Abstract:
Disclosed is a spectrum measuring apparatus for shortening such a measurement time period for an object being measured including two or more mutually different measurement portions as is required for the spectrum measurements of the lights from individual measurement portions. The spectrum measuring apparatus comprises a slit group having two or more slits, a spectroscope for separating the lights extracted by the slit group, for the individual slits, and a measuring unit for measuring the intensities of the individual components, which are separated by the spectroscope, for the slits. The individual slits extract such ones of the lights coming from an object being measured including two or more mutually different measurement portions, as come from the individual measurement portions.

Description:
FIELD OF THE DISCLOSURE 
     The present invention relates to a spectrum measuring apparatus for measuring light from a measured object as a spectrum, for example, a spectrum measuring apparatus mounted on a mobile body such as a vehicle. 
     BACKGROUND OF THE DISCLOSURE 
     In recent years, as a driving assistance technique applied to vehicles such as cars, an imaging device such as a CCD camera has been mounted on a vehicle to capture an image of the surrounding of the vehicle as a visible image. In such driving assistance technique, first, information on a subject requiring driving assistance, for example, a pedestrian, a traffic light and the like around the vehicle, is generated by processing the visible image captured by the imaging device, and driving assistance corresponding to the state surrounding the vehicle is performed based on the information thus generated. 
     However, the state of the pedestrian walking around the vehicle, such as the number of persons, body build, posture, carried items, and moving direction, varies each time the visible image around the vehicle is captured. Further, when the driving state of the vehicle, such as the turning direction of the vehicle and the attribute of a road on which the vehicle is running, varies, shape and size of the pedestrian and even the traffic light installed on the road in the visible image around the vehicle also vary. As a result, in an aspect of detecting the object necessary for driving assistance from the visible image of an imaging object including the object, driving assistance lacks precision. Thus, in the above-mentioned driving assistance technique, there is a demand for a technique for improving the detecting accuracy of the object in order to improve the accuracy of the driving assistance. 
     Among techniques for distinguishing an object based on its optical characteristics, patent document 1 describes a known technique using a hyper spectrum sensor as the spectrum measuring apparatus mounted on an artificial satellite for use in soil investigation on the earth. The hyper spectrum sensor described in patent document 1, for example, detects a spectrum so that light from the object is dispersed into components according to each wavelength and optical intensity at each wavelength is associated with the wavelength. In other words, a continuous spectrum with respect to wavelength is handled as the optical characteristics of the object.  FIG. 10  is a diagram showing an example of the optical structure of a hyper spectrum sensor serving as such spectrum measuring apparatus. 
     As shown in  FIG. 10 , an inlet  111 , a mirror  112 , a condenser  113 , a shielding plate  114 , a collimator  115 , a spectroscope  116 , an imager  117  and a measuring unit  118  are arranged in this order in a hyper spectrum sensor  100  along a light traveling direction. Each element of the hyper spectrum sensor  100  is configured so that optical characteristics are continuous in one direction intersecting a hypothetical light beam representing a light flux that passes the elements, that is, an optical axis (extending in a lateral direction in  FIG. 10 ). In the hyper spectrum sensor  100  having such structure, partial sunlight reflected on an object  120 , which is a ground surface serving as a measured object, first enters the apparatus through the inlet  111  and is guided to the condenser  113  by a reflecting action of the mirror  112 . The light incident on the condenser  113  is condensed by a condensing action of the condenser  113  toward the shielding plate  114 , and only light toward a single slit  114   a  is guided to the collimator  115  by a shielding action of the shielding plate  114 . The light passed through the single slit  114   a  in this manner is guided to the spectroscope  116  as collimated light by an optical action of the collimator  115  and each parallel beam is dispersed into wavelength components by a spectral action of the spectroscope  116 . The wavelength components dispersed by the spectroscope  116  (wavelength component λa to wavelength component λb) are image-formed on regions of the measuring unit  118 , which are divided according to wavelength, for example, light receiving elements  118   a ,  118   b  of a CCD image sensor or a CMOS image sensor, by an image-forming action of the imager  117 . 
     In such hyper spectrum sensor  100 , the spectrum of only the light passed through the single slit  114   a  of the light condensed by the condenser  113  is measured. In other words, in the light from the object  120  as the ground surface, only the light from a linear measuring part  120   a  in a direction in which the optical characteristics are continuous in the single slit  114   a , that is, a longitudinal direction Dm of the single slit  114   a , is extracted by the single slit  114   a . Then, only optical information on the linear measuring part  120   a  is input to the hyper spectrum sensor  100  each time. Thus, in the hyper spectrum sensor  100 , by repeating spectrum measurement of the one-dimensional measuring part  120   a  along a flight direction of the artificial satellite, the optical characteristics of the object  120 , which is a two-dimensional ground surface, are measured. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-145362 
       
    
     SUMMARY 
     Problems to be Solved by the Invention 
     In the above hyper spectrum sensor  100 , the direction in which the hyper spectrum sensor  100  moves with respect to the object  120  is the direction in which the measuring part  120   a  is arranged. The two-dimensional range serving as the spectrum measured object is limited by the moving direction Dr at all times. Thus, when measuring the spectrum of the measured object including two or more different measuring parts  120   a  arranged in a direction differing from the moving direction Dr, such as a scene around a vehicle that includes a pedestrian and a traffic light, is measured, the single slit  114   a  must scan in a direction intersecting the longitudinal direction Dm.  FIGS. 11(   a ),  11 ( b ) and  11 ( c ) are diagrams showing scanning examples of the single slit  114   a  together with optical operations. 
     As shown in  FIG. 11(   a ), the single slit  114   a  is arranged so that the measuring part  120   a  at an upper end of the object  120  is an object point and the single slit  114   a  provided on the shielding plate  114  is an image point to first measure the spectrum of the measuring part  120   a  at the upper end of the object  120 . Next, by repeating scanning in which the shielding plate  114  moves by a width of the single slit  114   a , as shown in  FIG. 11(   b ), the spectrum of the measuring part  120   a  at the upper end to the spectrum of the measuring part  120   a  at a lower end of the object  120  are sequentially measured. Then, as shown in  FIG. 11(   c ), by arranging the single slit  114   a  so that the measuring part  120   a  at the lower end of the object  120  is the object point and the single slit  114   a  provided on the shielding plate  114  is the image point, the spectrum is measured in the whole width of the object  120  in the vertical direction. As described above, even when the measuring parts in a scene are arranged in a direction differing from the moving direction, the spectrum of the scene can be measured by scanning the scene with single slit  114   a.    
     Although scanning in which only the shielding plate  114  moves by the width of the single slit  114   a  is repeated in  FIG. 10 , scanning is not limited in such a manner and may be repeated so that the shielding plate  114 , the collimator  115 , the spectroscope  116 , the imager  117  and the measuring unit  118  as a whole move with respect to the fixed single slit  114   a.    
