Abstract:
A spectrum information measurement method may include steps of; controlling a reference pixel accumulating charges based on an amount of light irradiated from a test specimen; controlling a plurality of measurement pixels accumulating the charge based on an amount of light that is irradiated from the test specimen and has a prescribed wavelength; generating and outputting a reference signal based on an amount of change in the charge that is accumulated in the reference pixel over the prescribed measurement time; generating and outputting a plurality of measurement signals based on an amount of change in the charge that is accumulated in each of the plurality of measurement pixels over the prescribed measurement time; determining whether or not any one or more of the plurality of measurement signals is greater than the reference signal, and determining that the measurement signal that is greater than the reference signal includes saturated output.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a spectrum information measurement method, a color sensor, and a virtual slide device. 
     Priority is claimed on Japanese Patent Application No. 2010-215905, filed Sep. 27, 2010, the content of which is incorporated herein by reference. 
     2. Description of the Related Art 
     All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains. 
     A reading circuit that reads at a high level of sensitivity while removing switching noise at the same time is disclosed in Japanese Unexamined Patent Application, First Publication No. 2007-336157 as an example of a reading circuit of a color sensor that is used to acquire spectrum information about a test specimen. The structure of a conventionally known solid-state imaging device will now be described with reference made to  FIG. 8 .  FIG. 8  is a schematic view illustrating the structure of a conventionally known solid-state imaging device. In the example shown in the drawing, a solid-state imaging device  100  is formed by an integrated circuit unit B 1 , a CDS (Correlated Double Sampling) circuit unit B 2 , and an S/H (Sample Hold) circuit unit B 3 . 
     In the integrated circuit unit B 1 , an anode of a photodiode  10  that is used to receive light and generate photoelectric current is connected to a non-inverting input terminal of an operational amplifier  50 , while a cathode of this photodiode  10  is connected to an inverting input terminal of the operational amplifier  50 . The non-inverting input terminal of the operational amplifier  50  is connected to a reference voltage supply  20 . In addition, an integrating capacitor  40  that is used to accumulate photoelectric current and a switching device  30  that is used to control the integration time are connected in parallel between the inverting input terminal and an output terminal of the operational amplifier  50 . 
     In the CDS circuit unit B 2 , one end of a capacitance element  60  is connected to the output terminal of the operational amplifier  50  forming part of the pixel unit B 1 , while the other end of the capacitance element  60  is connected to an inverting input terminal of an operational amplifier  90 . A non-inverting input terminal of the operational amplifier  90  is connected to a reference voltage supply  70 . One end of a capacitance element  80  is connected to an inverting input terminal of the operational amplifier  90 , while the other end of the capacitance element  80  is connected to one end of a switching device  120  and one end of a switching device  140 . The other end of the switching device  120  is connected to a reference voltage supply  130 , while the other end of the switching device  140  is connected to an output terminal of the operational amplifier  90 . One end of a switching device  110  is connected to one end of the capacitance element  80  and to a connection point between the inverting input terminal of the operational amplifier  90  and the capacitance element  60 , while the other end of the switching device  110  is connected to the output terminal of the operational amplifier  90 . 
     In the S/H circuit unit B 3 , one end of a switching element  150  is connected to the output terminal of the operational amplifier  90  forming part of the CDS circuit unit B 2 , while the other end of the switching element  150  is connected to a non-inverting input terminal of an operational amplifier  170 . One end of a sample hold capacitance element  160  is connected to the non-inverting input terminal of the operational amplifier  170 , while the other end of the capacitance element  160  is grounded. A signal output terminal  180  connects together the inverting input terminal and the output terminal of the operational amplifier  170 , and is connected to the output terminal of the operational amplifier  170 . 
     Operations of the solid-state imaging device will now be described with reference made to the timing chart shown in  FIG. 9 .  FIG. 9  is a timing chart illustrating the operation timings of a conventionally known solid-state imaging device  100 . On this timing chart, the respective switching devices are in a conductive state in the High-level intervals on the chart, and are in a non-conductive state in the Low-level intervals on the chart. φR shows the switch control timing of a switching device  30 , φRC shows the switch control timings of switching devices  110  and  120 , φT shows the switch control timing of a switching device  140 , and φSH shows the switch control timing of a switching device  150 . A voltage V 1  shows the voltage of the output terminal of the operational amplifier  50 , while a voltage V 2  shows the voltage of the output terminal of the operational amplifier  90 , and a voltage Vout shows the voltage of the signal output terminal  180 . Four time periods, namely, T 1  through T 4  are formed in the time axis direction. 
     The time period T 1  is a reset period, and φR, φRC, and φSH are set to a High state, while φT is set to a Low state. In the time period T 1 , the voltage V 1  changes to the voltage Vr 1  of the reference voltage supply  20 , the voltage V 2  changes to the voltage Vr 2  of the reference voltage supply  70 , and the voltage Vout is equivalent to the voltage Vr 2  of the output terminal of the CDS circuit unit B 2 . 
     In the time period T 2 , φRC and φSH are set to a High state, while φR and φT are set to a Low state. Photoelectric current generated by the photodiode  10  is accumulated in the capacitance element  40 . At this time, if the elapsed time from the point when φRC was first set to a High state is taken as TINTGW, then the voltage V 1  of the output terminal of the pixel unit B 1  is shown by the following Formula (1).
 
 V 1 =Vr 1+( Ipd×TINTGW )/ C 0  (1)
 
     Here, the value of the capacitance of the capacitance element  40  is C 0 , the amount of photoelectric current generated by the photodiode  10  is Ipd, and the voltage of the reference voltage supply  20  is Vr 1 . 
