Patent Publication Number: US-7902981-B2

Title: Image display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-278873, filed on Oct. 12, 2006, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an image display device such as liquid crystal projector having a theft prevention function. 
     Image display devices, such as a liquid crystal projector, have become popular. A liquid crystal projector is compact, easy to carry, and relatively expensive. As a result, theft of liquid crystal projectors is increasing. This has increased the need for theft prevention measures. 
     Theft prevention measures include the setting of passwords or the use of PC cards so that a liquid crystal projector has a theft prevention function or the attachment of a theft prevention device to the liquid crystal projector. 
     Japanese Laid-Open Patent Publication No. 7-160955 discloses a theft prevention device connected to a liquid crystal projector by a multi-core cable. More specifically, the theft prevention device includes an alarm control device and an alarm device. The alarm control device is connected to the liquid crystal projector by a multi-core cable including a plurality of signal lines. The alarm device is connected to the alarm control device and receives a theft detection signal generated by the alarm control device. The alarm control device generates the theft detection signal, and sends the theft detection signal to the alarm device when the multi-core cable is cut or when the liquid crystal projector is disconnected from the multi-core cable to carry away the liquid crystal projector. The alarm device generates a warning such as buzzing sound. 
     However, in the conventional theft prevention device, the function of the theft prevention device, that is, the alarm function of the alarm device is valid from when the device is shipped out of a factory to when the user starts use. Therefore, the theft prevention function may be erroneously activated after the alarm device is shipped out of the factory and before the user starts use (e.g., when packaging or transporting the theft prevention device). In such a case, a warning such as buzzing sound is given off even though theft of the liquid crystal projector has not occurred. This creates undesirable noise. 
     SUMMARY OF THE INVENTION 
     The present invention provides an image display device that prevents erroneous activation of the theft prevention function. 
     One aspect of the present invention is an image display device for production in a factory. The image display device includes a theft prevention unit having an alarm function for preventing theft of the image display device. A control circuit controls the theft prevention unit. The control circuit invalidates the alarm function of the theft prevention unit before the image display device is shipped out of the factory. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a schematic block diagram of an image display device according to a preferred embodiment of the present invention; 
         FIG. 2  is a flowchart showing the procedures of preventing erroneous activation of a theft prevention device for the image display device of  FIG. 1 ; and 
         FIG. 3  is a flowchart showing the procedures for validating an alarm function of the theft prevention device for the image display device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A liquid crystal projector  1  according to a preferred embodiment of the present invention will now be described with reference to the drawings.  FIG. 1  is a schematic block diagram of the liquid crystal projector  1 , which serves as an image display device of the present invention. 
     As shown in  FIG. 1 , the liquid crystal projector  1  includes a signal processor  2  for performing predetermined signal processing on an image signal (i.e., RGB video signal) provided from an external device such as computer  50  to the liquid crystal projector  1 . The liquid crystal projector  1  also includes a red liquid crystal driver  3 , a green liquid crystal driver  4 , and a blue liquid crystal driver  5  (hereinafter referred to as “liquid crystal drivers  3  to  5 ”), which receive the image signal that has been signal-processed by the signal processor  2  and respectively drive a red liquid crystal panel  6 , a green liquid crystal panel  7 , and a blue liquid crystal panel  8  (hereinafter referred to as “liquid crystal panels  6  to  8 ”). 
     A liquid crystal panel that incorporates a shift register and uses an active matrix type thin-film transistor (TFTs) is employed as the liquid crystal panels  6  to  8  driven by the liquid crystal drivers  3  to  5 . More specifically, a liquid crystal panel including an effective pixel section with an m×n matrix of a plurality of pixels, a vertical scanning circuit for driving each scanning line, a horizontal scanning circuit for scanning each horizontal line, and a thin-film transistor serving as a switching element can be used. 
     The liquid crystal projector  1  includes a CPU  12 , which serves as a control circuit for controlling the signal processor  2  and the liquid crystal drivers  3  to  5 . The liquid crystal projector  1  also includes a ROM  13  and a RAM  14 , each serving as a storage circuit. The ROM  13  and the RAM  14  are connected to the CPU  12 . The CPU  12  controls the signal processor  2  and the liquid crystal drivers  3  to  5  in accordance with programs stored in the ROM  13 . 