     However, even when such scanning is employed, during measurement of the spectrum of one scene, time for scanning of the single slit  114   a  is needed. Therefore, the spectrum of the scene that is shorter than the time necessary for scanning of the single slit  114   a  cannot be measured. 
     In particular, when the hyper spectrum sensor  100  is mounted on a mobile body such as the vehicle and movement is assisted based on a measurement result, measurement of the spectrum of one scene would be too late for the movement assistance. As a result, the movement assistance lacks precision. 
     Accordingly, it is an object of the present invention to provide a spectrum measuring apparatus that shortens the time necessary for measuring the spectrum of light from each of two or more different measuring parts that forms a measured object. 
     To achieve the above object, a spectrum measuring apparatus is provided with a slit group including two or more slits, a spectroscope that disperses the light extracted by the slit group for each of the slits, and a measuring unit that measures intensity of each component of light dispersed by the spectroscope for each of the slits. For a measured object including two or more different measuring parts, from light from the measured object, each of the slits extracts light from each of measuring parts; 
     In the spectrum measuring apparatus having such a structure, the spectrum of the light from each of the measuring parts can be measured without moving the slits. Thus, as compared to a structure in which the spectrum of the light from each of the measuring parts is measured while moving a single slit, time for measuring the spectrum can be shortened. Further, by mounting such a spectrum measuring apparatus on a mobile body, real-time spectrum measurement in the required moving state can be achieved. Thus, when assisting movement of the mobile body based on the spectrum measurement result, the accuracy of movement assistance can be improved. 
     The slit group is one of two or more different slit groups in the spectrum measuring apparatus. The spectrum measuring apparatus further includes a slit switch that allows switching of one slit group, which passes light that is to be dispersed to the spectroscope, between the two or more different slit groups. 
     When the measuring parts of the measured object differ in position, number, or the like, the light from such measuring parts also differ in position and amount. To extract such light from the light from the measured object, the slits in the slit group must also differ in position, number, or the like. In this regard, the spectrum measuring apparatus allows switching of one slit group, namely, the slit group used for measurement, between the two or more different slit groups. Thus, even when there are two or more different measured objects, if one of two or more different slit groups are applicable to each measured object, the spectrum of the measured objects can be measured. Thus, as compared to, for example, a structure including a single slit group, the degree of freedom in the attribute of the measuring parts, such as position and number of the measuring parts, can be increased. 
     The spectrum measuring apparatus further includes a slit controller that controls switching of the slit switch based on a control value that is in accordance with an attribute of the measuring parts. 
     In the spectrum measuring apparatus, the slit controller controls whether or not to change the slit group used for measurement with the slit switch or the switching to the slit group used for measurement based on the attribute of the measuring parts. Thus, even when there are a plurality of measured objects having different measuring part attributes, such as position and number of the measuring parts, spectrum measurement can be performed in real-time by the slit group suitable for the attribute of the measured part. 
     In the spectrum measuring apparatus, the slit controller determines the attribute of the measuring parts based on a distance between the measured object and the slit group. 
     A spatial range of the measured object becomes larger as the distance from the spectrum measuring apparatus to the measured object increases and conversely become smaller as the distance from the spectrum measuring apparatus to the measured object decreases. To effectively use such spatial range of the measured object, the measured part attribute, such as position and number of the measured part, is preferably varied in accordance with the spatial range of the measured object, that is, the distance from the spectrum measuring apparatus to the measured object. 
     For example, when the range of the measured objects becomes spatially large, if many measuring parts are scattered over a wide range in the measured object, the spectrum can be measured for the entire measured object, which is spatially wide, and measurement can be performed effectively using a spatially wide measured object. Conversely, when the range of the measured objects becomes spatially small, if spectrum measurement is performed in a small number of measuring parts, the measured object that is spatially restricted beforehand can be effectively measured. 
     In the spectrum measuring apparatus, the attribute of the measuring parts is determined by the slit controller based on the distance between the measured object and the slit group. In this structure, the changing of the slit group used for measurement is controllable based on the distance between the measured object and the slit group. Thus, spectrum measurement effectively using the range of the measured object as described above can be performed in real-time. 
     The measuring unit includes two or more light receiving elements that receive each component of the light dispersed by the spectroscope with each of the slits, and the spectrum measuring apparatus further includes a distance varying unit that allows varying of a distance between the spectroscope and the measuring unit. 
     The light dispersed by the spectroscope travels such that its cross-section is enlarged as the measuring unit becomes closer. Thus, the light receiving area light of the measuring unit becomes larger as the measuring unit moves away from the spectroscope and conversely becomes smaller as the measuring unit moves toward the spectroscope. The number of the light receiving elements receiving the dispersed light, that is, data amount of a measurement result, increases as the measuring unit moves away from the spectroscope and conversely decreases as the measuring unit moves toward the spectroscope. When the light receiving area of the measuring unit is small, more components enter the single light receiving element and decrease the resolution of the components. Conversely, when the light receiving area of the measuring unit becomes large, fewer components enter the single light receiving element and increase the resolution of the components. 
     The spectrum measuring apparatus further includes a distance controller that controls the varying of the distance varying unit based on a control value that is in accordance with an attribute of the slit group. 
     As mentioned above, the number of the light receiving elements receiving the dispersed light, that is, data amount of a measurement result, increases as the measuring unit moves away from the spectroscope and conversely decreases as the measuring unit moves toward the spectroscope. To keep the data amount of the measurement data at a certain amount or less, it is preferable that the number of light receiving elements used to measure intensity be kept at a certain number or less. 
     For example, when the distance between adjacent slits becomes shorter, the distance between light fluxes received by the measuring unit also becomes shorter. This increases the number of light receiving elements that receive such light fluxes. In this case, when the distance between the spectrometer and the measuring unit becomes short, the number of light receiving elements increased in this manner can be reduced, and the data amount of the measurement data can be kept at a certain amount. Further, when the distance between adjacent slits becomes longer, the distance between light fluxes received by the measuring unit also becomes longer. This decreases the number of light receiving elements that receive such light fluxes. In this case, when the distance between the spectrometer and the measuring unit becomes long, the number of light receiving elements decreased in this manner can be increased, and the data amount of the measurement data can be kept at a certain amount. 
     To maintain the resolution of each component at a certain value or greater, it is preferable that the number of light receiving elements used to measure intensity be kept at a certain number of greater. As mentioned above, when the distance between adjacent slits becomes longer, the distance between light fluxes received by the measuring unit also becomes longer. This decreases the number of light receiving elements that receive such light fluxes. In this case, when the distance between the spectrometer and the measuring unit becomes long, the number of light receiving elements decreased in this manner can be increased, and the number of components received by a single light receiving element can be reduced. 
