WO2009104117A1

WO2009104117A1 - Light controlled audio transducer

Info

Publication number: WO2009104117A1
Application number: PCT/IB2009/050595
Authority: WO
Inventors: Ronaldus M. Aarts; Aki S. HÄRMÄ
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2008-02-18
Filing date: 2009-02-13
Publication date: 2009-08-27
Anticipated expiration: 2010-08-18

Abstract

An audio-visual system comprises an optical sensor (OS) for sensing a property of light impinging on an area at or adjacent to a position of a sound transducer (LS) to supply a sense signal (SE) being dependent on the light property, and a controller (1) for receiving the sense signal (SE) to supply an output audio signal (MA) to the sound transducer (LS).

Description

Light controlled audio transducer

FIELD OF THE INVENTION

The invention relates to an audio-visual system and to a method of driving a sound transducer.

BACKGROUND OF THE INVENTION

In a stereo or multi-channel home theatre setup, video information is displayed on a display device and the associated stereo or multi-channel sound is produced by suitable arranged loudspeakers. Usually, the left and right front speakers are arranged at the left and right side of the display device, respectively. An optional centre speaker may be arranged on top of or below the display device. Further, optionally rear speakers and a subwoofer may be present. The display device may be a direct view display such as an LCD or plasma display, or a projector which projects the video information on a projection screen.

The screen may be positioned between the projector and the front speakers and/or the center speaker. The sound stage generated by the speakers may not optimally fit the content of the image.

SUMMARY OF THE INVENTION

It is an object of the invention to improve the correlation between the sound generated by a speaker and the associated displayed image. A first aspect of the invention provides an audio-visual system as claimed in claim 1. A second aspect of the invention provides a method of driving a sound transducer as claimed in claim 18. Advantageous embodiments are defined in the dependent claims.

An audio-visual system in accordance with the first aspect of the invention comprises an optical sensor which senses a property of light impinging on an area associated with a position of a sound transducer and supplies a sense signal which is dependent on the light property. A controller receives the sense signal to supply an output audio signal to the sound transducer.

Thus, the sound generated by the sound transducer depends on the light which impinges on the area associated with the sound transducer. Consequently, the sound produced by the sound transducer is better correlated with the actual impinging light. For example, if the light impinging on the area is a local sub-section of an image generated by a projector, the sound generated by the sound transducer can be tailored to the properties of the light in that sub-section of the image. Such an approach is especially useful in a system in which multiple loudspeakers are arranged, for example in a matrix, behind a projection screen. An optical sensor may be arranged adjacent each loudspeaker or adjacent a group of adjacent loudspeakers to influence the sound generated by each loudspeaker or each group of adjacent loudspeakers. For example, the optical sensor may be arranged adjacent a sound emitting surface of the sound transducer to sense light directed towards the sound emitting surface. Alternatively, the optical sensor may be integrated in a sound emitting surface of the sound transducer. In an embodiment, the optical sensor may be a camera which registers the actual image displayed and which processes the registered image to process the input audio signal. Alternatively, the approach may be useful for a system with a single loudspeaker which should respond on the light impinging on it. An example of such a system is a shadow projection device which uses a light source (for example a lamp) to project a shadow of an object on a projection area.

The sound image produced by the speakers of a prior art multi-channel speaker system is largely independent on the spatial light distribution on the projection screen. In the now following, with multi-channel speaker system is meant any system having at least two speakers for producing different channels of a stereo or any other multi-channel sound signal. The position of the screen with respect to the loudspeakers and the dimensions of the screen are not known to the system. Thus, although in a multi-channel system the sound created may change in horizontal direction between the speaker positions, there is no one to one relation with the actual position of the video information displayed. If such a one to one correlation would be required, a calibration of the system has to be performed such that the system knows which part of the image is associated with which loudspeaker.

