JP2006066990

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DESCRIPTION JP2006066990
PROBLEM TO BE SOLVED: To provide an infrared light receiving device capable of excluding an
interference voltage signal generated by interference infrared rays and extracting a desired
voltage signal generated by desired infrared rays with a simple configuration. SOLUTION: An
infrared signal transmitted through optical filters 11 and 21 having different light wavelength
pass attenuation characteristics is used as an input, and current signals converted
photoelectrically by PIN photodiodes respectively corresponding to the optical filters 11 and 21
are converted into current voltage. And a desired voltage signal, and an adder 14 for adding the
desired voltage signal and the inverted disturbance voltage signal from the inverter 24 for
inverting the disturbance voltage signal in reverse phase to extract the desired voltage signal.
[Selected figure] Figure 2
Infrared light receiver
[0001]
The present invention relates to an infrared light receiver suitable for use in a receiver for
transmitting, for example, an audio signal or a video signal.
[0002]
Conventionally, in audio devices and video devices, wireless transmission of audio signals and
video signals by infrared transmission has been performed.
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For example, various cordless headphones and cordless speakers by infrared transmission have
been put to practical use.
[0003]
For example, by using a cordless speaker, a viewing system that performs so-called multi-channel
audio reproduction does not need to connect an audio signal processing device (such as an
amplifier device) and each speaker with a cable, and performs cable wiring. Instead, the rear
speakers can be easily installed.
[0004]
FIG. 5 is a view showing a configuration example of a conventional infrared light receiving
apparatus used for this type of infrared transmission.
The configuration of the conventional infrared light receiving apparatus will be described
according to FIG. 5. The optical filter 1 for transmitting infrared light is disposed on the front
surface of the two PIN photodiodes 2a and 2b as photoelectric conversion means.
[0005]
The optical filter 1 is a filter that transmits infrared light of at least a band transmitted by this
system. That is, for example, as shown in FIG. 6, assuming that the band of infrared light
transmitted by this system is band IRa, it blocks light having a wavelength of less than 750 nm in
the visible region and transmits infrared light having a wavelength of 750 nm or more. The filter
of characteristic IRb is used.
[0006]
Infrared light transmitted through such an optical filter 1 is made incident on the light receiving
surfaces of the PIN photodiodes 2a and 2b, and the PIN photodiodes 2a and 2b obtain an output
of a current signal according to the input level of the infrared light. The current signal output
from the PIN photodiodes 2a and 2b is supplied to a current-voltage conversion unit 3 that
converts the current into a voltage. The voltage signal output from the current-voltage
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conversion unit 3 is supplied to the first-stage amplification unit 5 that constitutes an automatic
gain control unit. After amplification, the voltage signal input to the first-stage amplifier 5 is
supplied to the band pass filter 6 to pass only a specific signal of a specific band where a
transmission signal is obtained, and is input to the second-stage amplifier 7. The level of the
voltage signal input to the next-stage amplifier 7 is fed back to the first-stage amplifier 5 to
configure an automatic gain control amplifier that keeps the output signal voltage constant.
Then, the output signal of the next stage amplification unit 7 is supplied to the output unit 8 of
this infrared light receiving apparatus. The signal obtained at the output unit 8 is supplied to an
audio signal input unit of a speaker or the like.
[0007]
Patent Document 1 describes this type of infrared light receiver. JP 05-344071 A (FIG. 1)
[0008]
By the way, in this type of infrared signal receiver, noise contained in the received infrared signal
often causes a problem. Patent Document 1 described above describes a configuration for
preventing an erroneous operation due to noise of an inverter fluorescent light in a receiver for
an infrared signal for a remote control device.
[0009]
Although inverter fluorescent lamps have been known as noise sources of conventionally known
infrared signals, video display devices such as PDP (Plasma Display Panel) have become a
problem as noise sources of infrared signals larger than in recent years. . That is, in the case of a
video display device such as a PDP, many infrared signals are often output together with image
light from the video display screen, and the output level is also large. Therefore, when a video
display apparatus such as a PDP and the like and a cordless speaker (or cordless headphone) are
used in combination, much noise is mixed into the audio outputted from the speaker, and there is
a problem that good audio reproduction is difficult.
[0010]
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In the case of the configuration shown in FIG. 5, the two PIN photodiodes 2a and 2b, which are
photoelectric conversion means, allow the optical filter 1 to transmit also an infrared signal
having a wavelength longer than the band IRa of the infrared light to be transmitted. Therefore,
an infrared signal component having a wavelength longer than that of the band IRa is included as
noise. Here, in the case of the configuration of FIG. 5, although the noise is electrically removed
by the band pass filter 6, the noise removal is not sufficient only by the electrical processing. As a
result, the quality and the purity of the desired voltage signal obtained by the infrared light
receiving apparatus deteriorate, and there is a problem that the performance at the time of
demodulation of the output signal is also deteriorated by the influence of the interference signal.
