Abstract:
The invention discloses a scanner apparatus for performing bidirectional scanning by using an integration amplifying detector, which is capable of preventing the occurrence of jitters. To detect the n-th pixel from the left in a going direction, an integration timing setting circuit generates pulses indicating a resetting period Tr and a measuring period Ti by using the n-th pulse of a scanning position detecting clock as a reference, and then controls an integration circuit. To detect the n-th pixel from the left in a returning direction, an integration timing setting circuit generates a timing clock by delaying a difference period Td generated between the going and returning ways, with the n+1st pulse of the scanning position detecting clock from the left used as a reference, and then controls the integration circuit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a scanner apparatus, more particularly to a scanner apparatus using an integration amplifying detector as a detector. 
     2. Description of the Related Art 
     As a means for detecting light of low luminance with high sensitivity, a means using an integration amplifier has been available. This integration amplifying detection means is designed to accumulate output charges by the integration amplifier, which have been subjected to photoelectric conversion by a photomultiplier tube (PMT) or a photodiode, convert the charges into voltages and then read them out. 
     Conventionally, such an integration amplifying detector has mainly been used for performing one-point observation in a time-sequential manner. In recent years, however, in order to observe a sheet-form object to be measured, which emits weak light, an application of the integration amplifying detector to a scanner for performing two-dimensional scanning has been tried. 
     The scanner using the integration amplifying detector generates a scanning position detecting clock indicating a period of information acquisition according to a scanning speed during main scanning, generates a timing pulse by using the scanning position detecting clock as a reference, and then indicates, to the integration amplifying detector, a period for executing integration, i.e., a measuring period, or a resetting period for releasing charges accumulated in the integration amplifying detector by this timing pulse. 
     The use of the scanner employing such an integration amplifying detector is advantageous, for example, for detection of photostimulating light in a radiation image recording/reproducing system (Japanese Unexamined Patent Publication No. 55 (1980)-12429 or the like) presented by an applicant of the present invention. This system uses an stimulable phosphor (photostimulable phosphor), which accumulates a part of radiation energy when irradiated with radioactive rays (X rays, α rays, β rays, γ rays, electron beams, ultraviolet rays or the like) , and then shows phosphorescence according to the accumulated energy when irradiated with excitation light such as visible light. By using the stimulable phosphor, the system temporarily photographs and records the radiation image of an object, e.g., a human body, in the sheet-form stimulable phosphor, generates phosphorescent light by scanning the stimulable phosphor sheet with excitation light such as a laser beam, obtains an image signal by photoelectrically reading the generated phosphorescent light, and displays the radiation image of the object on a CRT based on the image signal by using an image recording/reproducing device or outputs the radiation image as a visible image on a photosensitive film. 
     In addition, to increase the readout speed (throughput) of the scanner apparatus using the above-described integration amplifying detector, bidirectional scanning should be desirably performed, which enables information to be detected in both going and returning ways, when a detection unit is scanned in a main scanning direction. 
     However, when bidirectional scanning is carried out by the scanner using the integration amplifying detector of the foregoing principle, a difference is generated in the integration starting time of the integration amplifying detector for obtaining information regarding each pixel between the going and returning ways of the scanner, causing a pixel positional deviation in the scanning direction between the going and returning ways. Consequently, jitters occur in the main scanning direction. 
     SUMMARY OF THE INVENTION 
     The present invention was made with the foregoing problems in mind, and it is an object of the invention to provide a scanner apparatus for performing bidirectional scanning by using integration amplifying detector, which is capable of eliminating jitters like those described above. 
     In accordance with the invention, a scanner apparatus having a bidirectional scanning function capable of scanning in both going and returning ways is provided. This scanner apparatus comprises: an integration amplifying detector for accumulating a detected quantity of light in a measuring period Ti within one cycle Tp, and releasing an accumulated quantity of light in a resetting period Tr; a scanning position detecting clock generator for generating a scanning position detecting clock of an interval equal to the cycle Tp for obtaining information by the integration amplifying detector; a timing pulse generator for deciding a resetting period Tr and a measuring period Ti of the integration amplifying detector based on the scanning position detecting clock, and generating timing pulses indicating the resetting period Tr and the measuring period Ti; and an A/D converter for converting a value of the quantity of light accumulated in the integration amplifying detector into a digital value. In this case, the timing pulse generator generates, in the returning way, the timing pulses by delaying a difference period Td generated between the going and returning ways. 
