Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/14—Systems for two-way working
  • H04N7/141—Systems for two-way working between two video terminals, e.g. videophone
  • H04N7/142—Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/14—Systems for two-way working
  • H04N7/141—Systems for two-way working between two video terminals, e.g. videophone
  • H04N7/142—Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
  • H04N7/144—Constructional details of the terminal equipment, e.g. arrangements of the camera and the display camera and display on the same optical axis, e.g. optically multiplexing the camera and display for eye to eye contact
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Definitions

• the present invention relates to visual communication devices and, more particularly, to an apparatus and method for achieving "face-to-face” visual communication, including two-way visual communication.
• Picture phones have enhanced utility over conventional forms of communication because they transmit images, as well as sound, and they allow for visual transmission of nuances such as expressions and gestures. They also can be especially useful in group situations, since more than two people can communicate with each other at the same time, keep track of who is speaking, and watch and listen to the reactions and gestures of the others.
• a user at one end of the picture phone who is viewing on a television screen the visual image of a person at the other end of the picture phone, has his image captured at an angle by the camera.
• This skewed image is presented to the person at the other end of the picture phone, who is also viewing a counterpart television screen and likewise has his image captured at an angle.
• image display is accomplished by selectively controlling individual monochromatic liquid crystal pixels identified by cartesian coordinates. This is a complex and time consuming process which limits the frame rate and resolution of the image and, thus, the ability to display a high quality moving image without smearing, blurring or the image appearing to be in "slow motion.”
• communication devices of this type are inherently limited in their scalability, in view of technological limits on minimum pixel size and maximum display surface size.
• the problems, costs and driving times controlling the display surface tend to increase exponentially as the size of the display surface increases while the contrast ratio drops. Frequently, malfunction of a single pixel can render the entire display surface defective.
• display devices of this type are rigorously limited in size by cost and technological constraints.
• the monochromatic nature of LCD displays also is a significant drawback which, in addition to the problems noted above, detracts from a -realistic and natural looking image.
• the present invention is embodied in a visual communication apparatus that provides a realistic "face-to-face” visual effect with enhanced image display capability.
• the apparatus comprises a projection surface in the form of a screen which can be selectively alternated between a transmissive state and a diffuse state.
• a transmissive state a camera mounted behind the screen records images of a user on the other side of the screen.
• a projector also behind the screen, projects an image onto the projection surface.
• the visual communication apparatus can be arranged as either a single station to provide visual communication for the benefit of one or more users at one location, or it can be arranged as two separate stations positioned at remote locations to provide two-way visual communication between one or more users positioned at each station.
• the visual communication device of this invention is intended to be reliable in operation. simple to use, easy to manufacture and capable of being utilized in a wide variety of sizes. Additionally, video rate transmission is easily accommodated, and the device does not require signifi- cant maintenance.
• the visual communication apparatus When the visual communication apparatus is arranged as a single station, a user on one side of the screen has his visual image captured by a camera on the other side of the screen.
• the camera which may be a video camera, produces a video signal which is fed to a projector on the same side of the screen as the camera.
• Appropriate processing of the video signal enables synchronized shuttering of the camera and projector, and changing of the projection surface between the transmissive state and the diffuse state. In this way, the projector projects the user's image only when the projection surface is in the diffuse state, and the camera records his image only when the projection surface is in the transmissive state.
• synchronized shuttering of the camera and projector is accomplished by using a sync stripper coupled to the camera for receiving the video signals produced by the camera.
• the sync stripper produces a periodic vertical sync pulse and a plurality of horizontal sync pulses.
• Each vertical sync pulse is sent from the sync stripper to a shutter controller coupled to the projector shutter to control shuttering of the projector.
• Both the horizontal sync and vertical sync pulses are sent from the sync stripper to a projection surface controller, which produces a control voltage in response to those pulses. This control voltage then commands the projection surface. which is normally diffuse, to become transmissive or translucent.
• the projection surface of the screen comprises a material that may be commanded to change between the transmissive state and the diffuse state by a control voltage.
• the material also preferably is arranged as a single cell that may be commanded to change state as a whole in response to a single command.
• the projection surface of the screen comprises a Taliq brand panel.
