US-12625238-B2 - Time-of-flight sensing circuitry, time-of-flight imaging portion, signal processing method

Abstract

The present disclosure generally pertains to a time-of-flight sensing circuitry configured to: ⋅ determine a first point of time, at which a first voltage signal ( 6 ) reaches a predetermined threshold ( 4 ); ⋅ determine a second point of time, at which a second voltage signal ( 7 ) reaches the predetermined threshold ( 4 ); and ⋅ determine a phase shift of detected light on the basis of a voltage difference between the first and the second voltage signal based on a time difference of the second point of time and the first point of time.

Inventors

• Rachit Mohan
• Ward Van Der Tempel

Assignees

• SONY SEMICONDUCTOR SOLUTIONS CORPORATION

Dates

Publication Date

20260512

Application Date

20200827

Priority Date

20190829

Claims (20)

1. 1 . A time-of-flight sensing circuitry comprising: a first circuit configured to determine a first point of time, at which a first voltage signal reaches a predetermined threshold; a second circuit configured to determine a second point of time, at which a second voltage signal reaches the predetermined threshold; and a third circuit configured to determine a phase shift of detected light on the basis of a voltage difference between a value of the first voltage signal at the first point of time and a value of the second voltage signal at the first point of time, wherein the voltage difference is based on a time difference between the second point of time and the first point of time.
2. 2 . The time-of-flight sensing circuitry of claim 1 , wherein the predetermined threshold is a function.
3. 3 . The time-of-flight sensing circuitry of claim 1 , wherein the first voltage signal is representative of a sampling of a first transfer gate and the second voltage signal is representative of a sampling of a second transfer gate.
4. 4 . The time-of-flight sensing circuitry of claim 1 , comprising: a first comparator configured to compare the first voltage signal and the predetermined threshold; a first clock associated with the first comparator, such that the first point of time is determined based on the comparison of the first voltage signal and the predetermined threshold; a second comparator configured to compare the second voltage signal and the predetermined threshold, a second clock associated with the second comparator, such that the second point of time is determined based on the comparison of the second voltage signal and the predetermined threshold.
5. 5 . The time-of-flight sensing circuitry of claim 1 , wherein the voltage difference is determined for the first point of time.
6. 6 . The time-of-flight sensing circuitry of claim 5 , wherein the voltage difference is further determined based on an extrapolation of the second voltage signal at the second point of time, thereby determining the value of the second voltage signal at the first point of time.
7. 7 . The time-of-flight sensing circuitry of claim 1 , wherein the voltage difference is based on the formula: V = V threshold ( 1 - t 1 t 2 ) , wherein V is the voltage difference, V threshold is a voltage level at the predetermined threshold, t 1 is the first point of time and t 2 is the second point of time.
8. 8 . A time-of-flight imaging portion, comprising: a time-of-flight signaling circuitry including a first transfer gate and a second transfer gate; and a time-of-flight sensing circuitry configured to: determine a first point of time, at which a first voltage signal reaches a predetermined threshold; determine a second point of time, at which a second voltage signal reaches the predetermined threshold; and determine a phase shift of detected light on the basis of a voltage difference between a value of the first voltage signal at the first point of time and a value of the second voltage signal at the first point of time, wherein the voltage difference is based on a time difference between the second point of time and the first point of time.
9. 9 . The time-of-flight imaging portion of claim 8 , wherein the predetermined threshold is a function.
10. 10 . The time-of-flight imaging portion of claim 8 , wherein the first voltage signal is generated in response to a sampling of the first transfer gate and the second voltage signal is generated in response to a sampling of the second transfer gate.
11. 11 . The time-of-flight imaging portion of claim 8 , wherein the voltage difference is determined for the first point of time.
12. 12 . The time-of-flight imaging portion of claim 11 , wherein the voltage difference is further determined based on an extrapolation of the second voltage signal at the second point of time, thereby determining the value of the second voltage signal at the first point of time.
13. 13 . The time-of-flight imaging portion of claim 8 , wherein one time-of-flight signaling circuitry is associated with one time-of-flight sensing circuitry.
14. 14 . A signal processing method comprising: determining a first point of time, at which a first voltage signal reaches a predetermined threshold; determining a second point of time, at which a second voltage signal reaches the predetermined threshold; and determining a phase shift of detected light on the basis of a voltage difference between a value of the first voltage signal at the first point of time and a value of the second voltage signal at the first point of time, wherein the voltage difference is based on a time difference between the second point of time and the first point of time.
15. 15 . The signal processing method of claim 14 , wherein the predetermined threshold is a function.
16. 16 . The signal processing method of claim 14 , wherein the first voltage signal is representative of a sampling of a first transfer gate and the second voltage signal is representative of a sampling of a second transfer gate.
