Optoelectronic Sensor Device and Method to Operate an Optoelectronic Sensor Device

Abstract

An optoelectronic sensor device and a method for operating an optoelectronic sensor device are disclosed. In an embodiment the optoelectronic sensor device includes a radiation-emitting semiconductor chip configured to emit radiation with a peak wavelength which depends on a temperature of the radiation-emitting semiconductor chip. The sensor device further includes a sensor chip configured to detect a part of the radiation reflected back to the sensor chip as well as a spectral filter component having an adjustable spectral transmission range. A wavelength determination unit is configured to determine the peak wavelength and a filter driver is configured to adjust the spectral transmission range to the determined peak wavelength.

Claims

1. An optoelectronic sensor device comprising: a radiation-emitting semiconductor chip configured to emit a radiation with a peak wavelength which depends on a temperature of the radiation-emitting semiconductor chip; a sensor chip configured to detect a part of the radiation reflected back to the sensor chip; a spectral filter component having an adjustable spectral transmission range; a wavelength determination unit configured to determine the peak wavelength; and a filter driver to adjust the spectral transmission range to the determined peak wavelength.

2. The sensor device of claim 1, wherein the filter component is an interference filter and the spectral transmission range is between 2 nm and 15 nm inclusive, and wherein a change of the peak wavelength depending on the temperature of the radiation-emitting semiconductor chip is between 0.1 nm/ C. and 0.9 nm/ C. inclusive and a spectral width of the emitted radiation is between 1 nm and 15 nm inclusive.

3. The sensor device of claim 2, wherein the filter component is a Fabry-Perot device, the transmission range is adjusted by a distance between two mirrors of the Fabry-Perot device, and wherein a size of the filter component in top view amounts to at most 5 mm5 mm.

4. The sensor device of claim 1, wherein the radiation-emitting semiconductor chip is a pulsed semiconductor laser, the peak wavelength of which is between 780 nm and 980 nm inclusive.

5. The sensor device of claim 1, wherein the filter driver comprises a voltage source to control a voltage to the filter component so that the spectral transmission range is controllable by adjusting the voltage at the filter component.

6. The sensor device of claim 1, wherein the filter driver comprises a temperature control unit to control a temperature of the filter component so that the spectral transmission range is controllable by adjusting the temperature of the filter component.

7. The sensor device of claim 1, wherein the filter driver comprises a temperature sensor to measure the temperature of the radiation-emitting semiconductor chip, and wherein the peak wavelength is calculated in the filter driver from the measured temperature of the radiation-emitting semiconductor chip.

8. The sensor device of claim 1, wherein the sensor device comprises at least two sensor chips and an optical element, wherein the optical element is configured to form a two-dimensional irradiation pattern of the radiation, and wherein the reflected irradiation pattern detected by the sensor chips allows for a three-dimensional measuring of an object illuminated with the irradiation pattern.

9. The sensor device of claim 1, wherein the sensor chip allows a time-of-flight measurement of the radiation from the radiation-emitting semiconductor chip.

10. The sensor device of claim 1, further comprising a distant mirror configured to reflect the radiation from the radiation-emitting semiconductor chip to the sensor chip, and wherein the sensor device is a light barrier.

11. The sensor device of claim 1, wherein the sensor chip comprises a plurality of pixels and an optical element so that the radiation reflected back to the sensor chip is imaged onto the pixels, and wherein the sensor device is a biometric recognition system.

12. The sensor device of claim 1, wherein the sensor device is a proximity sensor.

13. A method for operating an optoelectronic sensor device, wherein the optoelectronic sensor device comprises a radiation-emitting semiconductor chip, a sensor chip, a spectral filter component having an adjustable spectral transmission range, a wavelength determination unit and a filter driver, the method comprising: emitting, by the radiation-emitting semiconductor chip, a radiation with a peak wavelength which depends on a temperature of the radiation-emitting semiconductor chip; detecting, by the sensor chip, a part of the radiation which is reflected back to the sensor chip by an object in the exterior of the sensor device; determining, by the wavelength determination unit, the peak wavelength at least temporarily; and adjusting, by the filter driver, the spectral transmission range to the determined peak wavelength.