• shuttering of the camera and projector is carried out using a mechanical shutter in the form of a substantially circular disk having a circular inner section and an annular outer section surrounding the inner section.
• Each of these inner and outer sections has a transmissive portion and an opaque portion arranged such that the inner section shutters the camera and the outer section shutters the projector during rotation of the disk.
• a motor also is provided for rotating the disk with a frequency corresponding to the frequency of vertical sync pulses derived from video signals of the camera.
• a phase detector and a phase comparator also may be employed to adjust the speed of rotation of the disk so that the disk rotates at the same frequency as the vertical sync pulse, to thereby synchronize shuttering of the projector and camera in relation to changing of the projection surface between the transmissive state and the diffuse state.
• the shutter can be an electrical shutter incorporated into the camera and projector, instead of using a mechanical shutter.
• the visual image of a first user at the first station is recorded by the camera when the projection surface there is in the transmissive state. This image is then transmitted to the projector at the second station for projection onto the projection surface of that screen while it is in the diffuse state.
• the visual image of a second user at the second station is recorded by the camera when the projection surface there is in the transmissive state, where it is then transmitted to the projector at the first station for projection onto the projection surface of that screen while it is in the diffuse state.
• the visual communication apparatus of this invention provides for a very realistic and natural looking communication.
• a "face-to-face" visual effect is accom ⁇ plished, since the user essentially is facing the camera and projector located on the opposite side of the screen.
• the front of the user's face is recorded by the camera while he views the face of either himself or others as projected by the projector.
• the quality of the projected image also is exceptionally high, since back projection techniques are used to project the image onto the projection surface of the screen when it is in the diffuse state.
• the frame rate of the image is controlled only by the projector itself, and the ability to project a moving image is not impeded by smearing, blurring or the image appearing to be in "slow motion," as is the case with prior art visual communication devices that attempt to simulate a "face-to-face” visual effect.
• the scalability of the screen utilized in the apparatus of this invention is quite large, since the projection surface preferably is arranged as a single cell that may be commanded to quickly change state, as a whole, in response to a single command.
• the ability of the apparatus to provide a color image, rather than a black and white image characteristic of the monochromatic screens of the prior art helps to further provide the most realistic and natural looking image possible.
• FIG. 1 is a diagrammatic view of a first embodiment of a visual communication apparatus embodying the novel features of the present invention
• FIG. 2 is a diagrammatic view of a second embodiment of the invention in the form of a two-way visual communication apparatus
• FIG. 3 is a graph showing the relative light transmissiveness of a screen used in the apparatus of this invention, in which the screen has a projection surface that can be controlled to change between a diffuse state and a transmissive state;
• FIG. 4 is a graph indicating the relative operation of certain components of the apparatus with respect to time
• FIG. 5 is a block diagram of a controller for controlling the screen and changing the projection surface between the transmissive and diffuse states; and FIG. 6 is an elevational view of a mechanical shutter for shuttering a camera and a projector used in the apparatus of this invention.
• the present invention is embodied in a visual communication apparatus, generally referred to by the reference numeral 10, for use in providing a "face- to-face" visual effect, with high quality image projection and capture.
• the visual communication device 10 can be arranged as either a single station to provide visual communication for the benefit of users at one location, as shown in FIG. 1, or it can be arranged at two separate stations positioned at remote locations to provide two-way visual communication between users positioned at each station, as shown in FIG. 2. In either embodiment, a realistic and natural looking image is projected for viewing by the users.
• FIG. 1 illustrates a first embodiment of the invention, in which the communication apparatus 10 is arranged as a single station.
• the apparatus comprises a screen 12 having a projection surface 14 which can be selectively alternated between a transmissive state 16 in which light passes through the projection surface and a diffuse state 18 in which an image 20 can be projected onto the surface.
• the projection surface 14 of the screen 12 comprises a material arranged as a single cell that may be commanded to change state as a whole in response to a single command.
• the material may comprise a liquid crystal or other appropriate trans-illumination controllable material capable of quickly changing between a transmissive state 16 and a diffuse state 18.
