Abstract:
A projector includes: a first audio input section adapted to input a first sound signal; a second audio input section adapted to input a second sound signal; a first sound amplifier section adapted to amplify the first sound signal received through the second audio input section to generate a first amplified signal; a second sound amplifier section adapted to amplify the second sound signal received through the second audio input section to generate a second amplified signal; a first audio output section adapted to output a first sound based on the first amplified signal; a second audio output section adapted to output a second sound based on the second amplified signal; and a determination section adapted to determine whether or not the first sound signal is being input.

Description:
CROSS-REFERENCE 
     The entire disclosure of Japanese Patent Application No. 2009-142880, filed Jun. 16, 2009 is expressly incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a projector and an audio output method. 
     2. Related Art 
     In the case of a projector incorporating a microphone input terminal, a line input terminal, and a speaker, a sound signal from the microphone input terminal and a sound signal from the line input terminal are mixed, and then output from the speaker. 
     In, for example, JP-A-5-64286, there is a description that audio output without distortion is performed using a microphone mixer circuit provided with a switch, which is turned ON upon insertion of a microphone plug into a microphone input terminal, and a circuit, which lowers the level of a music signal input to a mixer when the switch is turned ON. 
     However, in the case in which the control of lowering the audio output level is performed as described in the publication described above, there are some cases in which a sufficient sound volume is not obtained even if the user performs an operation of increasing the volume. Because, in order for mixing a plurality of types of sound signals from a plurality of types of input terminals, it is required for the projector or the like to assign an output allowable range of the speaker or the like to each of the sound signals. For example, if the projector or the like assigns a half of the output allowable range to each of the sound signal from the microphone input terminal and the sound signal from the line input terminal, the sound pressure level corresponding to each of the sound signal is reduced, and even in the case in which the user performs an operation of increasing the volume, it is not achievable to obtain the sufficient sound volume. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve the problem described above and to provide a projector and an audio output method capable of more appropriately outputting a sound in the situation in which a plurality of types of sound signals can be input and then output simultaneously. 
     According to an aspect of the invention, there is provided a projector including a first audio input section adapted to input a first sound signal, a second audio input section adapted to input a second sound signal, a first sound amplifier section adapted to amplify the first sound signal received through the first audio input section to generate a first amplified signal, a second sound amplifier section adapted to amplify the second sound signal received through the first audio input section to generate a second amplified signal, a first audio output section adapted to output a first sound based on the first amplified signal, a second audio output section adapted to output a second sound based on the second amplified signal, and a determination section adapted to determine whether or not the first sound signal is being input. 
     According to the aspect of the invention, even in the situation in which a plurality of types of sound signals can be input and then output simultaneously, the projector can output the respective sounds from the separate audio output sections. Further, since the projector is provided with the determination section for determining whether or not the first sound signal is being input, the sound can more appropriately be output. It should be noted that since presence or absence of the input of the first sound signal can be determined based on whether or not one of the first sound signal and the first amplified signal exceeds a threshold level, it is possible to perform the determination more accurately. Since it is also possible to determine whether or not the first sound signal is being input by detecting the contact of the terminal in the first audio input section, the determination can more easily be performed. 
     Further, by providing a microphone input terminal, to which a microphone sound signal is input as the first sound signal, to the first audio input section, the projector can output the microphone sound more appropriately when inputting the microphone sound signal. 
     Further, by providing an audio input terminal, to which a sound signal from an audio output device is input as the second sound signal, to the second audio input section, the projector can output the sound more appropriately when inputting the sound signal from the audio output device. 
     Further, by providing a microphone amplifier for amplifying the microphone sound signal from the microphone input terminal, and stopping the power supply to the microphone amplifier when the microphone sound signal is not input, it is possible to provide a projector capable of appropriately controlling the amount of power consumption in accordance with the input condition of the sound signal. 
