Camera system lens and camera system

Abstract

The camera system mirror (100) comprises a substrate (101), a mirror layer (102), a fluorescent layer (103) and an excitation window layer (104). The substrate (101) is arranged at a position opposite to the objective lens of the infrared camera, allowing visible light and infrared light to pass through. The mirror layer (102) is arranged on the main surface of the substrate (101) on the side opposite to the infrared camera, reflecting visible light and allowing infrared light to pass through. The fluorescent layer (103) is arranged on at least a portion of the surface of the mirror layer (102), and emits at least infrared light by receiving a predetermined excitation light. The excitation window layer (104) is arranged in a manner covering the fluorescent layer (103), allowing the excitation light to pass through and at least reflecting infrared light.

Description

Technical Field

[0001] The present invention relates to a lens for a camera system and a camera system. Background Art

[0002] A camera system has been developed that has an infrared camera built into the back of the mirror.

[0003] For example, Patent Document 1 discloses technology related to a vehicle interior camera. This camera detects the angle of an interior mirror relative to the vehicle and estimates the position of a passenger's head within the vehicle based on the angle sensor's detection results. Based on this estimation, the camera changes the camera's imaging direction relative to the mirror so that the passenger's head is aligned with the camera's optical axis.

[0004] For example, Patent Document 2 discloses a technology related to a camera-integrated mirror device in which an infrared camera, an infrared light emitting device, and a shutter-synchronized light emitting drive device are disposed within a mirror box on the rear side of a cold light mirror. In the camera-integrated mirror device, the infrared light emitting device emits intermittent light in synchronization with the shutter operation of the infrared camera via the shutter-synchronized light emitting drive device.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-290545;

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2002-316580. Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, the wavelength of light emitted by the infrared light-emitting element used as a light source in the above-mentioned technology is easily affected by changes in ambient temperature, which may cause the image quality of the image captured by the infrared camera to become unstable.

[0011] The present invention has been made to solve such a problem, and provides a lens for a camera system and a camera system that suppress variations in image quality.

[0012] Means for solving problems

[0013] The camera system mirror of this embodiment comprises a substrate, a mirror layer, a fluorescent layer, and an excitation window layer. The substrate is arranged at a position opposite to the objective lens of the infrared camera, allowing visible light and infrared light to pass through. The mirror layer is arranged on the side of the substrate opposite to the infrared camera, i.e., the main surface side, and reflects visible light from the substrate while allowing infrared light to pass through. The fluorescent layer is arranged on at least a portion of the surface of the mirror layer and emits at least infrared light by receiving specified excitation light. The excitation window layer is arranged in a manner covering the fluorescent layer, allowing the excitation light to pass through and at least reflecting the infrared light.

[0014] Effects of the Invention

[0015] According to the present embodiment, a camera system lens and a camera system in which variations in image quality are suppressed can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of a moving object equipped with a camera system according to an embodiment.

[0017] Figure 2 It is a cross-sectional view of the infrared camera system in the embodiment.

[0018] Figure 3 This is a view of the camera system from the inside of the vehicle.

[0019] Figure 4 is a cross-sectional view showing the state of light in a camera system. DETAILED DESCRIPTION

[0020] The present invention will be described below by way of embodiments of the invention, but the inventions to which the claims relate are not limited to the following embodiments. In addition, not all structures described in the embodiments are necessary as means for solving the problems. In order to clarify the description, the following description and drawings have been appropriately omitted and simplified. In addition, in each of the drawings, the same reference numerals are used for the same elements, and repeated descriptions are omitted as needed.

[0021] (Implementation Method)

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 : is a diagram of a mobile object equipped with a camera system according to an embodiment. Figure 1 1 shows a car 90 as one embodiment of a mobile object. The car 90 includes a camera system 10 and an ECU 80 (Electronic Control Unit).

[0023] The camera system 10 is installed on the interior side of the windshield of the automobile 90 and functions as an interior rearview mirror. The interior rearview mirror may also be called a back mirror or a rearview mirror.

[0024] The camera system 10 also captures images of the interior of the car 90 from its installed position. More specifically, in the camera system 10, a light emitting unit that emits infrared light having a predetermined wavelength illuminates the interior, and the infrared camera captures images of the interior.

