Illumination device and imaging system

Abstract

An infrared light source (11) emits infrared light (IR). A white light source (12) emits white light (W). A control device (30) controls the timing at which the infrared light (IR) is emitted so as to co-operate with an imaging element (20) having sensitivity in at least the infrared wavelength range. The ratio of the radiance of the white light (W) to the radiance of the infrared light (IR) is greater than or equal to 6.0E-05.

Description

Illumination device and imaging system

[0001] The present disclosure relates to an illumination device that cooperates with an image sensor that is sensitive at least in the infrared wavelength range, and also to an imaging system that includes the illumination device and the image sensor.

[0002] Patent Literature 1 discloses a time-of-flight (TOF) camera system as an example of a system in which a light source capable of emitting infrared light and an image sensor work together. In this system, the distance to an object is determined based on the time it takes for the infrared light to be emitted from the light source and reflected by the object and detected by the image sensor, and an image including distance information is acquired.

[0003] Japanese Patent Application Publication No. 2009-257981

[0004] It is desired to make the red component that may be contained in the light emitted from the infrared light source invisible.

[0005] A first example aspect provided by the present disclosure is an illumination device comprising: an infrared light source capable of emitting infrared light; a white light source capable of emitting white light; and a control device that controls the timing of emission of the infrared light so as to cooperate with an image sensor having sensitivity at least in the infrared wavelength range, wherein a ratio of the radiance of the white light to the radiance of the infrared light is 6.0E-05 or more.

[0006] Depending on the emission spectrum distribution of the infrared light source, the emitted light may contain a red component. In this case, the emitted light from the infrared light source, which should be invisible, may be perceived as reddish light. In the lighting device according to the first aspect, white light is also emitted when emitting infrared light, thereby making the reddish light less noticeable.

[0007] On the other hand, when the infrared light source is turned on and off while the white light source is on, the visible light switches between a state in which the red component is included and a state in which the red component is not included, causing a change in the color of the white light. Such a change in color may cause discomfort to the observer.

[0008] In the lighting device according to the first embodiment, the ratio of the radiance of white light to the radiance of visible light is set appropriately based on the idea that changes in the color of the white light can be made unnoticeable regardless of whether the infrared light source is on or off, and the value of this ratio is set to be 6.0E-05 or greater. This makes it possible to prevent the color of the white light emitted from the white light source, which makes the red component less noticeable, from changing when the infrared light source is turned on or off. This makes it possible to avoid the discomfort caused by this change.

[0009] A second example embodiment provided by the present disclosure is an illumination device comprising: an infrared light source capable of emitting infrared light; a visible light source capable of emitting visible light; and a control device that controls the timing of emitting the infrared light so as to cooperate with an imaging element having sensitivity at least in the infrared wavelength range, wherein a straight line connecting a first point corresponding to the wavelength of the visible light and a second point corresponding to the wavelength of the red component contained in the infrared light on an xy chromaticity diagram of the CIE color system crosses a white region on the xy chromaticity diagram.

[0010] The fact that the line connecting the first point and the second point crosses the white region in the xy chromaticity diagram means that white can be generated by mixing colors by appropriately setting the radiance of the visible light emitted from the visible light source relative to the radiance of the red component contained in the light emitted from the infrared light source.

[0011] In the lighting device according to the second embodiment, by turning on the visible light source while turning on the infrared light source, a mixture of the red component contained in the light emitted from the infrared light source and the color of the visible light occurs, resulting in the lighting device appearing to emit white light, and the red component that may be contained in the light emitted from the infrared light source being invisible.

[0012] A third example aspect provided by the present disclosure is an illumination device comprising: an infrared light source capable of emitting infrared light; a first visible light source capable of emitting first visible light having a first wavelength in the visible wavelength range; a second visible light source capable of emitting second visible light having a second wavelength in the visible wavelength range; and a control device that controls the timing at which the infrared light is emitted so as to cooperate with an image sensor that has sensitivity at least in the infrared wavelength range, wherein a triangle having vertices at a first point corresponding to the first wavelength, a second point corresponding to the second wavelength, and a third point corresponding to the wavelength of the red component contained in the infrared light in an xy chromaticity diagram of the CIE color system surrounds a white region in the xy chromaticity diagram.

