OPTOELECTRONIC SENSOR ELEMENT FOR LIGHT MEASUREMENT WITH BUILT-IN REDUNDANCY, LIGHT MEASUREMENT SYSTEM AND LIGHT MEASUREMENT-BASED ELECTRONIC CONTROL SYSTEM

Abstract

Optoelectronic sensor component (100) for light measurement with: - a first signal channel (112) to provide a first electrical signal which represents the intensity of light (L) incident on the sensor element (100); - a second signal channel (114) that is technically separate from the first signal channel (112) to provide a second electrical signal that is independent of the first electrical signal and also represents the intensity of the light (L) incident on the sensor element (100); - a first light-sensitive detection arrangement (102) which is set up to generate the first electrical signal and is assigned to the first signal channel (112); - a second light-sensitive detection arrangement (104) which is set up to generate the second electrical signal and is assigned to the second signal channel (114), wherein the first detection arrangement (102) and the second detection arrangement (104) have identical spectral sensitivity and are therefore redundant to each other, wherein the spectral sensitivity of the first detection arrangement (102) and the second detection arrangement (104) has a photopic profile; and - a further light-sensitive detection arrangement (106) and a further signal channel (116) assigned to the further light-sensitive detection arrangement (106), wherein the further detection arrangement (106) is set up to detect only infrared light.

Description

[0001] The present invention relates to optoelectronic sensor devices and, in particular, to ambient light sensors, a system for light measurement and a system for light measurement-based electronic control.

[0002] The publication US 2014 / 0 138 784 A1 describes photodetectors for use as ambient light sensors.

[0003] The document US 2015 / 0 097 105 A1 concerns a photodiode with a compensated spectral response.

[0004] The document US 5 406 067 A describes an electrically adjusted mosaic filter for use as an optical sensor.

[0005] Document EP 3 252 445 A1 describes a photodetector arrangement with an adjustable output.

[0006] An ambient light sensor is an integrated optoelectronic sensor that detects the intensity of ambient light and outputs a signal proportional to the ambient light intensity. Typically, known ambient light sensors comprise a photodiode array and signal processing circuitry.

[0007] Ambient light sensors, for example, are installed in the dashboards of motor vehicles. There, they measure the light intensity in the passenger compartment. Based on this measurement, the backlighting of the dashboard displays can then be adjusted accordingly.

[0008] Particularly in the automotive sector, sensors used there must be suitable for integrity testing. This ensures that a functional test of each sensor can be performed, thus identifying any failed sensors.

[0009] Current ambient light sensors do not meet these requirements.

[0010] Furthermore, in the automotive sector, there is a requirement to control the brightness of the dashboard displays using proximity detection and gesture recognition. This requires a proximity detection function combined with an ambient light detection function. Proximity measurements can be performed using proximity sensors. These sensors consist of infrared emitters that illuminate the target object and infrared detectors that measure the reflected signal. The distance to the target object can be calculated based on the intensity of the reflected signal measured by the sensor.

[0011] Now, one could consider transferring the functional test already applied to discrete photodiode-based detectors to integrated optoelectronic sensors, such as ambient light sensors. Such a functional test works as follows: The photodiode's supply voltage is reversed. This causes the photodiode to be forward-biased rather than reverse-biased. The resulting forward current is measured. If the measured forward current lies within a predefined range, it is concluded that the photodiode is functioning properly.

[0012] However, this integrity check cannot be performed on integrated optical sensors because it is not possible to simply reverse the supply voltage of individual photodiodes without deactivating the entire integrated circuit.

[0013] Therefore, it would be desirable to have a sensor architecture that enables a different, reliable and simple integrity check, and that is also suitable for integrated circuits.

[0014] In particular, this architecture should be designed in such a way that it can be implemented in an integrated optoelectronic sensor component such as an ambient light sensor.

[0015] Accordingly, it is an object of the present invention to provide an optoelectronic sensor component in which a plausibility or functional check can be performed in a simple and convenient manner. The functional check should be possible, in particular, in real time during ongoing operation of the optoelectronic sensor component.

