Abstract:
An apparatus for connecting electrical power to an exposure lamp in an image scanner in response to the detection of ambient light by a light sensor located under the scanner&#39;s cover. Such an apparatus provides an apparent reduction in exposure lamp warm-up time, with associated improvement in operator productivity, while minimizing exposure lamp operational life degradation and excessive energy consumption caused by leaving the exposure lamp turned on. Once the exposure lamp is turned on, a timing circuit is used in the preferred embodiment to disconnect electrical power from the exposure lamp so that if the scanner&#39;s cover is left open or closed, the exposure lamp will not be left on for excessively long periods of time.

Description:
FIELD OF THE INVENTION 
     The present patent document relates generally to optical scanning devices used to translate the contents of printed documents into electronic format, and more particularly to the control of electrical power to such devices. 
     BACKGROUND OF THE INVENTION 
     Several different types of light sources or lamps have been incorporated into optical scanners in order to illuminate the item being scanned. Among other criteria, the choice of lamp type and style is often based upon cost, size, lamp life, light intensity, output spectrum, power requirements, and turn-on time. Such lamps include cold cathode fluorescent, hot cathode fluorescent, xenon, and light emitting diode (LED) light sources. 
     In modem scanner systems, especially those using the more popular cold cathode fluorescent lamps, the warm-up time for the scanner&#39;s light source is relatively long. For greater productivity, the scanner should be immediately available for use at any time. In a practical sense, the only technique by which this objective can be met is to leave the light source turned on all the time. However, if the light-source is on continuously, excessive power consumption and a large reduction in lamp operational life will result. As an example, cold cathode fluorescent lamps have an average lamp life of between 10,000 and 15,000 hours prior to burn-out. If a cold cathode lamp is on for only 1,000 hours per year, the operational life of the lamp is approximately 10 to 15 years, and even at 2,000 hours per year, it is 5 to 7.5 years. However, if on full time, the operational life of the lamp will be reduced to only 14 to 20 months. 
     The intensity and spectral balance in the light output from a lamp typically depends on its temperature. Therefore, light output is constantly varying while the lamp is warming up. Without elaborate compensation schemes, the user&#39;s first scan can be either of poor quality or can require a noticeable delay before it starts. 
     Some techniques exist for reducing operator perceived warm-up time for the lightsource, while minimizing degradation in lamp operational life. However, all previous techniques have some disadvantages associated with them. For example, Mustek 1200 IIIEP scanners use a mechanical switch to sense the position of the document lid. Warm-up of the light-source is initiated when the mechanical switch senses that the document lid is no longer closed. The time which the user consumes in document placement and other activities prior to pushing the start button reduces the perceived wait time. Disadvantages of this system are the requirement for a cable connecting the mechanical switch to the electronics controlling the light-source and the reliability of mechanical switches. 
     Essentially immediate scanning can be accomplished with some combination of the following techniques: (1) use of a stand-by current to keep the lamp near its long term operating temperature when the machine is not in use and (2) use of an instant-on lamp. A disadvantage of the stand-by current system is that significant power is still consumed during long periods of idle time. Also, if the idle current is turned off for some reason, such as after a long period of non-use, the next user will have to wait for the full warm-up to take place. Disadvantages of the instant-on lamp are its relatively high cost and the fact that the spectral output may not match that of the sensitivity of the light-sensor. 
     Other possible solutions include (1) sensing the light-source output while the page is being scanned and adjusting the power supplied to the lamp in order to hold the lamp output constant and (2) sensing the lamp output while the page is being scanned, and adjusting the sensitivity of the light sensor. A disadvantage of sensing the lamp output while the page is being scanned and adjusting power supplied to the lamp is that the lamp output is limited by initial lamp temperature, so the entire scan must be run at a slower speed, corresponding to the low lamp output at the beginning. This method also requires stability of the spectral output of the lamp, which takes a significant amount of time, as well as a light monitor window with associated additional detection pixels. Sensing the lamp output while the page is being scanned and adjusting the sensitivity of the light sensor has the disadvantage, once again, that the entire scan is run at slow speed, corresponding to the low lamp output at the beginning of the scan. Profile stability and the requirement for a light monitor window with associated additional pixels are issues here also. 
     Thus, there is a significant need to improve the scanner system so as to reduce, at least, the operator perceived warm-up time for the light-source, while minimizing degradation in lamp operational life. In particular, there is a need for a system to provide power to a scanner lamp that takes only approximately a minute or so to approach its long-term temperature after the operator has completed other activities prior to scanning. 
     SUMMARY OF THE INVENTION 
     Representative embodiments of the teachings of the present patent document provide enhanced capabilities not previously available to aid in the reduction of operator perceived lamp warm-up time in optical scanning systems, while minimizing degradation of lamp operational life and controlling energy consumption. These capabilities provide possible increased productivity for an operator of such systems. 