[0011]
The optical filter 1 is an optical filter configured as a so-called band-pass filter that passes only
the band IRa of infrared light to be transmitted instead of the filter of the characteristic IRb that
passes a specific wavelength or more as shown in FIG. By using a filter, it is possible to remove
infrared noise longer in wavelength than the band IRa. However, in order to configure an optical
filter as a band pass filter, a very complicated and expensive filter is required, and it is possible to
apply an optical noise removal configuration to a receiver of this type of infrared signal. It was
difficult.
[0012]
The present invention has been made in view of such circumstances, and an object thereof is to
effectively eliminate the disturbing voltage signal generated by the disturbing infrared.
[0013]
The present invention relates to a first optical filter that transmits only infrared light having a
longer wavelength than the first wavelength, and a first photoelectric conversion unit that
receives light transmitted through the first optical filter and converts it into an electrical signal. A
second optical filter for transmitting only infrared light of a second wavelength or more longer
than the first wavelength, and a second optical filter for receiving the light transmitted through
the second optical filter and converting it into an electric signal And photoelectric conversion
means, and subtraction means for subtracting the output signal of the second photoelectric
conversion means from the output signal of the first photoelectric conversion means.
[0014]
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By doing this, the infrared signal containing noise is photoelectrically converted by the first
photoelectric conversion means, but the infrared signal of only the noise band is photoelectrically
converted by the second photoelectric conversion means. By subtracting the output of the second
photoelectric conversion means from the output of the first photoelectric conversion means, the
signal in the noise band can be removed.
[0015]
According to the present invention, at the time of reception of infrared light, the interference
signal due to the mixed interference infrared signal can be eliminated inside the infrared light
receiving apparatus, and only the desired signal by the required desired infrared signal can be
taken out. is there.
[0016]
In this case, the subtracting means inverts the output signal waveform of the second
photoelectric conversion means and subtracts the signal adjusted to have substantially the same
strength as the first signal from the output signal of the first photoelectric conversion means.
Thus, the first photoelectric conversion means can be processed well even if the second
photoelectric conversion means has different output levels.
[0017]
In addition, the second optical filter and the second photoelectric conversion means are prepared
in a plurality of sets having different light reception angle ranges, and the outputs of the second
photoelectric conversion means of each set are added and supplied to the subtraction means.
This makes it possible to effectively remove noise incident from various directions.
[0018]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1
to 4.
In this embodiment, an example applied to an infrared light receiving apparatus as an audio
signal receiving unit for a cordless speaker will be described.
[0019]
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FIG. 1 is a perspective view showing an example of the external configuration of the infrared
light receiving apparatus 100 of this embodiment.
[0020]
The infrared light receiving apparatus 100 is installed such that the front surface portion, which
is the arrangement surface of the optical filter 11, faces the infrared light transmitting apparatus
that transmits an infrared signal (audio signal) (not shown).
On the other hand, an optical filter 21 having a characteristic different from that of the optical
filter 11 is installed (in this example, on the front and upper surfaces) so as to be able to receive
infrared light in a plurality of directions.
[0021]
For example, four PIN photodiodes 12 a to 12 d are disposed inside the back side of the optical
filter 11.
Further, two PIN photodiodes 22 a and 22 b are disposed inside the back side of the optical filter
21 disposed at a position close to the optical filter 11.
The details of the characteristics of the optical filters 11 and 21 will be described later.
The PIN photodiodes 12a to 12d, 22a and 22b have a function of converting an incident light
beam into a current signal.
[0022]
Although the number of PIN photodiodes is set as described above in this example, the number
may be increased or decreased as necessary.
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However, as the PIN photodiodes 12a to 12d that receive the signal including the desired wave
are relatively large in number, efficient reception can be performed, and the PIN photodiodes
12a and 12b that receive the interference wave are limited. The number is good.
Further, the position of the optical filter 11 disposed on the surface of the PIN photodiodes 12a
and 12b is not limited to only the direction of the infrared light transmitter and the upper
direction.
[0023]
Next, an example of the internal configuration of the infrared light receiving apparatus 100 will
be described with reference to FIG.
[0024]
In the infrared light receiving apparatus 100, optical filters 11 and 21 for blocking visible light
and transmitting infrared light are installed toward the outside.
The light beam transmitted through the optical filter 11 is input to the four PIN photodiodes 12a
to 12d. The optical filter 11 has, for example, an optical wavelength pass attenuation
characteristic IR2 of the optical filter 11 shown in FIG. 3A, and a light beam having a wavelength
of less than 750 nm is cut.