     However, in actual fact, clock feedthrough which is caused by the switching operations of the switching device  30  is superimposed on the voltage V 1  of the output terminal of the pixel unit B 1 . As a result, the voltage V 1  changes in the manner shown in Formula (2).
 
 V 1 =Vr 1+( Ipd×TINTGW )/ C 0 +Vn   (2)
 
     Here, the voltage changes caused by the clock feedthrough unit are shown as Vn. 
     In the time period T 3 , φT and φSH are set to a High state, while φR and φRC are set to a Low state. At this time, the voltage V 1  of the output terminal of the pixel unit B 1  is shown by the following Formula (3).
 
 V 1 =Vr 1+( Ipd×TINTG )/ C 0 +Vn   (3)
 
     Here, the elapsed time from the point when φR and φRC were first set to a Low state is taken as TINT. 
     In this period, the switching devices  140  and  150  are in a conductive state, while the switching devices  110  and  120  are in a non-conductive state, and the voltage V 2  of the output terminal of the CDS circuit unit B 2  temporarily changes to the voltage Vr 3  of the reference voltage supply  130 . Thereafter, because the operational amplifier  90  and the capacitance elements  60  and  80  make up a charge amplifier circuit, the voltage V 2  of the output terminal of the CDS circuit unit B 2  can be shown by Formula (4).
 
 V 2 =Vr 3−( C 1 /C 2)×( Ipd×TINTG )/ C 0  (4)
 
     Here, the value of the capacitance of the capacitance element  60  is taken as C 1 , while the value of the capacitance of the capacitance element  80  is taken as C 2 . 
     During this period, the switching device  150  is in a conductive state, and the operational amplifier  170  forms a voltage follower circuit. In addition, the voltage Vout of the signal output terminal  180  has the same voltage as the voltage V 2  of the output terminal of the CDS circuit unit B 2 . Accordingly, the voltage Vout of the signal output terminal  180  is shown by the following Formula (5).
 
 V out= Vr 3−( C 1 /C 2)×( Ipd×TINTG )/ C 0  (5)
 
     As a result of the operations during this period, the clock feedthrough voltage Vn which is caused by the switching operations of the switching device  30  can be removed. 
     In the time period T 4 , φR and φRC are set to a High state, while φT and φSH are set to a Low state. The switching device  150  is in a non-conductive state, and the voltage shown by Formula (5) is maintained in the signal output terminal  180 . It is possible for the signal to be amplified by the capacitance ratio of the capacitance element of the CDS circuit unit B 2  and then read. Any reset noise caused by the switching operations of the switching device  30  which is connected to the capacitance element  40  of the pixel unit B 1  can be removed by a correlated double reading of the CDS circuit unit B 2 . 
     A conventionally known solid-state imaging device can be used as a color sensor.  FIG. 10  is a schematic view illustrating the structure of a color sensor to which a conventionally known solid-state imaging device has been applied to. In a color sensor  200  shown in the drawing, a circuit corresponding to the integrated circuit unit B 1  of the conventionally known solid-state imaging device  100  is shown as an integrated circuit unit B 10 , while a circuit corresponding to the CDS integrated circuit unit B 2  of the conventionally known solid-state imaging device  100  is shown as an integrated circuit unit B 20 . Note that there is no depiction of any circuit that corresponds to the conventionally known S/D circuit unit B 3 . 
     In the example shown in the drawing, the color sensor  200  includes integrated circuit units B 10 - 1  to B 10 - 6 , gain circuits B 20 - 1  to B 20 - 6 , integration time calculation units  38 - 1  to  38 - 6 , gain calculation units  39 - 1  to  39 - 6 , and a drive control circuit  310 . The integrated circuit units B 10 - 1  to B 10 - 6  include pixels  31 - 1  to  31 - 6  that detect spectrum information about a subject by dividing it into respective wavelength transmission bands, reference voltage terminals  32 - 1  to  32 - 6 , switching elements  33 - 1  to  33 - 6 , capacitance elements  34 - 1  to  34 - 6 , and operational amplifiers  35 - 1  to  35 - 6 . Portions formed by the reference voltage terminals  32 - 1  to  32 - 6 , switching elements  33 - 1  to  33 - 6 , capacitance elements  34 - 1  to  34 - 6 , and operational amplifiers  35 - 1  to  35 - 6  are called read circuits  30 - 1  to  30 - 6 . 
     In the drawing an example is shown in which the pixels  31 - 1  to  31 - 6  provided in the integrated circuit units B 10 - 1  to B 10 - 6  detect six colors, namely, violet, blue, green, yellow, red, and orange. Specifically, the pixel  31 - 1  provided in the integrated circuit unit B 10 - 1  is a pixel that detects violet light. The pixel  31 - 2  provided in the integrated circuit unit B 10 - 2  is a pixel that detects blue light. The pixel  31 - 3  provided in the integrated circuit unit B 10 - 3  is a pixel that detects green light. The pixel  31 - 4  provided in the integrated circuit unit B 10 - 4  is a pixel that detects yellow light. The pixel  31 - 5  provided in the integrated circuit unit B 10 - 5  is a pixel that detects red light. The pixel  31 - 6  provided in the integrated circuit unit B 10 - 6  is a pixel that detects orange light. 