     Representative embodiments of the present patent document incorporate a light sensor and associated circuitry into a scanner system. When the document lid is raised, ambient room light enters the scanner. The rapid increase in light is detected by the light sensor and used as a trigger to turn on the scanning lamp. While the user arranges his document on the scanner, closes the document lid, enters any setup information into the computer, and any other activities that may be required, the lamp is warming up. By the time that the user finally initiates the scan, the lamp is already well on its way to being warmed up. The user now has to wait less additional time for the lamp to achieve necessary light output and the scan to begin than otherwise would be necessary. The potential for a reduction in operator perceived lamp warm-up time thus exists without requiring that the lamp be on continuously. 
     Since waiting for the exposure lamp in a scanner system to warm up can be expensive in terms of operator inefficiency, since lamp operational life is reduced in relation to the time the lamp is turned on, and since leaving a lamp on continuously consumes greater energy, representative embodiments of the present invention provide needed, enhanced capabilities not previously available. In addition, lamp warm-up can be initiated without the cost of a mechanical sensor and cable and without imposing constraints on lamp selection or limiting scan speed. Other aspects and advantages of the representative embodiments of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. The details disclosed in the specification should not be read so as to limit the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings provide visual representations which will be used to more fully describe the representative embodiments of the present patent document and which can be used by those skilled in the art to better understand it and its inherent advantages. In the drawings, like reference numerals identify corresponding elements and: 
     FIG. 1 is a drawing of an image scanner with scanner cover in closed position as described in various representative embodiments of the present patent document. 
     FIG. 2 is a drawing of an image scanner with scanner cover in open position as described in various representative embodiments of the present patent document. 
     FIG. 3 is a drawing of another image scanner with scanner cover in open position as described in various representative embodiments of the present patent document. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in the drawings for purposes of illustration, the present patent document relates to a novel apparatus for reducing operator perceived scanner exposure lamp warm-up time while minimizing lamp operational life degradation. Previously an operator would typically either incur excessively long warm-up times or significant reductions in lamp operational life with associated increased energy consumption when using optical scanning machines. Some previous techniques could reduce the perceived warm-up time without leaving the lamp on continuously, but were typically slower in operation or required more complicated or less reliable hardware. In the following detailed description and in the figures of the drawings, like elements are identified with like reference numerals. 
     FIG. 1 is a drawing of an image scanner  100  with a scanner cover  105  in closed position as described in various representative embodiments of the present patent document. In this representative embodiment, the image scanner  100  comprises the scanner cover  105 , a light sensor  110 , an electrical-power-control circuit  120 , and an exposure lamp  140 . The image scanner  100  is also referred to herein as the scanner  100 , and the scanner cover  105  is also referred to herein as the cover  105 . The electrical-power-control circuit  120  comprises a light intensity detection circuit  124  and an on/off circuit  128 . In closed position, the cover  105  is located so as to block substantially all light  115  otherwise incident on the light sensor  110 . In open position, the cover  105  is located so as to enable the light sensor  110  to detect incident ambient light  115 . In FIG. 1 the scanner cover  105  is closed, and the light sensor  110  will not detect the ambient light  115  of the location in which the scanner  100  is located. The light sensor  110  sends a signal to the light intensity detection circuit  124  indicating the intensity of the ambient light  115  incident upon it. Since the scanner cover  105  is closed in FIG. 1, ambient light  115  is not incident upon the light sensor  110 , and the signal sent to the light intensity detection circuit  124  will be below the threshold necessary for the light intensity detection circuit  124  to activate the on/off circuit  128  to connect electrical power from an electrical-power source  130  to the exposure lamp  140 . 
     FIG. 2 is a drawing of the image scanner  100  with the scanner cover  105  in open position as described in various representative embodiments of the present patent document. When the scanner cover  105  is opened as shown in FIG. 2, the light sensor  110  detects the ambient light  115  incident upon it from the location in which the scanner  100  is located. The light sensor  110  sends a signal to the light intensity detection circuit  124  in the electrical-power-control circuit  120  indicating that the light sensor  110  is now detecting ambient light  115 . When the intensity of light detected by the light sensor  110  is sufficiently great, i.e., above a preselected threshold level, it causes the on/off circuit  128  in the electrical-power-control circuit  120  to connect electrical power from the electrical-power source  130  to the exposure lamp  140 . While the user arranges his document on the scanner  100 , closes the scanner cover  105 , enters any setup information into the scanner computer which is not shown in the figures, and performs any other activities that may be required, the exposure lamp  140  is warming up. By the time that the user finally initiates the scan, the exposure lamp  140  is already well on its way to being warmed up. The user now has to wait less additional time for the exposure lamp  140  to achieve necessary light output and the scan to begin than otherwise would be necessary. The potential for a reduction in operator perceived exposure lamp  140  warm-up time thus exists without requiring that the exposure lamp  140  be on continuously. In a first representative embodiment, electrical power is removed from the exposure lamp  140  whenever the scanner cover  105  is closed and in a second representative embodiment, once electrical power is connected to the exposure lamp  140  by activation of ambient light  115 , it remains connected until disconnected by the operator. 
