Patent Application
20150355707
The invention relates to sensor assemblies that are used for the optically-supported detection of operator gestures or operator activities in motor vehicles.
In particular, the invention relates to sensor assemblies that can detect and evaluate information resolved in time and space in order to discern the operating intent of the user.
Optical methods are known in the prior art that discern actuations in reaction to an evaluation of image information and subsequently trigger e.g. switching procedures. For example, this includes automated video evaluations of monitoring systems that read out patterns or movements from individual images, or a sequence of images. Furthermore, numerous other optically-supported systems are known, light barriers or brightness sensor being among the most basic. However, optical systems of greater complexity frequently use an array of optically-sensitive detection units, generally termed pixels, that record optical information in parallel, for example in the form of a CCD array.
DE 10 2008 025 669 A1 discloses an optical sensor that detects a gesture, and a closing element of a vehicle is then automatically moved.
WO 2008/116699 A2 addresses an optical sensor chip and relates to an optical anti-pinch sensor device to monitor a window pane, sliding door, or a tailgate in a motor vehicle.
WO 2012/084222 A1 discloses an optical sensor for actuating and monitoring a closing element.
Since gesture control is gaining ever greater acceptance in various technical fields, attempts were also made to use such exclusively optical systems to discern operator intent in motor vehicles. With these systems, the detection of operations by means of capacitive systems still predominates.
DE 10 2011 089 195 A1 discloses a system for the contact-free detection of objects and operator gestures with an optically-supported device of a similar kind which can also be used for the invention. However, such systems are demanding in regard to energy consumption; continuous monitoring of access control in the vehicle's surroundings is problematic given the energy requirement.
The object of the invention is to provide an optically-supported and energy-optimized system for controlling operation in access systems for vehicles.
The object is achieved with a device having the characteristics of claim 1.
The system according to the invention uses optical detection, although not exclusively image detection. A pixel array is used with a timed activation which permits distance detection and can detect object movement by analyzing the distance information over time. Detection devices are known that detect pixel-related location information, in particular a distance from the sensor or detection device. These systems are for example designated “Time-of-Flight” systems or also “3D imagers” or “range imagers”, depending on the evaluation method used. The areas of application of such systems are in the field of industrial automation, safety engineering and the automotive sector. In an automobile, 3-D sensors are used in lane assist systems, for pedestrian protection or as parking assistance. Such concepts of triangulation as well as interferometry and Time-of-Flight (ToF) measurement can be implemented with optical sensors.
The system according to the invention has an array of light-sensitive pixels as well as a light source. The light source is arranged in the area of the array of sensitive pixels, for example at a slight distance from the array. A control circuit controls both the operation of the light source as well as the operation of the pixel array.
In this context, reference is made to developments thereof that describe the technical concepts and their realization in detail, in particular in the dissertation “Photodetektoren and Auslesekonzepte für 3D-Time-of-Flight-Bildsensoren in 0.35 μm-Standard-CMOS-Technologie” [Photodetectors and readout concepts for 3-D Time-of-Flight image sensors in 0.35 standard CMOS technology], Andreas Spickermann, Faculty of Engineering Sciences at the University of Duisburg-Essen, 2010.
Furthermore, reference is made to the publication “Optimized Distance Measurement with 3D-CMOS Image Sensor and Real-Time Processing of the 3D Data for Applications in Automotive and Safety Engineering”, Bernhard Konig, Faculty of Engineering Sciences at the University of Duisburg-Essen, 2008.
The above works describe the concept and realization of useful optical sensor systems; reference is therefore made in this application to their disclosure, and they will only be explained to clarify those aspects relevant to understanding the application.
The invention relates to a sensor array that uses the Time-of-Flight (ToF) method which will therefore be briefly explained at this juncture.
In the ToF method, a space is illuminated with a light source, and the propagation time of the light reflected by an object in the space is recorded by a surface sensor. The light source and sensor should be arranged as close to each other as possible. The distance between the sensor and object can be determined from the linear relationship of the light propagation time and speed of light. To measure the time delay, synchronization must exist between the light source and sensor. The methods can be optimized by using pulsed light sources since short light pulses (in the ns range) enable efficient suppression of background light. In addition, by using pulsed light, potential ambiguities are avoided in determining the distance as long as the distance is sufficiently large.
On the one hand, the light source is operated in a pulsed manner in this approach. On the other hand, the detection unit, i.e., the pixel array, is configured to be pulse-sensitive, i.e., the integration of the individual pixels is synchronized in time with the light source, and the duration of integration is limited. By comparing the results with different integration times, the effects of background light in particular can be calculated out.
It is pertinent that this detection method is not an image-based detection method. Each pixel determines distance information which occurs by detecting light over time. When a pixel array is used, a matrix of distance values exists that permits object movements to be interpreted and tracked during cyclical detection.
According to the invention, a distinction is drawn between different operating modes of the detection device. Groups of pixels are formed that can be activated for detection separately by the control device.
When a subgroup of the pixels is activated while simultaneously deactivating the other pixels, energy savings occurs.
According to the invention, the individual pixels of the array are combined into different groups, and one of the groups for example comprises all the pixels, and a second group can comprise only a part of the pixels. When to switch to a specific mode is determined from the evaluation of the pixel signals. This approach is termed the activation scheme in the context of this application. An activation scheme can hence comprise pixel selection and the associated control parameters (such as the time parameters).
If only a subgroup of the pixels is operated, they are activated and evaluated in the envisioned manner to determine the distance values of each of the individual pixels. The subset of pixels can be activated differently, especially with different time parameters, than activating when all the pixels are operated. If for example in a rectangular pixel arrangement on a pixel array only the group of pixels located at the outer edge is activated, this is sufficient to detect an approach of a user into the detection area of the sensor arrangement. Although the precision of this detection is not equivalent to detection with the entire number of pixels, that is unnecessary however since all the pixels are activated if improvement is needed.