• the projection surface 14 comprises a Taliq brand panel available from Taliq Corporation of Sunnyvale, California. Whatever material is used for the projection surface 14, it should also be capable of functioning as a rear projection surface adapted to display a projected image.
• One important advantage of using a screen 12 having a projection surface 14 arranged as a single cell is that there are relatively few limitations on its scalability. With the projection surface 14 arranged as a single cell that may be commanded to quickly change state, as a whole, in response to a single command, there are no significant problems or costs in connection with controlling the screen size or its associated driving times. This represents quite an advance over the prior art display surfaces utilizing multiple pixels which are fraught with disadvantages and complexities. Alternatively, the projection surface may comprise multiple cells to form a very large screen 12, depending upon the particular application involved.
• the controllable nature of the projection surface 14 inherently results in transient states when the material is undergoing a change from the transmissive state 16 to the diffuse state 18. As shown in FIG. 3, the projection surface 14 will have certain light transmission characteristics with respect to time. Thus upon receiving a command to change state, the projection surface 14 first undergoes a transient period 22 as it changes from the diffuse state 18 to the transmissive state 16. Following this transition, there is a period 16 in which the projection surface has optimal transmissiveness (i.e., the full transmissive state 16) , followed by another transient period 24 as the screen changes from being totally transmissive to totally opaque again. All of this occurs quite rapidly, so these transient periods are not sensed by the user. Preferably, changes between the trans ⁇ missive state 16 and diffuse state 18 take place approximately sixty times per second.
• the user 26 (in this case a man) is located on one side in front of the screen 12.
• various components comprising the visual communication apparatus 10, including a camera 28 and a projector 30.
• the camera 28 records the actual image of the user 26 on the opposite side of the screen 12 while the projection surface 14 is in the transmissive state 16
• the projector 30 projects the user's visual image 20 onto the projection surface 14 while it is in the diffuse state 18.
• Any suitable camera or projector may be used, such as a conventional video camera or video projector.
• a Panasonic Model PV530 Camcorder and a Kodak LC500 projector with a custom 1500 watt xenon light source have been used and found to be satisfactory.
• the projector 30 preferably is on the same side of the screen 12 as the camera 28 for rear projection of images, good results also are possible when the projector is on the same side of the screen as the user 26 for front projection of images.
• shuttering of the camera 28 and projector 30 may be accomplished either electrically or mechanically. If done electrically, the camera 28 and projector 30 may each employ their own electrically operated shutter 32 and 34 incorporated directly into the camera and projector, respectively. Alternatively, one mechanical shutter 36 may be posi ⁇ tioned between the projector 30 and the projection surface 14, and another mechanical shutter (not shown) may be positioned between the camera 28 and the projection surface 14.
• one preferred form of the mechanical shutter 36 comprises a substantially circular disk 38 having an opaque sector 40 and a relatively larger transmissive sector 42.
• the opaque sector 40 occupies approximately a 30 degree portion of the 360 degree circular disk 38.
• the disk 38 is rotated by a motor 44 having an output shaft 46 connected to the center of the disk.
• the disk 38 may be constructed from any suitable transparent material, such as clear plastic, with the opaque sector 40 being appropriately blanked out so that it is non-transmissive.
• the motor 44 preferably is an electrically operated motor, such as Model 0576008 made by ElectroCraft.
• a single mechanical shutter 48 may shutter both the camera 28 and the projector 30, as described in more detail below in conjunction with FIG. 6.
• the shutter 36 must be synchronized with the projection surface 14 so that the projector 30 projects images only when the projection surface 14 is in the diffuse state 18 and the camera 28 records images only when the projection surface 14 is in the transmissive state 16.
• this synchronization is carried out using a sync stripper 50, a shutter controller 52, and a projection surface controller 54.
• the sync stripper 50 is coupled to the camera 28 for receiving video signals 56 produced by the camera.
• the video signals 56 produced by the camera 28 also are sent to the projector 30 for projecting the user's image 20 onto the projection surface 14 of the screen 12 in front of him.
• the sync stripper 50 produces and outputs a periodic vertical sync pulse 58 and a plurality of horizontal sync pulses 60.
• Any suitable sync stripper may be used, such as Model TSG170A by Tektronics.