     In the spectrum measuring apparatus, the distance controller controls whether or not to increase the distance between the spectrometer and the measuring unit or whether or not the decrease the distance between the spectrometer and the measuring unit with the changing performed by the distance varying unit. In such a structure, even when there are a plurality of slit groups having different attributes, such as the distance between adjacent slits and the number of slits, the distance between the spectrometer and the measuring unit is controllable based on the attribute of the slit group. Thus, the data amount can be adjusted and the component resolution can be adjusted as described above. 
     The spectrum measuring apparatus further includes a band-pass filter that guides only a wavelength component in a measuring band to the spectroscope. 
     For example, in the light passed through each of the plurality of slits, when the wavelength components in the measuring band and the wavelength components outside the measuring band interfere with each other, the measuring accuracy of the measuring unit may be lowered. However, in the spectrum measuring apparatus, only the wavelength components in the measuring band are guided to the spectroscope. Thus, in the light passed through each of the slits, interference between light outside the measuring band and light in the measuring band can be avoided in the subsequent stage of the spectroscope. This allows the accuracy relating to the intensity of each component and, consequently, the accuracy of the spectrum to be improved. Further, since the spectroscope and the measuring unit do not require a structure for suppressing interference, structures of the spectroscope and the measuring unit are simplified. 
     In the spectrum measuring apparatus, the band-pass filter is configured so that the measuring band narrows as an interval between adjacent ones of the slits shortens. 
     When the interval between the adjacent slits is shorter, the interval between light fluxes passed through the slits is also shorter. For example, in comparison to when the interval between the adjacent slits is longer, each component dispersed by the spectrometer may easily cause interference in a preceding stage of the spectroscope. However, in the spectrum measuring apparatus, the measuring band narrows as an interval between adjacent ones of the slits shortens. This suppresses the above-mentioned interference. 
     In the spectrum measuring apparatus, each of the two or more slits includes an optical element that converts light passed through the slits into converged light or collimated light. 
     When the interval between the adjacent slits is shorter, the interval between light fluxes passed through the slits also narrows. Thus, the light flux passed through a slit may interfere with the light flux passed through another adjacent slit in a preceding stage of the spectroscope. However, in the spectrum measuring apparatus, the optical element of each slit converts light passed through the slits into converged light or collimated light. This suppresses the above-mentioned interference. 
     In the spectrum measuring apparatus, the two or more slits in the slit group are eccentric in their arrangement direction. 
     In the spectrum measuring apparatus, two or more slits are eccentric in their arrangement direction. Thus, spectrum measurement can be performed in real-time on the measured object, which is formed by two or more different and eccentric measuring parts. 
     In the spectrum measuring apparatus, two or more different slit groups differ from each other in number of the slits. 
     In the spectrum measuring apparatus, two or more different slit groups differ from each other in number of the slits. Thus, spectrum measurement can be performed in real-time on two or more measured objects, which differ from each other in number of measuring parts. 
     The spectrum measuring apparatus is mounted on a mobile body. 
     The characteristics of light received by a mobile body from its surrounding changes depending on the characteristics of the light irradiated in the surrounding and, in particular, depending on the optical characteristics of the surrounding that receives such light. The light irradiating the surrounding of the mobile body and the situation of the surrounding of the mobile body, such as the elements forming the surrounding of the mobile body, differ whenever the mobile body moves. The spectrum measuring apparatus performs spectrum measurement in rear-time so that the spectrum of the light from the surrounding of the mobile body is in correspondence with the movement of the mobile body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an optical structure in a spectrum measuring apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a plan view showing the structure of a shielding plate in a spectrum measuring apparatus according to a second embodiment of the present invention. 
         FIG. 3  is a diagram showing an optical structure in the spectrum measuring apparatus according to the second embodiment of the present invention. 
         FIG. 4  is a diagram showing an optical structure of a spectrum measuring apparatus according to a third embodiment the present invention. 
         FIG. 5  is a diagram showing an optical structure of a spectrum measuring apparatus according to a fourth embodiment the present invention. 
         FIG. 6  is a diagram showing one example of a measured object in the spectrum measuring apparatus according to the fourth embodiment of the present invention. 
         FIG. 7  is a block diagram entirely showing a spectrum measuring apparatus according to a fifth embodiment of the present invention. 
         FIG. 8  is a flowchart showing a spectrum measuring procedure performed with the spectrum measuring apparatus according to the fifth embodiment of the present invention. 
         FIG. 9  is a perspective view showing a modified example of shielding plate for a spectrum measuring apparatus. 
         FIG. 10  is a diagram showing one example of an optical structure when a hyper spectrum sensor, which is a conventional spectrum measuring apparatus, is mounted on an artificial satellite. 
         FIGS. 11(   a ), ( b ) and ( c ) are diagrams showing one example of scanning of a single slit provided on a shielding plate and its optical action when a mobile body such as a vehicle is provided with the hyper spectrum sensor as the conventional spectrum measuring apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A spectrum measuring apparatus according to a first embodiment of the present invention will now be described in detail with reference to  FIG. 1 . First, referring to  FIG. 1 , the optical structure of a spectrum measuring apparatus  10  in the present embodiment will be described. 
     In the spectrum measuring apparatus  10 , a condenser  11 , a shielding unit  12 , a band-pass filter  13 , a spectroscope  14 , and a measuring unit  15  are arranged in this order along a traveling direction of light from a measured object  20 . Each of the elements forming the spectrum measuring apparatus  10  is configured so that optical characteristics are continuous in one direction intersecting a hypothetical light beam representing a light flux that passes the elements, that is, an optical axis (extending in a lateral direction in  FIG. 1 ). In other words, the elements forming the spectrum measuring apparatus  10  extends in a direction perpendicular to the plane of  FIG. 1 . 
     The condenser  11  is an optical system formed by an optical element such as a lens for condensing or converging light emitted by the measured object  20  or light reflected on the measured object  20 , that is, light from the measured object  20 , without any loss, and has a function of orienting the condensed light to the shielding unit  12  as an optical element in a subsequent stage. 
     The shielding unit  12  includes a shielding plate  12   a  having a part for shielding a portion of light from the condenser  11  against the band-pass filter  13  as an optical element in a subsequent stage and a part for allowing a remaining portion of the light from the condenser  11  to pass to the band-pass filter  13 . The part for allowing the light to pass in the shielding plate  12   a  includes a slit group  12 G having two or more slits  12   b . Each of the two or more slits  12   b  forming the slit group  12 G is an aperture extending in one direction intersecting the light traveling direction (a longitudinal direction Dm of the slits  12   b ) such as a direction perpendicular to the plane of  FIG. 1 . The two or more slits are arranged at regular intervals in the other direction intersecting the light traveling direction (a width direction Dw of the slits  12   b ) such as a vertical direction in  FIG. 1 . Each of the slits  12   b  forming the slit group  12 G has an optical element  12   c  such as a collimating lens for converting light passed therethrough into collimated light at each slit  12   b  or a converting lens for converting light passed therethrough into converged light at each slit  12   b . That is, the shielding unit  12  has a function of orienting a portion of the light from the condenser  11  as the collimated light or the converged light at each slit  12   b  to the band-pass filter  13  as an optical element in a subsequent stage. 