14. The method of claim 13, wherein the filter driver varies the spectral transmission range.

15. The method of claim 13, further comprising: emitting test pulses for the spectral transmission ranges; measuring an intensity of the reflection of the test pulses by the sensor chip; determining the peak wavelength by the wavelength determination unit based on the measured intensities; and tuning the spectral transmission range by the filter driver to maximize the measured intensity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] An optoelectronic sensor device and a method described are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.

[0041] In the figures:

[0042] FIGS. 1 to 6 show schematic sectional representations of exemplary embodiments of optoelectronic sensor devices;

[0043] FIGS. 7A-7B show schematic sectional representations of radiation-emitting semiconductor chips for optoelectronic sensor devices;

[0044] FIGS. 8 to 10 show schematic sectional representations of exemplary embodiments of spectral filter components for optoelectronic sensor devices; and

[0045] FIG. 11 schematically shows a spectral behavior of an optoelectronic semiconductor device described herein in an exemplary method to operate said sensor device.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0046] FIG. 1 shows an exemplary embodiment of an optoelectronic sensor device 1. The sensor device 1 comprises a radiation-emitting semiconductor chip 2. The semiconductor chip 2 is to emit radiation R. Preferably, the semiconductor chip 2 is a laser diode. The radiation R can be emitted in just one direction as indicated in FIG. 1. In a deviation from FIG. 1, the radiation R can also be emitted over a larger angular range.

[0047] Further, the sensor device 1 comprises a sensor chip 3. For example, the sensor chip 3 is a photodiode or a CCD, preferably based on silicon or on InAlGaAs. The sensor chip 3 is to detect a part of the radiation R reflected back from an object 9 in the exterior of the sensor device 1.

[0048] A spectral filter component 4 is arranged on the sensor chip 3. The filter component 4 has a comparably small spectral transmission range which is adjusted to a spectral range of the emitted radiation R by means of a filter driver 6. In particular, a wavelength of the radiation R is dependent on a temperature of the semiconductor chip 2. Hence, a wavelength determination unit 5 can comprise a temperature sensor 51 to measure a temperature of the semiconductor chip 2. By means of the measured temperature, the spectral range of the emitted radiation R is determined and the filter component 4 is adjusted accordingly.

[0049] Thus, the spectral transmission range of the filter component 4 is adapted to match a spectral width and a peak wavelength of the radiation R. Hence, the sensor chip 3 is sensitive practically only in the spectral range of the radiation R due to the filter component 4. Thus, ambient light S coming from all directions and maybe also from the object 9 can be greatly suppressed as in the small spectral transmission range of the filter component 4 the ambient light S contributes to an overall intensity only to a comparably minor proportion. Thus, by means of the adjustable spectral filter component 4 the sensitivity of the sensor device 1 can be increased and/or the required intensity of the emitted radiation R can be decreased.

[0050] The semiconductor chip 2, the sensor chip 3, the filter component 4, the wavelength determination unit 5 and the filter driver 6 can be located on a carrier 8. The mentioned components can be realized as separate components that are applied to the carrier. Other than shown in FIG. 1, at least the wavelength determination unit 5 and the filter driver 6 can be integrated in the carrier at least in part. For example, the carrier 8 is made of silicon and can comprise electronics like transistors. That is, the carrier 8 can include integrated circuits or is fashioned as an IC chip.

[0051] According to FIG. 2, the radiation R is emitted in a larger angular range. For example, the object 9 is completely or nearly completely illuminated by the radiation R on a side facing the sensor device 1. In this case, the sensor device 1 can be an iris recognition sensor, for example. Hence, the sensor chip 3 can comprise a plurality of pixels to image the object 9.