• Each vertical sync pulse 58 is sent from the sync stripper 50 to the shutter controller 52.
• the shutter controller 52 then feeds a signal 62 to the motor 44 which rotates the shuttering disk 38 for shuttering the projector 30.
• This signal 62 controls the speed of the motor 44 and, thus, the speed of rotation of the shuttering disk 38.
• the shutter controller 52 can be configured to control shuttering of the camera 28 also, so that it records the user's actual image 26 only when the projection surface 14 is in the transmissive state 16.
• shuttering of the camera 28 is carried out using an electrically operated shutter 32 incorporated directly in the camera itself, and shuttering of the projector 30 is carried out using the mechanical shutter 36 described above.
• the sync stripper 50 also sends both the horizontal sync and vertical sync pulses 58 and 60 to the projection surface controller 54.
• the projection surface controller 54 produces a control voltage 64 in response to those pulses which then commands the projection surface 14 to change between the trans ⁇ missive state 16 and the diffuse state 18.
• the signal 56 which contains the video information for display is coupled not only to the projector 30 but also to the projection surface controller 54 for determining when the projection surface 14 should be diffuse.
• the video signal 56 is a standard video signal similar to an ordinary television signal. Each frame consists of 525 lines of video information and is refreshed approximately 60 times per second.
• the sync stripper 50 strips from the video signal 56 both the vertical sync pulses 58 (for which there are two per frame, each marking the beginning of each field of video information) and the horizontal sync pulses 60, which mark the beginning of each scan line of video information contained within each field.
• the vertical sync pulses 58 and the horizontal sync pulses 60 are both supplied to the projection surface controller 54, which controls the translucence of the projection surface 14.
• the projection surface controller 54 performs three tasks in providing a signal 64 for commanding the projection surface 14, which is normally diffuse, to become transmissive or translucent.
• the horizontal and vertical sync pulses 58 and 60 are utilized to determine the exact time with respect to the video signal 56 when the projection surface 14 should become transmissive.
• the vertical sync pulse 58 is supplied to the reset input 66 of a counter 68, with the horizontal sync pulses 60 fed to the counter's clock input 70.
• the counter 68 will count from 0 to approximately 275 before being reset.
• the numerical output 72 of the counter 68 is supplied to a comparator 74 which outputs a signal 76 when the counter 68 has reached a predetermined number, as determined by an input 78 from a 9 unit DIP switch package 80. Therefore, the comparator 74 will output a pulse 76 with the same frequency as the vertical sync pulse 58, but somewhat delayed in time in respect thereto.
• the projection surface controller 54 utilizes the comparator output 76 to determine the precise duration of time for which the projection surface 14 should be commanded to be transmissive.
• the comparator 74 supplies its output 76 to a down counter 82, and a second predetermined number 84 also is loaded into the down counter 82 from an 8 unit DIP switch package 86.
• the horizontal sync pulses 60 also are supplied to the clock input 88 of the down counter 82 and, thus, the down counter will decrement down for each horizontal sync pulse.
• the down counter output 90 will be zero for all times except when the down counter 82 is counting down from the second pre ⁇ determined number to zero, and it is this output 90 which represents the duration of time for which the projection surface 14 is to be transmissive.
• the projection surface controller 54 contains a high voltage driver section 92 which uses the down counter output 90 to drive the projection surface 14 at a higher voltage than is used for the projection surface controller circuitry just described.
• a high voltage driver section 92 which uses the down counter output 90 to drive the projection surface 14 at a higher voltage than is used for the projection surface controller circuitry just described.
• Teen skilled in electronics may easily select circuitry which is suitable for this task.
• FIG. 4 helps illustrate the timing as to when the projector 30 projects the user's visual image 20 and when the camera 28 records it.
• This image projection and capture is synchronized by a synchronization signal 94, shown as a horizontal counter signal or line trigger, which produces an inverted square pulse vertical sync or blanking signal 96 (delayed by about one millisecond) .
• the line trigger signal 94 commands the projection surface 14 (e.g., a Taliq panel) to become transmissive after a brief transient period 22 and is also used to trigger a video shutter 98 for shuttering the camera 28 and a light valve 100 for shuttering the projector 30.
