Patent Publication Number: US-9906673-B2

Title: Image forming apparatus, control method thereof and storage medium

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/847,217, filed Sep. 8, 2015, which claims the benefit and priority from Japanese Patent Application No. 2014-184538, filed Sep. 10, 2014, the disclosures of each of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus including a sensor that detects a person who comes close to the image forming apparatus, a control method thereof, and a storage medium. 
     Description of the Related Art 
     Among current image forming apparatuses, there is an image forming apparatus that is returned from a power saving state when a person is detected in front of the apparatus by a sensor, and performs control to reduce the return time felt by the user. However, such a sensor can detect a passerby simply passing in front of the apparatus and can erroneously return the apparatus from a power saving state. Japanese Patent Laid-Open No. 2012-114499 proposes a technique in which, after the sensor provided in the image forming apparatus detects a person coming close to the apparatus, the sensor causes the image forming apparatus to return from a power saving state by determining that the person has stopped in front of the image forming apparatus. More specifically, it proposes a technique of returning the image forming apparatus from the power saving state by determining that a person has stopped in front of the image forming apparatus when a pyroelectric sensor capable of detecting human motion cannot detect the person anymore. 
     The above-described related art, however, has a problem as described below. For example, in the related art, an operator in front of the apparatus must wait there until the image forming apparatus is returned from the power saving state since the image forming apparatus is returned from the power saving state after it is determined that the operator of image forming apparatus has stopped in front of the apparatus. The return time, in this case, is no different from the return time of a case in which the image forming apparatus is returned from the power saving state after the user has operated an operation panel or the like. Thus, the full effect of returning the image forming apparatus from a power saving state in advance by detecting a person with a sensor cannot be obtained. 
     SUMMARY OF THE INVENTION 
     The present invention enables realization of a mechanism for detecting a person in front of an apparatus and controlling whether to return from a power saving state by suitably determining whether the detected person is an operator of the apparatus. 
     One aspect of the present invention provides an image forming apparatus comprising: a detection unit configured to detect a distance between the image forming apparatus and an object located around the image forming apparatus; and a control unit configured to return the image forming apparatus from a power saving state when the distance detected by the detection unit is shorter than a predetermined distance; wherein the control unit returns the image forming apparatus from the power saving state, even if the distance detected by the detection unit is longer than the predetermined distance, in a case where the distance detected by the detection unit decreases every predetermined time. 
     Another aspect of the present invention provides a control method for an image forming apparatus, comprising: detecting a distance between the image forming apparatus and an object located around the image forming apparatus; and controlling to return the image forming apparatus from a power saving state when the distance detected in the detecting is shorter than a predetermined distance; wherein in the controlling, the image forming apparatus is returned from the power saving state, even if the distance detected in the detecting is longer than the predetermined distance, in a case where the distance detected in the detecting decreases every predetermined time. 
     Still another aspect of the present invention provides a non-transitory computer-readable storage medium storing a computer program for causing a computer to execute each step of a control method for an image forming apparatus, detecting a distance between the image forming apparatus and an object located around the image forming apparatus; and controlling to return the image forming apparatus from a power saving state when the distance detected in the detecting is shorter than a predetermined distance; wherein in the controlling, the image forming apparatus is returned from the power saving state, even if the distance detected in the detecting is longer than the predetermined distance, in a case where the distance detected in the detecting decreases every predetermined time. 
     Further features of the present invention will be apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows views of the outer appearance of an image forming apparatus according to the first embodiment; 
         FIG. 2  is a hardware block diagram of the image forming apparatus according to the first embodiment; 
         FIG. 3  is a diagram of a power supply circuit of the image forming apparatus according to the first embodiment; 
         FIG. 4  is a view showing the state transition of the image forming apparatus according to the first embodiment; 
         FIG. 5  is a diagram showing the standby state of the image forming apparatus according to the first embodiment; 
         FIG. 6  is a diagram showing the power saving state of the image forming apparatus according to the first embodiment; 
         FIG. 7  is a diagram showing the quiet return state of the image forming apparatus according to the first embodiment; 
         FIG. 8  is a diagram showing the display unit return state of the image forming apparatus according to the first embodiment; 
         FIG. 9  shows detailed views of an operation unit according to the first embodiment; 
         FIG. 10  shows views for explaining the power control transition according to a distance between an operator and the image forming apparatus according to the first embodiment; 
         FIG. 11  is a flowchart showing the power control sequence of the image forming apparatus according to the first embodiment; 
         FIGS. 12A to 12D  show views for explaining the determination of the image forming apparatus according to the distance between the operator and the image forming apparatus according to the first embodiment; 
         FIG. 13  shows a flowchart of a person detection sequence and a flowchart of an operator detection sequence, respectively, of the image forming apparatus according to the first embodiment; and 
         FIG. 14  is a view showing a person putting a hand over an operation unit of an image forming apparatus according to the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. 
     First Embodiment 
     Arrangement of Image Forming Apparatus 
     The first embodiment of the present invention will be described below with reference to  FIGS. 1 to 13 . First, the outer appearance of an image forming apparatus  100  according to the embodiment will be described with reference to  FIG. 1 . 
     The image forming apparatus  100  is an MFP (Multifunction Peripheral) which provides a plurality of functions such as a print function, a scanner function, a copy function, and a FAX function. The image forming apparatus  100  includes an ultrasonic sensor  15  for detecting a person who comes close to the image forming apparatus  100 . This embodiment will describe an example, as shown in  FIG. 1 , in which the ultrasonic sensor  15  is provided on an operation unit of the image forming apparatus. However, the present invention is not limited to this. The ultrasonic sensor  15  can be provided anywhere as long as the sensor is located where it can detect an object around the image forming apparatus  100 . When the ultrasonic sensor  15  detects that a person has come close to the image forming apparatus  100 , the image forming apparatus  100  is returned to a standby state, which allows any of the above functions to be used, from a power saving state which consumes less power than the standby state. 