In an embodiment, the controller receives the sense signal and an input audio signal and modifies a property of the input audio signal dependent on the sense signal to obtain an output audio signal. In an embodiment, a function may map the values of the sense signal to control parameters for modifying the property (or the properties) of the input audio signal. This function may be any monotonic function including a piecewise function characterized by a threshold value.

In an embodiment, the controller only supplies the output audio signal to the sound transducer if the associated sense signal indicates that a property of the light is above a particular threshold. The optical sensor may be sensitive to the intensity of the light or may have a particular spectral sensitivity to detect the color of the light. The optical sensor may be sensitive to any property of the light, for example the polarization. The sensor signal may be processed, for example filtered. The processed sensor signal may reflect temporal changes in the light impinging on the loudspeaker(s). For example the sensor signal may indicate rapid changes in the properties of the light or, alternatively, is only sensitive to relatively long exposures to a particular characteristic of the light. The rapid changes may be caused by modulating particular properties of the light with data.

In an embodiment, the property of the audio signal is its amplitude (including on/off), pitch, speed of playback, delay, phase response, frequency response, or genre. If the sensor is able to detect a single property of the light only one property of the sound can be controlled. If the sensor is able to detect a plurality of properties of the light, a plurality of properties of the sound can be controlled. For example, the intensity of the light may be used to control the amplitude of the sound, and a value related to a chromatic measure is used to control a delay of the sound. An array of such units would be able to implement a Wave Field Synthesis algorithm for positioned audio reproduction. If only slow changes are required, more than one property of the sound can be controlled by coding different messages in the light.

In an embodiment, the controller comprises a decoder for decoding a message coded in the sensed light signal due to a coding of a property of the light impinging on the area. Thus, the controller is able to decode the data encoded in the light. Such data can be used to control the property of the audio signal(s) to be modified. Alternatively or additionally, the message may comprise the input audio signal itself. The data may be encoded in any form. For example, the light may be FM modulated and the data to be transmitted may be coded as a particular frequency in the FM signal.

In an embodiment, the sound transducer has a flat surface which is used as a projection screen. For example, such flat panel speakers are produced by NXT.

In an embodiment, the audio-visual system comprises a plurality of optical sensors for sensing properties of light impinging on a plurality of areas associated with a position of sound transducers to supply a plurality of sense signals being dependent on the light properties. The controller receives the plurality of sense signals to control the plurality of sound transducers to create a sound image defined by the sensed properties. The sound transducers and optical sensors may both be positioned in a matrix arrangement. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

Fig. 1 schematically shows a block diagram of the audio visual system, Fig. 2 schematically shows an embodiment of a relative position of the optical sensor and the sound transducers,

Fig. 3 schematically shows an embodiment of a controller, Fig. 4 schematically shows another embodiment of the controller,

Fig. 5 schematically shows yet another embodiment of the controller, Fig. 6 schematically shows a projection system, and

Fig. 7 schematically shows an embodiment of an array of sensors and sound transducers of the projection system. It should be noted that items which have the same reference numbers in different Figures, have the same structural features and the same functions, or are the same signals. Where the function and/or structure of such an item has been explained, there is no necessity for repeated explanation thereof in the detailed description.

DETAILED DESCRIPTION

Fig. 1 schematically shows a block diagram of the audio visual system. The system comprises a controller 1 which receives an input audio signal AS and a sense signal SE from an optical sensor OS to supply an output audio signal MA to a sound transducer LS. The optical sensor OS may be a light sensitive device which is positioned adjacent the sound transducer LS to sense a property of the light impinging on an area adjacent to the sound transducer LS. Alternatively, the light sensitive device OS may be arranged in front of the sound transducer LS or the material of the sound transducer LS may be optically sensitive. The light sensitive device OS may be sensitive to the intensity, the color, the polarization or any other property of the light, or any combination thereof. The position of the optical sensor OS has to be selected such that there is a positional relation between light impinging on or adjacent a particular sound transducer LS and the associated optical sensor OS. Alternatively, the optical sensor may be a camera which registers the light pattern on or adjacent to the sound transducer LS. The sense signal SE supplies the sensed property or the sensed properties of the light to the controller 1. The sound transducer LS generates sound waves in accordance with the output audio signal LS and is for example a loudspeaker or an ultrasonic transmitter. The loudspeaker LS may comprise a flat panel or a cone speaker.