• the projection surface 14 (Taliq panel) enters the diffuse state 18 and the light valve 100 is opened to allow image projection by the projector 30.
• the projection surface 14 enters the transmissive state 16 and the light valve 100 is closed and the video shutter 98 is opened to allow image capture by the camera 28. This cycle is repeated about 60 times per second.
• the video shutter 98 (mechanical or electrical) remains in an open state for approximately 1/1000 seconds, so that the user's actual image 26 is captured through the projection surface 14 when it is in the transmissive state 16.
• the period of time for image capture is on the order of 1.2 milliseconds. Otherwise, the video shutter 98 remains closed.
• the projection surface 14 is commanded to become diffuse by the upward edge 102 of the vertical sync signal 96 so that it may be used as a rear projection surface.
• the transient period 24 associated with this change between the transmissive state 16 and the diffuse state 18 is on the order of 6 milliseconds.
• Image projection then occurs upon the projection surface 14 while it is in the diffuse state 18 and the light valve 100 is open, as described above.
• each station comprises a screen 12 and 112 with a projection surface 14 and 114 adapted to change between a transmissive state 16 and a diffuse state 18.
• On one side of each screen 12 and 112 are essentially the same components described above in connection with the first embodiment of the visual communication apparatus 10.
• station one has a user 26 (in this case a man) located on one side in front of his screen 12.
• the various components comprising the visual communication apparatus 10, including the camera 28 and the projector 30.
• Station one also includes the other components described above in connection with the first embodiment of the visual communication apparatus 10, including the sync stripper 50, the shutter controller 52, the projection surface controller 54, the motor 44 and the shuttering disk 38.
• station two another user 126 (in this case a woman) is located one side in front of her screen 112 at that station. On the other side behind her screen 112 are a separate camera 128 and a projector 130. As with station one, station two also includes a sync stripper 150, a shutter controller 152, a projection surface controller 154, a motor 144 and a shuttering disk 138. It will be appreciated that the components behind the screens 12 and 112 at station one and station two in this second embodiment of the invention operate in substantially the same manner as the components behind the screen 12 in the first embodiment of the visual communication apparatus 10, described in detail above. Therefore, that description will not be repeated.
• the actual image of the man 26 at station one is recorded by the camera 28 at that station when the projection surface 14 there is in the transmissive state 16.
• the video signal 56 corresponding to this image 20 is then transmitted to the sync stripper 50 at station one for appropriate processing and for controlling shuttering of the projector 30 and changing of the projection surface 14 between the transmissive state 16 and the diffuse state 18.
• the video signal 56 also is sent to the projector 130 at station two for projection onto the projection surface 114 of that screen 112 while it is in the diffuse state 18.
• the actual image of the woman 126 at station two is recorded by the camera 128 at that station when the projection surface 114 there is in the transmissive state 16.
• the video signal 156 corresponding to her image 120 is then transmitted to the sync stripper 150 at station two for appropriate processing and for controlling the shuttering of the projector 130 and changing of the projection surface 114 between the transmissive state 16 and the diffuse state 18.
• the video signal 156 also is sent to the projector 30 at station one for projection onto the projection surface 14 of that screen 12 while it is in the diffuse state 18.
• the woman 126 at station two viewing her screen 112 sees the visual image 20 of the man 26 at station one.
• the man 26 perceives a face-to-face visual effect with the woman 126, while the woman 126 likewise perceives a face-to-face visual effect with the man 26.
• the video signals 56 and 156 from the camera 28 at station one and the camera 128 at station two may be broadcast by various known methods.
• the video signals 56 and 156 may be broadcast by cable, telephone or electromagnetic transmission means. The manner of doing this will be apparent to those skilled in the art.
• a shuttering disk 48 may be provided to shutter both the camera 28 and the projector 30 simultaneously.
• the shutter 48 comprises a substantially circular disk 160 having a circular inner section 162 and an annular outer section 164 surrounding the inner section.
• the inner section 162 has a transmissive sector 166 and a relatively larger opaque sector 168 for shuttering the camera 28.