[0052] As possible in all the other exemplary embodiments, the spectral filter component 4 does not necessarily need to be in direct contact with the sensor chip 3 as illustrated in connection with FIG. 1, but can be arranged at some distance from the sensor chip 3, compare FIG. 2.

[0053] In FIG. 2 it is shown that the wavelength determination unit 5 and the filter driver 6 are at least in part incorporated in the carrier 8. As in all the other exemplary embodiments, it is possible that the wavelength determination unit 5 includes a spectral sensor 52. As an option, the peak wavelength of the radiation R emitted by the semiconductor chip 2 can be directly measured in the spectral sensor 52. The spectral sensor 52 can be present as an alternative or in addition, for example, to the temperature sensor 51 as indicated in FIG. 1.

[0054] According to FIG. 3, the sensor device 1 can be fashioned as a time-of-flight sensor to accurately measure the distance of objects 9a, 9b. The objects 9a, 9b are arranged at different distances to the sensor device 1. By means of the sensor chip 3 it is measured when portions of reflected radiation R reach the sensor chip 3. A distance of the objects 9a, 9b to the sensor device 1 can be comparatively large, for example, at least 5 m and/or at most 250 m.

[0055] As also possible in all other exemplary embodiments, there can be an optical element 71 in front of the sensor chip 3 and/or in front of the semiconductor chip 2. By means of the at least one optical element 71, the radiation R can be shaped and/or an imaging of the reflected radiation onto the sensor chip 3 is enabled.

[0056] As an option, there can be an optical barrier 73 between the semiconductor chip 2 and the sensor chip 3. Thus, direct optical crosstalk between the semiconductor chip 2 and the sensor chip 3 can be avoided or reduced.

[0057] In FIG. 4, the sensor device 1 emits an irradiation pattern 74 onto the object 9. The object 9, for example, is arranged at a comparably small distance to the sensor device 1, for example, just a couple of meters away. A surface of the object 9 facing the sensor device 1 can be comparably flat and can have a low contrast. The irradiation pattern 74 is, for example, a regular pattern of lines and/or dots.

[0058] Preferably, the sensor device 1 comprises a plurality of sensor chips 3, each provided with a spectral filter component 4. Thus, stereoscopic viewing is enabled and three-dimensional measurement of the object 9 is also enabled.

[0059] To form the irradiation pattern 74, preferably the optical element 71 is provided in front of the semiconductor chip 2. By means of the optical element 71, the radiation R is formed so that the irradiation pattern 72 occurs on the object 9. For example, the optical element 71 is a lens array or a mirror array or can also be a movable mirror like an MEMS component.

[0060] According to FIG. 5, the sensor device 1 is configured as a light barrier. Thus, the sensor device 1 comprises a further mirror 72 which is at a distance to the carrier 8 with the semiconductor chip 2 and the sensor chip 3. The sensor chip 3 detects the radiation R emitted from the semiconductor 2 and reflected back to the carrier 8 at the distant mirror 72. Thus, the sensor device 1 can detect the object 9 that disturbs an optical path between the semiconductor chip 2 and the distant mirror 72. The mirror 72 can be of a specular reflective manner or of diffusive reflective manner.

[0061] In the exemplary embodiment of FIG. 4, the sensor device 1 is configured as a proximity sensor. Thus, the sensor device 1 is sensitive to the object 9 just beginning at a distinct distance.

[0062] As in all other exemplary embodiments it is possible, as an option, that there is an additional spectral filter component 4b in front of the semiconductor chip 2. Thus, it is possible to match the spectrum of the radiation R emitted by the semiconductor chip 2 to the sensitivity of the sensor chip 3. Other than shown, it is possible that a common filter component spans over the sensor chip 3 as well as over the semiconductor chip 2.

