Patent Publication Number: US-9843762-B2

Title: Image display system for calibrating a sound projector

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to an image display system and an associated optical instrument for calibrating a sound projector. 
     Description of the Related Art 
     U.S. Pat. No. 8,274,611 discloses the use of an image display system for calibration of a sound projector. 
     Such U.S. Pat. No. 8,274,611 discloses, referring to FIGS. 8 and 9, that automatic calibration of the sound projector is achieved by providing the image display system with a television and a microphone. Particularly, the microphone is described as being embodied by a standalone device or adapted to be integrated in a control unit external to the television. 
     Such U.S. Pat. No. 8,274,611 also discloses that the microphone can be coupled over wire or by IR connection to the image display system. The microphone is designed to capture the average sound levels emitted by the sound projector and send them back to the television which uses them via special firmware to calibrate the emission of sounds by the sound projector. 
     Here, the microphone is usually placed in an area of the room in which the television and the sound projector are located. The microphone should be placed in one of the so-called “hot spots” of the room, i.e., in one of the areas in which the sound signals generated by the sound projector have the maximum sound pressure. Thus, the microphone will detect the “most significant” signals to be used for calibration of the sound projector, for the latter to emit signals that will spread out in the room with even distributions throughout the frequency spectrum. 
     Nevertheless, the user does not know where such hot spots are in the room, as their position is dependent on the geometry of the room. Therefore, the user shall empirically select the microphone position, which will usually not coincide with the location in which he/she watches the television screen. 
     This involves an apparent drawback, which will result in an less than optimal calibration of the sound projector. 
     Therefore, the need is felt for optimized calibration of the sound projector according to the location in which the user wants to watch the television. 
     BRIEF SUMMARY 
     One embodiment of the present disclosure is to provide an image display system and an associated optical instrument, that can obviate the above mentioned drawbacks of the described prior art. 
     One embodiment of the present disclosure includes a user-wearable optical instrument. 
     In one embodiment, the optical instrument comprises a frame and a pair of lenses, detection sensors and transmission devices, where the detection sensors are designed to receive at their input an audio signal having a frequency falling in a 20-20 kHz frequency band and to output a processed signal, and the transmission devices are designed to receive at their input the processed signal, and to output a calibration signal adapted to calibrate a sound projector. 
     Another embodiment of the present disclosure is an image display system, that comprises a television having a screen, a sound projector, a control unit in signal communication with the television screen and the sound projector, the control unit being configured for the sound projector to project one or more audible sound signals into a room and an optical instrument having a frame and a pair of lenses, detection sensors and transmission devices, where the detection sensors are designed to receive at their input an audio signal having a frequency falling in a 20-20 kHz frequency band and to output a processed signal, and the transmission devices are designed to receive at their input the processed signal, and to output a calibration signal, the control unit calibrating the sound projector according to the calibration signal. 
     Therefore, one embodiment provides an image display system and an associated optical instrument that can calibrate a sound projector according to the television-watching position of a user, by having the user wear the optical instrument. 
     Also, with the use of televisions having a technology that allows transmission of two distinct image streams (i.e., the so-called picture-in-picture or PIP feature, which is implemented, for instance in Blue-Ray and/or HD DVD specifications) and/or one stereoscopic image stream (i.e., a stream of three-dimensional images or in short 3D televisions), one embodiment can use a sound projector to project an audio signal for each image stream displayed on the television screen, so that the combination of the image stream and the audio signal is targeted to a particular optical instrument, and that optical instrument can calibrate the emission of audio signals from the sound projector. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The characteristics and advantages of the present disclosure will appear from the following detailed description of a practical embodiment, illustrated as a non-limiting example in the set of drawings, in which: 
         FIG. 1  shows a principle block diagram of the display system according to the present disclosure; 
         FIG. 2  shows a possible way of use of the display system according to of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Although this is not expressly shown, the individual features described with reference to each embodiment shall be intended as auxiliary and/or interchangeable with other features, as described with reference to other embodiments. 
     It shall be noted that, as used herein, the term image designates an individual static frame, whereas the term image stream designates a sequence of frames that can create a video flow, i.e., the images displayed on a television screen. 
     Referring to the accompanying figures, numeral  1  designates an image display system that can be placed in a viewing environment, such as a room. 
     The display system  1  comprises:
         a television  2 , having a screen, such as a screen with a LED, PLASMA or CRT technology,   a sound projector  3 ,   a control unit  4  in signal communication with the television screen  2  and the sound projector  3 , for controlling the operation of the television  2  and the sound projector  3 , through special firmware.       