[0013] The fact that a triangle with vertices corresponding to a point corresponding to the first wavelength, a point corresponding to the second wavelength, and a point corresponding to the wavelength of the red component surrounds the white region in the xy chromaticity diagram means that white can be generated by mixing colors by appropriately setting the radiance of the first visible light and the radiance of the second visible light relative to the radiance of the red component contained in the light emitted from the infrared light source.

[0014] In the lighting device according to the third aspect, by turning on the first visible light source and the second visible light source while the infrared light source is turned on, a mixture of the red component contained in the light emitted from the infrared light source, the color of the first visible light, and the color of the second visible light occurs, resulting in the lighting device appearing to emit white light, and the red component that may be contained in the light emitted from the infrared light source being invisible.

[0015] A fourth exemplary aspect provided by the present disclosure is an imaging system including: an illumination device according to any one of the first to third exemplary aspects; and an imaging element having sensitivity in at least the infrared wavelength range.

[0016] FIG. 1 illustrates a functional configuration of an imaging system according to an embodiment. FIG. 2 illustrates a vehicle on which the imaging system of FIG. 1 is mounted. FIG. 3 illustrates the operation of the imaging system of FIG. 1. FIG. 4 is a diagram for explaining the operation of the imaging system of FIG. 1. FIG. 5 illustrates a functional configuration of an imaging system according to another example. FIG. 6 illustrates the operation of the imaging system of FIG. 7. FIG. 7 is a diagram for explaining the operation of the imaging system of FIG. 7.

[0017] Examples of embodiments will be described in detail below with reference to the accompanying drawings. In the drawings used in the following description, the scales of the elements are changed as necessary to make them recognizable.

[0018] 1 illustrates the functional configuration of an imaging system 1 according to an embodiment. The imaging system 1 includes an illumination device 10, an imaging element 20, and a control device 30.

[0019] The lighting device 10 includes an infrared light source 11. The infrared light source 11 is configured to emit infrared light IR having a central wavelength in the infrared wavelength range with the highest radiance when turned on. The infrared light source 11 can be realized by a semiconductor light-emitting element such as a light-emitting diode or a laser diode.

[0020] The term "radiance" used in this specification does not refer to the radiance of light emitted from the light source itself, but rather to the radiance of light emitted to the outside from the lighting device 10 via an appropriate optical system.

[0021] The image sensor 20 is sensitive to at least the infrared wavelength range and is configured to output a detection signal DT corresponding to the intensity of incident light. The image sensor 20 may be of the CCD type or the CMOS type.

[0022] The control device 30 is configured to output an illumination control signal C1 that controls the operation of the illumination device 10 and an imaging control signal C2 that controls the operation of the imaging element 20. The illumination control signal C1 and the imaging control signal C2 are configured to coordinate the operation of the illumination device 10 and the operation of the imaging element 20.

[0023] The infrared light IR emitted from the infrared light source 11 can be reflected by the object OB. For example, the time from when the infrared light IR is emitted from the infrared light source 11 in response to the illumination control signal C1 until the infrared light IR is incident on the image sensor 20 can be determined based on the detection signal DT. The distance to the object OB can be measured based on this time. The timing at which the image sensor 20 receives the reflected infrared light IR can be controlled by the image sensor control signal C2.

[0024] The lighting device 10 includes a white light source 12. The white light source 12 is configured to emit white light W when turned on. The white light W is visible light. The white light source 12 can be realized by a semiconductor light-emitting element such as a light-emitting diode, a laser diode, or an EL element.

[0025] The control device 30 outputs an illumination control signal C1 so as to turn on the white light source 12 at least when the infrared light source 11 is turned on.

[0026] Depending on the emission spectrum distribution as a specification of the infrared light source 11, the emitted light may contain a red component. In this case, the emitted light from the infrared light source 11, which should be essentially invisible, may be perceived as reddish light. In the configuration according to this embodiment, white light W is also emitted when the infrared light IR is emitted, thereby making the reddish light less noticeable.

[0027] On the other hand, when the infrared light source 11 is turned on and off while the white light source 12 is on, the visible light switches between a state in which a red component is included and a state in which it is not included, thereby changing the color of the white light W. Such a change in color may cause an observer to feel uncomfortable.

[0028] In this embodiment, the value of the ratio (L2 / L1) of the radiance L2 of the white light W to the radiance L1 of the infrared light IR is set to be 6.0E-05 or more, based on the idea that if the ratio (L2 / L1) is appropriately set, changes in the color of the white light W can be made unrecognizable regardless of the on / off state of the infrared light source 11.