[0025] The camera system 10 is communicatively connected to the ECU 80 and can perform predetermined functions in cooperation with the ECU 80. For example, upon receiving a signal from the ECU 80 instructing the camera system 10 to capture an image, the camera system 10 captures the interior of the room in response to the received signal and provides the resulting image data to the ECU 80.

[0026] The ECU 80 is a control device installed in the vehicle 90 and includes an electronic circuit board including a CPU (Central Processing Unit) and other computing devices. The ECU 80 is communicatively connected to the camera system 10 and provides signals that instruct the camera system 10. Furthermore, the ECU 80 acquires image data related to images captured by the camera system 10. In other words, the ECU 80 is capable of operating the camera system 10.

[0027] Furthermore, the ECU 80 may be communicatively connected to other devices included in the vehicle 90. For example, the ECU 80 may be connected to a display device to provide image data received from the camera system 10 to the display device. The ECU 80 may also have wireless communication capabilities. In this case, the ECU 80 can also operate the camera system 10 by cooperating with external devices through the wireless communication capabilities. Furthermore, the camera system 10 and ECU 80 described above may be collectively referred to as the camera system 10.

[0028] Next, refer to Figure 2 , the camera system 10 is described. Figure 2 is a cross-sectional view of a camera system in an embodiment. Figure 2 Shown Figure 1 The camera system 10 mainly includes a camera system mirror 100 , a housing 110 , an infrared camera 120 , and a light source block 130 .

[0029] The camera system mirror 100 is a plate-shaped component that is fitted into the housing 110 in a manner that closes the opening 111 of the housing 110. In addition, the camera system mirror 100 is provided at a position opposite to the infrared camera 120 and the light-emitting portion 131. The camera system mirror 100 receives excitation light emitted by the light-emitting portion 131 housed in the housing 110 and emits infrared light to the outside. In addition, the camera system mirror 100 allows infrared light to pass through a predetermined area. By transmitting infrared light through the camera system mirror 100, the infrared camera 120 housed in the housing 110 can capture external images. The camera system mirror 100 has a substrate 101, a mirror layer 102, a fluorescent layer 103, and an excitation window layer 104 as main structures.

[0030] The substrate 101 is provided at a position facing the infrared camera 120. The substrate 101 is a transparent plate-shaped structure that transmits at least visible light and infrared light. The substrate 101 can be made of, for example, transparent glass, acrylic, or polycarbonate.

[0031] The mirror layer 102 is provided on the principal surface of the substrate 101 opposite the infrared camera 120, reflecting visible light while transmitting infrared light. In other words, the mirror layer 102 is provided on the principal surface side of the substrate 101 opposite the infrared camera 120, reflecting visible light while transmitting infrared light. Specifically, the mirror layer 102 can employ a so-called cold mirror.

[0032] The mirror layer 102 is provided on the main surface of the camera system mirror 100 on the side facing the infrared camera 120 , and reflects visible light and transmits infrared light.

[0033] The fluorescent layer 103 is provided on at least a portion of the surface of the mirror layer 102 and emits at least infrared light by receiving predetermined excitation light. The predetermined excitation light is light emitted by the light emitting portion 131 and has a wavelength in the 400 nm range, for example.

[0034] The fluorescent layer 103 can be formed, for example, by forming a film of a fluorescent substance on the surface of the mirror layer 102 by sputtering. Alternatively, the fluorescent layer 103 can be formed by adding a fluorescent substance to a light-transmitting film substrate. Rare earth elements can be used as the main raw material for the fluorescent substance. More specifically, Sm (samarium) can be selected from the rare earth elements. That is, the fluorescent layer 103 preferably comprises samarium-doped glass (Sm2O3-Sb2O3-B2O3-Bi2O3).

[0035] When fluorescent layer 103 receives excitation light in the 400nm wavelength range, it emits fluorescence in the infrared region. Furthermore, the fluorescence emitted by fluorescent layer 103 preferably occurs in the 940nm wavelength range. Sunlight in the 940nm wavelength range has a relatively high attenuation rate. Therefore, by using the 940nm wavelength range as illumination for infrared camera 120, camera system 10 is less susceptible to the effects of sunlight.