     By outputting a 40-kHz pulse wave in an inaudible frequency range and receiving a reflected wave of the pulse wave reflected by an object (a person or the like), the ultrasonic sensor  15  can detect the object located around the image forming apparatus. Based on the time taken to receive the reflected wave since the output of the pulse wave, the ultrasonic sensor  15  measures the distance between the object and the image forming apparatus  100 . The measurement is conducted for every predetermined time, and the transition of the distance between the image forming apparatus  100  and the object can be checked every predetermined time. Note that while a case in which the ultrasonic sensor  15  is used has been exemplified, as long as it is a sensor capable of detecting a person, the sensor may be an infrared receiving sensor which receives infrared rays emitted from a person. Additionally, instead of the ultrasonic sensor  15 , a capacitance sensor which measures the distance between the sensor and a target object based on the capacitance between the sensor and the target object may be used. Further, instead of the ultrasonic sensor  15 , an infrared array sensor having infrared receiving units arranged in a line or a matrix may be used. The ultrasonic sensor  15  also has a fan-shaped detection range A 1 . Note that in order to detect a person without being influenced by an obstacle such as a computer placed on a desk, the ultrasonic sensor  15  may be arranged so that the output direction of the pulse wave becomes upward. 
     The control arrangement of the image forming apparatus  100  will be described next with reference to  FIG. 2 . The image forming apparatus  100  includes a controller  11 , an operation unit  12 , a scanner unit  13 , a printer unit  14 , and the ultrasonic sensor  15 . 
     The controller  11  is communicably connected to the operation unit  12 , the scanner unit  13 , and the printer unit  14 . The controller  11  includes a CPU  301 , a RAM  302 , a ROM  303 , a power supply control unit  304 , an input/output I/F  305 , and a LAN controller  306 . The CPU  301 , the RAM  302 , the ROM  303 , the power supply control unit  304 , the input/output I/F  305 , and the LAN controller  306  are connected to a system bus  307 . Additionally, the controller  11  includes an HDD  308 , an image processing unit  309 , a scanner I/F  310 , and a printer I/F  311 . The HDD  308 , the image processing unit  309 , the scanner I/F  310 , and the printer I/F  311  are connected to an image bus  312 . 
     As well as collectively controlling the access of each connected device based on a control program or the like stored in the ROM  303 , the CPU  301  collectively controls each processing to be executed in the controller  11 . The RAM  302  is a system work memory for operating the CPU  301 . This RAM  302  is also a memory for temporarily storing image data. A boot program of the apparatus and the like are stored in the ROM  303 . 
     The power supply control unit  304  controls the power supply to each unit of the image forming apparatus  100 . Details of the power supply control unit  304  will be described later. The input/output I/F  305  is an interface unit to connect the system bus  307  and the operation unit  12 . This input/output I/F  305  receives image data to be displayed on the operation unit  12  from the system bus  307  and outputs the data to the operation unit  12 . The image input/output I/F  305  outputs, to the system bus  307 , information input from the operation unit  12 . The LAN controller  306  exchanges information with an external apparatus  20  connected to a network  30 . 
     The HDD  308  is a hard disk drive and stores system software and image data. The image processing unit  309  reads out image data stored in the RAM  302  and performs image processing such as color adjustment, enlargement or reduction such as JPEG or JBIG. The image data is data such as an image read by the scanner unit  13 , an image to be printed by the printer unit  14 , or an image received from an external apparatus  20 . The scanner I/F  310  is an interface unit to communicate with a scanner control unit  331  of the scanner unit  13 . The printer I/F  311  is an interface unit to communicate with a printer control unit  341  of the printer unit  14 . The image bus  312  is a transmission line for exchanging image data and is configured by a bus such as a PCI bus or an IEEE1394. 
     The scanner unit  13  optically reads an image from an original and generates image data. The scanner unit includes the scanner control unit  331  and a scanner driving unit  332 . The scanner driving unit  332  includes a driving unit for moving the reading head which reads an original and a driving unit for conveying the original to the reading position. The scanner control unit  331  controls the operation of the scanner driving unit  332 . The scanner control unit  331  receives setting information set by an user to perform scanning by communicating with the CPU  301  and controls the operation of the scanner driving unit  332  based on the setting information. 
     The printer unit  14  forms an image on a print medium (print sheet) in accordance with an electrophotography method. This printer unit  14  includes the printer control unit  341  and a printer driving unit  342 . The printer driving unit  342  includes a motor to rotate a photosensitive drum, a mechanism unit for pressurizing a fixing unit, and a heater. The printer control unit  341  controls the operation of the printer driving unit  342 . The printer control unit  341  receives setting information set by an user to perform printing by communicating with the CPU  301  and controls the operation of the printer driving unit  342  based on the setting information. 
     &lt;Power Supply Circuit&gt; 
     The arrangement of a power supply circuit of the image forming apparatus  100  will be described next with reference to  FIG. 3 . The image forming apparatus  100  includes a first power supply unit  501 , a second power supply unit  502 , and a third power supply unit  503 . 
     The first power supply unit  501  generates a DC power supply voltage of about 5.0 V from an AC power supply voltage supplied via a plug P. The first power supply unit  501  supplies the generated DC power supply voltage to the LAN controller  306 , the RAM  302 , the ultrasonic sensor  15 , the CPU  301 , the ROM  303 , the HDD  308 , and to a power saving button  204  and a microcomputer  203  of the operation unit  12 . The devices that receive a power supply voltage from the first power supply unit  501  will be referred to as first power supply system devices hereinafter. 