     In the color sensor  200 , light from a subject is irradiated onto the pixels  31 - 1  to  31 - 6 . The color sensor  200  also controls the integration time in the switching elements  33 - 1  to  33 - 6  using as a reference a reference voltage which is applied to the reference voltage terminals  32 - 1  to  32 - 6 , and integrates the light from the subject as voltage changes that correspond to the photoelectric current in the capacitance elements  34 - 1  to  34 - 6 . It then outputs the results to output terminals of the operational amplifiers  35 - 1  to  35 - 6 . 
     The color sensor  200  amplifies output changes from the output terminals of the operational amplifiers  35 - 1  to  35 - 6  using the gain circuits  36 - 1  to  36 - 6 , and then reads them. The integration times of each of the integrated circuit units B 10 - 1  to B 10 - 6  are calculated by the integration time calculation units  38 - 1  to  38 - 6  using information sent from the drive control circuit  310 . The gains of the respective gain circuits  36 - 1  to  36 - 6  are calculated by the gain calculation units  39 - 1  to  39 - 6  using information sent from the drive control circuit  310 . As a result of this, output signals are output from the output terminals  37 - 1  to  37 - 6  for the integration time and the gain that are set by the integration time calculation units  38 - 1  to  38 - 6  and the gain calculation units  39 - 1  to  39 - 6 . 
     The spectral characteristics of a multiband color sensor will now be described.  FIG. 11  is a graph illustrating the spectral characteristics of a multiband color sensor that is formed by coating color filters on the front surface of a light receiving element (i.e., a photodiode or pixel) of a light sensor in order to detect spectrum information about a test specimen. This graph shows a curve  2001  that shows the transmittance of a color filter that has been coated on the front surface of a color sensor that detects violet light, a curve  2002  that shows the transmittance of a color filter that has been coated on the front surface of the color sensor that detects blue light, a curve  2003  that shows the transmittance of a color filter that has been coated on the front surface of the color sensor that detects green light, a curve  2004  that shows the transmittance of a color filter that has been coated on the front surface of the color sensor that detects yellow light, and a curve  2005  that shows the transmittance of a color filter that has been coated on the front surface of the color sensor that detects red light. In this manner, the wavelengths of the light transmitted through each color filter differ in accordance with the color of the detected light. 
       FIGS. 12A and 12B  are timing charts illustrating the operation timings of a color sensor  200  to which a conventionally known solid-state imaging device has been applied.  FIG. 12A  is the timing chart obtained when the color sensor  200  acquires spectrum information normally.  FIG. 12B  is the timing chart obtained when a fixed quantity of light or more is irradiated onto the color sensor  200 . 
     If less than the fixed quantity of light is irradiated onto the color sensor  200 , then in the same way as was described using the timing chart illustrating the operation timings of the conventionally known solid-state imaging device  100  shown in  FIG. 9 , as is shown in  FIG. 12A , the color sensor  200  is able to acquire spectrum information normally. 
     However, when a fixed quantity or more of light is irradiated onto a specific pixel in a sensor having spectral characteristics such as those shown in  FIG. 11 , then as is shown in  FIG. 12B , V 1  becomes saturated in the time period T 2 . At this time, because there are no voltage changes in the time period T 3 , the final output voltage V 2  changes to zero and shows a false value. It is not possible to determine in this case whether the reference voltage was output with the zero changes in voltage being due to there being few irradiated wavelength components, or whether the reference voltage was output when saturation was reached in the time period T 2  as a result of a fixed amount of light or more being irradiated. 
       FIG. 13  is a graph illustrating a relationship between the amount of light and the output when the output from the gain circuits  36 - 1  to  36 - 6  dropped to zero when a fixed quantity or more of light was irradiated onto the color sensor  200 . The horizontal axis in the graph shows the amount of light, while the vertical axis shows the output from the gain circuits  36 - 1  to  36 - 6 . As is shown in the drawing, when the amount of light of the wavelength component irradiated onto a particular pixel of the color sensor  200  was a fixed amount of light or more, the output of the gain circuits  36 - 1  to  36 - 6  did not reach the saturation level output which is shown in the graph by the dotted line, and as is shown by the solid line, there was no saturation output and the amount of irradiated light dropped to zero. Because of this, false spectrum information is acquired by the color sensor  200 , and it is not possible for accurate spectrum information to be acquired. 
     SUMMARY 
     The present invention provides a spectrum information measurement method, a color sensor, and a virtual slide device that make it possible to acquire spectrum information about a subject more accurately. 
     A spectrum information measurement method may include steps of: controlling a reference pixel accumulating charges for a prescribed measurement time, the reference pixel accumulating the charges based on an amount of light irradiated from a test specimen; controlling a plurality of measurement pixels accumulating the charge for the prescribed measurement time, the plurality of measurement pixels accumulating the charge based on an amount of light that is irradiated from the test specimen and has a prescribed wavelength; generating and outputting a reference signal based on an amount of change in the charge that is accumulated in the reference pixel over the prescribed measurement time; generating and outputting a plurality of measurement signals based on an amount of change in the charge that is accumulated in each of the plurality of measurement pixels over the prescribed measurement time; determining whether or not any one or more of the plurality of measurement signals is greater than the reference signal, and determining that the measurement signal that is greater than the reference signal includes saturated output. 
     The spectrum information measurement method may further include a step of: determining that each one of the plurality of measurement signals is minimum value output if the reference signal and the plurality of measurement signals are all less than a prescribed value. 
     The prescribed value may be zero. 
     The spectrum information measurement method may further include a step of: discarding the reference signal and the plurality of measurement signals and lowering sensitivities of the reference pixel and the plurality of measurement pixels if it is determined that the saturated output is contained in the plurality of measurement signals. 