[0036] Furthermore, the fluorescence exhibited by rare earth elements arises from the migration of unpaired electrons in the inner shell 4f orbital. Therefore, the fluorescence of the fluorescent layer 103 is less susceptible to the effects of ambient temperature than light emission from an LED (light-emitting diode). Therefore, by using the camera system lens 100 including the fluorescent layer 103, the camera system 10 can suppress wavelength shifts in infrared light caused by changes in ambient temperature.

[0037] Furthermore, when the fluorescent layer 103 receives excitation light in the 400nm wavelength band, it exhibits fluorescence in the visible light region in addition to the aforementioned fluorescence in the 940nm wavelength band. For example, the samarium-doped glass described above has the characteristic of emitting orange visible light when receiving excitation light in the 400nm wavelength 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 outside the camera system 10.

[0038] The excitation window layer 104 is arranged to cover the fluorescent layer 103, allowing the excitation light to pass through while reflecting at least infrared light. More specifically, the excitation window layer 104 preferably transmits light with a wavelength in the 400nm band and reflects light with wavelengths longer than the 400nm band. In other words, the excitation window layer 104 is preferably a low-pass filter. Thus, the excitation window layer 104 reflects the visible light and infrared light contained in the fluorescence emitted by the fluorescent layer 103, preventing it from being emitted into the camera system 10. The excitation window layer 104 can be formed, for example, by vapor-depositing a dielectric multilayer film on the surface of the fluorescent layer 103.

[0039] The fluorescent layer 103 and the excitation window layer 104 have an opening region 105. The opening region 105 is a region of the camera system lens 100 where the fluorescent layer 103 and the excitation window layer 104 are not provided. The opening region 105 is provided within a range corresponding to the imaging range of the infrared camera 120.

[0040] exist Figure 2 In FIG, an opening area 105 is shown in the area where the infrared camera 120 and the camera system mirror 100 are opposite. The opening area 105 is an area 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 area 105 and transmits infrared light. Figure 2In FIG, the dotted line extending radially from the infrared camera 120 toward the outside of the camera system 10 represents the 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.

[0041] Reference Figure 3 , further describing the opening area 105. Figure 3 This is a view of the camera system from the inside of the vehicle. Figure 3 It is from Figure 2 Arrow III shown in FIG. 1 is a diagram of the camera system 10. Figure 3 In FIG, the camera system scope 100 is covered by a housing 110. An infrared camera 120 is indicated by a two-dot chain line in the center of the camera system scope 100. The infrared camera 120 is provided behind the camera system scope 100.

[0042] The unshaded area shown so as to surround the infrared camera 120 is the opening area 105. The substrate 101 and the mirror layer 102 are provided in this area, but the fluorescent layer 103 and the excitation window layer 104 are not provided. The area shown only with dotted hatching so as to surround the opening area 105 is the area where the excitation window layer 104 is provided. The fluorescent layer 103 is not provided in this area.

[0043] The hatched area where the dashed line and the solid line intersect is shown as a region surrounded by only dashed hatching, and is where the excitation window layer 104 and the fluorescent layer 103 are provided. Figure 2 As can be seen from the combined observation, the excitation window layer 104 is constructed so as to cover the fluorescent layer 103. With this structure, the camera system mirror 100 allows infrared light from the outside to appropriately enter the imaging range of the infrared camera 120 through the opening area 105, while preventing other light from leaking into the infrared camera 120 as stray light.

[0044] return Figure 2 , the structure of the camera system 10 is further described. The housing 110 is a casing formed by molding a resin material that does not transmit visible light or infrared light, for example, and has an opening 111 and a recess 112. The recess 112 accommodates the infrared camera 120 and the light-emitting unit 131. In addition, the housing 110 is fitted with the camera system mirror 100 in the opening 111. By fitting the housing 110 and the camera system mirror 100, the camera system 10 prevents leakage light other than desired light from entering the infrared camera 120 accommodated in the recess 112. The housing 110 may be made of a metal such as aluminum instead of the above-mentioned resin.

[0045] The infrared camera 120 is an imaging device having infrared sensors arranged in an array to detect predetermined infrared light. The infrared camera 120 has an objective lens facing the camera system mirror 100 and captures an image outside the camera system 10 through the opening area 105 of the camera system mirror 100 .