     A remote control signal receiver  16  is connected to the CPU  12 . The remote control signal receiver  16  provides the CPU  12  with a remote signal SG 1  received from a remote controller  17 . 
     The liquid crystal projector  1  receives from a computer  50  image signals R, G, and B that are provided to the signal processor  2  and signal-processed. More specifically, if the image signals are analog signals, the signal processor  2  samples the image signals R, G, and B received from the computer  50  at appropriate timings and converts the sampled signals into digital signals. Furthermore, the signal processor  2  adjusts the brightness and contrast and performs gamma correction. The signal processor  2  then converts the image signals R, G, and B from digital signals to analog signals. In this manner, the signal processor  2  generates the signal processed image signals R, G, and B. 
     The image signals R, G, and B, which are signal processed by the signal processor  2 , are provided to the liquid crystal drivers  3  to  5 . The liquid crystal drivers  3  to  5  drive the liquid crystal panels  6  to  8  based on the image signals R, G, and B, respectively. More specifically, the liquid crystal driver  3  performs AC inversion on the image signal R at a predetermined timing and provides and drives the liquid crystal panel  6  with the AC-inverted image signal R. The liquid crystal driver  4  performs AC inversion on the image signal G at a predetermined timing and provides and drives the liquid crystal panel  7  with the AC-inverted image signal G. The liquid crystal driver  5  performs AC inversion on the image signal B at a predetermined timing and provides and drives the liquid crystal panel  8  with the AC-inverted image signal B. 
     Each of the liquid crystal panels  6  to  8  writes the image signal R, G, and B that have been AC-inverted by the liquid crystal drivers  3  to  5  to a predetermined pixel while controlling write transfer in the horizontal direction and the vertical direction based at predetermined timings. This forms an image with each of the liquid crystal panels  6  to  8 . 
     Light from a light source (not shown) is transmitted through the images formed by the liquid crystal panels  6  to  8 . This generates image lights of red (R), green (G), and blue (B) colors. The generated image lights are synthesized by a cross-dichroic prism (not shown) and converted into color image light. A projection lens (not shown) magnifies and projects the color image light onto a screen. 
     The liquid crystal projector  1  has a theft prevention function. More specifically, the liquid crystal projector  1  includes a theft prevention unit  9  having an alarm function for preventing theft of the liquid crystal projector  1 . The theft prevention unit  9  includes a vibration sensor  10  and an alarm device  11 . The vibration sensor  10  serves as a detector for detecting theft of the liquid crystal projector  1 . The alarm device  11  generates a warning such as buzzing sound when the vibration sensor  10  detects theft of the liquid crystal projector  1 . The alarm device  11  functions as a notifier for notification of theft. Furthermore, the theft prevention unit  9  includes a CPU  15 , a ROM  18 , and a RAM  19 . The CPU  15  serves as another control circuit, connected to the vibration sensor  10  and the alarm device  11 , for controlling the vibration sensor  10  and the alarm device  11 . The ROM  18  and RAM  19  each serve as a storage circuit and are connected to the CPU  15 . The CPU  15  controls the theft prevention unit  9  in a centralized manner in accordance with programs stored in the ROM  18 . The theft prevention unit  9  also includes a rechargeable battery  30  for supplying power to the vibration sensor  10 , the alarm device  11 , and the CPU  15 . 
     In the preferred embodiment, the vibration sensor  10  uses a sensor capable of detecting vibrations caused by movement when the liquid crystal projector  1  is stolen. For example, an acceleration sensor or a distortion gauge sensor may be used as the vibration sensor  10 . The alarm device  11  may be at least one of a voice output device (not shown), such as buzzer, and a display output device (not shown), such as a display lamp (e.g., LED). 
