Self-mixing interferometric sensor device, method for operating self-mixing interferometric sensor device, and electronic device

Abstract

A self-mixing interferometric sensor device comprises a laser diode, a photodiode, a first readout unit for generating a first readout signal from a measurement signal of the photodiode, a second readout unit for generating a second readout signal from a junction voltage of the laser diode, and a switching unit adapted to generate an output signal in accordance with the first readout signal in the first operating mode and to generate an output signal in accordance with the second readout signal in the second operating mode. The sensor device is adapted to switch between operating in a first operating mode and operating in a second operating mode.

Description

[0001] This invention relates to a self-mixing interferometric measurement sensor device, a method for operating the self-mixing interferometric measurement sensor device, and an electronic device.

[0002] This patent application claims priority to German Patent Application No. 10 2023 128 608.0, the disclosure of which is incorporated herein by reference.

[0003] Self-mixing interferometry sensor devices are known in the prior art. Document US 11,243,686 B2 describes an example of a self-mixing interferometer-based sensor for characterizing user input.

[0004] The object of this invention is to provide a self-mixing interferometry sensor device. Another object is to provide a method for operating the self-mixing interferometry sensor device. Yet another object is to provide an electronic device. These objects are achieved by the self-mixing interferometry sensor device, the method for operating the self-mixing interferometry sensor device, and the electronic device described in the independent claims. Further variations are disclosed in the dependent claims.

[0005] A self-mixing interferometric measurement sensor device includes a laser diode, a photodiode, a first readout unit for generating a first readout signal based on a measurement signal from the photodiode, a second readout unit for generating a second readout signal based on the junction voltage of the laser diode, and a switching unit adapted to generate an output signal based on the first readout signal in a first operating mode and an output signal based on the second readout signal in a second operating mode. The sensor device is adapted to switch between operating in the first operating mode and operating in the second operating mode.

[0006] This sensor device enables the generation of an output signal based on a first readout signal generated from a measurement signal of a photodiode or a second readout signal generated from the junction voltage of a laser diode. Advantageously, this allows the generation of an output signal based on a readout signal that provides better signal quality. In particular, it allows the generation of an output signal based on a readout signal that provides a better signal-to-noise ratio. This enables the sensor device to be adapted to situations where background light interferes with the quality of the signal transmitted by the photodiode.

[0007] Some variations of the sensor device are adapted to detect the signal bias of the first readout signal. The sensor device is adapted to operate in a first operating mode when the first signal bias is below a threshold, and in a second operating mode when the signal bias exceeds the threshold. Advantageously, this allows the sensor device to switch to generating an output signal based on a second readout signal generated according to the junction voltage of the laser diode, in cases where an excessively large signal bias hinders the quality of the first readout signal generated based on the measurement signal from the photodiode. An excessively large signal bias may be caused by background light illuminating the photodiode.

[0008] Some variations of the sensor device are adapted to receive a switching signal for switching between operating in a first operating mode and operating in a second operating mode. Advantageously, this allows the sensor device to switch between the first and second operating modes by means of an external switching signal. This enables the sensor device to be adjusted to conditions that the sensor device cannot automatically detect.

[0009] Some variations of the sensor device also include a driver circuit for operating the laser diode with a first drive current in a first operating mode and a second drive current in a second operating mode. The first drive current is higher than the second drive current. Advantageously, this allows the sensor device to operate at an advantageous operating point in both the first and second operating modes. When the laser diode is operated with the first drive current instead of the second drive current, the signal-to-noise ratio (SNR) of the first readout signal generated from the photodiode's measurement signal can be higher. When the laser diode is operated with the second drive current instead of the first drive current, the SNR of the second readout signal generated from the laser diode's junction voltage can be higher. Simultaneously, at least in the absence of excessive background light, the first readout signal can provide a better SNR than the second readout signal when the laser diode is operated with the first drive current. When the laser diode is operated with the second drive current, the second readout signal can provide a higher SNR than the first readout signal. Operating the laser diode with the second drive current provides the additional benefit of reduced power consumption of the sensor device.

[0010] In some variations of the sensor device, the switching unit is adapted to generate an output signal based on both a first readout signal and a second readout signal in a first operating mode. Advantageously, using both the first and second readout signals to generate the output signal can provide higher signal quality and a higher signal-to-noise ratio.

[0011] In some variations of sensor devices, the laser diode is a VCSEL. Advantageously, such laser diodes are well-suited for applications involving self-mixing interferometry.