     The second power supply unit  502  generates a DC power supply voltage of about 12.0 V from the AC power supply voltage supplied via the plug P. The second power supply unit  502  supplies the generated DC power supply voltage to a display unit  201 , the image processing unit  309 , the printer control unit  341 , and the scanner control unit  331 . The devices that receive a power supply voltage from the second power supply unit  502  will be referred to as second power supply system devices hereinafter. 
     The third power supply unit  503  generates a DC power supply voltage of about 24.0 V from the AC power supply voltage supplied via the plug P. The third power supply unit  503  supplies the generated DC power supply voltage to the printer driving unit  342  and the scanner driving unit  332 . The devices that receive a power supply voltage from the third power supply unit  503  will be referred to as third power supply system devices hereinafter. 
     A seesaw switch  510  which is turned on and off according to the operation by the user is arranged between the first power supply unit  501  and the first power supply system devices. Additionally, a relay switch  511  is arranged in parallel with the seesaw switch  510  to supply power generated by the first power supply unit  501  to the first power supply system devices. Even when the seesaw switch  510  is turned off by the operation of the user, if the relay switch  511  is ON, power is supplied from the first power supply unit  501  to the first power system devices via the relay switch  511 . The power supply control unit  304  is notified, via a signal A, about the seesaw switch  510  being turned off. When the seesaw switch  510  is turned off, the power supply control unit  304  instructs the CPU  301  to execute shutdown processing. When the shutdown processing is executed by the CPU  301 , the power supply control unit  304  turns off the relay switch  511 . Thus, the image forming apparatus  100  is completely turned off. 
     A relay switch  512  which switches between supplying power and interrupting the supply of power from the plug P to the second power supply unit is arranged between the plug P and the second power supply unit  502 . A relay switch  513  which switches between supplying power and interrupting the supply of power from the plug P to the third power supply unit  503  is arranged between the plug P and the third power supply unit  503 . 
     A switch  514  which switches between supplying power and stopping the supply of power to the CPU  301 , the ROM  303 , and the HDD  308  is arranged between the first power supply unit  501  and the CPU  301 , the ROM  303 , and the HDD  308 . A switch  515  which switches between supplying power and stopping the supply of power to the scanner control unit  331  is arranged between the scanner control unit  331  and the second power supply unit  502 . A switch  516  which switches between supplying power and stopping the supply of power to the printer control unit  341  is arranged between the printer control unit  341  and the second power supply unit  502 . A switch  517  which switches between supplying power and stopping the supply of power to the display unit  201  is arranged between the display unit  201  of the operation unit  12  and the second power supply unit  502 . 
     Additionally, a switch  518  which switches between supplying power and stopping the supply of power to the scanner driving unit  332  is arranged between the scanner driving unit  332  and the third power supply unit  503 . A switch  519  which switches between supplying power and stopping the supply of power to the printer driving unit  342  is arranged between the printer driving unit  342  and the third power supply unit  503 . Note that each of the switches  511  to  519  may be configured by an FET switch. 
     Next, the details of the power supply control unit  304  will be described. The power supply control unit  304  is a programmable logic circuit capable of rewriting a circuit. The power supply control unit  304  of the embodiment is a CPLD (Complex Programmable Logic Device). The power supply control unit  304  detects a return factor for returning the image forming apparatus  100  from a power saving state ST 4  and performs power control in accordance with the detected return factor. The return factor includes the following factors: the seesaw switch  510  is turned on from OFF (a signal A), a specific packet (for example, a print job) is received from the external apparatus  20  (a signal P), a person comes close to the image forming apparatus  100  (a signal Q), and the power saving button  204  is pressed (operated) by the user (a signal R). 
     The signals A, P, Q, and R indicating the above return factors are input to the power supply control unit  304 . The signal A indicates the state (on/off) of the seesaw switch  510 , and is output from the seesaw switch  510 . The signal P indicates that the LAN controller  306  has received a specific packet (a print job or the like) from the external apparatus  20 , and is output from the LAN controller  306 . The signal Q indicates that the ultrasonic sensor  15  has detected an object such as a person, and is output from the ultrasonic sensor  15 . The signal R indicates that the power saving button  204  of the operation unit  12  has been pressed by the user, and is output from the power saving button  204 . 
     The power supply control unit  304  also outputs signals B, C, E, F, G, H, I (controls the logic levels of the signals B, C, E, F, G, H, I). The signal B switches on and off the relay switch  511 . The signal C respectively switches on and off the relay switches  512  and  513 . The signal D switches on and off the switch  514 . The signal E switches on and off the switch  515 . The signal F switches on and off the switch  516 . The signal G switches on and off the switch  517 . The signal H switches on and off the switch  518 . The signal I switches on and off the switch  519 . 
     When the seesaw switch  510  is turned off by the operation of the user, the logic of the signal A is set at low level. When the logic of the signal A is set at low level, the power supply control unit  304  instructs the CPU  301  to shut down the image forming apparatus  100 . The CPU  301  executes the shutdown processing in accordance with the instruction. The power supply control unit  304  also controls the signals B and C to turn off the relay switches  511 ,  512  and  513 . Thus, the image forming apparatus  100  is appropriately turned off after the shutdown processing. 
     When the LAN controller  306  receives a specific packet (a print job) from the external apparatus  20 , the logic of the signal P changes to high level. When the logic of the signal P is set at high level, the power supply control unit  304  controls the signals C, D, F, and I to turn on the relay switches  512 ,  513 ,  514 ,  516 , and  519 . Thus, printing based on the print job is executed by the printer unit  14 . 
     When the ultrasonic sensor  15  detects an object such as a person, the logic of the signal Q changes to high level. When the logic of the signal Q is set at high level, the power supply control unit  304  controls the signals C, D, E, F, H, and I to turn on the switches  512  to  516 ,  518 , and  519 . Additionally, when the ultrasonic sensor  15  detects an object such as a person, the power supply control unit  304  sets the logic of signals Y and X at high level. Further, when the ultrasonic sensor  15  detects a person, the display unit  201  lights up. 