The controller 1 processes the input audio signal AS into the output audio signal MA in accordance with the sensed property or the sensed properties. In an embodiment, the input audio signal AS is supplied to the sound transducer LS if a particular property of the light is detected to be present and no audio signal is supplied to the sound transducer LS if this particular property is not present. For example, the audio signal AS is only supplied to the sound transducer LS when the intensity of the sensed light is above a particular threshold value.

Fig. 2 schematically shows an embodiment of a relative position of the optical sensor and the sound transducers. In this embodiment, one optical sensor OS is associated with two adjacent loudspeakers LS. Alternatively, an optical sensor OS may be associated with each loudspeaker LS, or one optical sensor OS may be associated with more than two loudspeakers LS. The position of the optical sensor OS may be selected adjacent to, or in front of, the active area of the loudspeaker LS. If a single optical sensor OS is used for more than one loudspeaker LS, this optical sensor OS may be arranged such that its distances to the centers of the active areas of the loudspeakers LS is equal. Alternatively, the material of the loudspeaker LS, in particular of its active material, or of a projection screen in front of the loudspeakers LS may be optically sensitive. If the optical sensors OS are behind the projection screen, the projection screen should pass a portion of the light impinging thereon.

Fig. 3 schematically shows an embodiment of a controller. The controller 1 comprises a comparator 10 and a signal processor 11. The comparator 10 compares the received sense signal SE with a threshold TH to supply a signal SI which indicates whether the received sense signal SE passes the threshold TH. The processor 11 may forward the input audio signal AS as the output audio signal MA if the sense signal SE indicates that the sensed property of the light passed the threshold TH. Otherwise, the processor 11 blocks the input audio signal AS and thus the output audio signal MA is suppressed. For example, the output audio signal MA is muted or completely suppressed if the light intensity sensed is below the threshold TH, and the output audio signal MA is the input audio signal AS if the light intensity sensed is above the threshold TH.

Fig. 4 schematically shows another embodiment of the controller. The controller 1 comprises a decoder 20 and a signal processor 22. The decoder 20 receives the sense signal SE to decode a message ME which was coded in the light sensed. The message ME indicates which property of the input audio signal AS has to be processed how. The signal processor 22 processes the input audio signal AS in accordance to the message ME to obtain the output audio signal MA.

Fig. 5 schematically shows yet another embodiment of the controller. The controller 1 comprises a decoder 30 which receives the sense signal SE to decode the input audio signal AS which was coded in the light received and to supply the decoded audio signal as the output audio signal MA.

The property of the light may be, for example, its intensity, its color, or its polarization. The property of the input audio signal (AS) which may be modified is, for example, its amplitude, pitch, speed of playback, delay, phase response, frequency response, or its genre.

Fig. 6 schematically shows a projection system. The projector PJ projects an image on the projection screen PS. The projection screen PS is arranged in-between the projector and an array AR of loudspeakers LS and optical sensors OS (see Fig. 7). Fig. 7 schematically shows an embodiment of an array of sensors and sound transducers of the projection system. The array AR comprises a matrix of rows of sound transducers LS and optical sensors OS. In the example shown, every cell of the matrix AR comprises a loudspeaker LS and a sensor OS. Alternatively, a single optical sensor OS may be used for a cluster of loudspeakers LS of adjacent cells. It has to be noted that more than a single loudspeaker LS may be present in each cell. For example, in each cell a combination of a tweeter and a mid range or a mid and low range loudspeaker may be present. The mid and low range loudspeaker may be able to reproduce relatively low frequencies such that a separate woofer or sub-woofer is not required. Alternatively, a woofer or sub-woofer separate from the matrix AR may be implemented. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. An audio-visual system comprising an optical sensor (OS) for sensing a property of light impinging on an area at or adjacent to a position of a sound transducer (LS) to supply a sense signal (SE) being dependent on the light property, and a controller (1) for receiving the sense signal (SE) to supply an output audio signal (MA) to the sound transducer (LS).