     Further, according to another aspect of the invention, there is provided a projector including a first audio input section adapted to input a first sound signal, a second audio input section adapted to input a second sound signal including one of a first channel signal, a second channel signal, and first and second channel signals, a first sound amplifier section adapted to amplify one of the first channel signal of the second sound signal received through the second audio input section and the first sound signal received through the first audio input section to thereby generate a first amplified signal, a second sound amplifier section adapted to amplify the second channel signal of the second sound signal received through the second audio input section to thereby generate a second amplified signal, a first audio output section adapted to output a first sound based on the first amplified signal, and a second audio output section adapted to output a second sound based on the second amplified signal. 
     Further, according to still another aspect of the invention, there is provided an audio output method including (a) receiving a first sound signal, (b) receiving a second sound signal including one of a first channel signal, a second channel signal, and first and second channel signals, (c) amplifying one of the first channel signal of the second sound signal and the first sound signal to thereby generate a first amplified signal, (d) amplifying the second channel signal of the second sound signal to thereby generate a second amplified signal, (e) making a first audio output section output a first sound based on the first amplified signal, and (f) making a second audio output section output a second sound based on the second amplified signal. It should be noted that in the aspect of the invention, the first channel signal and the second channel signal constituting the second sound signal correspond respectively to an L sound signal and an R sound signal described later. 
     According to the aspects of the invention, even in the situation in which a plurality of types of sound signals can be input and then output simultaneously, the projector can output the respective sounds from the separate audio output sections, and therefore, the sound can more appropriately be output. 
     Further, the projector described above can further include the determination section adapted to determine whether or not the first sound signal is being input, and a selection section adapted to input the first channel signal of the second sound signal to the first sound amplifier section if input of the first sound signal is stopped, and input the first sound signal to the first sound amplifier section if the first sound signal is being input. 
     According to this configuration, the projector can select the sound signal to be used in accordance with presence or absence of the input of the first sound signal. Since presence or absence of the input of the first sound signal can be determined based on whether or not one of the first sound signal and the first amplified signal exceeds a threshold level, it is possible to perform the determination more accurately. Since it is also possible to determine whether or not the first sound signal is being input by detecting the contact of the terminal in the first audio input section, the determination can more easily be performed. 
     Further, by providing a microphone input terminal, to which a microphone sound signal is input as the first sound signal, to the first audio input section, the projector can output the microphone sound more appropriately when inputting the microphone sound signal. 
     Further, by providing an audio input terminal, to which a sound signal from an audio output device is input as the second sound signal, to the second audio input section, the projector can output the sound more appropriately when inputting the sound signal from the audio output device. 
     Further, by providing a microphone amplifier for amplifying the microphone sound signal from the microphone input terminal, and stopping the power supply to the microphone amplifier when the microphone sound signal is not input, it is possible to provide a projector capable of appropriately controlling the amount of power consumption in accordance with the input condition of the sound signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a functional block diagram of a projector according to a first embodiment of the invention. 
         FIG. 2  is a flowchart showing an audio output procedure in the first embodiment. 
         FIG. 3  is a functional block diagram of a projector according to a second embodiment. 
         FIG. 4  is a flowchart showing an audio output procedure in the second embodiment. 
         FIG. 5  is a circuit diagram of a microphone detection section in the second embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, some embodiments of the invention applied to a projector will be described with reference to the accompanying drawings. It should be noted that the embodiments described below do not at all limit contents of the invention as set forth in the appended claims. Further, not necessarily all of the constituents shown in the embodiments below are indispensable as the means for solving the problem in the invention set forth in the appended claims. 
     First Embodiment 
       FIG. 1  is a functional block diagram of a projector  101  according to the first embodiment. The projector  101  is configured including a microphone input terminal  110  as a first audio input section, a microphone amplifier section  112 , a line input terminal  120  as a second audio input section, and a level detection section  131 . 
     Further, the projector  101  is configured including a gain adjustment section  152  for adjusting a sound volume of a microphone sound, again adjustment section  153  for adjusting a sound volume of a line sound, a control section  141  for controlling the gain adjustment section  152  and so on in accordance with the level detected by the level detection section  131  and so on, a speaker amplifier section  171  as a first sound amplifier section, a speaker amplifier section  172  as a second sound amplifier section, a microphone speaker  181  as a first audio output section, and a main speaker  182  as a second audio output section. 