17. 17 . The signal processing method of claim 14 , further comprising: comparing the first voltage signal and the predetermined threshold; determining the first point of time based on the comparison of the first voltage signal and the predetermined threshold; comparing the second voltage signal and the predetermined threshold; and determining the second point of time based on the comparison of the second voltage signal and predetermined threshold.
18. 18 . The signal processing method of claim 14 , wherein the voltage difference is determined for the first point of time.
19. 19 . The signal processing method of claim 18 , further comprising: extrapolating the second voltage signal at the second point of time; and thereby determining the value of the second voltage signal at the first point of time.
20. 20 . The signal processing method of claim 14 , wherein the voltage difference is based on the formula: V = V threshold ( 1 - t 1 t 2 ) , wherein V is the voltage difference, V threshold is a voltage level at the predetermined threshold, t 1 is the first point of time and t 2 is the second point of time.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This Application is a national stage filing under 35 U.S.C. 371 of International Patent Application Serial No. PCT/EP/2020/073947, filed Aug. 27, 2020 which claims the foreign priority benefits under 35 U.S.C. § 119(a)-(d) or 35 U.S.C. § 365(b) of European application number 19194246.5, filed Aug. 29, 2019. The entire contents of these applications are incorporated herein by reference in their entirety. TECHNICAL FIELD The present disclosure generally pertains to a time-of-flight sensing circuitry, a time-of-flight imaging portion, and a signal processing method. TECHNICAL BACKGROUND Generally, time-of-flight (ToF) devices for determining a distance to a scene are known. It can be distinguished between direct ToF (dToF), wherein a distance information is acquired based on the run-time of emitted and reflected light, and indirect ToF (iToF), wherein a distance information is acquired based on a phase-shift of emitted and reflected light. In the case of iToF, the phase-shift is typically determined based on a measured pixel voltage at least at two locations within predetermined shifted time-windows, wherein the locations are typically transistor gates. This known way of determining the phase-shift, and thereby, the distance information, is known to be limited in that a dynamic range, which is generally known, is limited with the maximum pixel voltage (e.g. 1 Volt). Although there exist techniques for increasing a dynamic range, it is generally desirable to provide a ToF sensing circuitry, a ToF imaging portion, and a signal processing method. SUMMARY According to a first aspect the disclosure provides a time-of-flight sensing circuitry configured to: determine a first point of time, at which a first voltage signal reaches a predetermined threshold; determine a second point of time, at which a second voltage signal reaches the predetermined threshold; and determine a phase shift of detected light on the basis of a voltage difference between the first and the second voltage signal based on a time difference of the second point of time and the first point of time. According to a second aspect, the disclosure provides a time-of-flight imaging portion, comprising: a time-of-flight signaling circuitry including a first transfer gate and a second transfer gate; and a time-of-flight sensing circuitry configured to: determine a first point of time, at which a first voltage signal reaches a predetermined threshold; determine a second point of time, at which a second voltage signal reaches the predetermined threshold; and determine a phase shift of detected light on the basis of a voltage difference between the first and the second voltage signal based on a time difference of the second point of time and the first point of time. According to a third aspect, the disclosure provides a signal processing method comprising: determining a first point of time, at which a first voltage signal reaches a predetermined threshold; determining a second point of time, at which a second voltage signal reaches the predetermined threshold; and determining a phase shift of detected light on the basis of a voltage difference between the first and the second voltage signal based on a time difference of the second point of time and the first point of time. Further aspects are set forth in the dependent claims, the following description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments are explained by way of example with respect to the accompanying drawings, in which: FIG. 1 shows a coordinate system including voltage signals according to the present disclosure; FIG. 2 depicts a schematic diagram of a ToF pixel, as it is generally known; FIG. 3 depicts a schematic diagram of a ToF imaging portion according to the present disclosure; FIG. 4 depicts, in a coordinate system, an embodiment of a predetermined threshold according to the present disclosure; FIG. 5 depicts, in a coordinate system, a further embodiment of a predetermined threshold according to the present disclosure; FIG. 6 depicts, in a coordinate system, a further embodiment of a predetermined threshold according to the present disclosure; FIG. 7 depicts, in a block diagram, a method according to the present disclosure; FIG. 8 depicts a block diagram of a further method according to the present disclosure; FIG. 9 depicts a block diagram of a further method according to the present disclosure; and FIG. 10 depicts a block diagram an embodiment of a ToF imaging apparatus. DETAILED DESCRIPTION OF EMBODIMENTS Before a detailed description of the embodiments under reference of FIG. 3 is given, general explanations are made. As mentioned in the outset, it is generally desirable to increase a dynamic range in a ToF measurement, for example to account for offsets, ambient light, object distance, object reflectivity, specular reflection, e.g. to obtain a differential reflected signal, and the like. It has been recognized that known ToF d