[0029] This prevents the color of the white light W emitted from the white light source 12, which is used to make the red component less noticeable, from changing when the infrared light source 11 is turned on or off. This prevents the occurrence of discomfort caused by this change.

[0030] 2 , the imaging system 1 can be mounted on a vehicle 2. In this example, the lighting device 10 is disposed so that the infrared light IR emitted from the infrared light source 11 is directed toward the front of the vehicle 2.

[0031] In some regions, the emission of red light ahead of a vehicle is prohibited by law, and the above configuration is particularly advantageous in that it satisfies the relevant law by making it possible to prevent the red component contained in the light emitted ahead of the vehicle 2 from being visible.

[0032] 1, the control device 30 is configured to receive a status signal ST indicating the state of the vehicle 2. The status signal ST is transmitted from another control device mounted on the vehicle 2.

[0033] The control device 30 outputs an illumination control signal C1 to switch the infrared light source 11 on and off based on the status signal ST. Specifically, when the status signal ST indicates that the vehicle 2 is stopped, the control device 30 outputs an illumination control signal C1 to turn off the infrared light source 11. When the status signal ST indicates that the vehicle 2 is moving, the control device 30 outputs an illumination control signal C1 to turn on the infrared light source 11. Figure 3 illustrates this operation.

[0034] There are regions where regulations prohibit the emission of infrared light ahead of a stopped vehicle. The above operation is performed to comply with this regulation. According to the configuration relating to the ratio of the radiance of the white light W to the radiance of the infrared light IR described above, even if the infrared light source 11 is switched on and off when the vehicle 2 is stopped and moving, the observer cannot perceive a change in the color of the white light W. Therefore, this configuration is particularly advantageous in that it can comply with the regulation while avoiding the discomfort caused by a change in color.

[0035] As illustrated in Fig. 1, the lighting device 10 may include a visible light source 13. The visible light source 13 is configured to be able to emit visible light V having a wavelength λ1 that is located in the turquoise blue color region RT in the xy chromaticity diagram of the CIE color system illustrated in Fig. 4 when lit. The visible light source 13 may be realized by a semiconductor light-emitting element such as a light-emitting diode, a laser diode, or an EL element.

[0036] Wavelength λ2 on the xy chromaticity diagram corresponds to the wavelength of the red component contained in the light emitted from infrared light source 11. A line connecting the point corresponding to wavelength λ1 and the point corresponding to wavelength λ2 of turquoise blue visible light V emitted from visible light source 13 crosses white region RW. This fact means that white can be generated by mixing colors by appropriately setting the radiance of turquoise blue visible light V relative to the radiance of the red component contained in the light emitted from infrared light source 11.

[0037] 3, the control device 30 is configured to output an illumination control signal C1 that turns on the visible light source 13 when the infrared light source 11 is turned on. This causes a mixture of the red component contained in the light emitted from the infrared light source 11 and the turquoise blue of the visible light V emitted from the visible light source 13, thereby further suppressing the change in color of the white light W emitted from the white light source 12 that occurs when the infrared light source 11 is turned on.

[0038] Turquoise blue is recognized as a color that notifies those around the vehicle that the autonomous driving function is enabled. When the status signal ST indicates that the autonomous driving function of the vehicle 2 is enabled, the control device 30 outputs an illumination control signal C1 that turns off the white light source 12 and increases the radiance of the visible light V emitted from the visible light source 13. As a result, it appears as if turquoise blue light is being emitted from the illumination device 10.

[0039] With this configuration, the visible light source 13, which is used to make the red component contained in the light emitted from the infrared light source 11 less visible, can also be used as a light source to emit light that notifies that the autonomous driving function is enabled.

[0040] The level of the autonomous driving function that serves as the criterion for determining whether to increase the radiance of visible light V can be determined as appropriate.

[0041] Fig. 5 shows another example of the configuration of the imaging system 1. Components that are substantially the same as those in the example described with reference to Fig. 1 are given the same reference numerals, and repeated explanations will be omitted. An illumination device 10 according to this example includes an infrared light source 11 and a visible light source 13.

[0042] When lit, visible light source 13 is configured to emit visible light V having a wavelength λ1 that is located in the turquoise blue color region RT in the xy chromaticity diagram of the CIE color system, as shown in Fig. 4. Visible light source 13 can be realized by a semiconductor light-emitting element such as a light-emitting diode, a laser diode, or an EL element.