[0063] Moreover, as an option, it is possible that there is a radiation sensor 75. The radiation sensor 75 can be optically coupled to the semiconductor chip 2, in particular to a light output after the radiation R passes through the further filter component 4b. Thus, the spectral transmission range of the filter components 4, 4b can simply be adjusted to the wavelength range of the radiation R by maximizing the light intensity at the radiation sensor 75. Such a radiation sensor 75 can be comprised by the wavelength determination unit 5 and can also be present in the other exemplary embodiments.

[0064] In FIG. 7A it is shown that the radiation-emitting semiconductor chip 2 is an edge-emitting laser diode. The semiconductor chip 2 comprises a substrate 29 bearing a semiconductor layer sequence 21. The semiconductor layer sequence 21 has at least one active layer 22. The radiation R is emitted in a direction parallel to the active layer 22.

[0065] The semiconductor layer sequence is preferably based on a III-V compound semiconductor material. The semiconductor material is, for example, a nitride compound semiconductor material such as Al.sub.nIn.sub.1-n-mGa.sub.mN or a phosphide compound semiconductor material such as Al.sub.nIn.sub.1-n-mGa.sub.mP or also an arsenide compound semiconductor material such as Al.sub.nIn.sub.1-n-mGa.sub.mAs, wherein in each case 0n1, 0m1 and n+m1 applies. The semiconductor layer sequence may comprise dopants and additional constituents. For simplicity's sake, however, only the essential constituents of the crystal lattice of the semiconductor layer sequence are indicated, i.e., Al, As, Ga, In, N or P, even if these may in part be replaced and/or supplemented by small quantities of further substances. The semiconductor layer sequence is particularly preferably based on the AlInGaAs material system.

[0066] Contrary to FIG. 7A, the semiconductor chip 2 of FIG. 7B is designed as a vertical cavity surface-emitting laser, VCSEL for short. Hence, the radiation R is emitted in a direction perpendicular to the active layer 22.

[0067] In FIG. 7A as well as in FIG. 7B it is possible that there is an array of emitting regions on a facet or on a surface of the semiconductor layer sequence 21. Hence, more than one emitting region can be combined to form a greater emitting region, for example, an array of single VCSELs.

[0068] In FIG. 8 it is illustrated that the filter component 4 comprises a first mirror 41 and a second mirror 42. Thus, a Fabry-Perot interferometer is formed. For example, the second mirror 42 is movable so that a distance D can be adjusted by the filter driver 6, for example, by application of a voltage by means of a voltage source 62.

[0069] For example, the filter component 4 of FIG. 8 is configured as described in document US 2011/0279824 A1, the disclosure content of which is included by reference.

[0070] According to FIG. 9, the filter driver 6 comprises a temperature control unit 61, for example, a heating unit. Hence, the temperature of the spectral filter component 4 can be adjusted by the filter driver 6. By means of a defined temperature, the spectral transmission range of the filter component is adjusted.

[0071] In FIG. 10 it is schematically illustrated that the filter component 4 comprises at least one electrochromic material. By application of a voltage by means of the voltage source 62 in the filter driver 6, the spectral transmission of the filter component 4 can be adjusted.

[0072] In FIG. 11, the spectral properties of an exemplary sensor device 1 are illustrated. Depending on a temperature T1, T2, the radiation R emitted by the semiconductor chip 2 has different peak wavelengths L1, L2. A spectral width of the radiation R is similar to the spectral transmission ranges A1, A2 of the filter component 4. Thus, it is necessary to adjust the spectral transmission ranges A1, A2 to the peak wavelengths L1, L2. Hence, ambient light S is significantly suppressed due to the application of the small spectral transmission ranges A1, A2.

[0073] Otherwise, in a common device there is only one large spectral transmission range spanning the complete spectral range in which the radiation R can lie in an intended operational temperature range of a deviation of a sensor device. Thus, a significant amount of ambient light S is then collected in the sensor chip and only a comparably low signal-to-noise ratio can be achieved contrary to what the case is in the optoelectronic semiconductor device 1 described herein.

[0074] The invention described here is not restricted by the description given with reference to the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or exemplary embodiments.