[0016] According to the invention, this object is achieved by an optoelectronic sensor component for light measurement, comprising a first signal channel for providing a first electrical signal which maps the intensity of a light incident on the sensor component, a second signal channel which is signal-technically separate from the first signal channel for providing a second electrical signal which is independent of the first electrical signal and which likewise maps the intensity of the light incident on the sensor component, a first light-sensitive detection arrangement which is set up to generate the first electrical signal and is assigned to the first signal channel, and a second light-sensitive detection arrangement which is set up to generate the second electrical signal and is assigned to the second signal channel, wherein both detection arrangements have an identical spectral sensitivity and are thus redundant with respect to one another.The spectral sensitivity of both detection arrangements has a photopic curve.

[0017] Furthermore, the optoelectronic sensor component comprises a further light-sensitive detection arrangement and a further signal channel assigned to the further light-sensitive detection arrangement, wherein the further detection arrangement is configured to detect only infrared light.

[0018] By providing two separate detection arrangements that have identical spectral sensitivity and are thus redundant to each other, the optoelectronic sensor component according to the invention delivers the same measurement signal twice when functioning properly. This can be used for redundancy-based plausibility monitoring. Thus, an additional redundant light-sensitive detection arrangement is used to detect the same incident light. By comparing the mutually redundant signals, a possible malfunction of the sensor component can be determined.

[0019] According to preferred embodiments, the sensor component according to the invention can have one, several or all of the following features, in all technically possible combinations: - at least one signal processing circuit for processing the first and second electrical signals; - the two detection arrangements and each signal processing circuit are designed as a single integrated circuit with a common voltage supply; - a first signal processing circuit for processing the first electrical signal and a separate second signal processing circuit for processing the second electrical signal; - an additional light-sensitive detection arrangement and an associated additional signal channel, wherein the additional detection arrangement has an identical spectral sensitivity to the first and second detection arrangements and is shielded from ambient light so that it can provide a reference signal for darkness; - each detection arrangement comprises at least one photodiode; - a light-sensitive overall measuring surface which is divided into a number of measuring elements, the measuring elements being formed by the photodiodes of the detection arrangements; - the first detection arrangement defines a first light-sensitive measuring surface and the second detection arrangement defines a second light-sensitive measuring surface, wherein the area of ​​the first measuring surface is an integer multiple of the area of ​​the second measuring surface; - the sensor component is an ambient light sensor.

[0020] The additional light-sensitive detection arrangement and the associated additional signal channel for detecting infrared light can be used, for example, in applications where, in addition to the ambient light detection function, a proximity detection function is also desired. For the proximity detection function, an emitter configured, in particular, to emit only infrared light can be used to illuminate a target object. By means of the additional light-sensitive detection arrangement and the associated additional signal channel for detecting infrared light, the intensity of the infrared light reflected by the target object can be measured in addition to the intensity of the ambient light. The intensity of the reflected light can be used to calculate the distance between the detection arrangement and a target object.

[0021] Likewise, the additional light-sensitive detection arrangement and the associated additional signal channel for detecting infrared light can provide a reference signal for infrared light, which can be subtracted from the signal of the first and second detection arrangements in order to better adapt the spectral sensitivity of the two detection arrangements to a photopic profile. Accordingly, the spectral sensitivity of the human eye can be simulated as closely as possible. This can be done, for example, in a similar way to determining a reference signal for dark current, by subtracting the infrared signal detected by the detection arrangement from the signal of the first and second detection arrangements.

[0022] The invention also relates to a system for light measurement with functional testing, wherein the system comprises a sensor component having the above-mentioned features and a device for functional testing of the sensor component, wherein the device for functional testing is designed to compare the two electrical signals generated by the two first detection arrangements and to conclude, depending on the result of the comparison, that the sensor component is malfunctioning.

[0023] The light measuring system may preferably have one, several or all of the following features, in all technically possible combinations: - the comparison carried out by the functional test device consists in calculating the difference between the two electrical signals generated and inferring a malfunction if the magnitude of the difference exceeds a certain threshold; - the device for functional testing is further configured to compare the reference signal with the first two electrical signals and to conclude that the sensor component is malfunctioning if the magnitude of at least one of the two electrical signals is smaller than the magnitude of the reference signal.