     In the scanner apparatus of the invention, the bidirectional scanning function capable of scanning in both going and returning ways is not limited to one where an object to be scanned is mechanically reciprocated, but includes one where a scanning optical system is reciprocated with respect to a fixed object to be scanned. 
     According to the scanner apparatus of the invention, the scanning position detecting clock generator may change the cycle Tp of the scanning position detecting clock according to a measuring condition. 
     The measuring condition means one for a resolution priority mode designed to enhance resolution by reducing sensitivity, or for a sensitivity priority mode designed to enhance sensitivity by reducing resolution. 
     According to the scanner apparatus of the invention, the timing pulse generator may generate the timing pulses to set a positive value for the difference period Td, detect the scanning position detecting clock with detection accuracy variance of 1% or lower, or generate the timing pulses to set a measuring period Ti longer by four times or more than a resetting period Tr. Moreover, when no scanning position detecting clock is detected in a cycle longer by 1.5 times than the cycle Tp for obtaining the information, the timing pulse generator may generate a timing pulse indicating a resetting period Tr. 
     Now, a method for calculating the difference period Td will be described by referring to FIG. 2 showing a time relation between a scanning position detecting clock and a timing pulse. 
     In the drawing, a scanning direction  1  indicates the going way of a main scanning direction; a scanning direction  2  the returning way of the main scanning direction; Tp the cycle of the scanning position detecting clock; Tw the pulse width of the scanning position detecting clock; Tr the resetting period of the integrator of the integration amplifying detector; Ti the integrating period of the integration amplifying detector; and Td a difference period between the going and returning ways when the information of the same place is obtained in the main scanning direction. 
     The cycles Tp and the pulse widths Tw of the scanning position detecting clock are equal between the going and returning ways, and pulse generation positions are identical with respect to the position of main scanning. 
     In the scanning direction  1 , i.e., the going way of the detection unit, to detect an n-th pixel from the left, the timing pulse generator generates a pulse indicating resetting for the period Tr from the rising edge by using the rising edge of an n-th pulse of the scanning position detecting clock as a reference, and a pulse indicating measuring for the period Ti after the passage of time Tr from the rising edge. 
     In the scanning direction  2 , i.e., in the returning way of the detection unit, to detect a position substantially identical to an n-th place detected in the going way in the main scanning direction, the timing pulse generator generates a pulse indicating resetting for the period Tr from the rising edge by using the rising edge of the n+1st pulse from the left of the scanning position detecting clock as a reference, and a pulse indicating measuring for the period Ti after the passage of time Tr from the rising edge. 
     In this case, if the center of the measuring period Ti is set as a measuring position, then the center position of the measuring period Ti is shifted by the difference period Td between the going and returning ways. 
     The difference period Td is calculated by an equation (1) below. Since a difference is within one pixel, it is impossible to make corrections by moving positions left and right by pixel units for every main scanning line after the detection of information, causing jitters in this difference period Td. 
     
       
           Td=Tp×Tw −(2× Tr+Ti )  (1) 
       
     
     Thus, in the returning way, a timing pulse is generated by delaying an amount equal to the difference period Td, thus preventing the center shifting of the measuring period Ti between the going and returning ways. 
     With the scanner apparatus of the invention constructed in the foregoing manner, by changing the measuring timing of the integration amplifying detector between the going and returning ways, the center of the measuring period Ti can be prevented from being shifted for every main scanning line. As a result, it is possible to prevent the occurrence of jitters. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a scanner apparatus of the present invention. 
     FIG. 2 is a view showing a time relation between a scanning position detecting clock and a timing pulse. 
     FIG. 3 is a view showing a hybridized microarray chip to be read by a reader shown in FIG.  1 . 