[0012] In some variations of the sensor device, the first readout unit includes a transimpedance amplifier. Advantageously, this enables the generation of a voltage signal based on the current signal provided by the photodiode.

[0013] Some variations of sensor devices include ASIC chips mounted on a carrier. ASIC chips can provide the logic required to operate the sensor device.

[0014] In some variations of the sensor device, laser diodes and photodiodes are arranged adjacent to each other above the carrier. Advantageously, this provides a particularly simple arrangement of the components of the sensor device.

[0015] In some variations of sensor devices, photodiodes are integrated into ASIC chips. Advantageously, this makes it possible to construct sensor devices with reduced space dimensions.

[0016] In some variations of sensor devices, photodiodes and laser diodes are integrated into a common chip. Advantageously, this reduces the size of the sensor device.

[0017] In some variations of sensor devices, the laser diode is mounted on an ASIC chip. Advantageously, this also reduces the size of the sensor device.

[0018] In some variations, the sensor device is one of a force sensor, particle sensor, proximity sensor, eye-tracking sensor, range sensor, and autofocus sensor. Advantageously, self-mixed interferometry sensor devices can be adapted to each of these applications.

[0019] A method for operating a self-mixing interferometric measurement sensor device comprising a laser diode and a photodiode includes switching between operating in a first operating mode and operating in a second operating mode. The first operating mode includes generating a first readout signal based on a measurement signal from the photodiode and generating an output signal based on the first readout signal. The second operating mode includes generating a second readout signal based on the junction voltage of the laser diode and generating an output signal based on the second readout signal.

[0020] This method enables the generation of an output signal based on a first readout signal generated from a measurement signal of the photodiode or a second readout signal generated from the junction voltage of the laser diode. Advantageously, this allows the generation of an output signal based on a readout signal that provides better signal quality. In particular, it allows the generation of an output signal based on a readout signal that provides a better signal-to-noise ratio. This makes the method adaptable to situations where background light hinders the quality of the signal transmitted by the photodiode.

[0021] Some variations of this method include detecting the signal bias of the first readout signal, operating in a first operating mode when the signal bias is below a threshold, and operating in a second operating mode when the signal bias exceeds the threshold. Advantageously, this allows switching to generate an output signal based on a second readout signal generated according to the junction voltage of the laser diode if an excessively large signal bias hinders the quality of the first readout signal generated based on the measurement signal of the photodiode. An excessively large signal bias may be caused by background light illuminating the photodiode.

[0022] Some variations of this method involve receiving a switching signal and switching between operating in a first operating mode and operating in a second operating mode based on the switching signal. Advantageously, this makes it possible to switch between the first operating mode and the second operating mode by means of an external switching signal.

[0023] In some variations of this method, a first operating mode includes operating the laser diode with a first drive current, and a second operating mode includes operating the laser diode with a second drive current. The first drive current is higher than the second drive current. Advantageously, this allows the sensor device to be operated at an advantageous operating point in both the first and second operating modes. Operating the laser diode with the second drive current can provide the additional benefit of reduced power consumption of the sensor device.

[0024] In some variations of this method, the first operating mode includes generating a second readout signal based on the junction voltage of the laser diode, and generating an output signal based on both the first and second readout signals. Advantageously, using both the first and second readout signals to generate the output signal can provide even higher signal quality and signal-to-noise ratio.

[0025] Electronic devices include sensor devices of the aforementioned types.

[0026] The above-described features, characteristics, and advantages of the present invention, as well as the ways in which they are implemented, will become clearer and more fully understood in conjunction with the following description of exemplary variations, which will be explained in more detail with reference to the accompanying drawings, in which, in schematic representation:

[0027] Figure 1 A cross-sectional view of the sensor device of the electronic device is shown;

[0028] Figure 2 A schematic circuit diagram of the sensor device is shown;

[0029] Figure 3 The signal-to-noise ratio of the readout signal generated in the sensor device is shown;

[0030] Figure 4 A cross-sectional view of another variation of the sensor device is shown;

[0031] Figure 5 A cross-sectional view of another variation of the sensor device is shown;

[0032] Figure 6 A cross-sectional view of another variation of the sensor device is shown; and

[0033] Figure 7 A cross-sectional view of another variation of the sensor device is shown.