[0043] 6 , the control device 30 is configured to output an illumination control signal C1 that turns on the visible light source 13 when the infrared light source 11 is turned on. A line connecting a point corresponding to the wavelength λ1 of the turquoise blue visible light V emitted from the visible light source 13 and a point corresponding to the wavelength λ2 of the red component contained in the light emitted from the infrared light source 11 crosses the white region RW on the xy chromaticity diagram, resulting in a mixture of the red component contained in the light emitted from the infrared light source 11 and the turquoise blue of the visible light V emitted from the visible light source 13. As a result, white light appears to be emitted from the illumination device 10, and the red component that may be contained in the infrared light IR emitted from the infrared light source 11 can be made invisible.

[0044] When the status signal ST indicates that the autonomous driving function of the vehicle 2 is enabled, the control device 30 outputs an illumination control signal C1 that increases the radiance of the visible light V emitted from the visible light source 13. As a result, the illumination device 10 appears to emit turquoise blue light.

[0045] With this configuration, the visible light source 13, which is used to prevent the red component contained in the light emitted from the infrared light source 11 from being visible, can also be used as a light source to emit light that notifies that the autonomous driving function is enabled.

[0046] Fig. 7 shows another example of the configuration of the imaging system 1. Components that are substantially the same as those in the example described with reference to Fig. 1 are given the same reference numerals, and repeated description will be omitted. The illumination device 10 according to this example includes an infrared light source 11, a first visible light source 131, and a second visible light source 132.

[0047] First visible light source 131 is configured to emit first visible light V1 having a central wavelength with the highest radiance located in the visible wavelength range when lit. Second visible light source 132 is configured to emit second visible light V2 having a central wavelength with the highest radiance located in the visible wavelength range when lit. Each of first visible light source 131 and second visible light source 132 can be realized by a semiconductor light emitting element such as a light emitting diode, a laser diode, or an EL element.

[0048] As illustrated in FIG. 8, control device 30 is configured to output an illumination control signal C1 that turns on first visible light source 131 and second visible light source 132 when infrared light source 11 is turned on.

[0049] 9 corresponds to the wavelength of the red component contained in the light emitted from the infrared light source 11. A triangle having vertices corresponding to the central wavelength λ1 of the first visible light V1, the central wavelength λ2 of the second visible light V2, and the wavelength λ3 encloses a white region RW in the xy chromaticity diagram. This fact means that white can be generated by mixing colors by appropriately setting the radiance of the first visible light V1 and the radiance of the second visible light V2 relative to the radiance of the red component contained in the light emitted from the infrared light source 11.

[0050] That is, by turning on first visible light source 131 and second visible light source 132 while infrared light source 11 is turned on, a mixture of the red component contained in the light emitted from infrared light source 11, the color of first visible light V1, and the color of second visible light V2 occurs. As a result, white light appears to be emitted from lighting device 10, and the red component that may be contained in the light emitted from infrared light source 11 can be made invisible.

[0051] In addition, since the color of the first visible light V1 and the color of the second visible light V2 are mixed with a red component, the range of white colors that can be generated can be expanded while increasing the degree of freedom in selecting the wavelength of each visible light.

[0052] A straight line connecting a point corresponding to the central wavelength λ1 of first visible light V1 emitted from first visible light source 131 and a point corresponding to the central wavelength λ2 of second visible light V2 emitted from second visible light source 132 crosses turquoise blue color region RT on the xy chromaticity diagram. This fact means that turquoise blue can be produced by color mixing by appropriately setting the radiance of first visible light V1 and the radiance of second visible light V2.

[0053] 8 , when the status signal ST indicates that the autonomous driving function of the vehicle 2 is enabled, the control device 30 outputs an illumination control signal C1 that increases the radiance of the first visible light V1 emitted from the first visible light source 131 and the radiance of the second visible light V2 emitted from the second visible light source 132. As a result, turquoise blue light appears to be emitted from the illumination device 10.

[0054] With this configuration, the first visible light source 131 and the second visible light source 132, which are used to prevent the red component contained in the light emitted from the infrared light source 11 from being visible, can also be used as light sources for emitting light that notifies that the automatic driving function is enabled.