     In one aspect, the television  2  is configured to display one image stream V 1  and preferably also a second image stream V 2 . 
     For example, the television  2  is configured to display one image stream V 1 , or is configured to display a first image stream V 1 , such as a sports event, and at the same time an additional image stream V 2 , that may be different from such first image stream V 1 , or the television  2  is a 3D television that can display two stereoscopic image streams V 1 , V 2 . 
     The sound projector  3  is configured to project one or preferably two audio signals S 1 , S 2 . Such signals S 1  and/or S 2  are preferably of digital type. In one aspect, the signals S 1  and/or S 2  have a frequency falling in the 20-20 kHz frequency band. In other words, the signals S 1 , S 2  fall in the audible frequency bands. 
     It shall be noted that the number of audio signals that can be emitted by the sound projector  3  is preferably equal to the number of image streams V 1 , V 2  that can be displayed on the screen of the television  2 . 
     The sound projector  3  may be arranged to be external to or preferably integrated in the television  2 . 
     In one aspect, the sound projector  3  is manufactured with MEMS technology. 
     It shall be noted that, a sound projector manufactured with MEMS technology will be a device with improved performances as compared with a conventional loudspeaker. 
     Since current sound projection techniques are based on DSP, in conventional sound diffusion systems each element shall be controlled by a DAC. However, when the sound projector  3  is implemented with MEMS technology, digital to analog conversion D/A can be avoided, which will afford undoubted technical and economic advantages. 
     Furthermore, MEMS control of the sound projector  3  is directly provided on the individual MEMS elements, which will make it more efficient than conventional loudspeakers. 
     It shall be further noted that the sound projector  3  implemented with MEMS technology is free of the typical problem of saturation of a conventional loudspeaker membrane, and the sound projector  3  implemented with MEMS technology is not subject to clipping, because it is directly controlled by the driver. 
     Also, the sound projector  3  manufactured with MEMS technology has a lower harmonic distortion than a conventional membrane loudspeaker, which is also due to controlled saturation. 
     It shall be further noted that the number of components of the array of the sound projector  3  implemented with MEMS technology is definitely higher than in a conventional loudspeaker, and this characteristic improves the effectiveness of sound directivity. 
     Finally, the sound projector  3  implemented with MEMS technology is thinner, and can be directly integrated in the television  2 , even in case of a flat-screen television. 
     In one aspect, the control unit  4  is configured to manage the television  2  and the sound projector  3 , i.e., to ensure that an image stream V 1 , V 2  has a respective audio signal S 1 , S 2  associated therewith. 
     Therefore, the sound projector  3  emits an audio signal for each respective image stream; for example, the audio signal S 1  is emitted for the image stream V 1  and the audio signal S 2  is emitted for the image flow V 2 . 
     The control unit  4  may be arranged to be external or, preferably, internal to the casing of the television  2 . 
     Still referring to  FIG. 1 , it shall be noted that the audio signals S 2 , S 2  spread out in the room in which the television  2 , the sound projector  3  and the control unit  4  are located, to a plurality of paths. 
     In one aspect, the display system  1  comprises at least one optical instrument  5 , which will be described below with particular reference to the components of the present disclosure. 
     The optical instrument comprises a frame  5 A and a pair of lenses  10 , with the frame  5 A being adapted to support the pair of lenses  10 , see  FIG. 2 . 
     One embodiment of the optical instrument comprises detection sensors  6  and transmission devices  7 , wherein:
         the detection sensors  6  are designed to detect or receive at their input the audio signal S 1  or S 2 , e.g., generated by the sound projector  3 , such audio signal S 1  or S 2  having a frequency falling in a 20-20 kHz frequency band, preferably in the audible frequency band, and to output a processed signal S 3 ,   the transmission devices  7  are designed to receive the detected signal S 3  and to output a calibration signal S 4 .       

     For this purpose:
         the detection sensors  6  of the optical instrument  5  include a microphone  6 A which is preferably manufactured with MEMS technology;   the transmission system  7  comprises an advanced microphone processor  22  and a radio-frequency transmitter device  12 .       

