light. The predetermined excitation light is light emitted by the light emitting section 131, and has a wavelength in the 400 nm band, for example.

[0024] The fluorescent layer 103 may be formed, for example, by forming a film of a phosphor on the surface of the mirror layer 102 by sputtering. The fluorescent layer 103 may also be formed, for example, by adding a phosphor to a light-transmitting film substrate. A rare earth element may be used as a main raw material of the phosphor. More specifically, among rare earth elements, Sm (samarium) may be selected. That is, the fluorescent layer 103 preferably contains samarium-doped glass (Sm2O3-Sb2O3-B2O3-Bi2O3) as a component.

[0025] When the fluorescent layer 103 receives excitation light in the 400 nm band, it emits fluorescence having a wavelength band in the infrared range. The fluorescence emitted by the fluorescent layer 103 is preferably in the 940 nm band. The attenuation rate of sunlight is relatively high in the 940 nm band. Therefore, by using the 940 nm band as the illumination light for the infrared camera 120, the camera system 10 becomes less susceptible to the effects of sunlight.

[0026] The fluorescence exhibited by rare earth elements is due to the transition of unpaired electrons in the 4f orbital, which is the inner shell. Therefore, the fluorescence of the fluorescent layer 103 is less susceptible to the influence of the environmental temperature compared to the light emitted by an LED (light-emitting diode). Therefore, by using the camera system mirror 100 including the fluorescent layer 103, the camera system 10 can suppress the wavelength shift of infrared light caused by the change in the environmental temperature.

[0027] When receiving excitation light in the 400 nm band, the fluorescent layer 103 emits fluorescence in the visible light wavelength band in addition to the above-mentioned 940 nm band fluorescence. For example, the above-mentioned samarium-doped glass has the property of also emitting orange visible light when receiving excitation light in the 400 nm band. However, the fluorescent layer 103 is provided on the surface of the mirror layer 102. Therefore, the visible light emitted by the fluorescent layer 103 does not leak out to the outside of the camera system 10.

[0028] The excitation window layer 104 is provided so as to cover the fluorescent layer 103, and transmits the excitation light and reflects at least infrared light. More specifically, the excitation window layer 104 preferably transmits light having a wavelength in the 400 nm band and reflects light having a wavelength longer than the 400 nm band. That is, the excitation window layer 104 is preferably a low-pass filter. As a result, the excitation window layer 104 reflects visible light and infrared light contained in the fluorescence emitted by the fluorescent layer 103 and prevents them from being emitted into the camera system 10. The excitation window layer 104 can be formed, for example, by depositing a dielectric multilayer film on the surface of the fluorescent layer 103.

[0029] The above-mentioned fluorescent layer 103 and excitation window layer 104 have an opening region 105. The opening region 105 is a region in which the fluorescent layer 103 and the excitation window layer 104 are not provided in the camera system mirror 100. The opening region 105 is provided in a range corresponding to the imaging range of the infrared camera 120.

[0030] 2, an opening region 105 is shown in a region where the infrared camera 120 and the camera system mirror 100 face each other. The opening region 105 is a region where the fluorescent layer 103 and the excitation window layer 104 are not provided. That is, the camera system mirror 100 reflects visible light in the opening region 105 and transmits infrared light. In FIG. 2, a dotted line extending radially from the infrared camera 120 to the outside of the camera system 10 indicates an imaging range W120 of the infrared camera 120. The opening region 105 corresponds to the imaging range W120, and is configured so that the fluorescent layer 103 and the excitation window layer 104 do not overlap with the imaging range W120.

[0031] The opening region 105 will be further described with reference to Fig. 3. Fig. 3 is a view of the camera system mirror as seen from inside the vehicle compartment. Fig. 3 is a view of the camera system 10 observed from arrow view III shown in Fig. 2. In Fig. 3, the camera system mirror 100 is covered with an enclosure 110. In the center of the camera system mirror 100, an infrared camera 120 is indicated by a two-dot chain line. The infrared camera 120 is provided behind the camera system mirror 100.

[0032] The non-hatched region shown surrounding the infrared camera 120 is the aperture region 105. In this region, the substrate 101 and the mirror layer 102 are provided, but the fluorescent layer 103 and the excitation window layer 104 are not provided. The hatched region shown surrounding the aperture region 105 with only dashed lines is the region where the excitation window layer 104 is provided. In this region, the fluorescent layer 103 is not provided.

[0033] The hatched region where the dashed lines and solid lines intersect and which is shown to surround the hatching only with dashed lines is the region where the excitation window layer 104 and the fluorescent layer 103 are provided. As can be seen when observed together with Fig. 2, the excitation window layer 104 is configured to cover the fluorescent layer 103. With this configuration, the camera system mirror 100 allows infrared light from the outside to be suitably incident on the imaging range of the infrared camera 120 through the opening region 105, while preventing other light rays from leaking into the infrared camera 120 as stray light.

