Optical sensor and method for controlling optical sensor

Abstract

To improve appearance without significantly reducing sensing accuracy in an optical sensor including an optical filter.SOLUTION: An optical sensor includes: a light source emitting light in a predetermined wavelength range toward an object to be detected; a light receiving element detecting light reflected from the object to be detected; an optical filter disposed in front of the light receiving element and selectively transmitting light in the predetermined wavelength range; dimming glass disposed to cover the optical filter and switched between a transparent detectable state and a cloudy standby state when being energized; and a dimming control part switching the energized state of the dimming glass such that the detectable state and the standby state are alternately repeated.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an optical sensor and a method for controlling the optical sensor.

Background Art

[0002] Conventionally, for example, in home appliances having a human sensing function such as a warm water washing toilet seat in a toilet, an infrared sensor for detecting the presence or absence of a user is incorporated (Patent Document 1, etc.). This infrared sensor is configured to detect the presence or absence of a user by emitting infrared rays from a light source toward a predetermined detection area and sensing, with a light receiving element, the infrared rays reflected by a user (detection target) who has entered the detection area. In such an infrared sensor, a visible light cut filter that transmits infrared rays and cuts visible light is provided in front of the light receiving element so that only infrared rays can be received by the light receiving element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as described above, the infrared sensor is provided with a visible light filter. However, since this visible light filter generally exhibits a black color, it poses a design constraint in the household appliances to be incorporated, which is not preferable. In addition, some users may be concerned that a hidden camera may be installed in the portion of the visible light cut-off filter that exhibits black color, which is also not preferable. Conventionally, in order to improve the appearance of the visible light cut-off filter that exhibits black color, a special thin film or metal paint has been applied to the surface of the visible light cut-off filter so that the visible light cut-off filter cannot be seen directly. However, there is a problem that the transmittance decreases and the sensing accuracy decreases. Such problems are not limited to infrared sensors, but can also be said to be the same for other types of optical sensors having an optical filter.

[0005] The present invention has been made to solve the above problems, and an object thereof is to improve the appearance without significantly reducing the sensing accuracy in an optical sensor provided with an optical filter.

Means for Solving the Problems

[0006] That is, the optical sensor according to the present invention includes a light source that emits light of a predetermined wavelength toward a detection target, a light receiving element that detects light reflected by the detection target, an optical filter disposed in front of the light receiving element, a dimming glass that is disposed to cover the optical filter and switches between a transparent detectable state and a white turbid standby state when energized, and a dimming control unit that switches the energization state of the dimming glass so that the detectable state and the standby state are alternately repeated.

[0007] In such a case, a dimming glass is arranged to cover the optical filter, and it is configured such that the detectable state in which the dimming glass is transparent and the standby state in which the dimming glass is clouded alternate with each other. Therefore, in the detectable state where the reflected light is detected, the dimming glass becomes transparent and the decrease in the light transmittance can be suppressed. On the other hand, in the standby state where the reflected light is not detected, the dimming glass becomes cloudy and appears white, so that the optical filter can be hidden and the design can be improved. As a result, for example, in an infrared sensor having a visible light cut filter that exhibits black, the black appearance can be improved without significantly reducing the sensing accuracy. In this specification, clouding means that the optical filter becomes opaque to the extent that it cannot be visually recognized. For example, regardless of the hue, it may have a color such as a lightness of 8 or more and a chroma of 3 or less and become opaque.

[0008] Also, in the optical sensor, it is preferable that the dimming control unit switches the energization state of the dimming glass so that the time interval of the detectable state is about 20 milliseconds or less in each repetition cycle of the detectable state and the standby state. A change in the time length of about 20 milliseconds or less is considered to be difficult to be perceived by the human eye. Therefore, by setting the time interval during which the detectable state continues to be 20 milliseconds or less, it is possible to make it difficult to perceive the black color of the visible light cut filter that can be seen through the dimming glass in the detectable state.

[0009] Furthermore, in the optical sensor, it is preferable that the dimming control unit switches the energization state of the dimming glass so that the time interval of the standby state is longer than the time interval of the detectable state in each repetition cycle. In the optical sensor of the present invention in which a detectable state presenting a black appearance and a standby state presenting a white appearance are periodically and alternately repeated, the ratio of the time intervals of each state is recognized as the ratio of the mixed color of black and white. By making the ratio of the standby state presenting a white appearance larger than the ratio of the detectable state presenting a black appearance, the color recognized by the user can be made closer to white.