     The signal X is a signal for the scanner control unit  331  to switch between activation by driving the scanner driving unit  332  or activation without driving the scanner driving unit  332 . When the logic of the signal X is set at high level while power is supplied to the scanner control unit  331 , the scanner control unit  331  keeps the scanner driving unit  332  stopped and activates the scanner unit  13  (to be referred to as quiet activation of the scanner unit  13  hereinafter). When the logic of signal X is set at low level while power is supplied to the scanner control unit  331 , the scanner control unit  331  drives the scanner driving unit  332  and activates the scanner unit  13 . 
     The signal Y is a signal for the printer control unit  341  to switch between activation by driving the printer driving unit  342  or activation without driving the printer driving unit  342 . If the logic of the signal Y is set at high level when power is supplied to the printer control unit  341 , the printer control unit  341  keeps the printer driving unit  342  stopped and activates the printer unit  14  (to be referred to as quiet activation of the printer unit  14  hereinafter). When the logic of signal Y is set at low level when power is supplied to the printer control unit  341 , the printer control unit  341  drives the printer driving unit  342  and activates the printer unit  14 . 
     When the power saving button  204  is pressed by the user, the logic of the signal R changes to high level. When the logic of the signal R is set at high level, the power supply control unit  304  controls the signals C to I and turns on the relay switches  512  to  519 . When the power saving button  204  is pressed, the power supply control unit  304  sets the logic of the signal Y and X at high level. When the power saving button  204  is pressed, the display unit  201  lights up. 
     &lt;State Transition&gt; 
     The state transition of the image forming apparatus  100  will be described next with reference to  FIG. 4 . The image forming apparatus  100  has operation states of a standby state ST 1 , a display unit return state ST 2 , a quiet return state ST 3 , a power saving state ST 4 , and a power off state ST 5 . 
     The standby state ST 1  is a normal operation state in which it is possible to execute the reading operation by the scanner unit  13  and the printing operation by the printer unit  14 . In the standby state ST 1 , when the image forming apparatus  100  is not used for a predetermined time, for example, the operation unit  12  is not operated for a predetermined time and a job is not received from the external apparatus  20 , the image forming apparatus  100  shifts from the standby state ST 1  to the power saving state ST 4 . 
     The power saving state ST 4  is a state which consumes less power than the standby state ST 1 . In the power saving state ST 4 , power is supplied only to devices (the ultrasonic sensor  15 , the LAN controller  306 , and the like) necessary for returning the image forming apparatus from the power saving state ST 4 . In the power saving state ST 4 , when the ultrasonic sensor  15  detects a person, the image forming apparatus  100  shifts to the quiet return state ST 3  or the display unit return state ST 2  in accordance with the detection result. Whether the image forming apparatus  100  transits to the quiet return state ST 3  or the display unit return state ST 2  is determined based on the transition of the distance between the image forming apparatus  100  and the detection target detected by the ultrasonic sensor  15  for every predetermined time. The CPU  301  of the controller  11 , the image processing unit  309 , the HDD  308 , the scanner unit  13 , and the printer unit  14  are activated in the quiet return state ST 3 . Note that the printer control unit  341  and the scanner control unit  331  respectively restrict driving the printer driving unit  342  and the scanner driving unit  332 . This causes the image forming apparatus  100  to activate quietly. From the above activation, the CPU  301 , the image processing unit (ASIC)  309 , the CPU of the scanner control unit  331 , and the CPU of the printer control unit  341  perform initialization. 
     Additionally, in the power saving state ST 4 , when a print job is received from the external apparatus  20  to execute printing in the printer unit  14 , the image forming apparatus  100  shifts to the standby state ST 1 . Note that if the user presses the power saving button  204  in the power saving state ST 4 , the image forming apparatus  100  shifts to the display return state ST 2 . In this embodiment, since the user is supposed to be detected by the ultrasonic sensor  15  before the power saving button  204  is pressed, it is assumed in the power saving state ST 4  that the power saving button  204  will not be pressed. 
     When the power saving button  204  is pressed in the quiet return state ST 3 , the image forming apparatus  100  shifts to the display unit return state ST 2  in which the display unit  201  lights up. This allows the user to select a function provided by the image forming apparatus  100  via a main menu screen (a selection screen)  201   a  displayed by the display unit  201 . Details of the main menu screen (the selection screen)  201   a  will be described later with reference to  FIG. 9 . 
     When a function to be provided by the image forming apparatus  100  is selected via the main menu screen  201   a  displayed during the display unit return state ST 2 , the image forming apparatus  100  shifts to the standby state ST 1  in which the selected function can be executed. For example, when the print function is selected via the main menu screen  201   a , the driving restriction on the printer driving unit  342  is canceled, and the printer driving unit  342  is driven. Also, when the scanner function is selected via the main menu screen  201   a , the driving restriction on the scanner driving unit  332  is canceled and the scanner driving unit  332  is driven. 
     Additionally, when the seesaw switch  510  is turned off from ON by the operation of the user, the image forming apparatus  100  shifts to the power off state. 
     The control of power delivered to each load included in the image forming apparatus  100  in the aforementioned states will be described next with reference to  FIGS. 5 to 8 .  FIG. 5  shows power control in the standby state ST 1 . As shown in  FIG. 5 , in the standby state ST 1 , the switches  510  to  519  of the image forming apparatus  100  are turned on, and power is supplied to each unit of the image forming apparatus  100 . 
       FIG. 6  shows power control in the power saving state ST 4 . As shown in  FIG. 6 , in the power saving state ST 4 , power is supplied to only some of the first power supply system devices. In the power saving state ST 4 , the relay switch  511  for supplying power generated by the first power supply unit  501  is turned on, but the other switches  512  to  519  are turned off. Thus, power is supplied to the power supply control unit  304 , the RAM  302 , the LAN controller  306 , the ultrasonic sensor  15 , the power saving button  204 , and the microcomputer  203  in the power saving state ST 4 . Note that power may be supplied to the microcomputer  203  when the ultrasonic sensor  15  detects a person. 