[0034] Figure 1 A schematic cross-sectional view of an electronic device 10, including a sensor device 100, is shown. The sensor device 100 is a self-mixing interferometry sensor device based on the principle of amplitude modulation self-mixing interferometry. The sensor device 100 can be, for example, a force sensor, a particle sensor, a proximity sensor, an eye-tracking sensor, a ranging sensor, or an autofocus sensor. For example, the electronic device 10 can be headphones, an air purifier or other household appliance, a mobile phone, a tablet computer, a drone, a camera device, a robot, or a pair of smart glasses.

[0035] Sensor device 100 includes a laser diode 120, a photodiode 110, and an ASIC chip 130. Figure 1 In the depicted example, the laser diode 120, photodiode 110, and ASIC chip 130 are arranged adjacent to each other on the top side of the carrier 140. This achieves a low profile for the sensor device 100 and enables cost-effective production of the sensor device 100.

[0036] For example, laser diode 120 may be a VCSEL. Laser diode 120 is adapted to emit light 300 toward and through an optical interface 150 of sensor device 100. For example, optical interface 150 may include an optical lens. A portion of the emitted light 300 is reflected at optical interface 150 and arrives at photodiode 110 as reflected light 310. Photodiode 110 is adapted to measure the intensity of the reflected light 310 arriving at photodiode 110.

[0037] Sensor device 100 may be exposed to background light 320 reaching photodiode 110 through optical interface 150. The presence of background light 320 may distort the photodiode 110's measurement of the intensity of reflected light 310 because it generates a signal bias.

[0038] Figure 2 A schematic circuit diagram of a sensor device 100 is shown. The sensor device 100 includes a first readout unit 210, a second readout unit 220, a switching unit 230, a driver circuit 240, and a management unit 260. At least some of these components, or portions thereof, can be integrated into the ASIC chip 130 of the sensor device 100.

[0039] The first readout unit 210 is adapted to generate a first readout signal 211 based on the measurement signal 111 of the photodiode 110. For example, the measurement signal 111 may be a current (photocurrent). For example, the first readout unit 210 may include a transimpedance amplifier.

[0040] The second readout unit 220 is adapted to generate a second readout signal 221 based on the junction voltage 121 of the laser diode 120.

[0041] The driver circuit 240 is adapted to operate the laser diode 120 with a drive current 250. The driver circuit 240 can change the value of the drive current 250.

[0042] When the sensor device 100 is operated, both the first readout signal 211 and the second readout signal 221 are modulated based on the self-mixing interference occurring in the laser diode 120 of the sensor device 100. The first readout signal 211 and the second readout signal 221 can be used to detect the amplitude modulation caused by the self-mixing interference.

[0043] Figure 3 A schematic diagram depicts the signal-to-noise ratio (SNR) 212 of a first readout signal 211 and the SNR 222 of a second readout signal 221, depending on the drive current 250 used to operate the laser diode 120. The SNR 212 of the first readout signal 211 is higher under the first drive current 251 than under the second drive current 252. The SNR 222 of the second readout signal 221 is higher under the second drive current 252 than under the first drive current 251. The SNR 212 of the first readout signal 211 under the first drive current 251 can be greater than the SNR 222 of the second readout signal 221 under the second drive current 252.

[0044] The first drive current 251 is higher than the second drive current 252. For example, the first drive current 251 can be 2 mA. For example, the second drive current can be 0.5 mA.

[0045] Figure 3 It is shown that when the driver circuit 240 operates the laser diode 120 with the first drive current 251, the first readout signal 211 typically provides a better signal-to-noise ratio (SNR) than the second readout signal 221. When the laser diode 120 is operated with the second drive current 252, the second readout signal 221 provides a better SNR than the first readout signal 211. A particularly high SNR can be obtained by evaluating the first readout signal 211 under the first drive current 251. Even higher SNRs can be obtained by evaluating both the first readout signal 211 and the second readout signal 221 under the first drive current 251.

[0046] However, in the presence of background light 320, a bias is applied to the measurement signal 111 of photodiode 110. This bias may distort the first readout signal 211 and degrade its signal quality. For example, the distortion may be caused by dynamic range issues in the transimpedance amplifier 215. Therefore, in the presence of background light 320, the first readout signal 211 may become unusable. In this case, operating the laser diode 120 with the second drive current 252 and using the second readout signal 221 may be a better choice.