• the annular section 164 has a transmissive segment 170 and a relatively smaller opaque segment 172 for shuttering the projector 30.
• the transmissive sector 166 of the circular inner section 162 and the opaque segment 172 of the annular outer section 164 are annularly aligned to form an arcuate sector 174 on the disk 160.
• the camera 28 will be shuttered by the opaque sector 168 when the projection surface 14 is in the diffuse state 18 and the projector 30 will be allowed to project the image 20 through the transmissive segment 170 of the disk 160.
• the projector 30 will be shuttered by the opaque segment 172 when the projection surface 14 is in the transmissive state 16, allowing the camera 28 to record the image of the user 26 through the transmissive sector 166 of the disk 160.
• a phase detector 176 and a phase comparator 178 are employed to adjust the speed of rotation of the disk 38 so that the disk rotates at the same frequency as the vertical sync pulse 58 produced from the video signal 56 by the sync stripper 50.
• the phase detector 176 is adapted to detect when the opaque sector 40 of the disk 38 is located in a predetermined location during rotation of the disk.
• the phase detector 176 includes a light source 180 on one side of the shuttering disk 38 and a photodetector 182 on the other side. Both the light source 180 and the photodetector 182 are positioned along a common optical axis that is substantially parallel to the axis of rotation of the disk 38 along the output shaft 46. With this arrangement, the phase detector 176 is adapted to sense the location of the opaque sector 40 during rotation of the disk 38.
• the phase comparator 178 is coupled to the phase detector 176, the motor 44 and the sync stripper 50.
• the phase comparator 178 compares the vertical sync pulse 58 from the sync stripper 50 with the location of the opaque sector 40 and, based on the comparison, adjusts the speed of rotation of the disk 38 so that it rotates at substantially the same frequency as the vertical sync pulse 58.
• a light 184 may be provided adjacent to the screen 12 for illuminating the user 26 and supplementing other conventional light sources (not shown) , such as ceiling lighting, desk lighting or other sources of light illuminating the user 26.
• the light 184 adjacent to the screen 12 is a periodic light source adapted to emit illumi- nation that is contemporaneous with the transmissive state 16 of the projection surface 14.
• the light 184 comprises fluorescent light tubes whose periodicity is controlled by the control voltage 64 produced by the projection surface controller 54.
• the visual communication apparatus 10 of this invention By synchronizing illumi ⁇ nation of the light 184 with the transmissive state 16 of the projection surface 14, optimal lighting conditions are available so that the camera 28 can record the user's image under the best possible lighting conditions.
• One very significant advantage of the visual communication apparatus 10 of this invention is the high quality of the projected image 20. Since the image 20 is back projected onto the projection surface 14 by the proj ctor 30, a very realistic and natural looking visual communication is provided. Because the frame rate of the image 20 is controlled only by the projector 30 itself, the apparatus 10 is quite capable of projecting a moving image 20 that has the same high quality as any other video image.
• the visual communication apparatus 10 of this invention provides a desired "face-to-face" visual effect, since the user 26 is essentially facing the camera 28 and projector 30 located on the opposite side of the screen 12.
• the front of the user's face is recorded by the camera 28, he views the face of either himself (in the case of a single station visual communication apparatus) or others at a remote location (in the case of a two station visual communication apparatus) , as projected by the projector 30.
• the single station visual communication apparatus will have various applications where it is necessary for the user 26 to view himself in either real time or delayed time situations.
• the apparatus 10 essentially functions as a mirror to allow the user to view himself.
• Possible applications will include medical applications in which the patient desires to see the anticipated results of cosmetic surgery, or fashion applications in which the user can try on different clothing without actually wearing the clothes.
• the apparatus is used as a two-way visual communication device, the applications are quite varied.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Transforming Electric Information Into Light Information (AREA)

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Citations (9)

• 1992
  • 1992-02-04 WO PCT/US1992/000883 patent/WO1992014338A1/en not_active Application Discontinuation
  • 1992-02-04 JP JP4505758A patent/JPH06508486A/ja active Pending
  • 1992-02-04 EP EP19920906295 patent/EP0570494A4/en not_active Withdrawn

Patent Citations (9)

Non-Patent Citations (2)

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