     In one aspect, the implementation of the microphone  6 A with MEMS technology allows calibration of the system  1  and hence of the intensity information for the sound S 1 , S 2  captured thereby, which has to be transmitted to the sound projector  3  via the transmission devices  7 . 
     It shall be noted that, if the microphone  6 A had an analog implementation, the output signal emitted from such analog microphone would be necessarily converted for transmission. 
     In one aspect, the implementation of the microphone  6 A with MEMS technology allows the output signal S 3  to be readily available in digital format, such that A/D conversion can be avoided. 
     Due to this feature, the output signal S 3  is also immune from electromagnetic interference EM, which is a critical specification in a system integrating radio-frequency transmission devices  7 . 
     In one aspect, the microphone  6 A implemented with MEMS technology has a flat response throughout the 20-20 kHz band, and hence does not introduce sound intensity measurement errors in the signal S 3 . 
     In one aspect, the implementation of the microphone  6 A with MEMS technology provides a small and light-weight device, which can be easily integrated in the optical instrument  5 . 
     In one aspect, more than one MEMS microphone  6 A may be integrated in the optical instrument  5 , to generate multiple output signals S 3 , each for its respective microphone. 
     Concerning the advanced microphone processor  11 , it is designed to receive the detected signal S 3  and to generate a processed signal representative of characteristic parameters of the audio signal S 1 , S 2 . 
     Particularly, the advanced microphone processor  11  has two main purposes:
         converting the digital signal S 1 , S 2  captured by the microphones from PDM (1-bit digital stream) to I2S (the most common format for digital sound);   in case of integration of two or more microphones  6 A in the optical instrument  5 , processing the microphone signals S 3  to direct their sensitivity (i.e., beamforming).       

     The processed digital signal is finally delivered to the radio-frequency transmitter  12  to be sent back to the control unit  4  through a digital calibration signal S 4 . 
     The advantage of including beamforming and sound directivity techniques in the optical instrument  5  is to increase the calibration effectiveness of the microphones  6 A. 
     During calibration, the user might be close to walls or reflection-inducing elements and a system that can direct its sensitivity is immune from these less than ideal effects. 
     The radio-frequency transmitter device  12  receives the processed signal from the advanced microphone processor  11  and emits the calibration signal S 4  over a 20-20 kHz frequency band, i.e., according to the IEEE 802.11 technical specifications. 
     In one aspect, the calibration signal S 4  is a digital signal. 
     The control unit  4  receives such calibration signal S 4  and operates to calibrate the sound projector  3 . 
     For this purpose, the control unit  4  comprises a processing device  8  and a reception device  9 , in which:
         the reception system  9  is configured to receive at its input the calibration signal S 4  and to output a processed calibration signal, which is transmitted to the processing device  8 ,   according to the processed calibration signal, the processing device  8  generates a control signal S 5  that can calibrate the sound projector  3 , such that the signal S 1 , S 2  has an even distribution throughout the frequency spectrum.       

     For this purpose, sound projection techniques focus the beam of the signals S 1 , S 2 . In order to provide a directional sound, they use constructive and destructive interference of waves at various wavelengths. For the beam to be focused in a particular direction, the interference must be constructive, considering the target direction, and the otherwise directed sound must be eliminated. 
     An example of such techniques is disclosed in US20060153391. 
     In one embodiment, the reception system  9  comprises a radio-frequency receiving device having a frequency band compatible with the frequency band of the transmission device  7 . 
     It shall be noted that the optical instrument  5  is adapted to be worn by a user and, in a preferred embodiment, it consists of a device in the form of common eyeglasses. 
     In one aspect of the present disclosure, the detection sensors  6  and the transmission system  7  are associated with the frame  5 A of the optical instrument  5 , which comprises a front and at least one temple constrained by said front. 
     In one embodiment, the detection sensors  6  and the transmission system  7  may be associated to the front and/or the temple via suitable linkages. 
     According to an alternative embodiment, the detection sensors  6  and the transmission system  7  are embedded in the frame  5 A of the eyeglasses. 
     For instance, the detection sensors  6  and the transmission system  7  may be located within the thickness of the front and/or the temple. 
     This is advantageous in that the detection sensors  6  and the transmission system  7  are hidden to the user&#39;s view. 
     Therefore, the control unit  4  calibrates the sound projector  3  according to the calibration signal S 4  generated by the optical instrument  5 , which in turn is preferably located in the position in which a user watches the television  2 . 
     Referring to  FIG. 2 , a possible employment of the optical instrument  5  and hence the display system  1  is shown. 
     In one aspect of the display system  1 , as shown in  FIG. 2 , two distinct optical instruments  5 ′,  5 ″ are provided in addition to the television  2 . Particularly, two distinct image streams V 1 , V 2  may be simultaneously displayed on the screen of the television, and the sound projector  3  projects two audio signals S 2 , S 2 , each directed to its own optical instrument. 
     For instance, the exemplary configuration of  FIG. 2  shows an image stream V 1 , such as a sports event, with its own audio stream S 1 , and an image stream C 2 , such as a soap opera, with its audio stream S 2 , where the image steam V 1 —audio signal S 1  pair is designed for the optical instrument  5 ′, whereas the image stream V 2 —audio signal S 2  pair is designed for the optical instrument  5 ″. 
     In one aspect:
         the television  2  consists, for instance, of a stereoscopic television (and/or a television having a picture in picture feature),   the sound projector  3  is manufactured, for instance, with MEMS technology and   the optical instruments  5 ′,  5 ″ are of the type having lenses adapted for displaying and viewing stereoscopic images respectively.       