[0024] The invention also relates to a system for electronic control based on light measurement, comprising a sensor component as defined above and an electronic control unit, wherein the sensor component and the control unit are connected to one another via a digital communication interface so that the sensor component can transmit its measurement results in the form of digital data to the control unit, wherein the system provides a method for checking the error-free data transmission between the sensor component and the control unit, e.g. by means of a checksum, a cyclic redundancy check or an error correction method.

[0025] The invention also relates to a combination of the two systems defined above.

[0026] Various embodiments of the present invention will now be described in more detail with reference to the drawings, in which: Fig. 1 is a block diagram of a first embodiment of a sensor device according to the invention with one photodiode per channel and a common signal processing circuit; Fig. 2 is a block diagram of a second embodiment of a sensor device according to the invention with one photodiode per channel and one signal processing circuit per channel; Fig. 3 is a block diagram of a third embodiment of a sensor device according to the invention with four photodiodes per channel; and Fig. 4 is a block diagram of a possible hardware implementation of a sensor component according to the invention in the form of a chip with a measuring area divided into individual pixels.

[0027] The various sensor components 100, 200, 300, and 400 shown in the figures each represent a combined ambient light and proximity sensor. Such sensors provide an output signal that increases with the intensity of the light L incident on the sensor (see the arrows in the figures). Thus, such sensors can be used to measure the intensity of the light L prevailing in the environment in which the sensor is located. In addition, the sensor is also capable of detecting the approach of a human body part.

[0028] Such sensors can be installed, for example, in the dashboard of a vehicle. There, they measure the lighting conditions in the passenger compartment. Based on the measurement results, the backlighting of the dashboard displays can then be adjusted. Thanks to proximity detection, commands issued by a vehicle occupant can also be recognized.

[0029] Of course, the sensors shown in the figures can also be used in other areas.

[0030] The Fig. Figure 1 is a block diagram of a first embodiment 100 of an optoelectronic sensor component according to the invention. The sensor component 100 is in the form of an integrated circuit. The sensor component 100 can be implemented, for example, as a semiconductor chip. The sensor component 100 comprises four light-sensitive detection arrangements 102, 104, 106, and 108, as well as a common signal processing circuit 110. The semiconductor chip 100 is supplied with power via a terminal VDD. Typically, the chip also includes a ground terminal GND.

[0031] The chip 100 has four additional terminals, which are numbered consecutively from 1 to 4 in the figure. The semiconductor chip 100 also has a measuring surface, not shown here, for measuring the incident ambient light L. The detection arrangements 102, 104, 106, and 108 are part of the measuring surface.

[0032] In the present example, each of the four detection arrays consists of a photodiode 102 to 108. Each photodiode 102 to 108 corresponds to a signal channel 112 to 118 for providing an electrical signal. The four signal channels 112, 114, 116, and 118 are each signal-wise separated from each other. They each provide an electrical signal independent of the other electrical signals.

[0033] The first two photodiodes 102 and 104 have identical spectral sensitivity. They are thus redundant with each other. In other words, they deliver the same signal at the same incident ambient light L. The spectral sensitivity of photodiodes 102 and 104 has a photopic curve. This means that the spectral sensitivity of the two detection arrangements 102 and 104 mimics that of the human eye.

[0034] The third detection arrangement 106 has a photodiode whose spectral sensitivity differs from that of the first two photodiodes 102 and 104. The photodiode 106 is a photodiode sensitive to, in particular, only infrared radiation (IR photodiode). The fact that the photodiode 106 is a different photodiode from the other two photodiodes 102 and 104 is indicated by the black dot in the photodiode triangle.

[0035] The fourth detection arrangement 108 comprises a photodiode of the same type as the first two photodiodes 102 and 104. This means that the spectral sensitivity of the fourth photodiode 108 is identical to that of the photodiodes 102 and 104. The difference, however, is that the fourth photodiode 108 is shielded from the ambient light L, for example, by an opaque cover. This is indicated by the cross in the photodiode triangle.

[0036] Thus, the first signal channel 112 maps the intensity of the light L incident on the sensor component 100. Likewise, the second signal channel 114 maps the intensity of the ambient light L incident on the sensor component 100. The third signal channel 116 maps the intensity of the infrared light incident on the sensor component 100. The fourth signal channel 118, on the other hand, provides a constant reference signal for darkness.