[0010] Furthermore, in the optical sensor, it is preferable that the dimming control unit switches the energization state of the dimming glass so that the ratio occupied by the time interval of the detectable state is about 10% or less, preferably about 5% or less, more preferably about 1% or less in each repetition cycle. In this way, the color recognized by the user can be made extremely close to white (the color of the dimming glass in the standby state).

[0011] The optical sensor further includes a light emission control unit that controls the output of the light source, and it is preferable that the light emission control unit emits light from the light source only in the detectable state in each repetition cycle of the detectable state and the standby state. In this way, the infrared light source is not lit in the standby state, and the infrared light source is lit only in the light-on possible state, so that the power consumption can be suppressed.

[0012] In the optical sensor, it is preferable that the light emission control unit emits light from the light source in accordance with the timing of switching from the standby state to the detectable state. In this way, it is possible to omit the wasted time in which the infrared rays are not emitted while the dimming glass is transparent, and the time interval of the detectable state can be made even shorter.

[0013] As a specific embodiment of the optical sensor, it further includes a housing that houses the light source, the light receiving element, and the optical filter. An opening is formed in one side wall of the housing that faces the light emitting surface of the light source and the light receiving surface of the light receiving element, and the dimming glass is disposed so as to close the opening of the housing.

[0014] As an aspect that significantly exhibits the effects of the present invention, the light source is an infrared light source that emits infrared rays, and the optical filter cuts visible light and selectively transmits infrared rays.

[0015] The optical sensor of the present invention also includes a light source that emits light in a predetermined wavelength range toward a detection target, a light receiving element that detects light reflected by the detection target, an optical filter disposed in front of the light receiving element, a shutter mechanism disposed to cover the optical filter, and a dimming control unit that controls a driving unit of the shutter mechanism so that a detectable state in which the shutter mechanism is open and a standby state in which the shutter mechanism is closed alternate repeatedly. Even in such a case, the same operational effects as those of the above-described optical sensor can be achieved. That is, in the detectable state where the reflected light is detected, the shutter mechanism can be opened to suppress a decrease in the light transmittance. On the other hand, in the standby state where the reflected light is not detected, the shutter mechanism can be closed to hide the optical filter, thereby improving the design.

[0016] The control method of the optical sensor of the present invention is a control method of an optical sensor including a light source that emits light in a predetermined wavelength range toward a detection target, a light receiving element that detects light reflected by the detection target, an optical filter disposed in front of the light receiving element, and a dimming glass disposed to cover the optical filter and that is switched between a detectable state of being transparent and a standby state of being turbid when energized, and is characterized by switching the energized state of the dimming glass so that the detectable state and the standby state alternate repeatedly. With such a control method, the same operational effects as those of the optical sensor of the present invention described above can be achieved.

Advantages of the Invention

[0017] According to the present invention configured as described above, in an optical sensor provided with an optical filter, the appearance can be improved without significantly degrading the sensing accuracy.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0019] Hereinafter, an optical sensor 100 according to an embodiment of the present invention will be described with reference to the drawings.

[0020] As shown in FIG. 1, the optical sensor 100 of the present embodiment is, for example, attached to a warm water washing toilet seat S in a toilet to detect a user (detection target T) of the toilet. This optical sensor 100 is a reflection-type infrared sensor that emits infrared rays and senses the infrared rays reflected by the detection target T to detect the detection target T.

[0021] Specifically, as shown in FIG. 2, this infrared sensor 100 includes an infrared light source 1 that emits infrared rays toward a detection target T, a light receiving element 2 that faces the same direction as the infrared light source 1 and detects the infrared rays reflected by the detection target T, an optical filter 3 disposed in front of the light receiving element 2, a dimming glass 4 disposed to cover the optical filter 3, a control device 5, and a housing 6 that houses these components. Hereinafter, each component will be described. Note that the infrared light source 1 and the light receiving element 2 facing the same direction means that the infrared light source 1 and the light receiving element 2 are arranged in such a direction that the light receiving element 2 can receive the infrared rays emitted from the infrared light source 1 and reflected by the detection target.

[0022] The infrared light source 1 is a light emitting element whose wavelength is set to emit infrared rays, and specifically is a light emitting diode (LED). The emission timing of this infrared light source 1 is controlled based on the output signal output from the control device 5.

[0023] The light receiving element 2 utilizes the photovoltaic effect such as a photodiode or a phototransistor, for example, and is configured to output a signal proportional to the amount of light received on the light receiving surface to the control device 5. The light receiving element 2 is arranged such that its light receiving surface faces the light emission direction of the infrared light source 1.