     The liquid crystal projector  1  includes a power supply unit  20  connected to the theft prevention unit  9 . Power (AC voltage) is supplied from an AC power supply  23  to the power supply unit  20  through a power supply cable  21 . The power supply unit  20  converts the AC voltage supplied from the AC power supply  23  into DC voltage to supply the power from the AC power supply  23  to the theft prevention unit  9 . 
     As shown in  FIG. 1 , the theft prevention unit  9  includes an I/O port  22  serving as a power supply detector for detecting activation and deactivation of the AC power supply  23 . The I/O port  22  is connected to the CPU  15  and the power supply unit  20 . When power from the AC power supply  23  is supplied to the theft prevention unit  9 , the AC power supply  23  generates a high signal, which is provided to the CPU  15  via the I/O port  22 . In this case, the CPU  15  determines that the AC power supply  23  is in the activated state. When the AC power supply  23  does not supply power to the theft prevention unit  9 , the AC power supply  23  generates a low signal, which is provided to the CPU  15  via the I/O port  22 . In this case, the CPU  15  determines that the AC power supply  23  is in the deactivated state. In other words, the I/O port  22  serves as a port used by the CPU  15  to recognize the state of the AC power supply  23 . The rechargeable battery  30  is charged by the power supplied from the AC power supply  23  in the activated state. When the AC power supply  23  is in deactivated state, power is supplied to the theft prevention unit  9  from the rechargeable battery  30 . 
     The operation of the theft prevention unit  9  will now be discussed. 
     When a thief tries to steal the liquid crystal projector  1 , the vibration sensor  10  detects vibrations of the liquid crystal projector  1 . More specifically, if the vibration sensor  10  is an acceleration sensor, the acceleration sensor detects acceleration for three axes, which are in two horizontal and orthogonal directions (X axis and Y axis) and one vertical direction (Z axis) and detects vibration components of the liquid crystal projector  1 . The values of the acceleration detected by the acceleration sensor are then provided to the CPU  15 . The CPU  15  determines whether or not theft of the liquid crystal projector  1  is in progress based on the detection values of the acceleration sensor. More specifically, the CPU  15  calculates an inclination angle of the liquid crystal projector  1  based on the detection values of the acceleration sensor. Then, the CPU  15  compares the calculated inclination angle with a predetermined inclination angle of the liquid crystal projector  1  that is stored in the ROM  18 . 
     If the calculated inclination angle is greater than the predetermined inclination angle in the ROM  18 , the CPU  15  determines that theft of the liquid crystal projector  1  is in progress and generates a theft detection signal. In response to the theft detection signal, the alarm device  11  generates a warning, such as a buzzing sound, for an alert of the theft. In this manner, the alarm function of the theft prevention unit  9  is activated by the activation of the vibration sensor  10  and the alarm device  11 . 
     If the inclination angle calculated from the detection value of the acceleration sensor is less than the predetermined inclination angle, the CPU  15  determines that theft of the liquid crystal projector  1  is not in progress and does not generate the theft detection signal. Therefore, the alarm device  11  is not operated, and a warning, such as buzzing sound, for notification of a theft is not generated. 
     The theft prevention unit  9  operates in an anti-theft valid mode and an anti-theft invalid mode. In the anti-theft valid mode, the alarm device  11  generates a warning when the vibration sensor  10  detects vibrations. In the anti-theft invalid mode, the alarm device  11  does not generate a warning even if the vibration sensor  10  detects vibrations. The two modes are switched by operating a switch (not shown) arranged in the theft prevention unit  9 . When in the anti-theft valid mode, the alarm function of the theft prevention unit  9  is valid. 
     The prevention of erroneous activation of the alarm function in the theft prevention unit  9  will now be described.  FIG. 2  is a flowchart showing the procedures for preventing erroneous activation of the theft prevention device in the liquid crystal projector  1  of  FIG. 1 . The flowchart shows the procedures that are carried out before the liquid crystal projector  1  incorporating the theft prevention unit  9  is shipped out of a factory. 