     The band-pass filter  13  is a filter that has a high transmittance for light within a measuring band as a specific band and a low transmittance for light in a band other than the measuring band. The measuring band described herein refers to a wavelength band previously set in order to distinguish the measured object  20 , for example, a band that contains a visible band as well as an invisible band and includes a unique wavelength forming light from a distinguishing object. The band-pass filter  13  has a function of orienting the light passed through the slit group  12 G as light at each slit  12   b  to the spectroscope  14  as an optical element in a subsequent stage. 
     The spectroscope  14  is a spectral system for dispersing the light within the measuring band into wavelength components as continuous components. The spectroscope  14  disperses each light L at each slit  12   b  into wavelength components (wavelength component λa to wavelength component λb) in the width direction Dw of the slits  12   b  and orients the components as the light L at each slit  12   b  to the measuring unit  15  as an optical element in a subsequent stage. 
     The measuring unit  15  is a CCD image sensor or a CMOS image sensor in which light receiving elements are arranged in two directions orthogonal to the optical axis of the spectroscope  14 , that is, the longitudinal direction Dm and the width direction Dw of the slits  12   b . The measuring unit  15  is arranged so that the different wavelength components corresponding to the slits  12   b  enter the different light receiving elements in the width direction Dw of the slits  12   b . The measuring unit  15  is also arranged so that light from different positions on the measured object  20  enter different light receiving elements in the longitudinal direction Dm of the slits  12   b.    
     In the spectrum measuring apparatus  10  having such structure, the light from each part of the measured object  20  first enters the condenser  11 . The light entering the condenser  11  are condensed by the condensing action of the condenser  11  and sent toward the shielding unit  12 , and only the light sent toward the slit group  12 G passes through each of the optical element  12   c  by the action of the shielding unit  12 . In this manner, the light extracted by the slit group  12 G are converted into collimated light or converged light by the optical action of the optical element  12   c  and are guided to the band-pass filter  13 . In the light entering the band-pass filter  13 , only the light within the measuring band is guided to the spectroscope  14  by the filtering action of the band-pass filter  13  and is dispersed into the wavelength component λa to the wavelength component λb by the spectral action of the spectroscope  14 . In this embodiment, the band-pass filter  13  allows passage of light having a wavelength in the wavelength band of 400 nm to 2500 nm to pass. The wavelength components for the slits  12   b , which are dispersed by the spectroscope  14 , are received by the light receiving elements of the measuring unit  15 , which correspond to the slits  12   b.    
     In other words, in the spectrum measuring apparatus  10 , the light from the linear measuring parts extending in the longitudinal direction Dm among the light that can be condensed from the measured object  20  by the condenser  11  are extracted through the slits  12   b . Since the two or more slits  12   b  having this function are arranged in the width direction Dw, the light from the two or more measuring parts arranged in the width direction Dw are extracted at the same timing. Therefore, the spectrum measuring apparatus  10  having such structure measures the spectrum of the light from the two or more different measuring parts extending in the longitudinal direction Dm at the same timing. 
     Here, as described above, when the conventional hyper spectrum sensor  100  shown in  FIG. 11  measures the spectrum in one scene as the object  120 , at least time for scanning of one measuring part  120   a  corresponding to the single slit  114   a  over the whole range of the object  120  is needed. For example, one movement of the single slit  114   a  requires 0.033 seconds, and the spectrum of one scene is measured by movement of the single slit  114   a  of 400 times. This results in that spectrum measurement of one scene taking about 13 seconds. Thus, in order to measure the spectrum in one scene, the hyper spectrum sensor  100  and the object  120  must relatively stay still for about 13 seconds. If the spectrum measuring apparatus  10  of this embodiment were to include 400 slits  12   b , the above-mentioned scanning of the slit becomes unnecessary and, thus, the spectrum of each measuring part contained in one scene can be measured in real time. Further, even in a structure that does not have 400 slits  12   b , as long as the two or more slits  12   b  are included, the number of times of scanning of the slits  12   b  can be reduced, thereby shortening time necessary for spectrum measurement. 
     If the slit group  12 G does not perform scanning in the spectrum measuring apparatus  10 , the spatial resolution of the measured object  20  corresponds to the number of slits  12   b  forming the slit group  12 G. The wavelength resolution of the measured object  20  corresponds to the number of light receiving elements arranged in the width direction Dw among the light receiving elements receiving the light L from one slit  12   b.    
     For example, the measuring unit  15  in the spectrum measuring apparatus  10  may include light receiving elements arranged in a matrix in the longitudinal direction Dm and the width direction Dw, 300 light receiving elements provided in the longitudinal direction Dm, and 300 light receiving element provided in the width direction Dw. In such a case, when the number of the slits  12   b  forming the slit group  12 G in such structure is five, each of the five measuring parts is hypothetically divided into 300 regions in the longitudinal direction Dm. The spectrum of light from the measured object  20  is dispersed into the spectrum of the light from 5×300 spaces. Further, since the number of the light receiving elements arranged in the width direction Dw among the light receiving elements receiving the light L from one slit  12   b  becomes 300/5=60, the spectrum of the light from each of the measuring parts forming the measured object  20  is formed by 60 wavelength components. 
     Therefore, by changing the number of slits  12   b  forming the slit group  12 G, the spatial resolution of the measured object  20  can be changed. Further, by changing the number of the light receiving elements arranged in the width direction Dw among the light receiving elements receiving the light L from one slit  12   b , the wavelength resolution of the measured object  20  can be changed. 
     As described above, the spectrum measuring apparatus in the first embodiment has the advantages listed below. 
     (1) The spectrum measuring apparatus  10  includes the slit group  12 G having the two or more slits  12   b  for extracting the light from each of the two or more different measuring parts of the measured object  20 . The spectrum measuring apparatus  10  further includes the spectroscope  14  for dispersing the light extracted by the slit group  12 G at each slit  12   b  and the measuring unit  15  for measuring the intensity of each of the wavelength components corresponding to the respective slits  12   b , which are dispersed by the spectroscope  14 . Thus, the spectrum of the light from each of the measuring parts can be measured without moving the slits  12   b  with respect to the measured object  20  including the two or more different measuring parts. Thus, as compared to the structure in which the spectrum of the light from each of the measuring parts is measured while moving a single slit, time for measuring the spectrum can be shortened. Further, even when the slits  12   b  are moved, as long as the two or more slits  12   b  are included, the number of times of movement can be reduced as compared to the case of moving the single slit and therefore, time required to measure the spectrum can be shortened. 
     (2) Furthermore, since the spectrum of the light from the measuring parts is measured at the same timing, the spectrum over a wide range of the measured object  20  can be measured in real time. Mounting of the spectrum measuring apparatus  10  on the mobile body can realize real-time spectrum measurement in the required moving state. Thus, by assisting movement of the mobile body based on the spectrum measurement result, the accuracy of movement assistance can be improved. 