[0034] Returning to FIG. 2, the configuration of the camera system 10 will be described further. The enclosure 110 is a housing formed by molding, for example, a resin material that does not transmit visible light or infrared light, and has an opening 111 and a recess 112. The recess 112 houses the infrared camera 120 and the light emitting unit 131. The enclosure 110 also fits the camera system mirror 100 at the opening 111. By fitting the enclosure 110 and the camera system mirror 100, the camera system 10 prevents leakage light other than desired light rays from entering the infrared camera 120 housed in the recess 112. The enclosure 110 may be made of a metal such as aluminum instead of the above-mentioned resin.

[0035] The infrared camera 120 is an imaging device having infrared sensors arranged in an array to detect predetermined infrared light. The objective lens of the infrared camera 120 faces the camera system mirror 100, and captures an image outside the camera system 10 through the opening region 105 of the camera system mirror 100.

[0036] In this embodiment, the infrared camera 120 is provided to face the center of the camera system mirror 100, but the position at which the infrared camera 120 is placed is not limited to the center of the camera system mirror 100. The infrared camera 120 may be placed in an area close to the end of the camera system mirror 100. Furthermore, the optical axis of the infrared camera 120 does not need to be perpendicular to the camera system mirror 100, and the optical axis may have a predetermined angle with the camera system mirror 100.

[0037] The camera system 10 may have two or more infrared cameras 120 in the enclosure 110. In this case, the camera system mirror 100 may have a plurality of opening areas 105 corresponding to the respective infrared cameras 120.

[0038] The infrared camera 120 may be movable so that the imaging range can be changed. For example, the infrared camera 120 may be capable of panning, zooming, or tilting. In this case, the camera system mirror 100 has an opening area 105 that corresponds to the imaging range of the infrared camera 120 that changes.

[0039] The light source block 130 is a circuit board including a light emitting unit 131. The light source block 130 has the light emitting unit 131 mounted thereon, and is configured so that light emitted by the light emitting unit 131 irradiates the mirror 100 for the camera system.

[0040] The light emitting unit 131 is an LED that emits excitation light. As described above, the wavelength of the excitation light emitted by the light emitting unit 131 is preferably in the 400 nm band. The light emitting unit 131 is provided near the infrared camera 120, and irradiates the fluorescent layer 103 of the camera system mirror 100. With this configuration, the camera system 10 can suitably capture an image of an object that reflects fluorescence caused by the excitation light.

[0041] Next, the state of light rays in the camera system 10 will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view showing the state of light rays in the camera system 10. Fig. 4 shows the first excitation light L11, the first fluorescence L21, the second fluorescence L22, the third fluorescence L31, the visible light L41, and the returned light L51.

[0042] First excitation light L11 having a wavelength in the 440 nm band is emitted from the light emitting section 131, passes through the excitation window layer 104, and reaches the fluorescent layer 103. In the fluorescent layer 103, the first excitation light L11 is absorbed by the phosphor. When the phosphor receives the first excitation light L11, it emits a first fluorescence L21, a second fluorescence L22, and a third fluorescence L31, respectively.

[0043] The first fluorescence L21 is infrared light having a wavelength in the 940 nm band. When the first fluorescence L21 is emitted from the fluorescent layer 103, it passes through the mirror layer 102 and the substrate 101 and is radiated to the outside of the camera system 10. Based on this principle, the camera system 10 converts the excitation light into infrared light and radiates the converted infrared light into the imaging range of the infrared camera 120.

[0044] The second fluorescence L22 is infrared light having a wavelength in the 940 nm band, like the first fluorescence. When the second fluorescence L22 is emitted from the phosphor of the fluorescent layer 103, it travels toward the excitation window layer 104. The excitation window layer 104 has a property of reflecting infrared light. Therefore, when the second fluorescence L22 reaches the excitation window layer 104, it is reflected at the boundary surface between the fluorescent layer 103 and the excitation window layer 104. The reflected second fluorescence L22 changes direction, passes through the mirror layer 102 and the substrate 101, and is emitted to the outside of the camera system 10. In this way, the second fluorescence L22 emitted toward the excitation window layer 104 is reflected by the excitation window layer 104 and emitted to the outside of the camera system 10, so that the camera system 10 can improve the amount of infrared light used as illumination light.

[0045] The third fluorescence L31 is visible light emitted from the phosphor. When the third fluorescence L31 is emitted from the phosphor and reaches the mirror layer 102, it is reflected by the mirror layer 102, which reflects visible light. Therefore, the third fluorescence L31 changes direction and travels toward the excitation window layer 104. Then, when the third fluorescence L31 reaches the excitation window layer 104, it is reflected by the excitation window layer 104.