[0037] However, the fourth detection arrangement 108 may also have a spectral sensitivity that differs from that of the photodiodes 102, 104, and 106. Accordingly, in addition to detection arrangements with a spectral sensitivity with a photopic profile and a spectral sensitivity in the infrared range, the chip 100 may also include a detection arrangement that is sensitive to other spectral ranges.

[0038] All photodiodes 102 to 108 are connected to the same signal processing circuit 110. The signal processing circuit 110 therefore processes all signals supplied by the photodiodes 102 to 108. This is done serially, for example, so that the signal processing circuit converts the signals from the four different photodiodes one after the other.

[0039] Typically, the signal processing circuit 110 includes an amplifier and an analog-to-digital converter.

[0040] Terminal 1 is the data output of chip 100. The signals supplied by detection arrangements 102, 104, 106, and 108 and processed by signal processing circuit 110 are output via this output. Terminal 2 is a clock input for providing a clock frequency to chip 100. Terminal 3 is a so-called interrupt pin. Via this output, chip 100 can, for example, inform an external control unit that a large change in light intensity is taking place. Terminal 4 is a so-called address pin. Via this input, an external control unit can, for example, set an address of the sensor of the fourth photodiode 108.

[0041] The Fig. Figure 2 shows a second embodiment 200 of an optoelectronic sensor component according to the invention. The sensor component 200 has a similar structure to the sensor component 100 of Fig. 1. The only difference is that each signal channel 212, 214, 216, and 218 is assigned to its own separate signal processing circuit 210a to 210d. Thus, in the sensor component 200, the signals of the four different photodiodes 202 to 208 can be processed in parallel and simultaneously. In contrast to the sensor component 100 of Fig. 1, by providing separate signal processing circuits 210a and 210b for each of the two redundant channels 212 and 214, undesirable deviations between the two output signals, which can occur due to serial signal processing, can be eliminated. Furthermore, a faulty signal processing circuit can be detected in this second embodiment.

[0042] Accordingly, an infrared signal from photodiode 206 can be measured in parallel with an ambient light signal from photodiodes 202 and 204.

[0043] The block diagram according to Fig. 3 shows a third embodiment 300 of a sensor component according to the invention. The special feature of this variant is that each of the four channels 312, 314, 316, and 318 is assigned not just a single photodiode, but an entire photodiode group. In this example, each diode group comprises four photodiodes connected in parallel. Providing multiple photodiodes per channel results in a greater signal yield. In addition, any slight differences between the characteristics of the photodiodes, which could lead to undesirable deviations between the signals of the two redundant channels when using only one photodiode per channel, are less significant. Such differences in the characteristic curves can, for example, be a result of fluctuations in process parameters during photodiode production.

[0044] As in the example of Fig. 2, each individual channel 312 to 318 has its own signal processing circuit 310a to 310d.

[0045] The Fig. Figure 4 shows a hardware implementation of an optoelectronic sensor component 400 according to the invention. In this embodiment, the sensor component 400 is embodied as an integrated semiconductor chip. The semiconductor chip 400 has six contacts 420, 422, 424, 426, 428, and 430. A total measurement area 432 is formed in the center of the semiconductor chip 400. The total measurement area 432 is the light-sensitive region of the sensor component 400. In the present example, the total measurement area 432 is square.

[0046] The six contacts 420 to 430 frame the entire measuring area 432. Contact 420 at the top left supplies voltage to semiconductor chip 400. Contact 422 at the top right is the data output. The measurement signals supplied by sensor chip 400 are read out via this contact 422. Contact 422 can be configured as an I2C interface. Contact 424 in the center left serves to ground semiconductor chip 400. Contact 426 in the center right serves to connect a timer (clock) for data transmission, e.g., via an I2C interface. Contact 428 at the bottom left is for addressing. Contact 430 at the bottom right is an interrupt.

[0047] The total measuring area 432 is divided into a number of individual measuring elements. In this case, there are 4 × 4 = 16 measuring elements. The individual measuring elements are labeled 1 to 4. The individual square measuring elements here each correspond to a single photodiode.