     FIG. 3 is a drawing of another image scanner  100  with the scanner cover  105  in open position as described in various representative embodiments of the present patent document. In this representative embodiment which is the preferred embodiment, the image scanner  100  comprises the scanner cover  105 , the light sensor  110 , the electrical-power-control circuit  120 , and the exposure lamp  140 . The electrical-power-control circuit  120  in this embodiment comprises a light intensity rate of change detection circuit  350 , a timing circuit  360 , and the on/off circuit  128 . The light intensity rate of change detection circuit  350  is also referred to herein as the rate of change detection circuit  350  and is used to detect the rate at which light  115  incident on the light sensor  110  changes. The timing circuit  360  measures a preselected period of time once activated. The timing circuit  360  turns off or deactivates once the preselected period of time has passed, i.e., when the timing circuit  360  times out. In closed position, the cover  105  is located so as to block substantially all light  115  otherwise incident on the light sensor  110 . In open position, the cover  105  is located so as to enable the light sensor  110  to detect incident ambient light  115 . FIG. 3 shows the scanner cover  105  having just been opened. With the scanner cover  105  open, the light sensor  110  detects ambient light  115  of the location in which the scanner  100  is located. The light sensor  110  sends a signal to the light intensity rate of change detection circuit  350  indicating the rate of change of the intensity of the ambient light  115  incident upon the light sensor  140 . 
     In the preferred embodiment of FIG. 3, it is the rapid increase in light  115  as detected by the light sensor  110 , as for example when the scanner cover  105  is raised, that is used as a trigger by the light intensity rate of change detection circuit  350  to activate the timing circuit  360  which in turn activates the on/off circuit  128  to connect electrical power from the electrical-power source  130  to the exposure lamp  140 . The timing circuit  360  activates the on/off circuit  128  to maintain connection of electrical power to the exposure lamp  140  until after a preselected period of time. After the preselected period of time the timing circuit  360  times out and the on/off circuit  128  disconnects electrical power from the electrical-power source  130  to the exposure lamp  140 . Thus, if the operator leaves the scanner cover  105  open or closed without reopening for a period of time longer than the preselected period of time, electrical power will be removed from the exposure lamp  140  after that preselected period of time saving both electrical power and lamp life. Thus in the preferred embodiment, it is the rapid increase in light  115  that is detected by the light sensor  110  and used as a trigger to turn on the exposure lamp  140 . While the user arranges his document on the scanner  100 , closes the scanner cover  105 , enters any setup information into the scanner computer which is not shown in the figures, and any other activities that may be required, the exposure lamp  140  is warming up. By the time that the user finally initiates the scan, the exposure lamp  140  is already well on its way to being warmed up. The user now has to wait less additional time for the exposure lamp  140  to achieve necessary light output and the scan to begin than otherwise would be necessary. The potential for a reduction in operator perceived exposure lamp  140  warm-up time thus exists without requiring that the exposure lamp  140  be on continuously. After a period of time previously specified, unless the scanner cover  105  is reopened within that period of time, the timing circuit  360  disconnects electrical power of the electrical-power source  130  from the electrical-power-control circuit. 
     In a third representative embodiment, the timing circuit  360  is omitted and the light intensity rate of change detection circuit  350  is connected to the on/off circuit  128 . Once the rate of change of the ambient light  115  exceeds a preselected threshold value, the light intensity rate of change detection circuit  350  activates the on/off circuit  128  to connect electrical power from the electrical-power source  130  to the exposure lamp  140 . Once electrical power is connected to the exposure lamp  140  by activation of the change in ambient light  115 , it remains connected until disconnected by the operator in this third representative embodiment. 
     In any of the embodiments, the exposure lamp  140  could be for example a cold cathode fluorescent lamp, a hot cathode fluorescent lamp, a xenon lamp, or a light emitting diode (LED). 
     In practical cases, the electrical-power source  130  is the electric power provided by the wall electrical outlet of the building in which the scanner  100  is located. 
     Embodiments of the present patent document can be used to advantage in image scanners  100  which use any type of exposure lamp  145  having a non-instantaneous turn on time. A cold cathode fluorescent lamp is often used in commercial scanning machines and is an example of the type of exposure lamp  145  which would benefit from the advantages of incorporating a light sensor  110  into the scanner  100 , as described herein. 
     A primary advantage of the embodiments, as described in the present patent document, over previous techniques is the significant reduction in perceived exposure lamp warm-up time while minimizing lamp operational life degradation. Also, energy consumption is significantly less than if the scanner lamp is left on continuously. An added advantage is the fact that the decrease in perceived warm-up time can occur automatically, without additional operator action. Thus, embodiments of the present patent document solve important problems with operator productivity, lamp operational life, and energy consumption in the use of optical scanners.