     FIG. 4 is a view showing a state of the microarray chip of FIG. 3 before hybridization. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Next, the specific embodiment of the scanner apparatus of the invention will be described. FIG. 1 is a block diagram showing a scanner apparatus according to a first embodiment; FIG. 2 a view showing a time relation between a scanning position detecting clock and a timing pulse; FIG. 3 a view showing an example of a hybridized microarray chip  10  shown in FIG. 1 to be scanned by the scanner apparatus; and FIG. 4 a view showing an example of the microarray chip before hybridization. 
     A scanner apparatus  1  using the microarray chip as an image carrier shown in FIG. 1 specifically includes a stage moving unit  2 , an optical system  3 , and a signal processing unit  4 . 
     A microarray chip  10 ″ shown in FIG. 4 includes cDNA different from each other, which are coated in preset positions in a highly dense matrix form on a glass slide  11 . Each cDNA coated beforehand is known, and a correspondence between the coating position and the cDNA is apparent beforehand. DNA of a specimen having a hereditary disease is marked with a fluorescent dye and is hybridized in the microarray chip  10 ″ shown in FIG. 4. A microarray chip  10  shown in FIG. 3 is one having only such a hybridized connected matter (matter to be detected)  12  left on the sliding glass  11 . For the purpose of explanation, description is made such that the position of the remaining connected matter  12  can be identified with the naked eye by comparing the microarray chip  10 ″ shown in FIG. 4 with the microarray chip  10  shown in FIG.  3 . However, in an actual microarray chip, it is difficult to identify such a position with the naked eye because of the highly dense coating of the cDNA. 
     The microarray chip  10  is scanned by the excitation light L. When the connected matter  12  is present in a scanning position, the connected matter  12  is irradiated with the excitation light L. Accordingly, a fluorescent dye of the connected matter  12  is excited to emit fluorescence K. On the other hand, if there are no connected matters  12  in the scanning position irradiated with the exciting light L, no fluorescence K is emitted from the microarray chip  10 . 
     The stage moving unit  2  includes: a two-dimensionally movable light transmissive stage  21 , on which the microarray chip  10  shown in FIG. 2 is loaded; a first stepping motor  22  for moving the stage  21  in a Y axial direction and a second stepping motor  23  for moving the stage  21  in an X axial direction so as to scan the microarray chip  10  loaded on the stage  21  by the excitation light L; and a stepping motor control circuit  24  for driving the stepping motors  22  and  23 . Thus, in the XY plane of FIG. 1, the excitation light L scans the microarray chip  10  at a predetermined speed. 
     The optical system  3  includes: an excitation light source  31  for emitting the excitation light L; a collimator lens  32  for converting the excitation light L emitted from the excitation light source  31  into parallel luminous fluxes; a polarized beam splitter  33  for transmitting the excitation light L and reflecting the fluorescence K; and a focusing lens  34  for converging the excitation light L transmitted through the polarized beam splitter  33  on the microarray chip  10  loaded on the stage  21  so as to have a predetermined size. 
     The signal processing unit  4  includes: a photomultiplier  40  having a photomultiplier function for photoelectrically detecting the fluorescence K emitted from the microarray chip  10 ; an integration circuit  50  as an I/V conversion circuit for converting a current signal outputted from the photomultiplier  40  into a voltage signal; an offset compensation circuit  60  for reducing (canceling) an offset voltage which may be generated due to charge injection in the integrating operation of the integration circuit  50 ; a logarithmic conversion circuit  70  for subjecting the voltage signal outputted from the integration circuit  50  to logarithmic conversion; an A/D conversion circuit  80  for converting an analog voltage signal subjected to logarithmic conversion and compressed by the logarithmic conversion circuit  70  into a digital voltage signal by a sampling frequency fs of about 10 to 1000 KHz; an operation mode setting circuit  90 ; an integration timing setting circuit  91 ; and other peripheral circuits. 
     In the signal processing unit  4 , the scanning position of the exciting light L is correspondingly set by entering a scanning position detecting clock indicating the scanning position from the stepping motor control circuit  24 . The integration timing setting circuit  91  generates a timing pulse indicating the timing and the period of resetting or measuring for the integration circuit  50  in connection with the signal entered from the stepping motor control circuit  24 . 