[0025]
The four PIN photodiodes 12a to 12d convert an input beam having a wavelength of 750 nm or
more into a current signal. The outputs of the four PIN photodiodes 12 a to 12 d are added and
supplied to the current-voltage converter 13. The current-voltage conversion unit 13 converts
the supplied current signal into a voltage signal, and supplies the voltage signal to the adder 14.
[0026]
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On the other hand, the light beam transmitted through the optical filter 21 is input to the two
PIN photodiodes 22a and 22b. The optical filter 21 has, for example, an optical wavelength pass
attenuation characteristic IR3 of the optical filter 21 shown in (b) of FIG. 3, and a light beam
having a wavelength of less than 950 nm is cut.
[0027]
The two PIN photodiodes 22a and 22b convert an input beam having a wavelength of 950 nm or
more into a current signal. The outputs of the two PIN photodiodes 22 a and 22 b are added and
supplied to the current-voltage converter 23. The current-voltage conversion unit 23 converts
the received current signal into a voltage signal, and then supplies the voltage signal to an
inverter 24 that performs inversion processing to convert the voltage signal into an opposite
phase.
[0028]
The voltage signal supplied from the current-voltage conversion unit 13 and the voltage signal
inverted in reverse phase supplied from the inverter 24 are input to the adder 14 that adds the
voltage signals. With this configuration, the adder 14 functions as a subtraction unit that
subtracts the outputs of the two PIN photodiodes 22a and 22b from the four PIN photodiodes
12a to 12d. The output gain of the current-voltage conversion unit 13 and the output gain of the
inverter 24 are adjusted by the inverter 24 or the like so as to be substantially equal.
[0029]
The output voltage signal from the adder 14 is supplied to an initial stage amplification unit 15
that amplifies the voltage signal. The voltage signal amplified by the first-stage amplification unit
15 is supplied to the band pass filter 16 that passes only the voltage signal of a specific band,
and the voltage signal outside the specific band is attenuated to amplify the voltage signal.
Supplied at 17. Here, feedback of the output signal voltage is applied from the next-stage
amplification unit 17 to the first-stage amplification unit 15 to constitute an automatic gain
control amplification unit, and the output signal voltage from the next-stage amplification unit 17
to the output unit 18 is constant. Control to keep on is performed.
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[0030]
Here, an example of the light wavelength pass attenuation characteristic of the optical filter of
FIG. 3 will be described. In addition, the infrared rays of the wavelength used for transmitting a
signal are called desired infrared rays, and the infrared rays which cause noise are called
disturbance infrared rays. FIG. 3A shows an example of the light wavelength pass attenuation
characteristic of the optical filter 11. Here, for example, a characteristic IR2 of the optical filter
11 that transmits an infrared ray having a wavelength of 750 nm or more is shown, with the
infrared ray having a center wavelength of 877 nm as the desired infrared band IR1.
[0031]
FIG. 3B shows an example of the light wavelength pass attenuation characteristic of the optical
filter 21. As shown in FIG. Here, the characteristic IR3 of the optical filter 21 is a characteristic of
passing an infrared ray having a wavelength longer than that of the above-mentioned desired
infrared band IR1, for example, a wavelength of 950 nm or more.
[0032]
Next, an example of processing in the adder 14 will be described with reference to FIG. FIG. 4A
shows an example of the desired voltage signal waveform among the signals obtained from the
current-voltage conversion unit 13. FIG. 4 (b) shows an example of the interference voltage signal
waveform among the signals similarly obtained from the current voltage conversion unit 13. FIG.
4C shows an example of the inverted interference voltage signal waveform obtained by inverting
the interference voltage signal by the inverter 24. FIG. 4D shows an example of an output voltage
signal waveform as a result of adding the desired voltage signal, the interference voltage signal
and the reverse interference voltage signal in the adder 14.
[0033]
The disturbance voltage signal supplied to the inverter 24 is subjected to polarity inversion
processing for converting the phase of a certain waveform to the opposite phase, and is output as
an inverted disturbance voltage signal shown in FIG. 4 (c). The desired voltage signal and the
interference voltage signal input from the current voltage conversion unit 13 to the adder 14
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have completely different waveforms and amplitudes as shown in FIGS. 4 (a) and 4 (b). On the
other hand, the inverted interference voltage signal of FIG. 4 (c) is inverted in reverse phase to
the interference voltage signal of FIG. 4 (b), and the amplitude is equal. Therefore, when these
inverted disturbing voltage signals and the disturbing voltage signals are added, they are
mutually canceled. As a result, as shown in the example of the output voltage signal waveform of
the adder 14 of FIG. 4D, the output voltage signal from the adder 14 is only the desired voltage
signal of FIG. 4A.
