CN101650935B - Optical drive sound producing device - Google Patents

Abstract

A light-driven sound-generating device. The sounding device includes: a light source, a light modulator, an optical amplifier, a transmission fiber and a sounding film. The intensity of the output light generated by the light source is modulated by the audio signal through the optical modulator, and then amplified by the optical amplifier. Thermal expansion with varying intensity, causing a change in the density of the air medium, produces sound. The sounding process generated by the optical driving method of the present invention is a linear process, which does not cause harmonic distortion in principle and has extremely high sounding fidelity. Compared with the existing electric sounding device, the sounding device involved in the present invention does not need to use magnets and voice coils, so it has no response to the external magnetic field and can work normally in the environment where strong electromagnetic fields exist; the sounding device does not need to use metal or other Conductor material, the energy required for sound can be transmitted through space, or through optical fiber transmission.

Description

Light-driven sound generating device

【Technical field】：

The invention relates to a sounding device, in particular to a sounding device driven by an optical signal, and belongs to the technical fields of optics and sounding.

【Background technique】:

Existing sound generating devices and devices, such as loudspeakers (also known as horns) and earphones, are sound generating devices that convert electrical energy into sound energy. Although there are many types of existing loudspeakers and their working methods are not the same, the principle of sound generation is to generate mechanical vibration through certain vibrating parts, push the surrounding air, and cause the air medium to fluctuate so as to realize electrical energy to mechanical energy and then to sound energy. conversion. Loudspeakers can be divided into dynamic loudspeakers, electrostatic loudspeakers, and flat-panel loudspeakers. Among them, the most widely used is the dynamic speaker. Common electrodynamic loudspeakers are generally composed of basin frames, magnets, voice coils, vibrating cones, etc. When the audio current passes through the voice coil, the voice coil vibrates under the action of the magnetic field. The cone fixed with the voice coil pushes the surrounding air to move when it vibrates, so that the air density around the speaker changes to produce sound. There are many technical parameters to describe the performance of loudspeakers, the most important ones include: effective frequency range, characteristic sensitivity, rated maximum sinusoidal power, rated harmonic distortion, etc. With the continuous development of loudspeaker production materials, processes and technologies, loudspeaker products with various functions and uses have been developed. Nevertheless, existing loudspeakers all have the following inherent problems determined by their sounding principles:

1. Existing speakers are all driven by current, and the voice coil is easily disturbed and affected by the external environment. For example, in an environment where a strong electromagnetic field exists, the speaker will be disturbed by the electromagnetic field and cause noise, and in severe cases, it may even be unusable.

2. For existing loudspeakers, if they want to achieve good sound effects, they need to design their structures reasonably and carefully select various materials, and also consider their electrical properties and matching with audio amplifiers.

3. The nonlinear characteristics of the electromagnetic and mechanical motions in the existing loudspeaker cause the loudspeaker to generate high-order harmonics, which easily cause harmonic distortion, thereby affecting the fidelity of sound production.

【Invention content】：

The object of the present invention is to overcome the above-mentioned shortcomings in the prior art, and provide a new type of sounding device, especially a sounding device driven by an optical signal.

The sounding device is completely different from the existing electric sounding device in terms of driving mode and sounding mechanism. It drives the sounding film with the momentum and energy of light, or produces mechanical vibration, or produces temperature change, or the above two combined effects, Push the surrounding air, make the air medium fluctuate, and realize the conversion from light energy to sound energy. Compared with the existing electric sounding device, the sounding device involved in the present invention does not need to use magnets and voice coils, so it has no response to the external magnetic field and can work normally in the environment where strong electromagnetic fields exist; the sounding device does not need to use metal or other Conductor material, the energy required for sound can be transmitted through space, or through optical fiber transmission.