     As shown in  FIG. 2 , the AC power supply  23  is first activated so that adjustment of each unit (signal processor  2  and liquid crystal drivers  3  to  5 ) is performed in the liquid crystal projector  1  (step S 1 ). The remote control signal receiver  16  receives the remote control signal SG 1 , which is for performing factory shipment setting on the theft prevention unit  9 , from the remote controller  17 , and provides the remote control signal SG 1  to the CPU  12  (step S 2 ). “Factory shipment setting” is performed to set initial values for parameters related with the alarm function of the theft prevention unit  9 . Such parameters include volume and buzzing time of the alarm device  11  and sensitivity of the vibration sensor  10 . The CPU  12  then generates a control signal for controlling the theft prevention unit  9  based on the remote control signal SG 1  and provides the control signal to the CPU  15  of the theft prevention unit  9  (step S 3 ). The CPU  15  sets initial values for various parameters related with the alarm function of the theft prevention unit  9  in the ROM  18  based on the provided control signal (step S 4 ). After setting the initial values, the CPU  15  invalidates the alarm function of the theft prevention unit  9  (step S 5 ). In other words, the CPU  15  invalidates the functions of the vibration sensor  10  and the alarm device  11  based on the provided control signal. After the functions of the vibration sensor  10  and the alarm  11  are invalidated, switching between the anti-theft valid mode and the anti-theft invalid mode cannot be performed even if the switch (not shown) arranged in the theft prevention unit  9  is operated. 
     In this manner, the CPU  12  invalidates the alarm function of the theft prevention unit  9  before the liquid crystal projector  1  is shipped out of the factory. Therefore, after shipment from the factory (e.g., when packaging or transporting the theft prevention device), the alarm function of the theft prevention unit  9  is prevented from being erroneously activated until the user starts use. 
     After the liquid crystal projector  1  is deactivated, the AC power supply  23  is deactivated (step S 6 ). The AC power supply  23  generates a low signal and provides the low signal to the CPU  15  via the I/O port  22 . Therefore, the CPU  15  determines (detects) that the AC power supply  23  is deactivated. This stops the supply of power from the AC power supply  23  to the theft prevention unit  9  and starts the supply of power from the rechargeable battery  30  to the theft prevention unit  9  (step S 7 ). The CPU  15  sets the theft prevention unit  9  to a low power consumption mode (or standby mode) (step S 8 ). Specifically, the CPU  15  deactivates the function of each unit (e.g., ROM  18  and RAM  19 ) except for the CPU  15  and the I/O port  22  in the theft prevention unit  9  to suppress drainage of the rechargeable battery  30  when the AC power supply  23  is deactivated (i.e., when power is not being supplied from the AC power supply  23 ). The liquid crystal projector  1  is then shipped out of the factory. 
     Validation of the alarm function will now be described.  FIG. 3  is a flowchart showing procedures for validating the alarm function of the theft prevention device in the liquid crystal projector  1  of  FIG. 1 . The flowchart shows the procedures taken when the user starts to use the liquid crystal projector  1  incorporating the theft prevention unit  9  that has been shipped out of the factory. 
     As shown in  FIG. 3 , the AC power supply  23  is activated to start the use of the liquid crystal projector  1 . This starts the supply of power from the AC power supply  23  (step S 11 ). The CPU  12  then generates the control signal for validating the alarm function of the theft prevention unit  9  and provides the control signal to the CPU  15  (step S 12 ). The CPU  15  causes the theft prevention unit  9  to exit the low power consumption mode, which has been set before factory shipment, reads the initial value data of various parameters related with the alarm function of the theft prevention unit  9  from the ROM  18 , and provides the initial value data to the CPU  12  (step S 13 ). Then, the AC power supply  23  generates and provides a high signal to the CPU  15  via the I/O port  22 . Therefore, the CPU  15  determines (detects) that the AC power supply  23  is activated (step S 14 ). As a result, the supply of power from the rechargeable battery  30  is stopped, and the supply of power from the AC power supply  23  is started (step S 15 ). The CPU  15  validates the alarm function of the theft prevention unit  9  based on the control signal provided from the CPU  12  (step S 16 ). More specifically, the CPU  15  activates the vibration sensor  10  and the alarm device  11  based on the provided control signal. 