     (3) The spectrum measuring apparatus  10  includes the band-pass filter  13  for guiding only the wavelength components in the measuring band to the spectroscope  14 . In the light passed through each of the plurality of slits  12   b , when the wavelength components in the measuring band and the wavelength components outside the measuring band interfere with each other, the measuring accuracy of the measuring unit  15  may be lowered. In this embodiment, since the band-pass filter  13  guides only the wavelength components in the measuring band to the spectroscope  14 , in the light passed through each of the slits  12   b , interference between light outside the measuring band and light in the measuring band can be avoided in the subsequent stage of the spectroscope  14 . Therefore, the accuracy relating to the intensity of each component and, consequently, the accuracy of the spectrum can be improved. Furthermore, since the spectroscope  14  and the measuring unit  15  do not require a structure for suppressing interference, structures of the spectroscope  14  and the measuring unit  15  are simplified. 
     (4) Each of the two or more slits  12   b  in the spectrum measuring apparatus  10  includes the optical element  12   c  for converting the light passed through the slit  12   b  into the converged light or the collimated light. When the interval between the adjacent slits  12   b  is shorter, the interval between light fluxes passed through the slits  12   b  is also shorter. Thus, the light flux passed through one slit  12   b  easily interfere with the light flux passed through another slit  12   b  adjacent to the one slit  12   b  in the preceding stage of the spectroscope  14 . In this embodiment, since the optical element  12   c  of each of the slits  12   b  converts the light passed through the slit  12   b  into the converged light or the collimated light, such interference can be suppressed. 
     Second Embodiment 
     A spectrum measuring apparatus according to a second embodiment of the present invention will now be described with reference to  FIGS. 2 and 3 . The second embodiment includes a shielding unit  12  that is different from that of the first embodiment and further includes a slit switch  22  and a matching unit  23 . Otherwise the basic structure is the same as that of the first embodiment. Thus, only the differences will be described below in detail. 
     As shown in  FIG. 2 , four slit groups  12 G radially extending from the center of the disk-shaped shielding plate  12   a  forming the shielding unit  12  are arranged at regular intervals in the circumferential direction of the shielding plate  12   a . The four slit groups  12 G are different from one another in number, interval, and orientation of the slits  12   b  forming the slit groups  12 G. More specifically, in three slit groups  12 G (the slit groups  12 G on the upper side, the left side and the lower side in  FIG. 2 ) of four slit groups  12 G, the two or more slits  12   b  extending in a direction orthogonal to the radial direction of the shielding plate  12   a  are arranged at regular intervals in the radial direction. The three slit groups  12 G are different from one another in number and interval of the slits  12   b . In one slit group  12 G (the slit group  12 G on the right side in  FIG. 2 ) that differs from the other three slit groups  12 G, the two or more slits  12   b  extending substantially in the radial direction of the shielding plate  12   a  are arranged at regular intervals in a direction orthogonal to the radial direction. 
     The slit switch  22 , which can rotate the shielding plate  12   a  in 90 degree intervals in the circumferential direction of the shielding plate  12   a  about an axis of the shielding plate  12   a , is coupled to the center of the shielding plate  12   a . By rotating the shielding plate  12   a , the slit switch  22  switches one slit group for allowing the light L to transmit the spectroscope  14  for light dispersion, that is, the measuring slit group  12 G, among the four slit groups  12 G. 
     As shown in  FIG. 3 , the condenser  11 , the band-pass filter  13 , the spectroscope  14 , and the measuring unit  15  are coupled to the matching unit  23 , which can rotate each of these elements in forward and rearward directions about the optical axis in a movable range of 90 degrees. When the slit group  12 G (the slit group  12 G on the right side in  FIG. 2 ) having the slits  12   b  extending substantially in the radial direction of the shielding plate  12   a  is the slit group  12 G used for measuring, the matching unit  23  rotates each of the above-mentioned elements in the forward direction about the optical axis by 90 degrees. In this state, when the slit group  12 G (the slit group  12 G on the upper side, the left side or the lower side in  FIG. 2 ) having the slits  12   b  extending in the direction orthogonal to the radial direction of the shielding plate  12   a  becomes the slit group  12 G used for measuring, the matching unit  23  rotates each of the above-mentioned elements in the rearward direction about the optical axis by 90 degrees. That is, the matching unit  23  rotates each of the condenser  11 , the band-pass filter  13 , the spectroscope  14  and the measuring unit  15  so that the direction in which the optical characteristics in each of the condenser  11 , the band-pass filter  13 , the spectroscope  14  and the measuring unit  15  are continuous matches the long axis direction of the slits  12   b.    
     When the slit group  12 G having n slits  12   b  (n=3 in  FIG. 3 ) (n=3 in the slit group  12 G on the upper side in  FIG. 2 ) becomes the slit group  12 G used for measuring, light from measuring parts  20   a  at n points corresponding to the n slits  12   b  are extracted by the slits  12   b  at the same timing. Therefore, the spectrum measuring apparatus  10  having such structure measures the spectrum of the light from the measuring parts  20   a  at n points at the same timing. 
     Here, when the measuring parts  20   a  of the measured object  20  vary with each other in position, number, and the like, the light from the measuring parts  20   a  vary with each other in position and amount. In order to extract such light from the light from the measured object  20 , the slits  12   b  of the slit group  12 G must vary with each other in position, number, and the like. In the spectrum measuring apparatus  10  in this embodiment, the slit switch  22  switches the slit group  12 G used for measuring to any of the four different slit groups  12 G. Thus, even if the two or more different measuring parts  20   a  are measured, when the four slit groups  12 G are switched and one becomes applicable to the measured object  20 , spectrum measurement can be achieved. 
     As described above, the spectrum measuring apparatus  10  of the second embodiment has the advantages listed below in addition to advantages (1) to (4) of the first embodiment. 
     (5) The spectrum measuring apparatus  10  includes the four different slit groups  12 G and the slit switch  22 . The slit switch  22  can switch the slit group  12 G used for measuring to any of the four different slit groups  12 G. That is, the slit group  12 G for measuring can be switched to any of the four different slit groups  12 G by the slit switch  22 . Thus, even when two or more different measured objects  20  are measured, spectrum measurement can be achieved by applying any of the four different slit groups  12 G to each measured object  20 . In this embodiment, as compared to the structure including the single slit group  12 G, the degree of freedom in the attribute of the measuring parts  20   a  such as position and the number of the measuring parts  20   a  can be increased. 
     (6) In the spectrum measuring apparatus  10 , the three slit groups  12 G (the slit groups  12 G on the upper side, the left side and the lower side in  FIG. 2 ) are different from one another in the number of slits  12   b . In such a structure, since the different slit groups  12 G having different number of slits  12   b  can be used in the single spectrum measuring apparatus  10 , the spatial resolution can be switched in the same spectrum measuring apparatus  10 . 
