CAMERA

Description

[0001] The invention relates to a camera, in particular a 3D time-of-flight camera, according to claim 1.

[0002] Such a camera preferably operates according to a scanning principle, in which a light beam is emitted as a light pulse into a monitored area. The light beam reflected by an object is received again and the received signal is then electronically evaluated. This allows the camera to measure a distance and thus obtain depth information.

[0003] A 3D image, a distance image, or a depth map is generated from the captured three-dimensional image data with distance or range values for the individual pixels. Various methods are known for determining depth information. The time of flight of light is often measured using a well-known phase or pulse method to determine the distance to a scanned object. These methods are also called TOF (Time-Of-Flight) or LIDAR (Light Detection And Ranging).

[0004] 3D image data obtained in this way can be used in automation technology to control moving actuators, such as robots or vehicles.

[0005] For vehicles operating on public roads or in enclosed environments, especially in the field of factory and logistics automation, a 3D time-of-flight camera is used to capture the entire environment, and in particular a planned route, as completely and three-dimensionally as possible. This applies to virtually all conceivable vehicles, whether they are driver-driven vehicles such as cars, trucks, work machines, and forklifts, or driverless vehicles such as AGVs (Automated Guided Vehicles), AGCs (Automated Guided Carts), AMRs (Autonomous Mobile Robots), or industrial trucks.

[0006] The 3D image data is used, for example, to assist a driver or enable autonomous navigation, including to detect obstacles, avoid collisions or facilitate the loading and unloading of transport goods, including boxes, pallets, containers or trailers.

[0007] When using 3D time-of-flight cameras in one of the aforementioned mobile applications, the energy consumption of the 3D time-of-flight camera is crucial for the mobile vehicle's runtime. The illumination of the 3D time-of-flight camera, which generates the 3D depth information, and thus its power supply, contributes a large portion to energy consumption.

[0008] The aforementioned TOF method requires multiple measurements for phase estimation. For this purpose, the illumination is continuously switched on and off, resulting in load surges in the power supply of the 3D time-of-flight camera's illumination. Reading and processing phases of the depth data result in lighting pauses during which there is little or no load on the power supply of the 3D time-of-flight camera's illumination.

[0009] To control the power supply of the 3D time-of-flight camera's illumination, switching regulators are used that can operate in a continuous mode (also called continuous-current mode "CCM") or in a discontinuous mode (also called discontinuous-current mode "DCM").

[0010] In continuous mode, the switching regulator ensures continuous power supply to the 3D time-of-flight camera's illumination, even when the 3D time-of-flight camera's illumination is not emitting a light pulse. In discontinuous mode, the switching regulator is designed to supply power to the 3D time-of-flight camera's illumination only for the purpose of emitting the light pulse and to be de-energized outside of an illumination phase. This results in the switching regulator having a poor response to load surges, resulting in a degradation of the 3D time-of-flight camera's measurement performance.

[0011] From DE 102014105482 B4 and US 2015 / 0312983 A1, control circuits for the lighting units of a camera are known, with which certain lighting modes can be controlled.

[0012] It is an object of the invention to provide a camera with a high image capture and at the same time low energy consumption.

[0013] This object is achieved by a camera, in particular a 3D time-of-flight camera, having the features of claim 1. The camera according to the invention, in particular a 3D time-of-flight camera, comprises an illumination unit that emits light pulses during an illumination phase, an image sensor that generates images from the light pulses reflected by an object, a switching regulator that regulates current to the illumination unit, wherein the switching regulator is operable in a continuous and a discontinuous mode, and a control unit that is designed to activate and deactivate the continuous mode of the switching regulator depending on the illumination phase of the illumination unit.

[0014] This results in the technical advantage that a supply voltage applied to the switching regulator does not change and thus no different supply levels occur, since switching from continuous mode to discontinuous mode and vice versa is carried out within the switching regulator.

[0015] The control unit activates the continuous mode of the switching regulator before the lighting unit is switched on and deactivates the continuous mode of the switching regulator after the lighting unit is switched off. This makes it possible to provide the full current to the lighting unit at the beginning of the lighting phase, ensuring a consistent lighting pattern.

[0016] Likewise, the control unit activates the discontinuous mode between two lighting phases of the lighting unit, whereby power loss through the switching regulator itself is minimized, whereby no regulation of the supply voltage of the switching regulator is necessary.

[0017] Preferably, the illumination phase of the illumination unit consists of an envelope ranging from microseconds to milliseconds, encompassing light pulses in the nanosecond range. Activating the continuous mode of the switching regulator thus enables the implementation of a fast illumination pattern for the 3D time-of-flight camera. Furthermore, activating the discontinuous mode between the illumination phases enables significant savings in the switching regulator's power dissipation.

[0018] According to a preferred embodiment, the control unit is integrated into the image sensor, so that a compact design of the 3D time-of-flight camera is possible.

[0019] Advantageously, the control unit is provided for controlling the illumination phases of the illumination unit. This means that a single control unit can be provided for controlling the switching regulator, the illumination unit, and the image sensor, further improving the compactness of the 3D time-of-flight camera.

[0020] The camera according to the invention can be developed in a similar manner and thereby exhibits similar advantages. Such advantageous features are described by way of example, but not exhaustively, in the subclaims following the independent claims.

[0021] The invention will be explained in more detail below with regard to further features and advantages, using exemplary embodiments and with reference to the accompanying drawings. The figures of the drawing show: Fig. 1 is a schematic representation of a preferred embodiment of a circuit diagram of a camera according to the invention, and Fig. 2 is a schematic representation of an operating sequence of the camera according to the invention over time.