     In one aspect, the control unit  4  is configured to ensure that the image stream V 1  displayed by the television  2  is combined (or interlaced) with its audio signal S 1  projected by the sound projector  3 , the same being applicable with the image stream V 2  and its audio signal S 2 . 
     Such image stream-audio signal pairs V 1 , S 1  and V 2 , S 2  are captured by the sensors  6  (i.e., the MEMS microphones  6 A) of a respective optical instrument  5 ′ and  5 ″, which may be worn by respective users. 
     In one aspect, the image stream-audio signal pair V 1 , S 1  is designed, for instance, for the optical instrument  5 ′, whereas the other pair V 2 , S 2  is designed, for instance, for the other optical instrument  5 ″. 
     Each optical instrument  5 ′ and  5 ″ will emit its calibration signal S 4 ′, S 4 ″ to calibrate the sound projector  3  for emission of the two audio signals S 1  and S 2  towards their respective optical instruments  5 ′,  5 ″. 
     In other words, the sound projector  3  will calibrate both audio signals S 1  and S 2  for the latter to be projected towards their respective optical instruments  5 ′ and  5 ″ in the proper direction, according to their respective calibration signals S 4 ′, S 4 ″. 
     Therefore, the optical instrument  5 ′ may allow a user to view the image stream V 1  only, with the corresponding audio signal S 1  being projected by the sound projector  3  exactly in the direction of the optical instrument  5 ′, which can generate its own calibration signal S 4 ′ (via its transmission system  7 ). 
     The other optical instrument  5 ″ will allow another user to view the image stream V 2  only, with the corresponding audio signal S 2  being projected by the sound projector  3  exactly in the direction of the optical instrument  5 ″, which can generate its own calibration signal S 4 ″ (via its transmission system  7 ). 
     In this respect, the pair of lenses  10  of the optical instrument  5  may be either or active or preferably passive type. 
     In one aspect, the lenses  10  may be designed for filtered viewing of a single image stream, i.e., the image stream V 1  or the image stream V 2 , by linear or circular polarization of the lenses  10 . 
     In one aspect, the pair of lenses  10  may be identically polarized, i.e., the left eye lens has the same polarization as the right eye lens. 
     Therefore, an optical instrument such as the optical instrument  5 ′ will be configured for viewing the image stream V 1  only, whereas the other optical instrument, i.e., the optical instrument  5 ″ will be designed for viewing the image stream V 2  only. 
     Since the sound projector  3  projects the audible audio signal S 1  towards a target optical instrument, e.g., the optical instrument  5 ′, and the same applies to the audible audio signal S 2 , then a television system  1  is provided that, through the control unit  4 , is configured for:
         the television  2  to simultaneously provide two image streams V 1 , V 2 ,   the sound projector  3  to project the audio signals S 1 , S 2  towards their respective optical instruments  5 ′,  5 ″,   the control unit  4  to associate each image stream V 1 , V 2  with its audio signal S 1 , S 2 ,   each optical instrument  5 ′,  5 ″ worn by a respective user allows viewing of its image stream (e.g., the stream V 1  or V 2 ) and detection of the associated audible audio signal (e.g., the signal S 1  or S 2  respectively) and calibration of the sound projector  3  by the respective calibration signals S 4 ′, S 4 ″, to project the audio signals S 1 , S 2  exactly in the direction of the optical instrument  5 ′,  5 ″ respectively.       

     Therefore, a user that wears the optical instrument  5 ′ will only view the image flow V 1  and hear the audio signal S 1 , the latter being also detected by the sensors  6  of the optical instrument  5 ′ to generate a calibration signal S 4 ′ which is in turn sent to the sound projector  3  to calibrate the emission of the audio signal S 1  in the exact direction of the optical instrument  5 ′ only. The same applies to the optical instrument  5 ″. 
     Those skilled in the art will appreciate that a number of changes and variants may be made to the optical instrument and the display instrument as described hereinbefore to meet specific needs, without departure from the scope of the disclosure, as defined in the following claims. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.