[0047] Therefore, the sensor device 100 is adapted to operate in a first operating mode and a second operating mode, and is adapted to switch between operating in the first operating mode and operating in the second operating mode. For example... Figure 2 As shown, the switching unit 230 is adapted to generate an output signal 231 of the sensor device 100 based on a first readout signal 211 in a first operating mode, and to generate an output signal 231 based on a second readout signal 221 in a second operating mode. Therefore, the first operating mode includes generating the first readout signal 211 based on the measurement signal 111 of the photodiode 110, and generating the output signal 231 based on the first readout signal 211. The second operating mode includes generating the second readout signal 221 based on the junction voltage 121 of the laser diode 120, and generating the output signal 231 based on the second readout signal 221.

[0048] In the first operating mode, the drive current 240 operates the laser diode 120 using the first drive current 251. In the second operating mode, the driver circuit 240 operates the laser diode 120 using the second drive current 252. Since the second drive current 252 is less than the first drive current 251, operating in the second operating mode reduces the power consumption of the sensor device 100 compared to operating in the first operating mode.

[0049] The sensor device 100 can be adapted to detect a signal bias of a first readout signal 211, which can be caused by, for example, the presence of background light 320, and can distort the quality of the first readout signal 211. The sensor device 100 can be adapted to switch between a first operating mode and a second operating mode based on the signal bias, such that the sensor device 100 operates in the first operating mode when the signal bias is below a threshold, and operates in the second operating mode when the signal bias exceeds the threshold.

[0050] Alternatively or additionally, the sensor device may be adapted to receive a switching signal 235 and to switch between operating in a first operating mode and operating in a second operating mode based on the switching signal 235. The switching signal 235 enables the sensor device 100 to switch between operating in the first operating mode and operating in the second operating mode based on external factors such as a power-saving mode or on input from the user of the electronic device 10. Figure 2 In the exemplary depiction, the switching unit 230 is capable of receiving the switching signal 235.

[0051] In some variations, the switching unit 230 may be adapted to generate an output signal 231 based on both the first readout signal 211 and the second readout signal 221 in a first operating mode. In this case, the first operating mode further includes generating a second readout signal 221 based on the junction voltage 121 of the laser diode 120. Generating the output signal 231 based on both the first readout signal 211 and the second readout signal 221 may employ, for example, a differential mode, and may provide improved signal quality and signal-to-noise ratio.

[0052] Figures 4 to 7 A schematic cross-sectional view of alternative variations of the sensor device 100 is shown. In these variations, the components of the sensor device 100 are arranged differently. Figure 1 The arrangement is shown in the variant configuration. Except for the differences described below, the foregoing description of the sensor device 100 also applies. Figures 4 to 7 A variant of .

[0053] exist Figure 4 In the depicted variant, photodiode 110 is integrated into ASIC chip 130. This enables a smaller sensor device 100.

[0054] exist Figure 5 In the described variations, like Figure 4 In a variant, photodiode 110 is integrated into ASIC chip 130. Additionally, laser diode 120 is disposed on ASIC chip 130, adjacent to photodiode 110. This arrangement enables a smaller sensor device 100.

[0055] exist Figure 6 In this variant, photodiode 110 is integrated into ASIC chip 130. Laser diode 120 is disposed on ASIC chip 130. Figure 4In a variant, laser diode 120 is positioned on top of photodiode 110. In this variant, laser diode 120 emits light 300 not only toward optical interface 150 but also emits light 305 backward toward photodiode 110. Photodiode 110 does not detect the light 310 already reflected at optical interface 150, but detects the backward-emitted light 305. Figure 6 In the arrangement, the sensor device 100 is not easily affected by the background light 320.

[0056] exist Figure 7 In the variant shown, the laser diode 120 and the photodiode 110 are integrated into a common chip 115. The common chip 115 is disposed on the ASIC chip 130. In this arrangement, as in... Figure 6 In this arrangement, the photodiode 110 does not detect the light 310 that has already been reflected at the optical interface 150, but instead directly detects the light 305 emitted by the laser diode 120. This allows... Figure 7 The arrangement is not easily affected by the background light of 320.

[0057] The invention has been described and illustrated in more detail with the aid of exemplary variations. However, the invention is not limited to the disclosed examples. Rather, other variations can be derived by those skilled in the art.