[0022] Figure 1 shows a schematic representation of a preferred embodiment of a circuit diagram of a camera 1 according to the invention, which in particular comprises a 3D time-of-flight camera in which a TOF detection method is used.

[0023] The camera 1 comprises a lighting unit 2 which is intended to illuminate during a (in the Figure 2The illumination phase Bp (shown) is used to emit light pulses to illuminate a surveillance area. Furthermore, an image sensor 3 is present, which generates images from the light pulses reflected by an object (not shown). The images represent, in particular, a 3D image, a distance image, or a depth map.

[0024] The camera 1 further comprises a switching regulator 4 that regulates the current to the lighting unit 2. The switching regulator 4 can be operated in a continuous or discontinuous mode (CCM or DCM). This means that the switching regulator 4 is designed such that it can be switched between the continuous mode (CCM) and the discontinuous mode (DCM), and vice versa.

[0025] According to the invention, the camera 1 comprises a control unit 5 configured to activate and deactivate the continuous mode CCM of the switching regulator 4 depending on the illumination phase Bp of the illumination unit 2. By activating the continuous mode CCM of the switching regulator 4, in particular immediately before the start of the illumination phase Bp of the illumination unit 2, the switching regulator 4 is capable of providing the illumination unit 2 with the full current for the illumination phase Bp.

[0026] Deactivating the continuous mode CCM or activating the discontinuous mode DCM of the switching regulator 4 after the illumination phase Bp of the illumination unit 2 prevents high power loss in the switching regulator 4, since the current provided by the discontinuous mode DCM can, for example, be sufficient for the image sensor 3 to evaluate the acquired image data.

[0027] In addition, switching internally of the switching regulator 4 between these two modes CCM and DCM allows that a supply voltage Vin applied to the switching regulator 4 is not affected.

[0028] As in the Figure 1 As shown, the switching regulator 4 can also be designed to regulate current to the image sensor 3. This allows the control unit 5 to more easily regulate the current to the lighting unit 2 and to the image sensor 3 via the switching regulator 4. However, such a design is not mandatory, since current regulation of the image sensor 3 independent of the switching regulator 4 can also be advantageous.

[0029] As in the Figure 2As shown, the operating sequence of camera 1 or switching regulator 4 of camera 1 over time t proceeds as follows: When the supply voltage Vin is applied, switching regulator 4 is in discontinuous DCM mode. Before the start of the illumination phase Bp of illumination unit 2, control unit 5 of camera 1 switches switching regulator 4 to continuous CCM mode, so that at the start of illumination phase Bp of illumination unit 2, the full current is available for illumination unit 2 in order to ensure sufficient and stable illumination for image capture by image sensor 3.

[0030] After the end of the lighting phase Bp of the lighting unit 2, the control unit 5 deactivates the continuous mode CCM of the switching regulator 4 and switches the switching regulator 4 to the discontinuous mode DCM. This means that the full current is not present in the switching regulator 4, thus avoiding power loss.

[0031] Furthermore, the current provided by the discontinuous DCM mode can be sufficient for image sensor 3 to process and evaluate the acquired image data, thus avoiding image acquisition delays. Avoiding image acquisition delays allows for an improvement in the efficiency of camera 1.

[0032] Between two illumination phases Bp of the illumination unit 2, the switching regulator 4 is in the discontinuous mode DCM, so that the power loss of the switching regulator 4 can be significantly reduced, since this intermediate phase is considerably longer than the illumination phase Bp, which is preferably represented by an envelope curve that lies in a range of microseconds to milliseconds, such as 500µs, and envelops light pulses lying in a range of nanoseconds, such as 3ns.

[0033] As soon as the control unit 5 controls the lighting unit 2 again directly or (as shown) indirectly via the image sensor 3 to restart the lighting phase Bp, the control unit 5 activates the continuous mode CCM of the switching regulator 4 so that the switching regulator 4 switches back to the continuous mode CCM and deactivates the discontinuous mode DCM.

[0034] The illumination unit 2 thus receives the full current intensity for emitting the light pulse(s) at the start of the illumination phase Bp. The switching regulator 4 thus has no dead time, so that the efficiency of the camera 1 is further improved. List of reference symbols

[0035] 1Camera 2Lighting unit 3Image sensor 4Switching controller 5Control unit BpLighting phase DCMDiscontinuous mode CCMContinuous mode tTime VinSupply voltage

Claims

1. A camera (1), especially 3D time-of-flight camera, with an illumination unit (2) which emits light pulses during an illumination phase (Bp), an image sensor (3), which generates images from the pulses of light reflected by an object, a switching regulator (4) which regulates current to the lighting unit (2), wherein the switching regulator (4) is operable in a continuous and a discontinuous mode (CCM; DCM), characterized by a control unit (5) which is designed to activate and deactivate the continuous mode (CCM) of the switching regulator (4) depending on the illumination phase (Bp) of the lighting unit (2), wherein the control unit (5) activates the continuous mode (CCM) of the switching regulator (4) before switching on the lighting unit (2) and deactivates it after switching off the lighting unit (2), and wherein the control unit (5) activates the discontinuous mode (DCM) between two lighting phases (Bp) of the lighting unit (2).

2. The camera (1) according to any of the preceding claims, wherein the illumination phase (Bp) of the illumination unit (2) is represented by an envelope which lies in a range of microseconds to milliseconds and envelops light pulses lying in a range of nanoseconds.

3. The camera (1) according to any of the preceding claims, wherein the control unit (5) is intended to be integrated into the image sensor (3).

4. The camera (1) according to any of the preceding claims, wherein the control unit (5) is intended for controlling the illumination phases (Bp) of the illumination unit (2).