     In this case, as the integration circuit, two systems, i.e., a high-speed integration circuit  50   a  and a low-speed integration circuit  50   b  are provided. However, since only one group is prepared for adjustment input, an arrangement must be made to enable each of the two integration circuits to be adjusted by this group. Each of the integration circuits  50   a  and  50   b  is constructed to be a DC direct connection type for directly integrating a photomultiplier output current so as not to degrade the S/N ratio. In addition, each of the integration circuits  50   a  and  50   b  is constructed such that an integration timing can be set by the integration timing setting circuit  91 . 
     Next, peripheral circuits of the photomultiplier  40  will be described. Around the photomultiplier  40 , as shown in FIG. 1, there are a resistance division type (bleeder circuit type) high-voltage circuit  41  provided to drive the photomultiplier  40 , and an overcurrent protection circuit  42  provided to protect the photomultiplier  40  from an abnormal current. 
     A high voltage HV of about 900 V is applied from the high-voltage circuit  41  to the photomultiplier  40 . The high voltage HV is applied through an LC circuit in order to cut the switching noise of a not-shown high-voltage power source (HV noise measure). In addition, in order to monitor a voltage in the last stage of a dynode of the photomultiplier  40 , an arrangement is made to enable a circuit voltage in the last stage of the divided resistance of the high-voltage circuit  41  to be monitored. 
     The overcurrent protection circuit  42  is constructed in such a manner that by determining the photomultiplier  40  to be in an overcurrent state if either one of the outputs of the integration circuits  50   a  and  50   b  exceeds 5 V, a high voltage HV can be set to 0 V by an overcurrent detection output held in a not-shown flip-flop, and cleared by a reset signal (HV-RESET) after the removal of the cause of the overcurrent. 
     Noted that, as the overcurrent protection circuit  42  detects the outputs of the integration circuits  50   a  and  50   b , overcurrent protection may not be set or an erroneous operation may occur depending on a resetting interval of the integration operation. To prevent such a situation, it is advised that by considering a resetting interval, overcurrent protection functions if there is a photomultiplier maximum output when detection is made at, for example, an interval of 100 μsec. 
     The photomultiplier  40  has relatively high sensitivity, but a large dark current because of thermal noise from the photoelectric surface or the dynode of the photomultiplier  40 . Accordingly, to reduce such a dark current, a cooling unit  45  is provided to cool the photomultiplier  40 , the cooling unit including a Peltier element  46  having the photomultiplier  40  loaded thereon, and a driving circuit  47  for driving the Peltier element. Note that the cooling unit is not limited to the one using a Peltier element, but various well-known cooling methods can be used, e.g., a heat sink. Thus, the possibility of dark current influence is reduced when very weak light is detected. 
     Next, an operation of the scanner apparatus  1  according to the present embodiment will be described. 
     First, the microarray chip  10  shown in FIG. 2 is loaded in a predetermined position on the stage  21 . In this case, each predetermined position of the coated cDNA on the microarray chip  10  is set in a corresponding relation to the X and Y axial directions on the stage  21 . This correspondence is entered from the stepping motor control circuit  24  to each of the stepping motors  22  and  23 . 
     Meanwhile, the excitation light L is emitted from the excitation light source  31 , and this excitation light L is made incident on the collimator lens  32 , and converted into parallel luminous fluxes. The excitation light L converted into the parallel luminous fluxes is transmitted through the beam splitter  33 , and then converged by the focusing lens  34  on the microarray chip  10  loaded on the stage  21 . 
     Each of the stepping motors  22  and  23  drives the stage  21  in the XY plane and stops it in this position based on a scanning command entered from the stepping motor control circuit  24 , in order to irradiate a predetermined scanning position on the microarray chip  10  with the excitation light L. 
     With the rising edge of each pulse of the scanning position detecting clock used as a reference, the integration timing setting circuit  91  generates a pulse indicating resetting for the period of time Tr from the rising edge, and a pulse indicating measuring for the period of time Ti after the passage of the time Tr from the rising edge. Based on the indications of these pulses, the integration circuit  50  repeats resetting and measuring. 