[0024] The optical filter 3 is configured to selectively transmit light in a predetermined wavelength range. Specifically, this optical filter 3 is a visible light cut filter (long pass filter or band pass filter) having the characteristic of absorbing or reflecting visible light and selectively transmitting infrared rays. This visible light cut filter 3 exhibits a black color. The visible light cut filter 3 is plate-shaped and is arranged so as to cover at least the entire light receiving surface of the light receiving element 2.

[0025] The dimming glass 4 is configured such that the light transmittance can be adjusted by an applied electrical signal. The dimming glass 4 of this embodiment has the characteristic of becoming transparent when energized and becoming cloudy (referring to a state of being translucent or opaque and exhibiting a white color) when the power supply is stopped.

[0026] The dimming glass 4 of this embodiment is of the liquid crystal molecule type. For example, it includes a pair of transparent electrode films and a polymer matrix material (PDLC: polymer dispersed liquid crystal) in which liquid crystal particles showing optical anisotropy are dispersed between the pair of transparent electrode films. By applying a voltage between the pair of transparent electrodes, the transparent state and the cloudy state can be switched. The transparent electrodes are formed using, for example, indium tin oxide (ITO) films or fluorine-doped tin oxide (FTO) films. As the dimming glass, those with known configurations may be used. The dimming glass 4 of this embodiment is transparent when the liquid crystal particles are aligned in parallel with the electric field direction in a state where a voltage is applied and it is energized. On the other hand, when no voltage is applied and the power supply is stopped, the incident light is scattered by the liquid crystal particles, resulting in semi-transparency or opacity and presenting a white (milky white) appearance.

[0027] The control device 5 is a computer (specifically, a microcomputer) having a CPU, a memory, an A / D converter, a D / A converter, input / output ports, etc. Based on a predetermined program stored in the memory, the CPU and peripheral devices cooperate to perform at least the functions of a light emission control unit 51, an object detection unit 52, and a dimming control unit 53 as shown in FIG. 2. Note that the control device 5 may be an ASIC (application-specific integrated circuit) in which the control process is realized on a circuit in advance.

[0028] The light emission control unit 51 controls the light emission timing and light emission time of the infrared light source 1 by controlling the drive current supplied to the infrared light source 1. This light emission control unit 51 also has a function as a power supply that supplies drive power to the infrared light source 1.

[0029] The object detection unit 52 determines the presence or absence of the detection target T based on the output signal from the light receiving element 2. Then, the object detection unit 52 outputs a signal indicating the determination result to an external device (for example, the control unit of the warm water washing toilet seat S).

[0030] The dimming control unit 53 controls the driving voltage applied to the dimming glass 4 to switch its energized state, thereby controlling the switching timing between the transparency and clouding of the dimming glass 4 and the duration of each state. This dimming control unit 53 also has a function as a power supply for supplying power to the dimming glass 4.

[0031] The housing 6 forms an accommodation space 6s inside, and an opening 6w is formed in one of its side walls. The infrared light source 1, the light receiving element 2, the visible light cut filter 3, and the control device 5 described above are accommodated in the accommodation space 6s of the housing 6. In the accommodation space 6s, the infrared light source 1 and the light receiving element 2 are accommodated such that their light emitting surfaces and light receiving surfaces face the opening 6w. And the dimming glass 4 is arranged so as to close the opening 6w of the housing 6. Here, the dimming glass 4 is fitted into the opening 6w of the housing 6. In the present embodiment, the dimming glass 4 is arranged so as to cover all of the infrared light source 1, the light receiving element 2, and the visible light cut filter 3. Also, the outer surface of the housing 6 exhibits white (milky white), similar to the dimming glass 4 when not energized.

[0032] And in the infrared sensor 100 of the present embodiment, the dimming control unit 53 switches the energized state of the dimming glass 4 so that the dimming glass 4 alternates between a detectable state in which the dimming glass 4 is transparent and the detection target T can be detected, and a standby state in which the dimming glass 4 is clouded and the detection target T cannot be detected.

[0033] Specifically, as shown in FIG. 4, the dimming control unit 53 switches the energized state of the dimming glass 4 so as to switch from the standby state to the detectable state at a substantially constant repetition period.