[0046] In addition, while the infrared camera 120 in this embodiment is positioned opposite the center of the camera system lens 100, the location of the infrared camera 120 is not limited to the center of the camera system lens 100. The infrared camera 120 may also be positioned near an end of the camera system lens 100. Furthermore, the optical axis of the infrared camera 120 does not need to be perpendicular to the camera system lens 100; the optical axis may also be at a predetermined angle to the camera system lens 100.

[0047] The camera system 10 may include two or more infrared cameras 120 in the housing 110 . In this case, the camera system lens 100 may include a plurality of opening regions 105 corresponding to the respective infrared cameras 120 .

[0048] The infrared camera 120 may also be a movable camera capable of changing its imaging range. For example, the infrared camera 120 may be capable of panning, zooming, or tilting. In this case, the camera system lens 100 has an aperture area 105 corresponding to the variable imaging range of the infrared camera 120.

[0049] The light source block 130 is a circuit board including a light emitting unit 131. The light source block 130 is mounted with the light emitting unit 131, and is configured so that light emitted from the light emitting unit 131 illuminates the camera system lens 100.

[0050] Light-emitting unit 131 is an LED that emits excitation light. As mentioned above, the wavelength of the excitation light emitted by light-emitting unit 131 is preferably in the 400 nm band. Light-emitting unit 131 is positioned near infrared camera 120 to illuminate fluorescent layer 103 of camera system mirror 100. This configuration enables camera system 10 to appropriately capture objects that reflect the fluorescence generated by the excitation light.

[0051] Next, refer to Figure 4 , illustrating the state of light in the camera system 10. Figure 4 is a cross-sectional view showing the state of light in the camera system 10 . Figure 4 The first excitation light L11 , the first fluorescent light L21 , the second fluorescent light L22 , the third fluorescent light L31 , the visible light L41 , and the return light L51 are shown respectively.

[0052] First excitation light L11, having a wavelength in the 440 nm band, is emitted from light-emitting portion 131, passes through excitation window layer 104, and reaches fluorescent layer 103. In fluorescent layer 103, first excitation light L11 is absorbed by the phosphor. Upon receiving first excitation light L11, the phosphor emits first fluorescent light L21, second fluorescent light L22, and third fluorescent light L31.

[0053] The first fluorescent light L21 is infrared light with a wavelength in the 940 nm band. After emitting from the fluorescent layer 103, the first fluorescent light L21 transmits through the mirror layer 102 and the substrate 101, and is emitted outside the camera system 10. Based on this principle, the camera system 10 converts the excitation light into infrared light and emits the converted infrared light into the imaging range of the infrared camera 120.

[0054] The second fluorescence L22 is the same as the first fluorescence and is infrared light with a wavelength in the 940nm band. After being emitted from the phosphor of the fluorescent layer 103, the second fluorescence L22 moves toward the excitation window layer 104. The excitation window layer 104 has the characteristic 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, thereby enabling the camera system 10 to increase the amount of infrared light used as illumination light.

[0055] The third fluorescent light L31 is visible light emitted from the phosphor. When the third fluorescent light L31 reaches the mirror layer 102, it is reflected by the mirror layer 102, which also reflects visible light. Therefore, the third fluorescent light L31 changes direction and travels toward the excitation window layer 104. Then, when the third fluorescent light L31 reaches the excitation window layer 104, it is reflected by the excitation window layer 104.

[0056] Visible light L41 travels from outside the camera system 10 to the camera system mirror 100. Once visible light L41 passes through the substrate 101 and reaches the mirror layer 102, it is reflected by the mirror layer 102. Therefore, visible light L41 does not affect the interior of the camera system 10. Furthermore, by reflecting visible light L41, the camera system 10 can function as an interior rearview mirror. Furthermore, by setting the visible light transmittance of the substrate 101 to a predetermined characteristic, the camera system mirror 100 can achieve an appropriate anti-glare function.

[0057] Return light L51 is infrared light in the 940 nm wavelength band. It is emitted from fluorescent layer 103 to the outside of camera system 10, then reflected by an object and returned. Return light L51 passes through substrate 101 and mirror layer 102 and reaches infrared camera 120. This return light reaches camera system 10, allowing camera system 10 to capture images of the interior of vehicle 90.

[0058] Although the embodiment has been described above, the camera system lens 100 or the camera system 10 of the embodiment is not limited to the above configuration. For example, the infrared camera 120 may include a bandpass filter that transmits only a 940 nm wavelength band.