     The spectrum information measurement method may further include a step of: discarding the reference signal and the plurality of measurement signals and raising sensitivities of the reference pixel and the plurality of measurement pixels if it is determined that the minimum value output is contained in the plurality of measurement signals. 
     A color sensor may include: a reference pixel that accumulates a charge based on an amount of light irradiated from a test specimen; a plurality of measurement pixels that accumulate a charge based on an amount of light that is irradiated from the test specimen and has a prescribed wavelength; a drive control circuit that controls the reference pixel and the plurality of measurement pixels accumulating the charge for a prescribed measurement time; a reference signal generation circuit that generates and outputs a reference signal based on an amount of change in the charge accumulated in the reference pixel for the prescribed measurement time; a plurality of measurement signal generation circuits that generate and output measurement signals based on the amount of change in the charge accumulated in the plurality of measurement pixels for the prescribed measurement time; and a saturation determination unit that determines whether or not one or more of the plurality of measurement signals output by the plurality of measurement signal generation circuits is greater than the reference signal output by the reference signal generation circuit, and determines that the measurement signal that is greater than the reference signal includes a saturated output. 
     A virtual slide device may include: a color sensor that includes: a reference pixel that accumulates a charge based on an amount of light irradiated from a test specimen; a plurality of measurement pixels that accumulate a charge based on an amount of light that is irradiated from the test specimen and has a prescribed wavelength; a drive control circuit that controls the reference pixel and the plurality of measurement pixels accumulating the charge for a prescribed measurement time; a reference signal generation circuit that generates and outputs a reference signal based on an amount of change in the charge accumulated in the reference pixel for the prescribed measurement time; a plurality of measurement signal generation circuits that generate and output measurement signals based on the amount of change in the charge accumulated in the plurality of measurement pixels for the prescribed measurement time; and a saturation determination unit that determines whether or not one or more of the plurality of measurement signals output by the plurality of measurement signal generation circuits is greater than the reference signal output by the reference signal generation circuit, and determines that the measurement signal that is greater than the reference signal includes a saturated output; an image sensor that forms an image of the test specimen based on the light irradiated from the test specimen; and an image processing unit that performs an image processing of the image of the test specimen formed by the image sensor based on the plurality of measurement signals generated by the color sensor. 
     According to the present invention, control is performed such that a charge is accumulated for a predetermined measurement time on a reference pixel that accumulates a charge in accordance with the amount of irradiated light that is irradiated thereon from a test specimen. Control is also performed such that a charge is accumulated for a predetermined measurement time on a plurality of measurement pixels that accumulate a charge in accordance with the amount of irradiated light of a specific wavelength that is included in the irradiated light that is irradiated thereon from a test specimen. A reference signal is then generated from the amount of change in the predetermined measurement time of the charge accumulated in the reference pixel, and is output. A plurality of measurement signals are also generated from the amount of change in the predetermined measurement time of the charge accumulated in the plurality of measurement pixels, and are output. If any one or more of the plurality of measurement signals is greater than the reference signal, then it is determined that saturation output is included in that measurement signal. Because it is possible to determine as a result of this whether or not saturation output is included in a measurement signal, it is possible to acquire spectrum information about a subject more accurately. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view illustrating a structure of a color sensor in accordance with a first preferred embodiment of the present invention; 
         FIG. 2  is a schematic view illustrating a placement of pixels provided in the color sensor in accordance with the first preferred embodiment of the present invention; 
         FIG. 3  is a graph illustrating spectral characteristics of the pixels in accordance with the first preferred embodiment of the present invention; 
         FIG. 4  is a graph illustrating output voltage values of integrated circuit units, and changes in the output voltage values of the integrated circuit units in accordance with the first preferred embodiment of the present invention; 
         FIG. 5  is a flowchart illustrating processing steps of a saturation determination processing of a saturation determination unit in accordance with the first preferred embodiment of the present invention; 
         FIG. 6  is a flowchart illustrating processing steps of a saturation determination processing of a saturation determination unit in accordance with a second preferred embodiment of the present invention; 
         FIG. 7  is a block diagram illustrating a structure of a virtual slide device in accordance with a fifth preferred embodiment of the present invention; 
         FIG. 8  is a schematic view illustrating a structure of a solid-state imaging device in accordance with the related art; 
         FIG. 9  is a timing chart illustrating operation timings of the solid-state imaging device in accordance with the related art; 
         FIG. 10  is a schematic view illustrating a structure of a color sensor to which the solid-state imaging device in accordance with the related art has been applied; 
         FIG. 11  is a graph illustrating spectral characteristics of a multiband color sensor in accordance with the related art; 
         FIGS. 12A and 12B  are timing charts illustrating operation timings of a color sensor to which the solid-state imaging device in accordance with the related art has been applied; and 
         FIG. 13  is a graph illustrating a relationship between an amount of light and an output when the output from gain circuits dropped to zero when a fixed quantity or more of light was irradiated onto the color sensor in accordance with the related art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teaching of the present invention and that the present invention is not limited to the embodiments illustrated for explanatory purpose. 
     First Preferred Embodiment 
     A first preferred embodiment of the present invention will now be described with reference made to the drawings.  FIG. 1  is a schematic view illustrating the structure of a color sensor  1  in accordance with the first preferred embodiment of the present invention. In the example shown in the drawing, the color sensor  1  includes integrated circuit units  11 - 1  to  11 - 6 , gain circuits  12 - 1  to  12 - 6 , integration time calculation units  13 - 1  to  13 - 6 , gain calculation units  14 - 1  to  14 - 6 , a drive control circuit  15 , a saturation determination unit  16 , and output terminals  17 - 1  to  17 - 6 . 