[0048] The number of the measuring element (1 to 4) indicates which of the four measuring channels of the ambient light sensor 400 the respective measuring element is assigned to. Comparable to, for example, the Fig. 3, four photodiodes are assigned to each measurement channel. Measurement channels 1 and 2 are again redundant. The associated photodiodes have the same spectral sensitivity (e.g., they mimic the sensitivity of the human eye) and are used to detect the same spectral range. Measurement channel 3 is used to detect infrared light. Measurement channel 4, in turn, is assigned to four shielded photodiodes, which provide the aforementioned reference signal.

[0049] The 4x4 photodiodes are distributed across the overall measuring area 432 as follows: The redundant photodiodes for ambient light measurement are located in the corners and center of the square overall measuring area 432. The photodiodes for reference measurement and infrared light measurement are arranged centrally on the outer sides of the square overall measuring area 432.

[0050] This pixel arrangement has the advantage of a symmetrical geometry. Thus, there is a shielded photodiode and an infrared photodiode on each outer side of the active optical surface 432. This makes the signals independent of the angle of incidence.

[0051] In other words, the total measuring area 432 is divided into individual image elements or pixels.

[0052] The previous description has assumed that the measurement area covered by the photodiode(s) of the first channel and the measurement area covered by the photodiode(s) of the second channel are the same size. Alternatively, however, one measurement area can also be an integer multiple of the other measurement area.

[0053] A sensor component according to the present invention can be combined with a functional testing device to form a light measurement system with functional testing. The functional testing device then reads the first two channels 1 and 2 of the sensor component. It compares the two read signals and, depending on the result of the comparison, concludes that the sensor component is malfunctioning. The comparison is preferably performed by calculating the difference between the two signals supplied by the channels. If the difference between the two signals exceeds a certain threshold, it is assumed that the sensor component is defective. Since the photodiodes of the first channel and the photodiodes of the second channel are identical, the first two channels should also supply identical signals.If a significant deviation occurs between the two signals, there is good reason to believe that the photodiodes or the signal processing circuit are malfunctioning.

[0054] In addition, the functional test device can also compare the reference signal supplied by the fourth channel with the signals supplied by the first two channels. Since the corresponding photodiodes of the fourth channel are covered, the minimum signal expected when the area surrounding the sensor is completely dark is always present at output 4 of the sensor component. Accordingly, the magnitude of the signals from the first two channels should always be greater than or equal to that of the reference signal. If the magnitude of at least one of the two signals from the first two channels is smaller than the magnitude of the reference signal, a malfunction can also be assumed.

[0055] In the case where the measuring area of ​​the first channel is an integer multiple N of the measuring area of ​​the second channel, the signal I1 provided by the first channel will be an integer multiple N larger than that of the second channel I2. Here, the plausibility value P is then calculated according to the following equation: P=N×I2−I1, where N is the integer multiple, I1 is the signal of the first channel, and I2 is the signal of the second channel.

[0056] Here, too, a malfunction is concluded if the magnitude of the plausibility value P exceeds a certain threshold.

[0057] The sensor architecture with redundant optical channels can also be used to identify short circuits between the two redundant photodiode channels. This requires a sequential and a parallel measurement to be performed on both redundant channels. If a short circuit exists between the two photodiode channels, the measurement result of the sequential measurement will be twice as high as the measurement result of a parallel measurement. Without a short circuit, the same measurement result is expected for both measurements.

[0058] The sensor component according to the invention can also be combined with an electronic control unit to form a system for electronic control based on light measurement. The electronic control unit can be, for example, a so-called microcontroller (MCU). The sensor component and the control unit are then connected to each other via a digital communication interface. This interface is implemented, for example, by contact 422 and contact 426 in Fig. 4. This allows the sensor component to transmit its measurement results to the MCU in the form of digital data. A method for verifying error-free data transmission between the sensor component and the MCU can be provided, for example, using a checksum, a cyclic redundancy check, or an error correction method. LIST OF REFERENCE SYMBOLS 100, 200, 300, 400 sensor component 102, 104, 106, 108 light-sensitive detection arrangement 110, 210, 310 signal processing circuit 112, 114, 116, 118 signal channel 212, 214, 216, 218 signal channel 312, 314, 316, 318 signal channel 420 supply voltage connection 422 Data output 424 Ground connection 426 Clock connection 428 Addressing pin 430 Interrupt 432 total measuring area L Ambient light