The working principle of the light-driven sound generating device involved in the present invention: photons with frequency v have energy hv (h is Planck's constant). When light is incident on a non-reflective and non-transparent object, the energy of the light is absorbed, causing its temperature to rise. And the object acts as a heat source, and the heat will be transferred to its surrounding medium. In the case of still air as the surrounding medium, heat will be transferred from the object to the air mainly by heat conduction. If the heat capacity of the object is small, the absorbed light radiation energy will be transferred to the surrounding medium with high efficiency, that is, the function of the object is to realize the conversion from light energy to heat energy. If the intensity of the incident light changes with time, the temperature of the object also changes with time, and the result of heat conduction is that the density of the still air around it changes with time, that is, a sound field is generated and propagated in the air.

Since the heat generated by an object absorbing light radiation is linearly related to the intensity of incident light, the density change of air caused by heat conduction is also linearly related to the intensity of incident light. Therefore, the sounding process generated by the light-driven method is a linear process. The principle It will not cause harmonic distortion and has extremely high sound fidelity. On the other hand, the sound generation process is a conversion process of light energy to heat energy and then to sound energy, in which no electrical signal is involved and no conductive material is used. The transmission of optical signals can be completed using optical fibers, so the external electromagnetic field will not cause any interference to the transmission of signals.

Next consider the role of photon momentum. The momentum of a photon with a frequency v is hv/C (C is the speed of light). In general, the momentum of a photon is extremely small, and its effect can be ignored. When a light pulse with energy E is incident on an object at an angle of 90 degrees, assuming its surface reflectivity is R, and the rest is absorbed by the object, the momentum obtained by the incident light pulse is (1+R)E/ c. If the width of the incident light pulse is Δt, then the force of the incident light pulse on the object is (1+R)E/(CΔt). Therefore, for ultrashort laser pulses with extremely high peak power, the force on objects will become obvious. If the object is a film with an extremely thin thickness (on the order of nm), the action of the laser pulse will cause the film to vibrate, which will cause the air medium to fluctuate and produce sound.

The specific structure of the light-driven sounding device provided by the present invention includes in turn:

Light source: used to generate output light;

Light modulator: modulate the output light intensity generated by the light source according to the input audio signal;

Optical amplifier: amplifies the optical signal modulated by the optical modulator;

Transmission fiber: transmit the optical signal amplified by the optical amplifier to the sound-emitting film;

Acoustic film: The optical signal transmitted by the transmission fiber is incident on the acoustic film, and the sound film absorbs the incident light. The change of light intensity causes the temperature change of the sound film, which makes the air layer close to the sound film thermally expand with the change of light intensity, causing the air medium Density changes, producing sound.

The light source can be a continuous light source or a pulsed light source.

Specifically, the light source may be a continuous output fiber laser or a pulse output fiber laser; or a continuous output semiconductor laser or a pulse output semiconductor laser.

The optical amplifier is an optical fiber amplifier.

The light-driven sounding device provided by the present invention can also be realized by using a current drive circuit, and the device includes in turn:

Current drive source: used to generate a drive current modulated by an audio signal;

Semiconductor light-emitting device: used to generate output light whose light intensity changes with the driving current;

Transmission fiber: transmit the light signal to the sound-emitting film;

Acoustic film: The optical signal transmitted by the transmission fiber is incident on the acoustic film, and the sound film absorbs the incident light. The change of light intensity causes the temperature change of the sound film, which makes the air layer close to the sound film thermally expand with the change of light intensity, causing the air medium Density changes, producing sound.

The semiconductor light emitting device is a semiconductor laser; or a semiconductor light emitting diode.

Advantage and positive effect of the present invention:

Compared with the existing electric sounding device, the sounding device involved in the present invention does not need to use magnets and voice coils, so it has no response to the external magnetic field and can work normally in the environment where strong electromagnetic fields exist; the sounding device does not need to use metal or other Conductor material, the energy required for sound can be transmitted through space, or through optical fiber transmission.

The sounding process generated by the optical drive method is a linear process, which will not cause harmonic distortion in principle, and has extremely high sounding fidelity.