     (7) When the interval between adjacent slits  12   b  becomes shorter, the interval between the light fluxes from the adjacent slits  12   b  also becomes shorter. Further, when the measuring band becomes wider as the band-pass filter  13  changes, the width direction Dw of dispersed light also becomes wider. Thus, for example, when the interval between adjacent slits  12   b  is fixed even though the width of the dispersed light in the width direction Dw increases, the light from adjacent slits may interfere with each other in the subsequent stage of the spectroscope  14 . In the spectrum measuring apparatus  10  of this embodiment, the interval between adjacent slits  12   b  can be switched. This suppresses the above-described interference. 
     (8) The three slit groups  12 G (on the upper side, the left side, and the lower side in  FIG. 2 ) of the spectrum measuring apparatus  10  are different from the remaining one slit group  12 G (on the right side in  FIG. 2 ) in the long axis direction of the slits  12   b  with respect to the measured object  20 . The matching unit  23  rotates each of the condenser  11 , the band-pass filter  13 , the spectroscope  14 , and the measuring unit  15  so that the direction in which the optical characteristics in each of the condenser  11 , the band-pass filter  13 , the spectroscope  14  and the measuring unit  15  are continuous matches the long axis direction of the slits  12   b . In such a structure, the slit groups  12 G having the different long axis directions of the slits  12   b  can be used in the single spectrum measuring apparatus  10 . In other words, in the single spectrum measuring apparatus  10 , the long axis direction of the measuring part  20   a  can be switched. 
     Third Embodiment 
     A spectrum measuring apparatus according to a third embodiment of the present invention will now be described with reference to  FIG. 4 . The fourth embodiment includes a distance varying unit  24 . Otherwise, the basic structure is the same as that of the first embodiment. Thus, only the differences will be described below in detail. 
     As shown in  FIG. 4 , the distance varying unit  24 , which can vary the distance between the spectroscope  14  and the measuring unit  15 , is coupled to the measuring unit  15  of the spectrum measuring apparatus  10 . Due to the distance varying unit  24 , the measuring unit  15  is movable along the direction of the optical axis between a position at which the measuring unit  15  is farthest from the spectroscope  14  (position indicated by a double-dashed line in  FIG. 4 ) and a position at which the measuring unit  15  is closest to the spectroscope  14  (position indicated by a solid line in  FIG. 4 ). The position at which the measuring unit  15  is farthest from the spectroscope  14  is set under the condition that the wavelength components λa, λb from one slit  12   b  do not interfere with the wavelength component λa, λb from another adjacent slit  12   b  in the preceding stage of the light receiving element. 
     Here, the light dispersed by the spectroscope  14  advances so that its cross section extends toward the measuring unit  15  in the width direction Dw. Accordingly, a light receiving area of the measuring unit  15  becomes larger as the measuring unit  15  moves away from the spectroscope  14  and conversely becomes smaller as the measuring unit  15  moves close to the spectroscope  14 . The number of the light receiving elements receiving the dispersed light, that is, data amount of a measurement result, becomes larger as the measuring unit  15  moves away from the spectroscope  14  and becomes smaller as the measuring unit  15  moves toward the spectroscope  14 . When the light receiving area of the measuring unit  15  is small, more wavelength components enter the single light receiving element and decrease the resolution of the wavelength components. When the light receiving area of the measuring unit  15  is large, less wavelength components enter the single light receiving element and increases the resolution of the wavelength components. 
     For example, when the distance between the measuring unit  15  and the spectroscope  14  is extended to a first distance La, the number of the light receiving elements receiving the light from one slit  12   b  in the width direction Dw is defined as a first element number ka. When the distance between the measuring unit  15  and the spectroscope  14  is shortened to a second distance Lb, the number of the light receiving elements receiving the light from one slit  12   b  in the width direction Dw is defined as a second element number kb. The number of the light receiving elements in the second distance Lb, that is, the second element number kb is smaller than the number of the light receiving elements in the first distance La, that is, the first element number ka, in accordance with the decreased light receiving area of the measuring unit  15 . In this case, since more wavelength components enter the light receiving elements forming the second element number kb than the light receiving elements forming the first element number ka, the resolution of the wavelength components of each light receiving element forming the second element number kb decreases. 
     In this manner, by moving the measuring unit  15  to shorten the distance between the spectroscope  14  and the measuring unit  15 , the data amount of the spectrum can be decreased while maintaining the number of slits  12   b , that is, the spatial resolution of the measured object  20 . In contrast, by moving the measuring unit  15  to extend the distance between the spectroscope  14  and the measuring unit  15 , the resolution of the wavelength components can be improved while maintaining the number of slits  12   b , that is, the spatial resolution of the measured object  20 . 
     As described above, the spectrum measuring apparatus  10  in the third embodiment has the advantages listed below in addition to advantages (1) to (4) of the first embodiment. 
     (9) The spectrum measuring apparatus includes the distance varying unit  24  that can vary the distance between the spectroscope  14  and the measuring unit  15 . Thus, the distance between the spectroscope  14  and the measuring unit  15  can be varied by the distance varying unit  24 . Thus, for example, as compared to the structure in which the distance between the spectroscope  14  and the measuring unit  15  is fixed, the degree of freedom in the data amount of the spectrum measuring result and the resolution of each wavelength component can be increased. 
     Fourth Embodiment 
     A spectrum measuring apparatus according to a fourth embodiment of the present invention will now be described with reference to  FIGS. 5 and 6 . The fourth embodiment includes a shielding unit  12  and a band-pass filter  13 , which differ from those of the first embodiment. Otherwise, the basic structure is the same as that of the first embodiment. Thus, only the differences will be described below in detail. 
     As shown in  FIG. 5 , in the shielding unit  12  of the spectrum measuring apparatus  10 , three slits  12   b  are eccentrically arranged substantially at the center in the width direction Dw, which is the arrangement direction of the slits  12   b . Further, two slits  12   b  that sandwich the three slits  12   b  therebetween are arranged at opposite ends of the shielding unit  12  in the width direction Dw of. The five slits  12   b  are arranged so that an interval between the three slits  12   b  eccentrically located at the center in the width direction Dw is shorter than an interval from the slits  12   b  at the two ends in the width direction Dw to the three slits  12   b.    
     The band-pass filter  13  includes two first band-pass filters  13   a  for receiving light from the slits  12   b  at the both ends in the width direction Dw and a second band-pass filter  13   b  for receiving light from the three slits  12   b  that are eccentric at the center in the width direction Dw. A band in which the first band-pass filters  13   a  has a high transmittance (wavelength component λa to wavelength component λb) is configured so as to contain a band in which the second band-pass filters  13   b  has a high transmittance (wavelength component λc to wavelength component λd) and to be wider than the wavelength component λc to wavelength component λd. In other words, the band-pass filter  13  is configured so that as the interval between adjacent slits  12   b  becomes shorter, the measuring band becomes narrower. 