     It should be noted that the control section  141  also functions as a determination section for determining whether or not the level of the microphone sound as the first sound signal the level detection section  131  has detected exceeds a predetermined threshold value, thereby determining whether or not the first sound signal is being input. 
     Further, for example, the level detection section  131  and the gain adjustment sections  152 ,  153  can be a digital signal processor (DSP) or the like functioning as an audio controller, and the control section  141  can be a CPU or the like. Other sections are typical terminals, amplifiers, speakers, and so on. 
     Then, an audio output procedure in the projector  101  using these sections will be explained.  FIG. 2  is a flowchart showing the audio output procedure in the first embodiment. 
     The microphone input terminal  110  receives a microphone sound signal from the microphone, and the line input terminal  120  as a kind of audio input terminal for inputting a sound signal from an external audio output device (e.g., a CD player, and an amplifier) receives a line sound signal from the audio output device (step S 1 ). The microphone amplifier section  112  amplifies the microphone sound signal from the microphone input terminal  110 . 
     The level detection section  131  detects a voltage level of the microphone sound signal from the microphone amplifier section  112 , and further, detects the voltage level of the line sound signal from the line input terminal  120  (step S 2 ). 
     The control section  141  determines (step S 3 ) whether or not the voltage level of the microphone sound signal exceeds a predetermined threshold level. It should be noted that it has long been known that when plotting the sound pressure, which can be sensed by human, on a graph having a vertical axis representing sound pressure and a horizontal axis representing frequency with respect to each frequency, a so-called bathtub curve is drawn. This shows a human aural characteristic that the audible sound pressure level in low-frequency range and high-frequency range is higher than the audible sound pressure level in the midrange. Therefore, it is possible to adopt a value corresponding to a sound pressure level in the midrange, which can be heard by human with normal sense of hearing, as the predetermined threshold level. Here, the midrange denotes a range no lower than 100 Hz and no higher than 10 kHz. It should be noted that the threshold level described above is preferably set so as to correspond to the audible sound pressure level in a range from 300 Hz to 1 kHz, which is a frequency range often used by human for conversations in particular in the midrange. 
     If the sound pressure level of the microphone sound signal exceeds the threshold level, the control section  141  controls the gain adjustment section  152  to adjust (step S 4 ) the gain of the microphone sound signal, and controls the speaker amplifier section  171  to amplify (step S 5 ) the microphone sound signal, and then the microphone speaker  181  outputs (step S 6 ) the microphone sound based on the microphone sound signal thus amplified. 
     Further, the control section  141  controls the gain adjustment section  153  to adjust (step S 7 ) the gain of the line sound signal irrespective of the voltage level of the microphone sound signal, controls the speaker amplifier section  172  to amplify (step S 8 ) the line sound signal, and then the main speaker  182  outputs (step S 9 ) the line sound based on the line sound signal thus amplified. 
     As described above, according to the present embodiment, even in the situation in which a plurality of types of sound signals can be input and then output simultaneously, the projector  101  is capable of outputting each of the sounds from separate audio output sections, and therefore, it is not required to mix the sounds internally. Thus, the projector  101  can assure a sufficient sound volume, and further prevent the noise sound due to the sound switching and so on from occurring, and therefore, can output the sounds more appropriately. 
     Further, according to the present embodiment, the projector  101  can determine whether or not the microphone sound signal is actually input by determining whether or not the sound pressure voltage level of the microphone sound signal exceeds the threshold level, and therefore, can more accurately perform the determination. Further, according to the present embodiment, the user can switch between the simultaneous output of the microphone sound and the line sound and the output of the line sound alone by taking out and putting in the microphone plug without performing particular setting. 
     Second Embodiment 
     As the first embodiment, the projector  101  having a plurality of speakers is hereinabove explained. Then, a projector having a single speaker set will be explained. 
       FIG. 3  is a functional block diagram of a projector  102  according to the second embodiment. The projector  102  is configured including a microphone input terminal  110  as a first audio input section, a microphone amplifier section  112 , a line input terminal  120  as a second audio input section, and a level detection section  131 . 