     The integrated circuit units  11 - 1  to  11 - 5  include pixels  111 - 1  to  111 - 5  (i.e., measurement pixels) that detect spectrum information about a subject by dividing it into respective wavelength transmission bands, reference voltage terminals  112 - 1  to  112 - 5 , switching elements  113 - 1  to  113 - 5 , capacitance elements  114 - 1  to  114 - 5 , and operational amplifiers  115 - 1  to  115 - 5 . The integrated circuit unit  11 - 6  includes a pixel  111 - 6  (i.e., a reference pixel) that detects light from a subject, a reference voltage terminal  112 - 6 , a switching element  113 - 6 , a capacitance element  114 - 6 , and an operational amplifier  115 - 6 . Note that portions formed by the reference voltage terminals  112 - 1  to  112 - 6 , switching elements  113 - 1  to  113 - 6 , capacitance elements  114 - 1  to  114 - 6 , and operational amplifiers  115 - 1  to  115 - 6  are called read circuits  110 - 1  to  110 - 6 . 
     The pixel  111 - 1  provided in the integrated circuit unit  11 - 1  is a pixel on which a filter that transmits violet light has been coated so that it detects violet light. The pixel  111 - 2  provided in the integrated circuit unit  11 - 2  is a pixel on which a filter that transmits blue light has been coated so that it detects blue light. The pixel  111 - 3  provided in the integrated circuit unit  11 - 3  is a pixel on which a filter that transmits green light has been coated so that it detects green light. The pixel  111 - 4  provided in the integrated circuit unit  11 - 4  is a pixel on which a filter that transmits yellow light has been coated so that it detects yellow light. The pixel  111 - 5  provided in the integrated circuit unit  11 - 5  is a pixel on which a filter that transmits red light has been coated so that it detects red light. The pixel  111 - 6  provided in the integrated circuit unit  11 - 6  is a pixel on which no filter has been coated so that it detects all light. 
     The color sensor  1  irradiates light from a subject (i.e., a test specimen) onto the pixels  111 - 1  to  111 - 6 . It also controls the integration time (i.e., a predetermined measurement time) in the switching elements  113 - 1  to  113 - 6  using as a reference a reference voltage which is applied to the reference voltage terminals  112 - 1  to  112 - 6 , and integrates the light from the subject as voltage changes that correspond to the photoelectric current in the capacitance elements  114 - 1  to  114 - 6 . It then outputs the results to output terminals of the operational amplifiers  115 - 1  to  115 - 6 . These outputs are the changes in voltage that correspond to the amount of light irradiated onto the pixels  111 - 1  to  111 - 5 . 
     The color sensor  1  amplifies the output changes from the output terminals of the operational amplifiers  115 - 1  to  115 - 5  using the gain circuits  12 - 1  to  12 - 5  (i.e., measurement signal generation circuits) while removing switching noise therefrom, and then reads them. The color sensor  1  amplifies the output change from the output terminal of the operational amplifier  115 - 6  using the gain circuit  12 - 6  (i.e., a reference signal generation circuit) while removing switching noise therefrom, and then reads it. 
     The integration times of each of the integrated circuit units  11 - 1  to  11 - 6  are calculated by the integration time calculation units  13 - 1  to  13 - 6  using information sent from the drive control circuit  15 . The gains of the respective gain circuits  12 - 1  to  12 - 6  are calculated by the gain calculation units  14 - 1  to  14 - 6  using information sent from the drive control circuit  15 . As a result of this, output signals that correspond to the integration time and the gain that are set by the integration time calculation units  13 - 1  to  13 - 6  and the gain calculation units  14 - 1  to  14 - 6  are output from the output terminals  17 - 1  to  17 - 6 . 
     Output terminals of the gain circuits  12 - 1  to  12 - 6  are connected to the saturation determination unit  16 , and output signals from the gain circuits  12 - 1  to  12 - 6  are input into the saturation determination unit  16 . Based on the output signals (i.e., the measurement signals) input from the gain circuits  12 - 1  to  12 - 5  and on the output signals (i.e., the reference signal) input from the gain circuit  12 - 1 , the saturation determination unit  16  performs saturation determination processing to determine whether or not the integrated circuit units  11 - 1  to  11 - 6  are in a saturated state. A saturated state is a state in which the amount of light of the wavelength component that is irradiated onto the color sensor  1  is equal to or more than a fixed amount of light, and in which the amount of light able to be detected by the integrated circuit units  11 - 1  to  11 - 6  has been exceeded and the output voltage values from the integrated circuit units  11 - 1  to  11 - 6  are saturated. The output voltage values from the integrated circuit units  11 - 1  to  11 - 6  at this time are taken as the saturation output. The processing steps of this saturation determination processing are described below. The drive control circuit  15  controls each unit provided in the color sensor  1 . By employing this structure, the color sensor  1  is able to acquire spectrum information about a subject based on output signals from the gain circuits  12 - 1  to  12 - 5 . 