[0034]
Then, since the PIN photodiodes 12a to 12d, 22a and 22b attached to the infrared light receiving
apparatus 100 are close to each other, infrared rays obtained from the infrared light transmitting
apparatus (not shown) can obtain substantially the same intensity. Here, assuming that the
strength of the current obtained by a single PIN photodiode is T, the strength of the signal
current obtained from the PIN photodiodes 12a to 12d is 4T. On the other hand, the strength of
the signal current obtained from the PIN photodiodes 22a and 22b is 2T. A voltage signal can be
obtained by passing each current to the current-voltage conversion units 13 and 23. However,
since the voltage strength is different, it is necessary to adjust the strength in order to cancel the
interference voltage signal. In this example, the adjustment of the strength of the voltage signal is
performed by the inverter 24. For example, by setting the signal voltage on the side of the PIN
photodiodes 22a and 22b to 2T × 2 = “4T”, an inverted disturbing voltage signal having the
same voltage strength as that of the disturbing voltage signal is obtained, and the adder 14
disturbs. It is possible to cancel the voltage signal.
[0035]
As described above, the infrared light receiving apparatus 100 according to the present
embodiment has an infrared photoelectric conversion circuit equipped with the optical filters 11
and 21 having two different light wavelength pass attenuation characteristics even when the
desired infrared light and the interference infrared light are input simultaneously. In
combination, it is possible to remove the disturbing voltage signal due to the disturbing infrared
light, to output only the desired voltage signal according to the desired infrared light, and not to
deteriorate the output signal demodulation performance without being affected by the disturbing
voltage signal.
[0036]
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As described above, since it is possible to photoelectrically convert the interfering infrared light
and eliminate the interfering voltage signal generated from the interfering infrared light
immediately after current-voltage conversion, it is unnecessary before inputting to the automatic
gain control amplifier in the subsequent stage. The noise signal can be eliminated and does not
affect the automatic gain control amplifier.
This has the effect of being able to maintain a constant output level for the output voltage signal
at the output section 18 of the desired voltage signal.
[0037]
Further, since the interfering infrared rays are eliminated in the infrared light receiving
apparatus 100, the influence of unnecessary noise can be suppressed on an output signal
demodulation circuit (not shown) in the output unit 18 and thereafter, so that the desired voltage
signal is demodulated. There is an effect that the performance is not reduced.
[0038]
Alternatively, when infrared light of a wavelength other than that of the above-described
embodiment is used as a signal transmission means, any desired infrared light may be used, since
it is only necessary to use an optical filter having an optical wavelength pass attenuation
characteristic suitable for the form. It is easy to set the infrared.
[0039]
And since it has the effect of excluding interfering infrared rays other than the desired infrared
rays, when a plurality of desired infrared rays of different wavelengths are used, the signals are
mixed by installing optical filters having the corresponding optical wavelength pass attenuation
characteristics. There is an effect that coexistence of a plurality of communication systems
becomes possible because communication can be performed without agreement.
[0040]
In the above-described embodiment, although an example using an infrared light receiving
apparatus for receiving an audio signal has been described, the present invention is not limited to
this and can be applied to other infrared light receiving apparatuses. .
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For example, the present invention may be applied to an infrared light receiving apparatus that
receives a video signal.
[0041]
It is the perspective view which showed the example of an external structure of the infrared-light
receiver in one embodiment of this invention.
FIG. 3 is a block diagram showing an example of the internal configuration of an infrared light
receiving device according to an embodiment of the present invention.
It is explanatory drawing which showed the example of the light wavelength pass attenuation
characteristic of the optical filter in one embodiment of this invention. It is an explanatory view
showing an example of an input-and-output voltage signal waveform of an adder in a 1
embodiment of the present invention. It is the block diagram which showed the internal
structural example of the conventional infrared light receiver. It is explanatory drawing which
showed the example of the light wavelength pass attenuation characteristic of the conventional
optical filter.
Explanation of sign
[0042]
DESCRIPTION OF SYMBOLS 1 ... Optical filter, 2a, 2b ... PIN photodiode, 3 ... Current-voltage
conversion part, 5 ... First stage amplification part, 6 ... Band pass filter, 7 ... Next stage
amplification part, 8 ... Output part, IRa ... Band, IRb ... Characteristics 11 Optical filter 12a to 12d
PIN photodiode 13 Current voltage conversion unit 14 Adder 15 First stage amplification unit 16
Band pass filter 17 Second stage amplification unit 18 Output unit , 21: optical filter, 22a, 22b:
PIN photodiode, 23: current-voltage converter, 24: inverter, 100: infrared light receiver, IR1:
band, IR2: characteristic, IR3: characteristic
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