Patent Application
20200150249
The technical field relates generally to lidar sensors and particularly to flash lidar sensors.
Flash lidar sensors generate a pulse of light, typically with a laser. The light may reflect off one or more objects and be sensed by a plurality of light sensitive detectors (e.g., an array of photodetectors), typically referred to as a focal plane array. By using the position of the photodetectors that are illuminated and the elapsed time since the pulse of light was generated, it is possible to determine dimensions and distance information of the one or more objects.
One difficulty is that when one or more detectors are subject to a very strong light return, crosstalk may occur due to internal electrical effects of the focal plane array. This crosstalk may affect neighboring detectors, and their associated pixels, by blinding them in a way that signals of lower intensity may be overlooked.
As such, it is desirable to present a sensor assembly and method in which such crosstalk is reduced or eliminated. In addition, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.
In one exemplary embodiment a lidar sensor assembly includes a light source to generate light. An optic is in optical communication with the light source to generate a field of illumination of the light. A focal plane array is configured to receive light reflected off one or more objects. The lidar sensor assembly also includes an attenuating element configured to selectively attenuate at least a portion of the light.
In one exemplary embodiment a method of operating a lidar sensor assembly includes generating light with a light source. The method also includes generating a field of illumination of the light with an optic in optical communication with the light source. The method further includes receiving light reflected off one or more objects with a focal plane array configured. The method also includes selectively attenuating at least a portion of the light with an attenuating element.
Other advantages of the disclosed subject matter will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a lidar sensor assembly 100 is shown and described herein. As appreciated by those skilled in the art, the term “lidar” is an abbreviation for “light detection and ranging”. The term is often used interchangeably with “ladar” by those skilled in the art.
The lidar sensor assembly 100 includes a light source 102 to generate light. In the exemplary embodiments, the light source 102 is a laser (not separately numbered). The laser of the exemplary embodiments is configured to generate pulses of light, i.e., a pulsed laser light output, where the laser turns “on” and “off” for predetermined lengths of time.
The laser may be a solid-state laser, monoblock laser, semiconductor laser, fiber laser, and/or an array of semiconductor lasers. It may also employ more than one individual laser. The pulsed laser light output, in the exemplary embodiment, has a wavelength in the infrared range. More particularly, the pulsed laser light output has a wavelength of about 1064 nanometers (nm). However, it should be appreciated that other wavelengths of light may be produced instead of and/or in addition to the 1064 nm light. The lidar sensor assembly 100 also includes one or more optics 104, 105, e.g., lenses, optically coupled with the light source 102. In the exemplary embodiment, a first optic 104 is a collimator or beam expander configured to transform the light source to shape light distribution.
A second optic 105 may also be utilized to further distribute the light. The second optic 105 may be implemented with a microlens array to create an array of independent sources, hence providing homogeneity and eye safety. The second optic 105 may alternatively be implemented with a macroscopic lens where homogeneity is achieved within or before the LCD.
Still referring to
The light sensitive detectors of the focal plane array 107 are configured to receive light reflected off one or more objects 108. Each detector generates an electrical signal corresponding to the received reflected light, as is well known to those skilled in the art. A receiving lens 109 may be configured and disposed to receive light prior to the focal plane array 107. In the exemplary embodiment shown in
As described above, one or more of the detectors may be illuminated by a very strong light return, as is shown in two instances on
Referring again to
In the exemplary embodiment, the controller 110 is in communication with the light source 102 and is configured to control operation of the light source. That is, the controller 110 commands the light source 102 as to when to illuminate, the length of such illuminations, etc. Furthermore, the light source 102 may provide data back to the controller 110.
The controller 110 of the illustrated embodiment is also in communication with the focal plane array 107. The controller 110 may include an analog-to-digital converter (“ADC”) (not shown) to convert the electrical signals from the focal plane array 107 to digital and/or numerical form, as appreciated by those skilled in the art. Image data is transmitted from the focal plane array 107 to the controller 110. Of course, other data may be transferred between the focal plane array 107 and the controller 110.
The controller 110 is configured to determine a highly illuminated area of the focal plane array 107. That is, the controller 110 may analyze the image data received from the focal plane array 107 and determine the particular pixel 300 or pixels 300 where light reflected from an object 108 exhibits a high intensity that can result in “crosstalk” between pixels 300, as shown in
Still referring to
In the embodiment shown in
A polarizer 200, as shown in
The pixels of the LCD 112 are selectable between a generally transparent state where light may be freely transmitted therethrough, and an opaque state, where the pixels reduce or block the transmission of light.
The controller 110 is in communication with the attenuating element 111. Further, the controller 110 is configured to control the attenuating element 111 based on data received from the focal plane array 107. Particularly, the controller 110 is configured to control the attenuating element 111 to selectively attenuate at least a portion of the light corresponding to the highly illuminated area of the focal plane array 107.
For example, in response to one or more detectors of the focal plane array 107 being subject to a high level of illumination, the controller 110 may instruct corresponding pixels of the LCD 112 to darken, i.e., become opaque. This will darken a region 114 in the field of illumination 106, thus lessening the level of illumination that is reflected back to the focal plane array 107. As such, crosstalk in the focal plane array 107 is reduced and other objects 108 in the field of view, if present, may be adequately detected.
It should be appreciated that the term “high level of illumination” may refer to energy levels that would cause saturation of photo elements in the focal plane array 107 which can cause an incorrect intensity reading, e.g., the signal is out of the valid input range, and cause artifacts in other pixels of the focal plane array 107 as the pixels share common circuitry (e.g., a power supply) and crosstalk (i.e., electrical coupling) can occur.
In this embodiment, the attenuating element 111 is a digital mirror device (“DMD”) 400. The DMD 400 may alternately be referred to as a digital micromirror device. The DMD 400 in this embodiment is a micro-opto-electromechanical system (“MOEMS”) having a plurality of microscopic mirrors (not shown) arranged in a rectangular array. The mirrors may be individually rotated to an “on” or “off” state. That is, each mirror may direct light toward the focal plane array 107 or away from the focal plane array 107. The mirrors of the DMD 400 may correspond to the detectors (or pixels) of the focal plane array 107.
In the embodiment shown in
In response to one or more detectors of the focal plane array 107 being subject to a high level of illumination, the controller 110 may instruct corresponding mirrors of the DMD 400 to not direct light towards said detectors. This will lessen the level of light that is reflected back to the focal plane array 107 when a high level of illumination exists. As such, crosstalk in the focal plane array 107 is reduced and other objects 108 in the field of view, if present, may be adequately detected.
It should be appreciated that, in other embodiments, the DMD 400 may be disposed in the transmit path, e.g., between the laser source 102 and the optics 105.
A method 500 of operating a lidar sensor assembly 100 is shown in
The method 500 may also include, at 508, determining a highly illuminated area of the focal plane array 107 with a controller 110. The controller 110 then determines which, if any, of the detectors of the focal plane array 107 are being subjected to a high level of illumination. In response to one or more of the detectors being subjected to a high level of illumination, the method 500 may include, at 510 selectively attenuating at least a portion of the light with an attenuating element 111.
The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.