2. An audio-visual system as claimed in claim 1, wherein the controller (1) is constructed for further receiving an input audio signal (AS) to modify a property of the input audio signal (AS) dependent on the sense signal (SE) to obtain the output audio signal (MA).

3. An audio-visual system as claimed in claim 2, wherein the controller (1) comprises a comparator (10) for comparing the sense signal (SE) with a threshold (TH), and a signal processor (11) for only forwarding the input audio signal (AS) as the output audio signal (MA) if the sense signal (SE) indicates that a property of the light is above the threshold (TH).

4. An audio-visual system as claimed in claim 2, wherein the controller (1) comprises a decoder (20) for receiving the sense signal (SE) to decode a message (ME) comprising the property of the input audio signal (AS) to be processed, and a signal processor (22) for supplying the output audio signal (MA) being the input audio signal (AS) having the property modified in accordance with the message (ME).

5. An audio-visual system as claimed in claim 1, wherein the sense signal (SE) comprises the input audio signal (AS).

6. An audio-visual system as claimed in claim 5, wherein the controller (1) comprises a decoder (30) for decoding the input audio signal (AS) being coded in the sense signal (SE) to obtain the output audio signal (MA).

7. An audio -visual system as claimed in claim 1, comprising the sound transducer (LS).

8. An audio-visual system as claimed in claim 7, wherein the optical sensor (OS) is arranged adjacent a sound emitting surface of the sound transducer (LS) for sensing light directed towards the sound emitting surface.

9. An audio-visual system as claimed in claim 7, wherein the optical sensor (OS) is integrated in a sound emitting surface of the sound transducer (LS).

10. An audio -visual system as claimed in claim 1 or 7, further comprising a light source (PJ) for generating the light impinging on the area.

11. An audio -visual system as claimed in claim 10, wherein the light source (PJ) is a projector for projecting images or video information.

12. An audio -visual system as claimed in claim 10, further comprising a projection screen (PS) arranged between the light source (PJ) and the sound transducer (LS) and/or the optical sensor (OS).

13. An audio-visual system as claimed in claim 10, wherein the sound transducer

(LS) has a flat surface forming a projection screen (PS).

14. An audio-visual system as claimed in claim 10 or 11, comprising a plurality of optical sensors (OS) for sensing properties of light impinging on a plurality of areas adjacent positions of sound transducers (LS) or groups of sound transducers (LS) to supply a plurality of sense signals (SE) being dependent on the light properties, and wherein the controller (1) is constructed for receiving the plurality of sense signals (SE) to control the plurality of sound transducers (LS) to create a sound image defined by the sensed light properties.

15. An audio-visual system as claimed in claim 14, wherein the controller (1) is arranged for only supplying the audio signal (AS) to a particular one of the sound transducers (LS) if the corresponding sense signal (SE) indicates that a property of the light impinging on the associated optical sensor (OS) is above a particular threshold (TH).

16. An audio-visual system as claimed in any one of the preceding claims, wherein the property of the light is its intensity, its color, or its polarization.

17. An audio-visual system as claimed in anyone of the claims 1 to 15, wherein the property of the audio signal (AS) is its amplitude, pitch, speed of playback, delay, phase response, frequency response, or its genre.

18. A method of driving a sound transducer in an audio-visual system, the method comprising sensing (OS) a property of light impinging on an area at or adjacent to a position of the sound transducer (LS) to supply a sense signal (SE) being dependent on the light property, and modifying (1) a property of an audio signal (AS) dependent on the sense signal (SE) to obtain a modified audio signal (MA) for supply to the sound transducer (LS).