     Here, as described above, the light dispersed by the spectroscope  14  advances so that its cross section extends toward the measuring unit  15  in the width direction Dw. Accordingly, the light receiving area of the measuring unit  15  becomes larger as a transmission band of the band-pass filter  13  widens and becomes smaller as the transmission band of the band-pass filter  13  narrows. When the interval between adjacent slits  12   b  becomes shorter, an interval between the light passed through the slits  12   b  also automatically becomes shorter. Conversely, when the interval between adjacent slits  12   b  becomes longer, the interval between light passed through the slits  12   b  also automatically becomes longer. 
     In this embodiment, the wavelength band of the light L passed through the second band-pass filters  13   b  is narrower than the wavelength band of the light L passed through the first band-pass filters  13   a . Thus, for the light receiving area of the measuring unit  15 , the light receiving area of the light passed through the second band-pass filters  13   b  is smaller than the light receiving area of the light passed through the first band-pass filters  13   a . An interval between the light L passed through the second band-pass filters  13   b  and the adjacent light L becomes relatively shorter in correspondence with the interval between corresponding slits  12   b . An interval between the light L passed through the first band-pass filters  13   a  and the adjacent light L becomes relatively longer in correspondence with the interval between corresponding slits  12   b . Thus, by narrowing the measuring band with the band-pass filter  13  as the interval between adjacent slits  12   b  becomes shorter, interference between light from the adjacent slits  12   b  can be suppressed in the light receiving elements of the measuring unit  15  or the preceding stage of the measuring unit  15 . 
     In addition, the number of the light receiving elements receiving the light L passed through the first band-pass filters  13   a  is larger than the number of the light receiving elements receiving the light L passed through the second band-pass filters  13   b . That is, the resolution of the wavelength components is high for the measuring parts corresponding to the long interval between adjacent slits  12   b , the resolution of the wavelength components is low for the measuring parts corresponding to the short interval between adjacent slits  12   b . Accordingly, when the optical characteristics, that is, the measuring parts of which physical properties should be measured in detail, can be identified in advance in the measured object  20 , it is preferred that the slits  12   b  having a long interval therebetween by arranged for the measuring parts. In such a structure, the spectrum having a high resolution of the wavelength components for the optical characteristics, that is, the measuring parts of which physical properties should be measured in detail, can be measured. 
     For example, as shown in  FIG. 6 , a road, a sidewalk, a building, a wall, the sky, a tree (roadside tree), a bicycle, and a bonnet of a vehicle are observed around the front of the vehicle when viewed from the inside of the vehicle driven along a road. In the vicinity of the front of the vehicle, a pedestrian, a bicycle, and the like, which required vehicle driving assistance, are generally observed in the region between the bonnet of the vehicle and the sky. When the surrounding at the front of the vehicle is the measured object  20  and the spectrum measuring apparatus  10  is mounted on the vehicle, with the following structure, the spectrum having both of the high spatial resolution and high resolution of the wavelength components for the measuring parts such as the pedestrian and the bicycle can be measured. 
     Here, it is assumed that the direction from the bonnet of the vehicle toward the sky is the width direction Dw, and the slit group  12 G is configured so that the interval between adjacent slits  12   b  becomes relatively shorter around the center of the width direction Dw of the measured object  20  (refer to  FIG. 5 ). In such a structure, the spatial resolution is high around the center of the measured object  20  and the resolution of the wavelength components is high around both ends of the measured object  20  in the width direction Dw. Thus, when the pedestrian, the bicycle, and the like exist near the center of the measured object  20 , that is, the object necessary for the driving assistance exists far away from the vehicle, first, its spatial characteristics can be measured with the high spatial resolution. When the object necessary for the driving assistance exists around both ends of the measured object  20  in the width direction Dw, that is, the object necessary for the driving assistance exists near the vehicle, its optical characteristics can be measured with the high resolution of the wavelength components. 
     Thus, even when the slit group  12 G is not switched in the shielding unit  12 , the object that is far away from the vehicle can be distinguished with the high spatial resolution. The object near the vehicle can be distinguished with the high resolution of the wavelength components. Therefore, an object that is far away from the vehicle can be spatially distinguished to determine whether or not driving assistance is necessary. An object near the vehicle can be distinguished to determine whether it is a pedestrian, an animal, or a bicycle. 
     As described above, the spectrum measuring apparatus  10  in the fourth embodiment has the advantages listed below in addition to advantages (1) to (4) of the first embodiment. 
     (10) In the slit group  12 G of the spectrum measuring apparatus  10 , two or more slits  12   b  are eccentric in the arrangement direction. Thus, the spectrum from the measured object  20 , including two or more different measuring parts, can be measured in real time. 
     (11) At the measuring parts corresponding to the two or more eccentric slits  12   b , the spatial resolution of the measured object  20  can be improved. Conversely, at the measuring parts corresponding to the slits  12   b  other than the eccentric slits  12   b , the spatial resolution of the measured object  20  can be suppressed. Accordingly, one spectrum measuring apparatus  10  can set a plurality of spatial resolutions of the measured object  20  without requiring switching of the slit group  12 G. 
     (12) The spatial resolution can be improved at the two or more eccentric measuring parts, while the resolution of the wavelength components can be improved at the measuring parts excluding the eccentric measuring parts. Thus, one measured object  20  may include a part of which the spectrum can be measured with the high spatial resolution and a part of which the spectrum can be measured with the high resolution of the wavelength component. 
     (13) The band-pass filter  13  in the spectrum measuring apparatus  10  is configured so that as the interval between adjacent slits  12   b  becomes shorter, the measuring band is becomes narrower. Thus, even when the interval between adjacent slits  12   b  is shortened due to eccentricity, interference between light passed through the slits can be suppressed. 
     Fifth Embodiment 
     A spectrum measuring apparatus according to a fifth embodiment of the present invention will now be described with reference to  FIGS. 7 and 8 . In the fifth embodiment, the spectrum measuring apparatus  10  is mounted on a vehicle. Otherwise, the basic structure is similar to that of the above embodiments. Thus, only the differences will be described below. 
     The spectrum measuring apparatus  10  in this embodiment includes the shielding unit  12  and the slit switch  22 , which are described in second embodiment, and the distance varying unit  24  described in the third embodiment. 
     The spectrum measuring apparatus  10  in this embodiment includes a first actuator  22 A, which drives the slit switch  22 , and a second actuator  24 A, which drives the distance varying unit  24 . The spectrum measuring apparatus  10  further includes a control unit  26  forming a slit controller and a distance controller, which input driving amounts of the actuators  22 A,  24 A as control values to the actuators  22 A,  24 A, respectively. An example in which vehicle driving assistance is performed based on a measurement result of the spectrum measuring apparatus  10  having such structure will now be described. 