       FIG. 7  shows power control in the quiet return state ST 3 . As shown in  FIG. 7 , in the quiet return state ST 3 , power is supplied to the CPU  301 , the HDD  308 , the ROM  303 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13  in addition to the devices that receive power in the power saving state ST 4 . Note that the printer control unit  341  and the scanner control unit  331  respectively restrict the printer driving unit  342  and the scanner driving unit  332  from being driven. 
       FIG. 8  shows power control in the display unit return state ST 2 . As shown in  FIG. 8 , in the display unit return state ST 2 , power is supplied to the display unit  201  in addition to the devices that receive power in the quiet return state ST 3 . Thus, the display unit  201  can display various kinds of information. When an instruction is input via the display unit, the microcomputer  203  controls the switch  519  and switch  520  to be ON from OFF and cancels the driving restriction on the printer driving unit  342  and the scanner driving unit  332 . Thus, it becomes possible to switch from the restricted supply of power to supply of power that allows normal operation of the printer driving unit  342  and the scanner driving unit  332 . 
     &lt;Operation Unit&gt; 
     Details of the operation unit  12  will be described next with reference to  FIG. 9 . As shown in  220 , the operation unit  12  includes the display unit  201 , buttons  202 , and the microcomputer  203  shown in  FIG. 3 . Note that while an example in which the microcomputer  203  is implemented in the operation unit  12  will be described, the present invention is not limited to this. The microcomputer  203  may be implemented in another component. 
     The display unit  201  displays various kinds of images. As shown in  221 , the microcomputer  203  displays the main menu screen (the selection screen)  201   a  for selecting the copy function, the print function, the scan function, and the like on the display unit  201 . Also, as shown in  222 , the microcomputer  203  displays, on the display unit  201 , a setting screen  201   b  for executing the function selected on the main menu screen  201   a.    
     As shown in  220 , in the power off state ST 5 , the power saving state ST 4 , and the quiet return state ST 3 , the display unit  201  changes to a non-display state in which no image is displayed. This non-display state may be a state in which an image to be displayed on the display unit  201  is rendered, but the backlight is OFF or a state in which the display unit  201  is OFF and no image is rendered on the display unit  201 . In contrast, as shown in  221  and  222 , a state in which a screen is displayed on the display unit  201  is called a display state. 
     As shown in  221 , the main menu screen  201   a  contains a copy icon  211  for executing the copy function, a print icon  212  for executing the print function, and a scan icon  213  for executing the scanner function. The main menu screen  201   a  also contains saved file use icon  214  for using a file saved in the HDD  308 , and a FAX icon  215  for executing the FAX function. The main menu screen  201   a  also contains an inbox icon  216  for checking received email, and an information icon  217  for displaying various kinds of information. 
     As shown in  222 , the setting screen  201   b  contains a start button  218  for instructing the execution of a selected job.  222  shows a scene in which “JOB B” has been selected. 
     The buttons  202  include a start key  206  for instructing the execution of starting an operation such as copying or scanning. The buttons  202  also include the power saving button  204 . If the power saving button  204  is pressed (operated) by the user when the image forming apparatus  100  is in the standby state ST 1 , the image forming apparatus can shift to the power saving state ST 4 . If the power saving button  204  is pressed by the user when the image forming apparatus  100  is in the power saving state ST 4 , the image forming apparatus  100  can shift to the standby state ST 1 . The buttons  202  also include a ten-key pad  205  for inputting a numerical value such as the number of copies to be printed. 
     &lt;Power Control&gt; 
     The power control transition according to the distance between the image forming apparatus  100  and an operator will be described next with reference to  FIG. 10 . In  FIG. 10, 1001  shows the relationships concerning the distances between the image forming apparatus  100  and the operators, and  1002  shows power states of the image forming apparatus  100  when the operators are present in respective positions shown in  1001 . In  1002 , as the power state of the image forming apparatus  100 , the total supplied power and the components to which power is supplied in the respective operational states are indicated. 
     As shown in  1011 , in a state T 1  when it is determined that no person is present within a detection range A 1  of the ultrasonic sensor  15  or the person who entered the detection range A 1  is a passerby, the image forming apparatus  100  stands by in the power saving state ST 4 . In this power saving state ST 4 , power supply is restricted to certain devices such as the ultrasonic sensor  15 . More specifically, in the power saving state ST 4 , power is supplied to the LAN controller  306 , the RAM  302 , the ultrasonic sensor  15 , the microcomputer  203 , and the power saving button  204 . 
       1012  indicates a state T 2  in which the presence of a person is detected in the detection range A 1  of the ultrasonic sensor  15 . In  1012 , however, power is only supplied to the controller  11  and the like since it is a state in which the person has not been determined as the operator. More specifically, in the state T 2 , power is supplied to the scanner unit  13 , the printer unit  14 , the image processing unit  309 , the HDD  308 , and the CPU  301  in addition to the devices that receive power in the power saving state ST 4 . Thus, activation of the controller  11 , the scanner unit  13 , and the printer  14  is started. Note that although the activation may start, since the scanner control unit  331  restricts the scanner driving unit  332  from being driven and the printer control unit  341  restricts the printer driving unit  342  from being driven, the activation starts in a state free from the driving noise of the printer driving unit  342 . 
     Note that in this embodiment, at the point of the state T 2 , no power is supplied to the display unit  201  through which the operator uses the image forming apparatus  100 . In the state T 2 , however, the power saving button  204  will blink or light up in order to guide a person intending to use the image forming apparatus  100  to the next operational portion. 