[Description of drawings]:

FIG. 1 is a schematic structural diagram of an optically modulated optical signal driving a sounding device.

In the figure: 101 is a light source; 102 is a light intensity modulator; 103 is a voltage amplifier; 104 is an input audio signal; 105 is an optical fiber amplifier; 106 is a transmission optical fiber; .

Fig. 2 is a schematic diagram of the structure of the sound generating device driven by the electrical modulation optical signal.

In the figure: 201 is the current drive source; 202 is the optical fiber output semiconductor light emitting device; 104 is the input audio signal; 106 is the transmission optical fiber; 107 is the shell of the sounding body; 108 is the sounding film; 109 is the sound field.

Fig. 3 is a schematic diagram of a continuous optical signal with intensity modulation. In the figure: 301 is a curve of light intensity changing with time.

Fig. 4 is a schematic diagram of an intensity-modulated pulsed light signal. In the figure: 401 is a curve of light intensity changing with time.

Fig. 5 is a sound-emitting film fabricated on a substrate. In the figure: 501 is the incident light; 502 is the sound-emitting film; 503 is the substrate.

【Detailed ways】:

Example 1:

As shown in Figure 1, the light source 101 adopts the PIL106 semiconductor laser provided by Pilas, A.L.S.GmbH, Germany. The semiconductor laser can generate continuous output or pulse output, and its output mode is set by its current control unit EIG1000D. The output wavelength of PIL106 semiconductor laser is 1060nm, and the continuous output power is greater than 400mW. The optical intensity modulator 102 adopts a high-speed variable optical fiber attenuator (VOA) μVOA302 provided by BATI of the United States. The VOA uses electro-optic ceramics as the switch material, the dynamic response time is 1μS, and the insertion loss to the wavelength of 1060nm is less than 0.6dB. The dynamic attenuation range is 25dB, and the reflection loss is greater than 55dB. Electro-optic ceramics have a strong Kerr effect, the electro-optic coefficient is 2 orders of magnitude larger than that of niobium lithium oxide, and the half-wave voltage is much lower than that of lithium niobate crystal. Experiments have found that for the selected variable optical fiber attenuator, the switching voltage is in the range of 100-150V. The light intensity modulator 102 is driven by a voltage amplifier 103 . The voltage amplifier 103 adopts a voltage amplifying circuit provided by BATI of the United States, and its output signal voltage amplitude is continuously adjustable between 50V-150V. The signal input terminal of the voltage amplifier 103 is connected to the input audio signal 104 .

The input audio signal 104 is loaded on the intensity of the continuous light output by the semiconductor laser through the light intensity modulator 102, as shown in FIG. 3 . Then it is amplified by the optical fiber amplifier 105 and transmitted to the housing 107 of the sounding device through the transmission fiber 106, and the optical signal is incident on the sounding film 108 from the output end of the transmission fiber 106 at a divergence angle and through a spatial transmission distance. The housing 107 of the sounding device is made of non-metallic materials such as plastic or nylon, and the sounding film 108 is made of plastic or other non-metallic materials with a thickness on the order of submicron. The sound-generating film 108 is fixed on the housing 107 of the sound-generating device. Another form of the sound-emitting film 108 is a sound-emitting film made on a substrate, as shown in FIG. 5 .

The optical signal whose intensity is modulated by the audio signal 104 is absorbed by the sound-emitting film 108 and converted into heat energy, so that the temperature of the sound-emitting film 108 changes with the audio signal 104, and the temperature change causes the thermal expansion of the sound-emitting film 108 as the audio signal 104 changes, causing its The surrounding air density changes to generate a sound field 109 to realize sound generation.