       FIG. 2  is a schematic view illustrating the placement of the pixels  111 - 1  to  111 - 6  provided in the color sensor  1  in accordance with the first preferred embodiment of the present invention. In the example shown in the drawing, the pixel  111 - 6  on which no filter has been coated so that it is able to detect all of the light is placed on the top left side. The pixel  111 - 1  on which a filter that transmits violet light has been coated so that it is able to detect violet light is placed on the top right side. The pixel  111 - 2  on which a filter that transmits blue light has been coated so that it is able to detect blue light is placed in the top center. The pixel  111 - 3  on which a filter that transmits green light has been coated so that it is able to detect green light is placed in the bottom center. The pixel  111 - 4  on which a filter that transmits yellow light has been coated so that it is able to detect yellow light is placed on the bottom right side. The pixel  111 - 5  on which a filter that transmits red light has been coated so that it is able to detect red light is placed on the bottom left side. The placement of the pixels  111 - 1  to  111 - 6  is not limited to the placement shown in the drawing, and other desired placements may also be used. 
     The spectral characteristics of the pixels  111 - 1  to  111 - 6  will now be described.  FIG. 3  is a graph illustrating the spectral characteristics of the pixels  111 - 1  to  111 - 6  in accordance with the first preferred embodiment of the present invention. This graph shows a curve  1001  that shows the transmittance of a color filter that has been coated on the pixel  111 - 1  that detects violet light, a curve  1002  that shows the transmittance of a color filter that has been coated on the pixel  111 - 2  that detects blue light, a curve  1003  that shows the transmittance of a color filter that has been coated on the pixel  111 - 3  that detects green light, a curve  1004  that shows the transmittance of a color filter that has been coated on the pixel  111 - 4  that detects yellow light, a curve  1005  that shows the transmittance of a color filter that has been coated on the pixel  111 - 5  that detects red light, and a curve  1006  that shows the transmittance of light when no filter has been coated on the pixel. In this manner, the wavelengths of the light transmitted through each color filter are different. The light transmittance when no filter was coated was higher across all of the wavelength bands compared to the transmittance when a filter was coated. Because of this, compared with the outputs from the pixels  111 - 1  to  111 - 5  on which filters were coated, the output from the pixel  111 - 6  on which no filter was coated showed the highest output changes irrespective of the wavelength of the irradiated light. 
     In the first preferred embodiment, a description is given of the output voltage values of the integrated circuit units  11 - 1  to  11 - 6  when the output voltage value of one of the integrated circuit units  11 - 1  to  11 - 6  has become saturated.  FIG. 4  is a graph illustrating the output voltage values of the integrated circuit units  11 - 1  to  11 - 6  during the time periods T 2  and T 3 , and changes in the output voltage values of the integrated circuit units  11 - 1  to  11 - 6  during the time period T 3 . The time periods T 2  and T 3  are the same periods as the time periods T 2  and T 3  shown in  FIG. 9 . The changes in the output voltage values of the integrated circuit units  11 - 1  to  11 - 6  during the time period T 3  correspond to the output voltage values of the gain circuits  12 - 1  to  12 - 6 . 
       FIG. 4  ( 1 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 6  which has the pixel  111 - 6  that detects the light of all of the colors.  FIG. 4  ( 2 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 5  which has the pixel  111 - 5  that detects red light.  FIG. 4  ( 3 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 2  which has the pixel  111 - 2  that detects blue light.  FIG. 4  ( 4 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 1  which has the pixel  111 - 1  that detects violet light.  FIG. 4  ( 5 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 3  which has the pixel  111 - 3  that detects green light.  FIG. 4  ( 6 ) is a graph illustrating the output voltage value of the integrated circuit unit  11 - 4  which has the pixel  111 - 4  that detects yellow light. 
     As was described in the description of the related art, when a fixed amount of light or greater is irradiated onto the specific pixels  111 - 1  to  111 - 5 , because the output voltage values of the integrated circuit units  11 - 1  to  1106  reach saturation level during the time period T 2 , there are zero changes in output during the time period T 3 . Because of this, the output voltage values of the gain circuits  12 - 1  to  12 - 6  are zero. Note that the term zero includes values adjacent to zero. 
     In the example shown in the drawing, the output changes from the integration circuit unit  11 - 6  which has the pixel  111 - 6  that detects light of all of the colors that are shown in  FIG. 4  ( 1 ), and the output changes from the integration circuit unit  11 - 3  which has the pixel  111 - 3  that detects green light that are shown in  FIG. 4  ( 5 ) are both zero, while the other output changes are not zero. In this case, there is a value of zero for the output voltage of the gain circuit  12 - 6  which reads the output changes of the integrated circuit unit  11 - 6  which has the pixel  111 - 6  that detects light of all of the colors. In addition, there is a value of zero for the output voltage of the gain circuit  12 - 3  which reads the output changes of the integrated circuit unit  11 - 3  which has the pixel  111 - 3  that detects green light. The output voltage values of the gain circuits  12 - 1 ,  12 - 2 ,  12 - 4 , and  12 - 5  which read the output changes of the integrated circuit units  11 - 1 ,  11 - 2 ,  11 - 4 , and  11 - 5  which have the other pixels  111 - 1 ,  111 - 2 ,  111 - 4 , and  111 - 5  are not zero. Namely, the values of the output voltages of the gain circuits  12 - 1 ,  12 - 2 ,  12 - 4 , and  12 - 5  are larger than the value of the output voltage of the gain circuit  12 - 6 . 