Claims

[1] Optoelectronic sensor component (100) for measuring light with: - a first signal channel (112) for providing a first electrical signal which represents the intensity of a light (L) incident on the sensor component (100); - a second signal channel (114) which is signal-technically separated from the first signal channel (112) for providing a second electrical signal which is independent of the first electrical signal and which also represents the intensity of the light (L) incident on the sensor component (100); - a first light-sensitive detection arrangement (102) which is arranged to generate the first electrical signal and is assigned to the first signal channel (112); - a second light-sensitive detection arrangement (104) which is arranged to generate the second electrical signal and is assigned to the second signal channel (114), wherein the first detection arrangement (102) and the second detection arrangement (104) have an identical spectral sensitivity and are thus redundant to each other, wherein the spectral sensitivity of the first detection arrangement (102) and the second detection arrangement (104) has a photopic profile; and - a further light-sensitive detection arrangement (106) and a further signal channel (116) associated with the further light-sensitive detection arrangement (106), wherein the further detection arrangement (106) is arranged to detect only infrared light. [2] Sensor component (100) according to claim 1, further comprising at least one signal processing circuit (110) for conditioning the first and second electrical signals. [3] Sensor component (100) according to claim 2, wherein the first detection arrangement (102) and the second detection arrangement (104) and each signal processing circuit (110) are formed as a single integrated circuit with a common voltage supply (VDD). [4] Sensor component (200) according to claim 2 or 3, comprising a first signal processing circuit (210a) for conditioning the first electrical signal and a separate second signal processing circuit (210b) for conditioning the second electrical signal. [5] Sensor component (100) according to one of the preceding claims, comprising an additional light-sensitive detection arrangement (108) and an associated additional signal channel (118), wherein the additional detection arrangement (108) has an identical spectral sensitivity as the first (102) and second (104) detection arrangement and is shielded from ambient light so that it can provide a reference signal for darkness. [6] Sensor component (100) according to one of the preceding claims, wherein each detection arrangement comprises at least one photodiode. [7] Sensor component (100) according to claim 6, having a light-sensitive overall measuring surface (432) which is divided into a number of measuring elements, wherein the measuring elements are formed by the photodiodes of the detection arrangements. [8] Sensor component (100) according to one of the preceding claims, wherein the first detection arrangement (102) defines a first light-sensitive measuring area and the second detection arrangement (104) defines a second light-sensitive measuring area, and wherein the area of ​​the first measuring area is an integer multiple of the area of ​​the second measuring area. [9] Sensor component (100) according to one of the preceding claims, wherein the sensor component (100) is an ambient light sensor. [10] System for light measurement with functional testing, wherein the system comprises a sensor component (100) according to one of the preceding claims and a device for functional testing of the sensor component (100), wherein the device for functional testing is designed to compare the two electrical signals generated by the first detection arrangement (102) and the second detection arrangement (104) and to conclude a malfunction of the sensor component (100) depending on the result of the comparison. [11] System according to claim 10, wherein the comparison made by the functional test device consists in forming the difference between the two electrical signals generated by the first detection arrangement (102) and the second detection arrangement (104) and inferring a malfunction if the amount of the difference exceeds a certain threshold value. [12] System according to claim 10 or 11, comprising a sensor component (100) according to claim 5, wherein the device for functional testing is further configured to compare the reference signal with the two electrical signals and to conclude that the sensor component (100) is malfunctioning if the magnitude of at least one of the two electrical signals is smaller than the magnitude of the reference signal. [13] System for light measurement-based electronic control with a sensor component (100) according to one of claims 1 to 9 and an electronic control unit, wherein the sensor component (100) and the control unit are connected to one another via a digital communication interface so that the sensor component (100) can transmit its measurement results in the form of digital data to the control unit, wherein the system provides a method for checking the error-free data transmission between the sensor component (100) and the control unit, e.g. by means of a checksum, a cyclic redundancy check or an error correction method.

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