[0058] Figure Labels 10 Electronic devices 100 Sensor Devices 110 photodiode 111 Measurement Signal 115 Public Chips 120 laser diode 121 Junction Voltage 130 ASIC chip 140 carriers 150 Optical Interface 210 First Readout Unit 211 First readout signal 212 Signal-to-noise ratio 215 Transimpedance Amplifier 220 Second Readout Unit 221 Second readout signal 222 Signal-to-noise ratio 230 Switching Unit 231 Output Signal 235 Switching Signal 240 driver circuit 250 drive current 251 First driving current 252 Second drive current 260 Management Unit 300 emitted light 305 Light emitted backward 310 Reflected light 320 backlight

Claims

1. A self-mixing interferometric measurement sensor device (100), comprising: Laser diode (120). Photodiode (110). The first readout unit (210) is used to generate a first readout signal (211) based on the measurement signal (111) of the photodiode (110). The second readout unit (220) is used to generate a second readout signal (221) based on the junction voltage (121) of the laser diode (120). A switching unit (230) is adapted to generate an output signal (231) based on the first readout signal (211) in a first operating mode, and to generate the output signal (231) based on the second readout signal (221) in a second operating mode. The sensor device (100) is adapted to switch between operating in the first operating mode and operating in the second operating mode.

2. The sensor device (100) according to claim 1. in, The sensor device (100) is adapted to detect the signal bias of the first readout signal (211). The sensor device (100) is adapted to operate in the first operating mode when the signal bias is below a threshold, and to operate in the second operating mode when the signal bias exceeds the threshold.

3. The sensor device (100) according to any one of the preceding claims. in, The sensor device (100) is adapted to receive a switching signal (235) for switching between operating in the first operating mode and operating in the second operating mode.

4. The sensor device (100) according to any one of the preceding claims. It also includes a driver circuit (240) for operating the laser diode (120) with a first drive current (251) in the first operating mode and with a second drive current (252) in the second operating mode. in, The first drive current (251) is higher than the second drive current (252).

5. The sensor device (100) according to any one of the preceding claims. in, The switching unit (230) is adapted to generate the output signal (231) in the first operating mode based on both the first readout signal (211) and the second readout signal (221).

6. The sensor device (100) according to any one of the preceding claims. in, The laser diode (120) is a VCSEL.

7. The sensor device (100) according to any one of the preceding claims. in, The first readout unit (210) includes a transimpedance amplifier (215).

8. The sensor device (100) according to any one of the preceding claims. in, The sensor device (100) includes an ASIC chip (130) disposed on a carrier (140).

9. The sensor device (100) according to claim 8. in, The laser diode (120) and the photodiode (110) are arranged adjacent to each other above the carrier (140).

10. The sensor device (100) according to any one of claims 8 or 9. in, The photodiode (110) is integrated into the ASIC chip (130).

11. The sensor device (100) according to claim 8. in, The photodiode (110) and the laser diode (120) are integrated into a common chip (115).

12. The sensor device (100) according to any one of claims 8 to 11. in, The laser diode (120) is arranged on the ASIC chip (130).

13. The sensor device (100) according to any one of the preceding claims. in, The sensor device (100) is one of a force sensor, a particle sensor, a proximity sensor, an eye-tracking sensor, a range sensor, and an autofocus sensor.

14. A method for operating a self-mixing interferometric measurement sensor device (100), The sensor device (100) includes a laser diode (120) and a photodiode (110). The method includes switching between working in a first working mode and working in a second working mode. in, The first working mode includes: A first readout signal (211) is generated based on the measurement signal (111) of the photodiode (110). An output signal (231) is generated based on the first readout signal (211); The second working mode includes: A second readout signal (221) is generated based on the junction voltage (121) of the laser diode (120). The output signal (231) is generated based on the second readout signal (221).

15. The method according to claim 14, in, The method includes: Detect the signal bias of the first readout signal (211); When the signal bias is below a threshold, it operates in the first operating mode; When the signal bias exceeds the threshold, the system operates in the second operating mode.

16. The method according to any one of claims 14 and 15, in, The method includes: Receive switching signal (235); The switching is performed between operating in the first operating mode and operating in the second operating mode according to the switching signal (235).

17. The method according to any one of claims 14 to 16, in, The first working mode includes: The laser diode (120) is operated with a first drive current (251); The second working mode includes: The laser diode (120) is operated with a second drive current (252); The first driving current (251) is higher than the second driving current (252).

18. The method according to any one of claims 14 to 17, in, The first working mode includes: A second readout signal (221) is generated based on the junction voltage (121) of the laser diode (120). The output signal (231) is generated based on both the first readout signal (211) and the second readout signal (221).

19. An electronic device (10), comprising: The sensor device (100) according to any one of claims 1 to 13.

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