     However, as is shown in  FIG. 3 , the transmittance of the light when no filter is coated is higher across all wavelength bands than the transmittance when a color filter was coated. Because of this, in cases in which saturation has not occurred, the output voltage value of the gain circuit  12 - 6  which reads the output changes of the integrated circuit unit  11 - 6  which has the pixel  111 - 6  on which no filter has been coated shows the highest output change irrespective of the wavelength of the irradiated light compared with the values of the output voltages of the gain circuits  12 - 1  to  12 - 5  which read the output changes of the integrated circuit units  11 - 1  to  11 - 5  that have the pixels  111 - 1  to  111 - 5  on which filters have been coated. 
     As a result of this, in the example shown in  FIG. 4 , because the change in the output voltage values of the integrated circuit units  11 - 1 ,  111 - 2 ,  111 - 4 , and  111 - 5 , namely, the values of the output voltages of the gain circuits  12 - 1 ,  12 - 2 ,  12 - 4 , and  12 - 5  during the period T 3  are not zero, it is understood that light is being irradiated onto the color sensor  1 . Accordingly, in the example shown in  FIG. 4 , because the value of the output voltage from the integrated circuit unit  11 - 6  does not reach saturation level during the time period T 2 , there is zero change in the output from the integrated circuit unit  11 - 6  during the time period T 3 , and it is understood that the value of the output voltage from the gain circuit  12 - 6  is zero. Namely, it can be understood that a false result, namely, that the amount of light irradiated onto the integrated circuit unit  11 - 6  is zero is output. In the same way, because the output from the gain circuit  12 - 3  during the time period T 3  is zero, it can be understood that there is a possibility that the value of the output voltage from the integrated circuit unit  11 - 3  during the period T 2  has become saturated. 
     Next, the processing steps of the saturation determination processing of the saturation determination unit  16  of the first preferred embodiment will now be described.  FIG. 5  is a flowchart illustrating the processing steps of the saturation determination processing of the saturation determination unit  16  in accordance with the first preferred embodiment of the present invention. 
     In step S 101 , the saturation determination unit  16  acquires output voltage values from the gain circuits  12 - 1  to  12 - 5  that read output changes from the integrated circuit units  11 - 1  to  11 - 5  that have the pixels  111 - 1  to  111 - 5  on which filters have been coated, and an output voltage value from the gain circuit  12 - 6  that reads the output change from the integrated circuit unit  11 - 6  that has the pixel  111 - 6  that detects light of all of the colors and on which a filter has not been coated. Thereafter, the saturation determination unit  16  moves to the processing of step S 102 . 
     In step S 102 , the saturation determination unit  16  compares the output voltage values of the gains circuits  12 - 1  to  12 - 5  that were acquired in step S 101  with the value of the output voltage from the gain circuit  12 - 6 . Thereafter, the saturation determination unit  16  moves to the processing of step S 103 . 
     In step S 103 , if, based on the result of the comparison in step S 102 , the value of any of the output voltages from the gain circuits  12 - 1  to  12 - 5  is greater than the value of the output voltage from the gain circuit  12 - 6 , the saturation determination unit  16  determines that saturated output is contained therein and that a saturation state has been reached. Thereafter, the saturation determination processing is ended. If, however, the saturation determination unit  16  determines in the saturation determination processing that a saturation state has not been reached, it determines that the spectrum information acquired at this time is invalid. 
     As has been described above, according to the first preferred embodiment of the present invention, the saturation determination unit  16  the output voltage values from the gain circuits  12 - 1  to  12 - 5  that read changes in output from the integrated circuit units  11 - 1  to  11 - 5  that have the pixels  111 - 1  to  111 - 5  on which filters have been coated with the output voltage value from the gain circuit  12 - 6  that reads the change in output from the integrated circuit unit  11 - 6  that has the pixel  111 - 6  on which a filter has not been coated. If the value of any of the output voltages from the gain circuits  12 - 1  to  12 - 5  is greater than the value of the output voltage from the gain circuit  12 - 6 , the saturation determination unit  16  determines that a saturation state has been reached. If, however, the saturation determination unit  16  determines in the saturation determination processing that a saturation state has not been reached, it determines that the spectrum information acquired at this time is invalid. As a result of this procedure, the color sensor  1  is able to accurately acquire spectrum information. 
     Second Preferred Embodiment 
     A second preferred embodiment of the present invention will now be described. The point of difference between the second preferred embodiment and the first preferred embodiment is that, in the saturation processing of the second preferred embodiment, when the values of the output voltages from the gain circuits  12 - 1  to  12 - 5  that read the changes in output from the integrated circuit units  11 - 1  to  11 - 5  that have the pixels  111 - 1  to  111 - 5  on which filters have been coated are zero, then a determination is made as to whether or not this output voltage value is a correct output voltage value. Note that the structure of the color sensor  1  of the second preferred embodiment is the same as the structure of the color sensor  1  of the first preferred embodiment. 
     The processing steps of the saturation determination processing of the saturation determination unit  16  of the second preferred embodiment will now be described.  FIG. 6  is a flowchart illustrating the processing steps of the saturation determination processing of the saturation determination unit  16  in accordance with the second preferred embodiment of the present invention. 
     The processing of steps S 201  to S 202  is the same as the processing of steps S 201  to S 202  of the first preferred embodiment. 
     In step S 203 , based on the result of the comparison in step S 202 , the determination processing unit  16  determines whether or not the values of the output voltages from the gain circuits  12 - 1  to  12 - 5  that read output changes from the integrated circuit units  11 - 1  to  11 - 5  that have the pixels  111 - 1  to  111 - 5  on which filters have been coated, and the value of the output voltage from the gain circuit  12 - 6  that reads output changes in the integrated circuit unit  11 - 6  that has the pixel  111 - 6  on which a filter has not been coated are all zero. If the saturation determination unit  16  determines that the values of the output voltages from the gain circuits  12 - 1  to  12 - 5  and the value of the output voltage from the gain circuit  12 - 6  are all zero, it moves to the processing of step S 204 , while in all other cases it moves to the processing of step S 205 . 