       1013  shows a state T 3  in which the user who has come close to the image forming apparatus  100  presses the power saving button  204  or the person who falls within the range has been determined as the operator. In the state T 3 , power is supplied to the display unit  201  and the display unit  201  displays the screen. In this embodiment, since the operator presses the power saving button  204  with the intention of using the image forming apparatus  100 , power is supplied to the display unit  201  at the timing when the power button  204  is pressed. When the power saving button  204  is pressed, the display unit  201  displays the main menu screen  201   a  for selecting a function (for example, the copy function, the print function, the scan function, the BOX function, and the FAX function) provided by the image forming apparatus  100 . 
       1014  shows a state T 4  in which the operator has selected a function on the main menu screen  201   a . In state T 4 , power is supplied to portions necessary for executing the function. A case will be described in which the print icon  212  displayed on the main menu screen  201   a  is selected. When the print icon  212  is selected on the main menu screen  201   a , the printer control unit  341  cancels the driving restriction on the printer driving unit  342 . 
     &lt;Processing Procedure&gt; 
     Processing to be executed by the microcomputer  203  of the operation unit  12  will be described next with reference to  FIG. 11 .  FIG. 11  shows a series of operations performed by the image forming apparatus  100  from the power saving state ST 4  till its return to the standby state ST 1 . The processing to be described below is executed when the microcomputer  203  of the operation unit  12  executes a program. 
     First, the image forming apparatus  100  stands by in the power saving state ST 4 . In step S 101 , the microcomputer  203  determines whether a person is present in the detection range A 1  of the ultrasonic sensor  15 . The process advances to step S 102  if a person is present. Otherwise, the process returns to the determination in step S 101 . More specifically, the microcomputer  203  receives, from the ultrasonic sensor  15 , a signal output by the ultrasonic sensor  15  when a person is detected, and determines that a person has entered (is present in) the detection range A 1  of the ultrasonic sensor  15 . The entry of a person is not determined (S 101 : NO), however, if the distance between the ultrasonic sensor  15  and the person increases immediately after the start of the detection or if the person was detected only for a short period. 
     In step S 102 , when it is determined that a person is present in the detection range A 1  of the ultrasonic sensor  15 , the microcomputer  203  instructs the power supply control unit  304  to supply power to the CPU  301 , the HDD  308 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13 . More specifically, the signal Q is set at high level. The power supply control unit  304 , having received the instruction, controls the logic of the signals C, D, E, F, G, H, and I so that power is supplied to the CPU  301 , the HDD  308 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13 . The CPU  301 , the HDD  308 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13  supplied with power, start to activate. Note that at this point, no power is supplied to the display unit  201 . In addition, at this point, due to the driving restriction on the printer driving unit  342  and the scanner driving unit  332 , the above activation is free from the driving noise of the printer driving unit  342  and the scanner driving unit  332 . 
     Subsequently, in step S 103 , the microcomputer  203  determines whether the detected person is the operator of the image forming apparatus  100  based on the transition of the distance measured by the ultrasonic sensor  15  for every predetermined time. The determination method will be described in detail later. If the person can be determined as the operator, the process advances to step S 107  and the microcomputer  203  causes the display unit  201  to display a screen. Otherwise, the process advances to step S 104  and the microcomputer  203  transits to the quiet return state ST 3  without displaying the screen. 
     In the quiet return state ST 3 , the microcomputer  203  determines whether the power saving button  204  is pressed (operated) in step S 104 . If the power saving button  204  is not pressed, the process advances to step S 105 . Otherwise, the process advances to step S 107 . In step S 105 , the microcomputer  203  determines whether a predetermined time has passed without the power saving button  204  being pressed since detecting the presence of the person who falls within the detection range A 1  in step S 101 . If the predetermined time has passed, the process advances to step S 106 . Otherwise, the process returns to step S 104 . 
     In step S 106 , the microcomputer  203  instructs the power supply control unit  304  to stop supplying power to the CPU  301 , the HDD  308 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13 . The power supply unit  304 , having received the instruction, controls the logic of the signals C, D, E, F, G, H, and I so that power supply to the CPU  301 , the HDD  308 , the image processing unit  309 , the printer unit  14 , and the scanner unit  13  is stopped. Thus, the image forming apparatus  100  shifts to the power saving state ST 4 . 
     On the other hand, if it is determined that the power saving button  204  has been pressed, the process advances to step S 107 , and the microcomputer  203  causes the display unit  201  to display the main menu screen  201   a . In step S 108 , the microcomputer  203  determines whether the user has selected the copy icon  211  on the displayed main menu screen  201   a . If it is determined that the copy icon  211  is selected, the process advances to S 109 . Otherwise, the process advances to step S 110 . In step S 109 , the microcomputer  203  cancels the driving restriction on the printer driving unit  342  and the scanner driving unit  332  necessary for executing the copy function, thereby setting the standby state ST 1  capable of executing the copy function. 
     On the other hand, in step S 110 , the microcomputer  203  determines whether the user has selected the print icon  212  on the main menu screen  201   a . If the print icon  212  is selected, the process advances to step S 111 . Otherwise, the process advances to step S 112 . In step S 111 , the microcomputer  203  cancels the driving restriction on the printer driving unit  342  necessary for executing the print function, thereby setting the standby state ST 1  capable of executing the print function. 
     On the other hand, in step S 112 , the microcomputer  203  determines whether the user has selected the scan icon  213  on the main menu screen  201   a . If it is determined that the scan icon  213  is selected, the process advances to step S 113 . Otherwise, the process returns to step S 104 . In step S 113 , the microcomputer  203  cancels the driving restriction on the scanner driving unit  332  necessary for executing the scan function, thereby setting the standby state ST 1  capable of executing the scan function. 