[0034] And the dimming control unit 53 switches the energization state of the dimming glass 4 so that the time interval during which the detectable state continues is about 20 milliseconds or less, preferably about 1 millisecond or less, more preferably about 0.5 millisecond or less, and even more preferably about 0.2 millisecond or less, in each repetition cycle of the detectable state and the standby state. By setting the continuous time interval of the detectable state within such a range, it becomes difficult for the user to recognize the black color of the visible light cut filter 3 that can be seen through the dimming glass 4. From the viewpoint of making the infrared sensor 100 look white, the shorter the continuous time interval of the detectable state is, the more preferable it is. However, if it is extremely short, there may not be enough light for the light receiving element 2 to respond. Therefore, it is preferable that the time interval during which the detectable state continues is about 0.1 millisecond or more.

[0035] Also, in the present embodiment, the dimming control unit 53 controls the energization state of the dimming glass 4 so that the time interval during which the standby state continues is longer than the time interval during which the detectable state continues in each repetition cycle. More specifically, the dimming control unit 53 switches the energization state of the dimming glass 4 so that the ratio of the time interval during which the detectable state continues is about 10% or less, preferably about 5% or less, and more preferably about 1% or less, in each repetition cycle. In the present embodiment, the time interval of the detectable state is about 20 milliseconds and the time interval of the standby state is about 380 milliseconds in each repetition cycle, and the ratio of the time interval during which the detectable state continues is about 5%. The time interval of the repetition cycle is the sum of the time intervals during which the detectable state and the standby state continue, respectively.

[0036] In this embodiment, the light emission control unit 51 causes the infrared light source 1 to emit infrared light only in a detectable state in each repetition period. That is, the light emission control unit 51 prevents the infrared light source 1 from emitting infrared light in the standby state. Specifically, as shown in FIG. 5, the light emission control unit 51 causes the infrared light source 1 to emit light in accordance with the timing of switching from the standby state to the detectable state. In this embodiment, the timing at which the light emission control unit 51 causes the infrared light source 1 to emit light is synchronized with the timing at which the dimming control unit 53 applies a voltage to the dimming glass 4, and the light emission control unit 51 is configured to cause the infrared light source 1 to emit light simultaneously when the dimming control unit 53 applies a voltage to the dimming glass 4. Note that the infrared light source 1 may be caused to emit light with a delay with respect to the timing at which the dimming control unit 53 applies a voltage to the dimming glass 4.

[0037] According to the infrared sensor 100 of this embodiment configured as described above, the dimming glass 4 is disposed so as to cover the visible light cut filter 3, and the detectable state in which the dimming glass 4 is transparent and the standby state in which the dimming glass 4 is whitened are alternately switched. Therefore, in the detectable state in which infrared rays are detected, the dimming glass 4 becomes transparent and the decrease in the transmittance of infrared light can be suppressed. On the other hand, in the standby state in which infrared rays are not detected, the black color of the visible light cut filter 3 can be hidden by whitening and making it white, thereby improving the design. As a result, compared with the conventional infrared sensor 100 in which the visible light cut filter 3 having a black color is exposed, the black appearance can be improved without significantly reducing the sensing accuracy.

[0038] Particularly in this embodiment, in each repetition period of the detectable state and the standby state, the energization state of the dimming glass 4 is switched so that the time interval of the detectable state is about 20 milliseconds or less and the ratio of the time interval of the detectable state is about 5%. Therefore, the color recognized by the user can be made extremely close to white (the color of the dimming glass 4 in the standby state).

[0039] Note that the present invention is not limited to the above-described embodiments. For example, in the above-described embodiments, the repetition periods of the detectable state and the standby state were always constant, but the present invention is not limited to this. In other embodiments, the repetition period while the detection target T is not being detected may be longer than the repetition period while the detection target T is being detected. In other words, the ratio of the detectable state in the repetition period while the detection target T is not being detected may be made smaller than the ratio of the detectable state in the repetition period while the detection target T is being detected.

[0040] Also, in the above-described embodiments, the timing of emitting light from the infrared light source 1 was simultaneous with or after the timing of switching from the standby state to the detectable state, but the present invention is not limited to this. In other embodiments, the infrared light source 1 may be made to emit light from the end stage of the standby state and continue to emit light so as to straddle the timing of switching from the standby state to the detectable state.

[0041] Also, the infrared sensor 100 in the above-described embodiments was incorporated into the warm water washing toilet seat S, but the present invention is not limited to this. The infrared sensor 100 in other embodiments can be incorporated into any other household electrical appliance having a human sensing function.

[0042] Also, in the above-described embodiments, an infrared sensor was given as an example of the optical sensor 100, but the present invention is not limited to this. In other embodiments, the optical sensor 100 is not limited to detecting the reflected light by emitting infrared light to the detection target, and may detect the reflected light by emitting visible light.