Example 2:

As shown in Figure 1, the light source 101 adopts PIL106 semiconductor laser, and its output mode is set as pulse output by its current control unit EIG1000D, the pulse width is selected as 40ps, and the repetition frequency is set as 1MHz. The optical intensity modulator 102 adopts the high-speed variable optical fiber attenuator μVOA302 provided by BATI in the United States, and the optical fiber amplifier 105 is a high peak power pulse amplifier. The connection mode of various devices is similar to that of Embodiment 1. The difference is that the pulse energy of the sequence of light pulses is modulated by the audio signal 104 through light intensity, as shown in FIG. 4 . The sound-emitting film 108 is a gold foil with a thickness on the order of submicron. When a light pulse is incident on the surface of the gold foil, part of the light is reflected and part is absorbed. The absorbed light energy is converted into heat energy, forming the same sounding process as in Example 1. At the same time, the momentum of the light pulse causes the gold foil to vibrate, which causes the air medium to fluctuate and produce sound.

Example 3:

As shown in FIG. 2 , the semiconductor light emitting device 202 adopts a 6397 series semiconductor laser with pigtail output from JDSU Company of the United States. The semiconductor laser is multi-mode continuous output, the continuous output wavelength is 915nm, the maximum output is 6.5W, the output pigtail fiber core diameter is 105 microns, and the driving current is greater than 6A. Current driving source 201 adopts THORLABSLDC340 semiconductor laser current driving source, and audio signal 104 is connected to the modulation input (MOD IN) end of LDC340. The output of the semiconductor laser whose light intensity is modulated is connected to the shell of the sounding body 107 through the transmission fiber 106 , and is incident on the sounding film 108 . The optical signal whose intensity is modulated by the audio signal 104 is absorbed by the sound-emitting film 108 and converted into heat energy, so that the temperature of the sound-emitting film 108 changes with the audio signal 104, and the temperature change causes the thermal expansion of the sound-emitting film 108 as the audio signal 104 changes, causing its The surrounding air density changes to generate a sound field 109 to realize sound generation.

It is clear to those skilled in the art that the idea of the present invention can be implemented in other ways than the specific implementations listed above.

Claims (5)

1. A light-driven sounding device, characterized in that the device comprises successively: Light source: used to generate output light; the light source is a fiber laser with continuous output or a fiber laser with pulse output; Light modulator: modulate the output light intensity generated by the light source according to the input audio signal; Optical amplifier: amplifies the optical signal modulated by the optical modulator; Transmission fiber: transmit the optical signal amplified by the optical amplifier to the sound-emitting film; Acoustic film: The optical signal transmitted by the transmission fiber is incident on the acoustic film, and the sound film absorbs the incident light. The change of light intensity causes the temperature change of the sound film, which makes the air layer close to the sound film thermally expand with the change of light intensity, causing the air medium Density changes, producing sound. 2. The light-driven sounding device according to claim 1, characterized in that said optical amplifier is a fiber amplifier. 3. A light-driven sounding device, characterized in that the device comprises successively: Light source: used to generate output light; the light source is a semiconductor laser with continuous output or a semiconductor laser with pulse output; Light modulator: modulate the output light intensity generated by the light source according to the input audio signal; Optical amplifier: amplifies the optical signal modulated by the optical modulator; Transmission fiber: transmit the optical signal amplified by the optical amplifier to the sound-emitting film; Acoustic film: The optical signal transmitted by the transmission fiber is incident on the acoustic film, and the sound film absorbs the incident light. The change of light intensity causes the temperature change of the sound film, which makes the air layer close to the sound film thermally expand with the change of light intensity, causing the air medium Density changes, producing sound. 4. The light-driven sounding device according to claim 3, characterized in that said optical amplifier is a fiber amplifier. 5. A light-driven sounding device, characterized in that the device comprises successively: Current drive source: used to generate a drive current modulated by an audio signal; Semiconductor laser or light-emitting diode: used to generate output light whose light intensity varies with the driving current; Transmission fiber: transmit the light signal to the sound-emitting film; Acoustic film: The optical signal transmitted by the transmission fiber is incident on the acoustic film, and the sound film absorbs the incident light. The change of light intensity causes the temperature change of the sound film, which makes the air layer close to the sound film thermally expand with the change of light intensity, causing the air medium Density changes, producing sound.

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