If for example the aforementioned pixel frame is kept active in sleep mode, detection with this pixel frame can occur at greater intervals than inactive mode, and a rougher evaluation occurs of whether a potential approach by a user exists. If this is the case, the sensor arrangement is transferred into a different operating mode—active mode—in which a different pixel group such as all the pixels is activated and evaluated. The frequency at which the evaluation occurs can also be different in the different operating modes.
As already mentioned above, the pixel groups can have overlaps, and one pixel group can entirely encompass another pixel group.
An evaluation scheme always belongs to each of the activation schemes. The evaluation scheme can be adapted in regard to the activation scheme.
If such a sensor arrangement is used in a vehicle to monitor the exterior and to control entrance into a vehicle, the activation of a subset of the pixels is sufficient to determine at least the approach of a user. If the user is within this region, this is detected by characteristic signal changes in the distance values in a majority of the pixels. Precise gesture recognition is not possible with the reduced resolution of the pixel array in sleep mode; this is however also not necessary. The general recognition of a user's approach leads to a change in activation by the control device such that a different pixel group, possibly the pixel group comprising the first pixel group, is activated. The gestures of movement can be detected with increased resolution.
In a preferred embodiment of the invention, the pixels lying in the outer regions, such as the edge of the pixel array, are activated as the first group by a pixel array. By means of this measure, the spatial extent and difference between the signals with a simultaneously reduced number of pixels is optimally exploited.
In another embodiment of the invention, the query frequency in the operating mode with the first pixel group, sleep mode, is reduced relative to the query frequency at which the expanded pixel group is operated for gesture recognition in active mode. According to the invention, it is sufficient if the detection of the approach of a user is checked with less frequency than the fine resolution detection of user gestures.
The selected pixel groups on the sensor array can also be arranged in a manner that varies over time. For example, one fourth of the sensor surface can be alternately queried cyclically such that the number of pixels is basically the same during each query in low-power mode; however, not always the same pixels are used for this power-saving query. In the aforementioned example when one fourth of the pixels are used, the sectors of fourths can for example be varied cyclically so that each pixel is only activated during each fourth query.
It is pertinent that by activating a pixel subgroup of the array, the sensor itself is operated in a different operating mode as a low-power activation sensor. This procedure according to the invention has structural advantages in comparison to the use of a separate activation sensor since fewer components are required.
According to the invention, the detection which occurred in power saving mode, even if it is a first, rough detection, can also be used for the subsequent, fine resolution detection of gestures.
The invention will now be explained in more detail using an exemplary embodiment.
As shown in
The device 2 has a light source 10 which is formed in this example by a laser diode 11 and an expanding lens system 12. The lens system 12 expands the beam cross-section to form a wide detection area 3 which a user 4 can enter and in which he can perform gestures. This can be for example a simple plastic lens system such as a Fresnel lens.
A detection array 20 is arranged adjacent to the light source aligned with the sensitive region facing the detection region 3. The array 20 contains columns and lines of sensitive pixels and is configured in this example as a CCD array. Both the light source 10 as well as the array 20 are coupled to a control device 30 which enables clocked and time-controlled operation of the light source and the detection device. If the light source is activated to transmit a light pulse and the pixel array is activated to detect, the individual pixels integrate the incident light energy. The charges of each pixel which are then available after integration are evaluated in the control device such that a detection value characteristic of the integration time period is generated for each pixel.
By means of this scheduled and synchronized activation of both the light source 10 as well as the detection device 20, detection of the light propagation time and hence distance detection is possible for each pixel of the detection device 20. In regard to the precise functions, reference is made to the subject matter disclosed in the aforementioned publications, especially the known Time-of-Flight devices.
In an example,
The control and evaluation device 30 records the contact information and recalculates it in an array of distance information. A 3-D map of the surroundings can be generated thereby. 3-D information of spatial changes and object movements within the detection region 3 can be detected by means of a temporal sequence of manual controls. For example, the swinging of a hand of a user 4 can be detected. The control device 30, and the entire detection device 2 through the control device 30, is coupled to a central control device 50 of the motor vehicle. Gestures can be recognized by means of a library in the control and evaluation device 30, or a temporal sequence of 3-D spatial data is fed to the central control device 50 to be evaluated there. The central control 50 then initiates the triggering of the function of the motor vehicle depending on the detected data, such as the lowering of a side window or the opening of a door.
As shown in
Alternately, much simpler evaluation schemes can also be used. For example, the signal change over time which indicates the approach of any object can be used to switch to active mode. One simple option is also to use the average of the signals of the active pixels, and then use a change over time and values around a threshold within a given period as a trigger.
In the event that detection with a reduced number of pixels according to the activation scheme of the pixels in
If no gesture control is detected within a certain time window and if the object leaves the detection range, the device returns to the first detection mode in which power consumption is reduced.
It is pertinent for the activation query to occur by means of the same sensor field as the actual sensitive and detail-rich subsequent evaluation.
The switch between operating modes is performed by the control device 30 using the detected information. However, the control device 30 can also be supplied with a signal from the central vehicle device 50 that indicates the change in other vehicle parameters. For example, all of the sensors can be activated for a specific period when a remote control transmitter is actuated by a user. Furthermore in the event that for example the vehicle is locked up, there can be an intentional switch to power-saving mode.
Apart from that, the activation schemes shown in
It is pertinent to the invention that the pixel fields of a 3-D detection device for access to a vehicle can be activated in groups that enable a low-power mode for detection and activation recognition.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 100 521.7 | Jan 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/050106 | 1/7/2014 | WO | 00 |