[0046] Visible light L41 reaches the mirror 100 for a camera system from outside the camera system 10. When the visible light L41 passes through the substrate 101 and reaches the mirror layer 102, it is reflected by the mirror layer 102. Therefore, the visible light L41 does not affect the inside of the camera system 10. Furthermore, the reflection of the visible light L41 allows the camera system 10 to function as an inner mirror. Note that the mirror 100 for a camera system can achieve a suitable anti-glare function by setting the visible light transmittance of the substrate 101 to a predetermined value.

[0047] The return light L51 is infrared light in the 940 nm band that is emitted from the fluorescent layer 103 to the outside of the camera system 10 and then reflected by an object and returned. The return light L51 passes through the substrate 101 and the mirror layer 102 and reaches the infrared camera 120. The return light reaches the camera system 10 in this manner, allowing the camera system 10 to capture an image of the interior of the automobile 90.

[0048] Although the embodiment has been described above, the mirror for camera system 100 and the camera system 10 according to the embodiment are not limited to the above-mentioned configuration. For example, the infrared camera 120 may have a bandpass filter that transmits only the 940 nm band.

[0049] Although the camera system 10 according to the present embodiment is shown as capturing images of the interior of an automobile, the present invention is not limited to this. The camera system 10 may be used in various moving bodies such as ships, aircraft, rockets, spacecraft, and submarines. The camera system mirror 100 according to the present embodiment may be used, for example, in a surveillance camera installed at a predetermined position.

[0050] In general, infrared cameras are equipped with a bandpass filter that transmits only the 940 nm band. However, when using LEDs as illumination for infrared cameras, the following problems arise. That is, the peak wavelength of the light emitted by LEDs changes as the ambient temperature changes. Specifically, for example, the temperature inside a car can vary from minus 40 degrees Celsius to plus 80 degrees Celsius depending on the weather. In such an environment, the peak wavelength of LEDs can change by about 50 nm. In this case, in low-temperature and high-temperature environments, the infrared light that is the illumination light is significantly outside the 940 nm band. As a result, images captured by infrared cameras may be insufficiently bright.

[0051] On the other hand, if the transmission bandwidth of the bandpass filter is expanded to avoid insufficient brightness, the infrared camera will capture too much sunlight in the expanded bandwidth, resulting in images with poor contrast.

[0052] The wavelength of light emitted by the rare earth element contained in the fluorescent layer 103 used in this embodiment is not easily affected by temperature changes. Therefore, the camera system 10 does not need to widen the transmission bandwidth of the bandpass filter provided in the infrared camera 120. Therefore, the camera system 10 can suppress the influence of sunlight by adopting the camera system mirror 100. Also, as described above, the fluorescent layer 103 has a small change in wavelength due to changes in the environmental temperature. Therefore, the infrared camera 120 can suppress deterioration of image quality due to changes in the environmental temperature.

[0053] As described above, according to the embodiments, it is possible to provide a mirror for a camera system and a camera system that suppresses variations in image quality.

[0054] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0055] 10 Camera System 80 ECU 90 Automobiles 100 Mirror for Camera System 101 Substrate 102 Mirror Layer 103 Fluorescent Layer 104 Excitation Window Layer 105 Open area 110 Enclosure 111 Opening 112 Recess 120 Infrared Camera 130 Light source block 131 Light emitting part

Claims

1. a substrate that is disposed in a position facing the infrared camera and transmits visible light and infrared light; a mirror layer provided on a main surface side of the substrate facing the infrared camera, the mirror layer reflecting visible light and transmitting infrared light; a fluorescent layer provided on at least a portion of a surface of the mirror layer and emitting at least infrared light when exposed to a predetermined excitation light; an excitation window layer that is provided to cover the fluorescent layer, transmits the excitation light, and reflects at least the infrared light; Mirror for camera system.

2. the fluorescent layer and the excitation window layer have an opening area in a range corresponding to an imaging range of the infrared camera; 2. The mirror for a camera system according to claim 1.

3. The fluorescent layer contains a rare earth element as a phosphor that emits fluorescence upon receiving the excitation light.

3. A mirror for a camera system according to claim 1 or 2.

4. The infrared camera; A light emitting unit that emits the excitation light; A camera system comprising: an enclosure having an opening and a recess, housing the infrared camera and the light-emitting unit in the recess, and fitting a mirror for a camera system described in any one of claims 1 to 3 in the opening.

5. Installed in the room of the moving body, The light emitting unit illuminates the interior of the room, The infrared camera captures an image of the interior of the room. The camera system of claim 4.

Images