     In this case, to detect the n-th pixel from the left during the going scanning of the Y axial direction, the pulses of the resetting period Tr and the measuring period Ti are generated by using the pulse of the n-th scanning position detecting clock as a reference, and the integration circuit  50  is controlled. 
     If there is a connected matter  12  in the scanning position irradiated with the excitation light L, the connected matter  12  is irradiated with the excitation light L. The fluorescent dye of the connected matter  12  is thereby excited, emitting fluorescence K. On the other hand, if there are no connected matters  12  in the scanning position irradiated with the excitation light L, no fluorescence K is emitted from the microarray chip  10 . 
     When the connected matter  12  is present, and the fluorescence K is emitted, the fluorescence K is successively passed through the focusing lens  34  and the polarized beam splitter  33 , and made incident on the photomultiplier  40 . Then, the fluorescence K is converted into a current signal according to the quantity of light, entered to the integration circuit  50  of the subsequent step to be converted into a voltage signal. The voltage signal is then subjected to logarithmic compression by the logarithmic conversion circuit  70 , and converted by the A/D conversion circuit  80  into a digital signal by a scale factor suited to the width of signal amplitude. 
     After the passage of predetermined time from the irradiation of the first scanning position with the exciting light L, a next scanning position is entered from the stepping motor control circuit  24  to the stepping motors  22  and  23 . Then, for example only the stepping motor  23  is driven to move the stage  21  in the X axial direction by a predetermined distance, and stops it after the movement to the next scanning position where it will be irradiated by the excitation light L. Subsequently, this next scanning position is irradiated with the excitation light L; if there is connected matter  12  as in the above-described case, the fluorescence K is emitted, and detected by the photomultiplier  40 . If no connected matters  12  are present, no detection is carried out. 
     After scanning is completed up to the end of the microarray chip  10 , the stage  21  is moved by the stepping motor  22  in the Y axial direction by a distance corresponding to one pixel, then again in the X axial direction, main scanning of a returning direction is carried out in a direction opposite the going direction. 
     During the scanning of the returning direction, as in the case of the going direction, by using the rising edge of each pulse of a scanning position detecting clock as a reference, the integration timing setting circuit  91  generates a pulse indicating resetting for the period of time Tr from the rising edge, and a pulse indicating measuring for the period of time Ti after the passage of time Tr from the rising edge. However, to detect the n-th pixel from the left in the returning direction, by using the n+1st pulse of the scanning position detecting clock from the left as a reference, a difference period Td generated between the going and returning directions, obtained by the foregoing principle, is delayed to generate a timing clock, and the integration circuit  50  is controlled thereby. 
     The foregoing process is repeated for the entire surface of the microarray chip  10 . The signal indicating the scanning position has been entered from the stepping motor control circuit  24  to the signal processing unit  4 , a correspondence is set among the scanning position of the exciting light L, the presence or absence of detected fluorescence K and the quantity of light, and an image is outputted based on the digital signal outputted from the A/D conversion circuit  80 . As a result, functional analysis is performed for the DNA of the specimen having a hereditary disease based on the aforementioned correspondence. 
     The preferred embodiment of the scanner apparatus of the invention has been described. However, the invention is not limited to the embodiment and, for example, the scanning optical system may be moved while an object to be measured is fixed. 
     In addition, according to the embodiment, the scanner apparatus of the invention is constructed as a fluorescent scanner, which uses the microarray chip. However, there should be no limitation placed in this regard, and the invention can be applied to a scanner apparatus used for a fluorescence detecting system using one other than the microarray chip for genetic analysis such as gene expression analysis, base sequence determination, mutational analysis, polymorphous analysis, and so on. 
     Furthermore, the invention may be applied to a scanner apparatus used for autoradiography designed to display image data on a screen of a CRT or the like as an image, which is obtained by converting positional information of a radiation marked substance in a sample into an electric signal using, for example an stimulable phosphor sheet, autoradiography designed to analyze the positional information of a gene utilizing a hybridization method based on Southern blotting, autoradiography designed to separate and identify protein by polyacrylamide gel electrophoresis, or evaluate a molecular weight and a characteristic, a detecting system by an electron microscope, a radiation diffracted image detecting system or the like.