     Note that although the example has been described in which the copy icon  211 , the print icon  212 , and the scan icon  213  of the main menu screen  201   a  are selected, the same processing procedure will be applied if another icon is selected. If another icon is selected, power is supplied to a functional unit (for example, a FAX unit) necessary for executing the function corresponding to the selected other icon. For example, if the FAX icon  215  is selected on the main menu screen  201   a , power is supplied to the scanner unit  13  necessary for transmitting a FAX. 
     &lt;Determination Criteria of Person Detection&gt; 
     Determination criteria of person detection (of a passerby and an operator) in steps S 101  and S 103  in  FIG. 11  will be described next with reference to  FIGS. 12A to 12D . Four case examples shown in  FIGS. 12A to 12D  will be used to explain how the microcomputer  203  of the operation unit  12  makes the determination between a passerby and an operator of the image forming apparatus  100  based on the transition of the distance measured by the ultrasonic sensor  15  for every predetermined time.  FIGS. 12A to 12D  show the transition of the distance between the image forming apparatus  100  and the person for every predetermined time. For each case in  FIGS. 12A to 12D , distances between the image forming apparatus  100  and the operators are illustrated on the left portion, and each measured distance and the corresponding determination of the image forming apparatus  100  are indicated in a table on the right portion. In addition, the item “distance” for each table is defined by dividing the detection start position into three-steps of “far”, “middle”, and “near” within the detection range A 1 . 
     &lt;Case: 1&gt; 
     Case 1 shows a case in which a person directly heads toward the image forming apparatus  100  and comes close to the apparatus. The microcomputer  203  of the operation unit  12  determines that an object has been detected in the “far” area within the detection range A 1  at the point of T 1 . Subsequently, the microcomputer  203  determines that a person is present in the detection range A 1  (YES in step S 101  of  FIG. 11 ) since the measured distance has decreased in T 2  from the measurement result of T 1 . Further, as the distance continues to decrease from T 1  to T 4 , the person who continues to come close to the image forming apparatus  100  is determined as the operator (YES in step S 103  of  FIG. 11 ). 
     &lt;Case: 2&gt; 
     Case 2 shows a case in which a person comes close from a near distance to use the image forming apparatus  100 . The microcomputer  203  of the operation unit  12  determines that an object has been detected in the “near” area within the detection range A 1  at the point of T 1 . Since the distance from the object becomes shorter at the point of T 2 , the microcomputer  203  determines that a person is present (YES in step S 101  of  FIG. 11 ). However, since there is no increase/decrease (variation) in the distance from T 2  to T 4 , the microcomputer  203  cannot determine whether the person is present in the detection range A 1  with the purpose to use the image forming apparatus  100 . Hence, operator determination is not made until T 4 . When the person is continuously detected in the “near” area up to T 5  after a predetermined time has passed, the detected person is determined as the operator of the image forming apparatus  100  (YES in step S 103  of  FIG. 11 ). Consequently, in this case, the operator is made to wait until the time passes in T 3  and T 4 . In such a case like this, the power saving button can be pressed (step S 104  of  FIG. 11 ) to display the screen (step S 107  of  FIG. 11 ). 
     &lt;Case: 3&gt; 
     Case 3 shows a case in which a person passes in front of the image forming apparatus  100 . The microcomputer  203  of the operation unit  12  determines that an object has been detected in the “near” area within the detection range A 1  at the point of T 1 . However, at the point of T 2 , since the distance immediately increases, it is determined that no person is present (NO in step S 101  of  FIG. 11 ). The distance also increases at T 3 , and the ultrasonic sensor  15  loses the response at T 4  and T 5  (NO in step S 101  of  FIG. 11 ). 
     &lt;Case: 4&gt; 
     Case 4 shows a case in which a person accesses a space next to the image forming apparatus  100 . The microcomputer  203  of the operation unit  12  determines that an object has been detected in the “far” area within the detection range A 1  at the point of T 1 . Next, at points of T 2  and T 3 , the microcomputer  203  confirms, in addition to decreasing of the measured distance, the rate of the decrease of the distance. If the rate of the decrease of the distance is small, it is determined that no person is present. When a person accesses a space next to the main body such as in this case, since the person will diagonally pass in front of the image forming apparatus  100 , the rate of the decrease of the distance becomes smaller than in the aforementioned Case 1. The microcomputer  203  of the operation unit  12  determines the magnitude of this rate of the decrease and determines not to detect the object as a person. Subsequently, at the points of T 4  and T 5 , the ultrasonic sensor  15  loses the response (NO in step S 101  of  FIG. 11 ) since the person has moved outside the detection range A 1 . 
     With the above-described determination criteria, an interval for measuring a person&#39;s action for every predetermined time for T 0 , T 1 , T 2 , . . . , and a time till it is detected that person is present within the detection range A 1  (parameters for person/operator determination criteria) can be set. These setting values can become factors which make the operator feel, for example, that the return from the power saving state is fast/slow or that there are many/few erroneous returns. This also applies to setting a time to determine that an operator is present based on the presence of a person, over a predetermined time such as in Case 2, in front of the image forming apparatus  100 . For example, if the image forming apparatus  100  is installed standalone and will only be visited by the operator, it is desirable to cause the apparatus to return as soon as a person comes. If the image forming apparatus  100  is installed on the side of a path, in order to prevent a detection error when a person comes, it is desirable not to detect the person for a certain time after the person has come within the detection range A 1 . It is desirable for these setting values (the parameters for person/operator determination criteria) to be arbitrarily set in consideration of the installation environment of the image forming apparatus  100 , the specifications of the apparatus, and the like. Thus, the operation unit  12  may display a menu to adjust these setting values and allow the setting values to be changed according to user input. 
     &lt;Processing Procedure of Person Detection&gt; 
     Processing procedure for the determination of person detection (person determination) by the microcomputer  203  of the operation unit  12  described in  FIGS. 12A to 12D  will be explained next with reference to the flowchart of  FIG. 13 . The processing to be described below is executed by the microcomputer  203  for each periodic measurement of the distance after an object is detected. The microcomputer  203  can measure the distance to the object present in the detection range A 1  for every predetermined time, store the distance data for every predetermined time, and compare the latest measured distance with past measured distances. 
