CAMERA

Abstract

In order to enable high image acquisition rate with simultaneous low energy consumption of a camera 1, a camera (1), in particular a 3D time-of-flight camera, is provided, comprising an illumination unit (2) which emits light pulses during an illumination phase (Bp), an image sensor (3) which generates images from the light pulses reflected by an object, a switching controller (4) which controls current to the illumination unit (2), the switching controller (4) being operable in a continuous and a discontinuous mode (CCM; DCM), and a control unit (5) which is designed to activate and deactivate the continuous mode (CCM) of the switching controller (4) as a function of the illumination phase (Bp) of the illumination unit (2).

Claims

1. Camera (1), in particular 3D time-of-flight camera, with an illumination unit (2) that emits light pulses during an illumination phase (Bp), an image sensor (3) that generates images from the light pulses reflected from an object, a switching controller (4) that controls current to the illumination unit (2), the switching controller (4) being operable in a continuous and a discontinuous mode (CCM; DCM), and a control unit (5) designed to activate and deactivate the continuous mode (CCM) of the switching controller (4) as a function of the illumination phase (Bp) of the illumination unit (2).

2. Camera (1) according to claim 1, wherein the control unit (5) activates the continuous mode (CCM) of the switching controller (4) before a switch-on of the illumination unit (2) and deactivates it after a switch-off of the illumination unit (2).

3. Camera (1) according to claim 1, wherein the control unit (5) activates the discontinuous mode (DCM) between two illumination phases (Bp) of the illumination unit (2).

4. Camera (1) according to claim 1, wherein the illumination phase (Bp) of the illumination unit (2) is represented by an envelope curve that ranges from microseconds to milliseconds and envelopes light pulses lying in a range of nanoseconds.

5. Camera (1) according to claim 1, wherein the control unit (5) is integrated in the image sensor (3).

6. Camera (1) according to claim 1, wherein the control unit (5) is provided for controlling the illumination phases (Bp) of the illumination unit (2).

Description

[0020] The invention is also explained in more detail below with respect to further features and advantages by way of example with reference to embodiments and with reference to the accompanying drawing. The figures of the drawing show in:

[0021] FIG. 1 a schematic representation of a preferred embodiment of a circuit diagram of a camera according to the invention, and

[0022] FIG. 2 a schematic representation of an operating sequence of the camera according to the invention over time.

[0023] FIG. 1 shows a schematic representation of a preferred embodiment of a circuit diagram of a camera 1 according to the invention, which comprises in particular a 3D time-of-flight camera in which a TOF detection method is used.

[0024] The camera 1 comprises an illumination unit 2, which is provided to emit light pulses for illuminating a monitoring area during an illumination phase Bp (shown in FIG. 2). Furthermore, an image sensor 3 is provided which generates images from the light pulses reflected from an object not shown. The images represent in particular a 3D image, a distance image or a depth map.

[0025] Furthermore, the camera 1 comprises a switching controller 4 that controls current to the illumination unit 2, wherein the switching controller 4 is operable in a continuous mode, referred to as CCM, or a discontinuous mode, referred to as DCM. That is, the switching controller 4 is configured to be switchable between the continuous mode CCM and the discontinuous mode DCM and vice versa.

[0026] According to the invention, the camera 1 comprises a control unit 5 configured to activate and deactivate the continuous mode CCM of the switching controller 4 depending on the illumination phase Bp of the illumination unit 2. By activating the continuous mode CCM of the switching controller 4, in particular immediately before a start of the illumination phase Bp of the illumination unit 2, the switching controller 4 is able to provide the full current to the illumination unit 2 for the illumination phase Bp.

[0027] Deactivating the continuous mode CCM or activating the discontinuous mode DCM of the switching controller 4 after the illumination phase Bp of the illumination unit 2 prevents high power dissipation in the switching controller 4, since the current provided by the discontinuous mode DCM may be sufficient for the image sensor 3 to evaluate the acquired image data, for example.

[0028] In addition, switching internally of the switching controller 4 between these two modes CCM and DCM allows a supply voltage Vin applied to the switching controller 4 to be unaffected.

[0029] As shown in FIG. 1, the switching controller 4 can also be provided to regulate current to the image sensor 3. This allows the control unit 5 to regulate the current to the illumination unit 2 and to the image sensor 3 more easily via the switching controller 4. However, such a design is not mandatory, since current control of the image sensor 3 independently of the switching controller 4 can also be advantageous.

[0030] As shown in FIG. 2, an operational sequence of the camera 1 or the switching controller 4 of the camera 1 runs over time t as follows:

[0031] When the supply voltage Vin is applied, the switching controller 4 is in the discontinuous mode DCM. Before the start of the illumination phase Bp of the illumination unit 2, the control unit 5 of the camera 1 switches the switching controller 4 to the continuous mode CCM, so that at the start of the illumination phase Bp of the illumination unit 2, the full current is available for the illumination unit 2 in order to ensure sufficient and stable illumination for a capture of the images by the image sensor 3.

[0032] After the end of the illumination phase Bp of the illumination unit 2, the control unit 5 deactivates the continuous mode CCM of the switching controller 4 and switches the switching controller 4 to the discontinuous mode DCM. As a result, no full amount of current is present in the switching controller 4, so that power dissipation can be avoided.

[0033] Further, the current provided by the discontinuous mode DCM may be sufficient for the image sensor 3 to process and analyze the captured image data, thereby avoiding an image capture delay. Avoiding the delay in image acquisition enables an improvement in the efficiency of the camera 1.

[0034] Between two illumination phase Bp of the illumination unit 2, the switching controller 4 is in the discontinuous mode DCM, so that the power dissipation of the switching controller 4 can be significantly reduced, since this intermediate phase is much longer than the illumination phase Bp, which is preferably represented by an envelope curve ranging from microseconds to milliseconds, e.g. 500 μs, and enveloping light pulses lying in a range of nanoseconds, e.g. 3 ns.

[0035] As soon as the control unit 5 activates the illumination unit 2 again directly or (as shown) indirectly via the image sensor 3 in order to restart the illumination phase Bp, the control unit 5 activates the continuous mode CCM of the switching controller 4, so that the switching controller 4 again switches to the continuous mode CCM and deactivates the discontinuous mode DCM.

[0036] The illumination unit 2 thus receives the full current to emit the light pulse(s) with the start of the illumination phase Bp. The switching controller 4 thus has no dead time, so that the efficiency of the camera 1 is further improved.

LIST OF REFERENCE SIGNS

[0037] 1 Camera

[0038] 2 Lighting unit

[0039] 3 Image sensor

[0040] 4 Switching controller

[0041] 5 Control unit

[0042] Bp Lighting phase

[0043] DCM discontinuous mode

[0044] CCM continuous mode

[0045] T Time

[0046] Vin Supply voltage