[0055] The control device 30 having the various functions described above may be realized by a general-purpose microprocessor operating in cooperation with a general-purpose memory. Examples of the general-purpose microprocessor include a CPU, an MPU, and a GPU. Examples of the general-purpose memory include a ROM and a RAM. In this case, a computer program that realizes the function may be stored in the ROM. The general-purpose microprocessor specifies at least a portion of the program stored in the ROM, deploys it on the RAM, and executes the above-described processing in cooperation with the RAM. The computer program may be pre-installed in the general-purpose memory, or may be downloaded from an external server device via a communication network and then installed in the general-purpose memory.

[0056] The control device 30 may be realized by a dedicated integrated circuit such as a microcontroller, ASIC, or FPGA that can execute the computer program. In this case, the computer program is pre-installed in a memory element included in the dedicated integrated circuit. The control device 30 may also be realized by a combination of a general-purpose microprocessor and a dedicated integrated circuit.

[0057] The various configurations described above are merely examples for facilitating understanding of the present disclosure. Each configuration example can be appropriately modified or combined with other configurations within the scope of the present disclosure.

[0058] The advantages of mounting the imaging system 1 on the vehicle 2 so that the infrared light IR is emitted forward are as described above. However, the emission direction of the infrared light IR can be determined appropriately depending on the positional relationship between the object to be imaged and the vehicle 2.

[0059] 2 is merely an example. The shape of the vehicle 2 on which the imaging system 1 is mounted and the number of wheels can be determined appropriately as long as the vehicle 2 is capable of traveling on roads.

[0060] The imaging system 1 does not necessarily have to be mounted on the vehicle 2. The imaging system 1 may be installed at a fixed point to perform imaging using infrared light.

[0061] The contents of Japanese Patent Application No. 2023-110741 filed on July 5, 2023 are incorporated by reference as part of this disclosure.

Claims

1. An illumination device comprising: an infrared light source capable of emitting infrared light; a white light source capable of emitting white light; and a control device that controls the timing of emission of the infrared light so as to cooperate with an imaging element having sensitivity at least in the infrared wavelength range, wherein the ratio of the radiance of the white light to the radiance of the infrared light is 6.0E-05 or more.

2. The lighting device according to claim 1, which is mounted on a vehicle so that the infrared light is emitted forward.

3. The lighting device according to claim 2, further comprising a visible light source capable of emitting visible light of a wavelength located in the turquoise blue color region in the xy chromaticity diagram of the CIE color system, wherein the control device causes the visible light source to emit the visible light while the vehicle is traveling, and increases the radiance of the visible light when an autonomous driving function is enabled in the vehicle.

4. An illumination device comprising: an infrared light source capable of emitting infrared light; a visible light source capable of emitting visible light; and a control device that controls the timing of emission of the infrared light so as to cooperate with an imaging element having sensitivity at least in the infrared wavelength range, wherein a straight line connecting a first point corresponding to the wavelength of the visible light on an xy chromaticity diagram of the CIE color system and a second point corresponding to the wavelength of the red component contained in the infrared light crosses the white region on the xy chromaticity diagram.

5. The lighting device according to claim 4, which is mounted on a vehicle so that the infrared light is emitted forward.

6. The lighting device of claim 5, wherein the first point is located in a turquoise blue color region in the xy chromaticity diagram, and the control device increases the radiance of the visible light when an autonomous driving function is enabled in the vehicle.

7. An illumination device comprising: an infrared light source capable of emitting infrared light; a first visible light source capable of emitting first visible light having a first wavelength in the visible wavelength range; a second visible light source capable of emitting second visible light having a second wavelength in the visible wavelength range; and a control device that controls the timing of emission of the infrared light so as to cooperate with an imaging element having sensitivity at least in the infrared wavelength range, wherein a triangle having vertices on an xy chromaticity diagram of a CIE color system, the vertices of which are a first point corresponding to the first wavelength, a second point corresponding to the second wavelength, and a third point corresponding to the wavelength of the red component contained in the infrared light, surrounds a white region on the xy chromaticity diagram.

8. The lighting device according to claim 7, which is mounted on a vehicle so that the infrared light is emitted forward.

9. The lighting device of claim 8, wherein a straight line connecting the first point and the second point crosses a turquoise blue color region in the xy chromaticity diagram, and the control device increases the radiance of the first visible light and the second visible light when an autonomous driving function is enabled in the vehicle.

10. An imaging system comprising: an illumination device according to any one of claims 1 to 9; and an imaging element having sensitivity at least in the infrared wavelength range.