     Further, the projector  102  is configured including a gain adjustment section  154  for adjusting a sound volume of a microphone sound, again adjustment section  155  for adjusting a sound volume of a line sound, a control section  142  for controlling the gain adjustment section  154  and so on in accordance with the level and so on detected by the level detection section  131 , a speaker amplifier section  173  as a first sound amplifier section, a speaker amplifier section  174  as a second sound amplifier section, a main speaker  183  as a first audio output section, and a main speaker  184  as a second audio output section. It should be noted that the main speaker  183  and the main speaker  184  are formed integrally, and are configured so that in normal operations the main speaker  183  outputs an R sound (a sound of a right channel) based on an R sound signal (a sound signal of the right channel) while the main speaker  184  outputs an L sound (a sound of a left channel) based on an L sound signal (a sound signal of the left channel). 
     Further, the projector  102  is configured including a microphone detection section  190  for determining whether or not the microphone plug has contact with the microphone input terminal  110  and a selection section  192  for selecting one of the sound signal of the R channel from the gain adjustment section  155  and the microphone sound signal from the gain adjustment section  154  in accordance with the control of the control section  142 . 
     Some microphone jacks procurable in the market are provided with a detection switch for detecting connection to the microphone plug. Such a microphone jack can be adopted as the microphone input terminal  110 . The microphone detection section  190  can be configured with the detection switch described above and a comparator combined with each other.  FIG. 5  is a diagram showing a circuit configuration of the microphone detection section  190  in the present application example. One end of a detection switch  1901  included in the microphone input terminal  110  is connected to a power supply Vcc via a resistor R 1 , and the other end of the detection switch  1901  is connected to an input terminal of a comparator  1902 . The other end of the detection switch  1901  is grounded via a resistor R 2 . It is assumed in the present embodiment that the resistance value of the resistor R 2  is sufficiently large compared with that of the resistor R 1 . In other words, since the microphone detection section  190  is configured so as to satisfy R 1 &lt;&lt;R 2 , a voltage Vdet applied to the input terminal of the comparator  1902  becomes a high level in the condition in which the microphone plug is not connected to the microphone input terminal  110 , and the voltage Vdet applied to the input terminal of the comparator  1902  becomes a low level in the condition in which the microphone plug is connected to the microphone input terminal  110 . The comparator  1902  is connected to a reference voltage Vref, and outputs a voltage Vcomp corresponding to the result of comparison between the voltage Vdet and the reference voltage Vref. The microphone detection section  190  outputs the result of detection of the microphone plug as the voltage Vcomp. The control section  142  functioning as the determination section determines whether or not the microphone plug is connected to the microphone input terminal  110  based on the voltage Vdet input from the microphone detection section  190 . The selection section  192  can be, for example, a selector. The hardware constituents other than these sections are substantially the same as in the first embodiment, and therefore, the explanations therefor will be omitted. 
     Then, an audio output procedure in the projector  102  using these sections will be explained.  FIG. 4  is a flowchart showing the audio output procedure in the second embodiment. 
     The microphone sound signal is input to the microphone input terminal  110  from the microphone, and the line sound signal is input to the line input terminal  120  (step S 11 ). The level detection section  131  detects a voltage level of the microphone sound signal from the microphone amplifier section  112 , and further, detects the voltage level of the line sound signal from the line input terminal  120  (step S 12 ). 
     The control section  142  controls the gain adjustment section  155  to adjust (step S 13 ) the gain of the line sound signal. 
     The control section  142  determines (step S 14 ) whether or not the microphone plug has contact with the microphone input terminal  110  using the voltage Vdet input from the microphone detection section  190 . 
     If the microphone plug has contact therewith, namely the microphone is inserted, the control section  142  controls the gain adjustment section  154  to adjust (step S 15 ) the gain of the microphone sound signal, makes the selection section  192  select (step S 16 ) the microphone sound signal, and controls the speaker amplifier section  173  to amplify (step S 17 ) the microphone sound signal, and the main speaker  183  outputs (step S 18 ) the microphone sound based on the microphone sound signal thus amplified. 