     In step S 204 , the saturation determination unit  16  determines that the values of the output voltages from the gain circuits  12 - 1  to  12 - 5  and the value of the output voltage from the gain circuit  12 - 6  are all zero (i.e., are a minimum value output). Namely, the saturation determination unit  16  determines that the values of the output voltage from the gain circuits  12 - 1  to  12 - 5  and the value of the output voltage from the gain circuit  12 - 6  are correct values. Thereafter, the processing is ended. 
     The processing of step S 205  is the same as the processing of step S 103  of the first preferred embodiment. 
     As has been described above, according to the second preferred embodiment of the present invention, when there is a value of zero for the output voltage from the gain circuit  12 - 6  that reads output changes in the integrated circuit unit  11 - 6  that has the pixel  111 - 6  on which a filter has not been coated, it is possible to correctly determine whether the value of the output voltage is zero because the amount of light irradiated onto the color sensor  1  was too great and caused saturation to occur, or whether the value of the output voltage is zero because the amount of light irradiated onto the color sensor  1  was too small. As a consequence, it is possible to acquire spectrum information more accurately. 
     Third Preferred Embodiment 
     A third preferred embodiment of the present invention will now be described. The point of difference between the third preferred embodiment and the first preferred embodiment is that, in the third preferred embodiment, when the saturation determination unit  16  has determined in the saturation determination processing that a state of saturation has been reached, the drive control circuit  15  lowers the photosensitivity of each of the integrated circuit units  11 - 1  to  11 - 6  so that the state of saturation is terminated, and spectrum information is once again acquired. The method used to lower the photosensitivity of the respective integrated circuit units  11 - 1  to  11 - 6  may be one in which, for example, the drive control circuit  15  controls the gain values calculated by the gain calculation units  14 - 1  to  14 - 6  such that these values are small. 
     As has been described above, according to the third preferred embodiment of the present invention, when the saturation determination unit  16  has determined in the saturation determination processing that a state of saturation has been reached, the drive control circuit  15  lowers the photosensitivity of each of the integrated circuit units  11 - 1  to  11 - 6  so that the state of saturation is terminated, and spectrum information is once again acquired. As a result, the color sensor  1  is able to acquire spectrum information more accurately. 
     Fourth Preferred Embodiment 
     A fourth preferred embodiment of the present invention will now be described. The point of difference between the fourth preferred embodiment and the second preferred embodiment is that, in the fourth preferred embodiment, when the saturation determination unit  16  has determined in the saturation determination processing that the value of the voltage output is zero because a small amount of light is irradiated onto the color sensor  1 , the drive control circuit  15  raises the photosensitivity of each of the integrated circuit units  11 - 1  to  11 - 6 , and once again acquires the spectrum information. The method used to raise the photosensitivity of the respective integrated circuit units  11 - 1  to  11 - 6  may be one in which, for example, the drive control circuit  15  controls the gain values calculated by the gain calculation units  14 - 1  to  14 - 6  such that these values are large. 
     As has been described above, according to the fourth preferred embodiment of the present invention, when the saturation determination unit  16  has determined in the saturation determination processing that the value of the voltage output is zero because a small amount of light is irradiated onto the color sensor  1 , the drive control circuit  15  raises the photosensitivity of each of the integrated circuit units  11 - 1  to  11 - 6 , and once again acquires the spectrum information. As a result, the color sensor  1  is able to acquire spectrum information more accurately. 
     Fifth Preferred Embodiment 
     A fifth preferred embodiment of the present invention will now be described.  FIG. 7  is a block diagram illustrating the structure of a virtual slide device in accordance with the fifth preferred embodiment of the present invention. In the example shown in the drawing, a virtual slide device  500  includes a color sensor  1 , an objective lens  81 , a half-mirror  82 , an RGB image sensor  83 , and an image processing unit  84 . 
     The color sensor  1  is the same as any one of the color sensors  1  described in the first through fourth preferred embodiments, and is able to more accurately acquire spectrum information about a sample. The objective lens  81  condenses light that is irradiated onto a sample. The half-mirror  82  splits the light from the objective lens in the directions of the color sensor  1  and the RGB image sensor  83 . The RGB image sensor  83  generates images based on images of a subject photographed via the objective lens  81  and the half-mirror  82 . The image processing unit  84  performs image processing such as corrections and the like on images acquired by the RGB image sensor  83  based on spectrum information for the sample acquired by the color sensor  1 . 
     As has been described above, according to the fifth preferred embodiment of the present invention, the color sensor  1  is able to acquire spectrum information about a subject more accurately. As a result, the image processing unit  84  is able to perform image processing such as corrections and the like more accurately on images acquired by the RGB image sensor  83 . 
     A first through fifth preferred embodiment of this invention have been described above in detail with reference made to the drawings, however, the specific structure thereof is not limited to these preferred embodiments and various other designs may be considered insofar as they do not depart from the spirit or scope of this invention. 
     For example, in the above described examples, the color sensor  1  includes the five pixels  111 - 1  to  111 - 5  that serve as pixels on which filters have been coated, however, this invention is not limited to this and it is also possible for the color sensor to be simply provided with a plurality of pixels on which filters have been coated. 
     While preferred embodiments of the present invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the claims.