[0043] Also, in the above-described embodiment, the light-receiving element 2 and the optical filter 3 are configured as independent members, but the present invention is not limited to this. In other embodiments, the light-receiving element 2 and the optical filter 3 may be integrated. Further, the optical filter 3 may be configured by, for example, a condenser lens that condenses reflected light onto the light-receiving element 2. In this case, for example, the condenser lens may be configured by a material having a filter function, or the lens surface of the condenser lens may be coated with a film having a filter function.

[0044] Also, the optical sensor 100 of the above-described embodiment conceals the optical filter 3 by using the dimming glass 4, but the present invention is not limited to this. The optical sensor 100 of other embodiments may be configured by using a shutter mechanism 7 whose open / closed state is switched by being energized. This shutter mechanism 7 is, for example, a mechanical shutter including a front curtain and a rear curtain, and as shown in FIG. 6, it is disposed in front of the optical filter 3 and opens and closes a window formed in the housing 6. And in this embodiment, the dimming control unit 53 outputs a control signal to a drive unit (not shown) of the shutter mechanism 7 so that the detectable state in which the shutter mechanism 7 opens the window and the standby state in which the shutter mechanism 7 closes the window alternate repeatedly.

[0045] Also, in other embodiments, the control device 5 may be provided outside the housing 6, and various signals may be supplied to each device housed in the housing 6 from outside the housing 6 by wire or wirelessly.

[0046] Needless to say, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit thereof.

Explanation of Reference Numerals

[0047] 100 ··· Infrared sensor (optical sensor) 1 ··· Infrared light source (light source) 2 ··· Light-receiving element 3 ··· Visible light cut filter (optical filter) 4 ··· Dimming glass 53 ··· Dimming control unit T ··· Detection target

Claims

1. A light source that emits light in a predetermined wavelength range toward a detection target, a light receiving element that detects light reflected by the detection target, an optical filter disposed in front of the light receiving element, a dimming glass that is disposed to cover the optical filter and, when energized, switches between a transparent detectable state and an opaque standby state, A light sensor comprising a dimming control unit that switches the energization state of the dimming glass so that the detectable state and the standby state are alternately repeated.

2. The light sensor according to claim 1, wherein the dimming control unit switches the energization state of the dimming glass so that the time interval of the detectable state is about 20 milliseconds or less in each repetition period of the detectable state and the standby state.

3. The light sensor according to claim 2, wherein the dimming control unit switches the energization state of the dimming glass so that the time interval of the standby state is longer than the time interval of the detectable state in each repetition period.

4. The light sensor according to claim 3, wherein the dimming control unit switches the energization state of the dimming glass so that the ratio of the time interval of the detectable state occupies about 10% or less, preferably about 5% or less, more preferably about 1% or less in each repetition period.

5. Further comprising a light emission control unit that controls the output of the light source, The light sensor according to claim 1, wherein the light emission control unit causes the light source to emit light only in the detectable state in each repetition period of the detectable state and the standby state.

6. The light sensor according to claim 5, wherein the light emission control unit causes the light source to emit light in accordance with the timing of switching from the standby state to the detectable state.

7. Further comprising a housing that houses the light source, the light receiving element, and the optical filter, An opening is formed in one side wall of the housing that faces the light emission surface of the light source and the light receiving surface of the light receiving element, The light sensor according to claim 1, wherein the dimming glass is disposed so as to close the opening of the housing.

8. The light source is an infrared light source that emits infrared rays, The light sensor according to claim 1, wherein the optical filter cuts visible light and selectively transmits infrared rays.

9. A light source that emits light in a predetermined wavelength range toward a detection target, a light receiving element that detects light reflected by the detection target, An optical filter disposed in front of the light receiving element; A shutter mechanism disposed so as to cover the optical filter; A light sensor comprising a dimming control unit that controls a drive unit of the shutter mechanism so that a detectable state in which the shutter mechanism is open and a standby state in which the shutter mechanism is closed are alternately repeated.

10. A light source that emits light in a predetermined wavelength range toward a detection target, a light receiving element that detects light reflected by the detection target, an optical filter disposed in front of the light receiving element, and an optical filter disposed so as to cover the optical filter, and that becomes transparent in a detectable state and turbid in a standby state when energized. A control method for a light sensor comprising a dimming glass that switches between states, comprising: A control method for switching the energization state of the dimming glass so that the detectable state and the standby state are alternately repeated.

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