     On the other hand, if the microphone plug does not have contact therewith, namely the microphone is not inserted, the control section  142  controls the selection section  192  to select (step S 19 ) the R sound signal included in the line sound signal, and controls the speaker amplifier section  173  to amplify (step S 20 ) the R sound signal, and the main speaker  183  outputs (step S 21 ) the R sound based on the R sound signal thus amplified. 
     Further, the control section  142  controls the speaker amplifier section  174  to amplify (step S 22 ) the L sound signal included in the line sound signal regardless of the contact of the microphone plug, and the main speaker  184  outputs (step S 23 ) the L sound based on the L sound signal thus amplified. 
     As described above, according also to the present embodiment, the projector  102  has substantially the same functions and advantages as in the first embodiment. For example, in the case in which the line sound signal and the microphone sound signal are input, the projector  102  can simultaneously output the microphone sound and the L sound, and in the case in which the line sound signal is input alone, the projector  102  can output the R sound and the L sound at the same time. 
     Further, according to the present embodiment, since the speaker dedicated to the microphone is not required, the manufacturers can manufacture the projector  102  with cost lower than in the first embodiment. 
     Other Embodiments 
     It should be noted that applications of the invention is not limited to the embodiments described above, but various modifications thereof are possible. For example, it is also possible for the control section  141  to determine whether or not the microphone sound signal is being input from the microphone input terminal  110  based on the level of the sound signal amplified by the speaker amplifier section  171 . Further, it is also possible to provide a signal channel for bypassing the microphone amplifier section  112 , and determine whether or not the microphone sound signal is being input from the microphone input terminal  110  based on the level of the sound signal not amplified by the microphone amplifier section  112 . 
     Further, the number of microphone input terminals  110  or the number of audio input terminals is not limited to one, but it is also possible to provide a plurality of terminals. Further, the audio input terminal is not limited to the line input terminal  120  as a stereo mini-terminal, but can be, for example, an RCA terminal composed of an R terminal and an L terminal, or an optical digital audio terminal. 
     Further, it is also possible to provide the microphone detection section  190  of the second embodiment to the projector  101  according to the first embodiment, or to provide the determination section of the first embodiment for determining whether or not the voltage level exceeds the threshold level to the projector  102  according to the second embodiment instead of the microphone detection section  190 . 
     It should be noted that although the configuration of the microphone detection section  190  including the comparator  1902  is described as an example in the explanation of the second embodiment, the invention is not limited thereto. For example, it is possible to adopt a configuration of connecting the other end of the detection switch  1901  to an input port of a CPU or the like incorporating an AD converter. Similarly to the control section  141  described above, it is possible to configure the control section  142  with a CPU or the like, and even with such a configuration, advantages equivalent to those of the aspect of the invention described as the second embodiment can be obtained. 
     Further, in the case in which the microphone sound signal is not input, it is also possible for the control section  141  to control the power supply section to stop the power supply to the speaker amplifier section  171  and the microphone speaker  181 . According to this configuration, the projector  101  can operate with smaller electrical energy. 
     Further, the first sound signal and the second sound signal are not limited to the microphone sound signal and the line sound signal. For example, the first sound signal can be a sound signal or the like representing the microphone sound converted into sound data. 
     Further, in the second embodiment, it is also possible that the selection section  192  selects either one of the microphone sound signal and the L sound signal, the main speaker  183  outputs the R sound, and the main speaker  184  outputs either one of the microphone sound and the L sound. 
     Further, although in the embodiments described above it is assumed that the second sound signal is the sound signal including the L sound signal and the R sound signal, namely a stereo sound signal, the invention is not limited thereto. For example, the second sound signal can be a monaural sound signal. In this case, the first channel signal and the second channel signal according to the aspects of the invention are recognized as terms both denoting the second sound signal. 
     Further, the projectors  101 ,  102  are not limited to a liquid crystal projector (a transmissive type, a reflective type such as LCOS), but can be, for example, a projector using a digital micromirror device (DMD). Further, the function of the projectors  101 ,  102  can be distributed in two or more devices (e.g., a PC and a projector).