[0059] While the camera system 10 of this embodiment is shown as being used to capture images of the interior of a car, the present invention is not limited thereto. The camera system 10 can also be used on various mobile objects, such as ships, aircraft, rockets, spacecraft, and submarines. Furthermore, the camera system lens 100 of this embodiment can also be used, for example, in surveillance cameras installed at predetermined locations.

[0060] However, infrared cameras are generally equipped with a bandpass filter that only allows the 940nm band to pass. However, when using LEDs as illumination light for infrared cameras, there are the following issues. That is, as the ambient temperature changes, the peak wavelength of the light emitted by the LED changes. Specifically, for example, the temperature inside a car varies from -40 degrees Celsius to around +80 degrees Celsius depending on the weather. In such an environment, the peak wavelength of the LED can vary by about 50nm. In this case, in low-temperature or high-temperature environments, the infrared light used as illumination light deviates significantly from the 940nm band. Therefore, the image captured by the infrared camera is sometimes not bright enough.

[0061] On the other hand, if the transmission bandwidth of the bandpass filter is expanded to avoid insufficient brightness, the infrared camera will excessively capture sunlight in the expanded wavelength band, which will reduce the contrast of the image captured by the infrared camera.

[0062] The wavelength of light emitted by the rare earth elements in the fluorescent layer 103 used in this embodiment is not easily affected by temperature fluctuations. Therefore, the camera system 10 does not need to expand the transmission bandwidth of the bandpass filter provided in the infrared camera 120. Therefore, by using the camera system lens 100, the camera system 10 can suppress the influence of sunlight. Furthermore, as mentioned above, the wavelength of the fluorescent layer 103 rarely changes with changes in ambient temperature. Therefore, the infrared camera 120 can suppress the degradation of image quality caused by changes in ambient temperature.

[0063] As described above, according to the embodiments, a camera system lens and a camera system in which image quality variations are suppressed can be provided.

[0064] In addition, the present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within a scope not departing from the gist of the invention.

[0065] This application claims priority from Japanese patent application No. 2021-106833, filed on June 28, 2021, and incorporates herein in its entirety the disclosure of which is incorporated herein by reference.

[0066] Industrial Applicability

[0067] The present invention can be utilized in, for example, an interior rearview mirror for an automobile or a mirror system with a built-in camera used indoors in other mobile vehicles.

[0068] Explanation of symbols

[0069] 10-camera system

[0070] 80ECU

[0071] 90 Car

[0072] 100 camera system lenses

[0073] 101 substrate

[0074] 102 mirror layers

[0075] 103 fluorescent layer

[0076] 104 excitation window layer

[0077] 105 opening area

[0078] 110 shell

[0079] 111 opening

[0080] 112 recess

[0081] 120 infrared camera

[0082] 130 light source blocks

[0083] 131 luminous part

Claims

1. A lens for a camera system, comprising: a substrate, disposed at a position opposite to the infrared camera, allowing visible light and infrared light to pass through; a mirror layer disposed on a principal surface side of the substrate, reflecting visible light and transmitting infrared light, wherein the principal surface side is a side of the substrate opposite to the infrared camera; a fluorescent layer provided on at least a portion of the surface of the mirror layer and emitting at least infrared light by receiving predetermined excitation light; as well as an excitation window layer, configured to cover the fluorescent layer, allowing the excitation light to pass through and at least reflecting the infrared light, The fluorescent layer and the excitation window layer have an opening area within a range corresponding to the imaging range of the infrared camera. The opening area is an area where the fluorescent layer and the excitation window layer are not provided in the camera system mirror.

2. The camera system lens according to claim 1, wherein: The fluorescent layer contains rare earth elements as a fluorescent substance, and the fluorescent substance emits fluorescence when receiving the excitation light.

3. A camera system comprising: the infrared camera; a light emitting portion, emitting the excitation light; as well as The housing has an opening and a recessed portion, wherein the infrared camera and the light emitting unit are housed in the recessed portion, and the camera system lens according to claim 1 or 2 is fitted into the opening.

4. The camera system of claim 3, wherein: The camera system is installed in the interior of the mobile body. The light emitting unit illuminates the room. The infrared camera takes pictures of the room.

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