     The CPU  12  operates the alarm function of the theft prevention device when the supply of power from the AC power supply  23  starts after factory shipment of the liquid crystal projector  1 . Therefore, the alarm function of the theft prevention unit  9  becomes valid through a simple structure when the user starts using the liquid crystal projector  1  that has been shipped out of the factory. 
     After activating the functions of the vibration sensor  10  and the alarm device  11 , the anti-theft valid mode and the anti-theft invalid mode may be switched by operating the switch (not shown) arranged in the theft prevention unit  9 . Therefore, the user can set the anti-theft valid mode whenever necessary. 
     The liquid crystal projector  1  of the preferred embodiment has the advantages described below. 
     (1) The liquid crystal projector  1  includes the theft prevention unit  9 , which has an alarm function for preventing theft of the liquid crystal projector  1 , and the CPU  12 , which generates the control signal for controlling the theft prevention unit  9 . The CPU  12  invalidates the alarm function of the theft prevention unit  9  before the liquid crystal projector  1  is shipped out of a factory. Therefore, the alarm function of the theft prevention unit  9  is prevented from being erroneously activated from when the liquid crystal projector  1  is shipped out of the factory until when the user starts using the liquid crystal projector  1  (e.g., when packaging or transporting the liquid crystal projector  1 ). This prevents the generation of a warning, such as buzzing sound, caused by erroneous activation of the alarm function. 
     (2) The theft prevention unit  9  includes the vibration sensor  10  for detecting theft of the liquid crystal projector  1 , the alarm device  11  for notification of theft of the liquid crystal projector  1  based on the detection result of the vibration sensor  10 , and the CPU  15  for controlling the vibration sensor  10  and the alarm device  11 . The CPU  15  deactivates the vibration sensor  10  and the alarm device  11  based on the control signal generated by the CPU  12 . Therefore, erroneous activation of the alarm function of the theft prevention unit  9  is easily prevented by the control signal of the CPU  12 . 
     (3) The theft prevention unit  9  further includes the rechargeable battery  30  for supplying power to the theft prevention unit  9 . When the supply of power from the AC power supply  23  is stopped, the rechargeable battery  30  supplies power to the theft prevention unit  9 . When power is supplied from the rechargeable battery  30  to the theft prevention unit  9 , the CPU  15  sets the theft prevention unit  9  to the low power consumption mode. This effectively suppresses drainage of the rechargeable battery  30  until the user starts to use the liquid crystal projector  1  that has been shipped out of the factory. 
     (4) When the supply of power from the AC power supply  23  is started after the liquid crystal projector  1  is shipped out of the factory, the CPU  12  validates the alarm function of the theft prevention unit  9 . Therefore, the alarm function of the theft prevention unit  9  is validated through a simple structure when the user starts to use the liquid crystal projector  1  after the liquid crystal projector  1  is shipped out of the factory. As a result, the troublesome operations are unnecessary, and convenience for the user is improved. 
     (5) The CPU  15  activates the functions of the vibration sensor  10  and the alarm device  11  based on the control signal generated by the CPU  12 . Therefore, the CPU  15  validates the alarm function of the theft prevention unit  9  with a simple structure based on the control signal of the CPU  12 . 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     When using the liquid crystal projector  1 , the anti-theft valid mode may be canceled by operating a button (not shown) arranged in the theft prevention unit  9  and inputting a password. This would prevent a person other than the user from canceling the anti-theft valid mode. 
     A further notifier (not shown) for providing notification of drainage of the rechargeable battery  30 , the setting of anti-theft valid mode, and changes in the password may be arranged in the theft prevention unit  9 . For example, an LED may be arranged as the further notifier. In this case, for example, the LED is lighted for a predetermined time (e.g., 20 seconds) when the rechargeable battery  30  is drained to notify the user that the rechargeable battery is drained. 
     The image display device of the present invention is not limited to the liquid crystal projector  1  that uses a liquid crystal panel and is applicable to an image display devices incorporating other image light generation systems. 
     Furthermore, the image display device of the present invention may be a front projection type image display device or a rear projection type image display device. 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.