     First, in step S 1301 , the microcomputer  203  measures the distance to an object by using the ultrasonic sensor  15  in order to determine whether the object is present in the detection range A 1 . After the distance is measured, the process advances to step S 1302 , and the microcomputer  203  determines whether the object measured in step S 1301  is present in the “far” area of the detection range A 1 . If the object is present in the “far” area, the process advances to step S 1303 . Otherwise, the process advances to step S 1304 . In step S 1303 , the microcomputer  203  compares current and previous measured distances to determine whether the distance is decreasing. In other words, it is determined whether the detected object is coming close to the image forming apparatus  100 . 
     If the previous distance measurement result was not measurable, it is determined that the distance has not decreased. If the distance has not decreased, the process returns to step S 1301 . If the distance has decreased, the process advances to step S 1305 , and the microcomputer  203  determines whether the magnitude of the rate of the decrease is large, that is, more than a predetermined threshold. If the decrease is large (more than a predetermined threshold), the process advances to step S 1306 . Otherwise, the process returns to step S 1301 . Person detection is stopped in step S 1305  if a person comes close the image forming apparatus  100  diagonally as in Case 4 of  FIG. 12D . On the other hand, if the rate of the decrease is large, the process advances to step S 1306 , and the microcomputer  203  detects the object as a person. 
     If it is determined in step S 1302  that the object is present in the “near” area, the microcomputer  203  determines, in step S 1304 , whether the distance has decreased/not changed from the previous measured distance, or if it is otherwise. If there is no change or the distance has decreased, the process advances to step S 1306 . Otherwise, the process returns to step S 1301 . In step S 1306 , the microcomputer  203  detects the object as a person. After the object is detected as a person, the process advances to determine whether the person is an operator. Also, if the object is detected as a person, the image forming apparatus  100  transits from the power saving state ST 4  to the quiet return state ST 3  as shown in  FIG. 10 . 
     The procedure of detecting whether the person detected as a person is the operator (operator determination) will be described next. First, in step S 1310 , the microcomputer  203  initializes (N=0) a variable N stored in the microcomputer  203 . Next, in step S 1311 , the microcomputer  203  determines whether there is an object which falls within the range. If no object is present, the process shifts in step S 1312  to the object detection in step S 1301 . If an object is present, the process advances to step S 1313 , and the microcomputer  203  determines the area of the detection range A 1  in which the person is detected. If the person is detected in the “far” area, the process advances to step S 1314 , and the microcomputer  203  determines whether the distance is decreasing. If the distance is decreasing, the process advances to step S 1315 , and the microcomputer  203  determines the person to be the operator and ends the process. On the other hand, if the detection range is in the “near” area in step S 1313 , the process advances to step S 1316 , and the microcomputer  203  determines whether the distance has decreased/not changed or if it is otherwise. If the distances has decreased/not changed, the process advances to step S 1317 , and the microcomputer  203  determines whether the value of the variable N is equal to or more than 3 (equal to or more than a predetermined number of times). If the variable N is less than 3, the process advances to step S 1318 , and the microcomputer  203  increments the variable N by 1 and the process returns to step S 1311 . On the other hand, if the variable N is equal to or more than 3, the process advances to step S 1315 , and the microcomputer  203  detects the person as an operator. After it changes to a person detection state, unless the person is detected in the “near” area for a predetermined number of times (3 in this example), he/she is not detected as the operator. This corresponds to the control of determining the person as an operator when the operator has been detected over a predetermined time such as in Case 2 of  FIG. 12B . Other determination criteria may be applied to the present invention, as a matter of course. 
     Second Embodiment 
     The second embodiment of the present invention will be described below with reference to  FIG. 14 . The above-described first embodiment described an example in which the display unit  201  displays a screen at the timing when the power saving button  204  is pressed. However, the present invention is not limited to this. In this embodiment, a capacitance sensor  250  incorporated in an operation unit  12  detects that the hand of the operator has been put over the proximity of the operation unit  12 , and a main menu screen  201   a  is displayed on the display unit  201 . Note that, in this embodiment, the capacitance sensor  250  may be further provided in addition to the ultrasonic sensor  15  in the above-described first embodiment. In the following description, only control and arrangements that differ from the above-described first embodiment will be described. 
       FIG. 14  shows a person putting a hand over the display unit  201  of an image forming apparatus  100  according to this embodiment. As shown in  FIG. 14 , the operation unit  12  according to the embodiment is provided with the capacitance sensor (antenna)  250 . This capacitance sensor  250  detects a person who comes close to the apparatus in accordance with the capacitance of a capacitor arranged between the hand of the person coming close to the operation unit  12  and the capacitance sensor  250 . More specifically, when the capacitance is equal to or more than a predetermined amount, the microcomputer  203  determines that a hand has been put over the operation unit and determines the detected person as the operator. When the hand of the person enters a detection range A 2  of the capacitance sensor  250 , power is supplied to the display unit  201 , and the main menu screen  201   a  is displayed on the display unit  201 . 
     &lt;Modification&gt; 
     The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, although an example using the ultrasonic sensor  15  was described in the first embodiment, a camera may be used instead of the ultrasonic sensor  15 . In addition, the camera need not only be a camera provided in the image forming apparatus  100 . A camera provided in the room where the image forming apparatus  100  is installed, that is, a camera (for example, a surveillance camera) provided in a position apart from the main body of the image forming apparatus  100  may be used. Also, although an example in which the main menu screen  201   a  is displayed on the display unit  201  by using the capacitance sensor was described, a touch panel sensor of the display unit  201  may be used instead of the capacitance sensor. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.