     As shown in  FIG. 7 , a vehicle C with the spectrum measuring apparatus  10  includes an in-vehicle sensor  31  formed by an ignition sensor, which detects whether an ignition is turned on or off, and an objective sensor such as an infrared radar, a millimeter-wave radar, and an in-vehicle camera, which detects the distance between the vehicle C and an object near the vehicle C. A data processing unit  32  for acquiring various detection results from the in-vehicle sensor  31  and generating various types of information necessary for spectrum measuring processing is arranged in the vehicle C that includes the in-vehicle sensor  31 . Specifically, the data processing unit  32  generates information indicating whether or not the spectrum measuring apparatus  10  is to be activated based on a detection result from the ignition sensor and generates information indicating the distance between a candidate object necessary for driving assistance and the vehicle C based on a detection result from the objective sensor. 
     The control unit  26  for determining activation of the spectrum measuring apparatus  10  and controlling the driving amounts of the actuators  22 A,  24 A based on various types of information from the data processing unit  32  is arranged in the spectrum measuring apparatus  10  of the vehicle C. 
     The control unit  26  stores attribute data formed by a map in which the distance between the candidate object necessary for driving assistance and the vehicle C, that is, the distance between the measuring part and the slit group  12 G, is associated with the number of measuring parts  20   a  of the measured object  20 . Specifically, in the attribute data, the distance between the measuring parts and the slit group  12 G is associated with the number of measuring parts  20   a  so that as the distance between the measuring parts  20   a  and the slit group  12 G becomes shorter, the number of measuring parts  20   a  of the measured object  20  becomes smaller. 
     When the control unit  26  acquires information indicating the distance between the candidate object necessary for driving assistance and the vehicle C from the data processing unit  32 , the control unit  26  refers to the attribute data and determines the number of measuring parts  20   a , which corresponds to the distance between the candidate object and the vehicle C. 
     The control unit  26  also stores driving amount data DB 1  that includes a table or the like in which the number of measuring parts  20   a  of the measured object  20  is associated with the driving amounts of the actuators  22 A,  24 A. Specifically, in the driving amount data DB 1 , the number of measuring parts  20   a  of the measured object  20  is associated with the driving amount of the first actuator  22 A so that as the number of measuring parts  20   a  of the measured object  20  becomes smaller, the interval between adjacent slits  12   b  becomes longer. Further, in the driving amount data DB 1 , the driving amount of the first actuator  22 A is associated with the driving amount of the second actuator  24 A so that as the interval between adjacent slits  12   b  becomes longer, the distance between the spectroscope  14  and the measuring unit  15  becomes longer. 
     When the number of measuring parts  20   a  is determined, the control unit  26  refers to the driving amount data DB 1  and calculates the driving amount of the first actuator  22 A, which corresponds to the number of measuring parts  20   a , and the driving amount of the second actuator  24 A, which corresponds to the driving amount of the first actuator  22 A. Then, the control unit  26  controls the actuators  22 A,  24 A with the corresponding driving amounts. 
     A spectrum data analyzing unit  33  for distinguishing each of the measuring parts based on the spectrum data acquired by the spectrum measuring apparatus  10  is arranged in the vehicle C including the spectrum measuring apparatus  10 . The spectrum data analyzing unit  33  stores dictionary data DB 2  formed by a table or the like in which data indicating various specific amounts of the spectrum is associated with various objects necessary for driving assistance. Specifically, in the dictionary data DB 2 , amounts of unique spectrum, such as a unique wavelength, intensity of the unique wavelength, peak shape of the unique wavelength, are associated with various objects necessary for driving assistance such as traffic light, signs, pedestrians, bicycles, and animals. 
     The spectrum data analyzing unit  33  that acquires the spectrum data from the spectrum measuring apparatus  10  refers to the dictionary data DB 2  and generates an identification result of the object associated with each of the unique amounts of the spectrum data, that is, the measuring part, as identification data. Next, the spectrum data analyzing unit  33  outputs the identification data to each unit performing driving assistance, including a warning unit and a display unit that prompts the driver of the vehicle C to be careful, and various actuators of the vehicle C, based on the generated identification data, and allows each unit to perform driving assistance based on the identification data. 
     The series of spectrum measuring processes performed in the vehicle C including the spectrum measuring apparatus  10  in this embodiment will now be described with reference to  FIG. 8 . The spectrum measuring processing in this embodiment is repeatedly performed in predetermined operation cycles when the power state of the vehicle C is in an ACC (Accessory) ON state. 
     As shown in  FIG. 8 , in the spectrum measuring processing, the control unit  26  first determines whether the ignition is turned on or off based on a detection result of the ignition sensor to determine activation of the spectrum measuring apparatus  10  (step S 1 ). When it is determined that the ignition is turned off, the control unit  26  finishes the spectrum measuring processing. When it is determined that the ignition is turned on, the control unit  26  acquires information indicating the distance between the candidate object necessary for driving assistance and the vehicle C through the data processing unit  32  and determines the number of measuring parts  20   a , which corresponds to the distance, with reference to the attribute data. That is, the control unit  26  determines the number of measuring parts, or the attribute of the measuring parts, so that as the distance between the measuring parts  20   a  and the slit group  12 G becomes shorter, the number of measuring parts of the measured object  20  becomes smaller (step S 2 ). 
     When the attribute of the measuring parts is determined in this manner, the control unit  26  refers to the driving amount data DB 1 , calculates the driving amount of the first actuator  22 A, which corresponds to the number of measuring parts  20   a , and controls the first actuator  22 A with the driving amount corresponding to the number of measuring parts  20   a  (step S 3 ). That is, the control unit  26  selects the slit group  12 G for measuring from the two or more different slit groups  12 G so that as the number of measuring parts  20   a  of the measured object  20  becomes smaller, the interval between adjacent slits  12   b  becomes longer. 
     Next, the control unit  26  calculates the driving amount of the second actuator  24 A, which is associated with the driving amount of the first actuator  22 A, with reference to the driving amount data DB 1 , and controls the second actuator  24 A with the driving amount corresponding to the driving amount of the first actuator  22 A (step S 4 ). In other words, the control unit  26  changes the distance between the spectroscope  14  and the measuring unit  15  based on the slit group  12 G for measuring so that as the interval between adjacent slits  12   b  becomes longer, the distance between the spectroscope  14  and the measuring unit  15  becomes longer. 
     When the distance varying unit  24  associates the distance between the spectroscope  14  and the measuring unit  15  with the slit group  12 G used for measuring by selecting the slit group  12 G used for measuring in this manner, the control unit  26  acquires data indicating the intensity at each wavelength component of each measuring part from the measuring unit  15 . Then, the spectrum data is generated so that the optical intensity at each wavelength component is associated with the wavelength (step S 5 ). 
     At this time, when the distance between the candidate object necessary for driving assistance and the vehicle C is short, time required to perform driving assistance for the object also becomes short. Thus, high resolution of the wavelength components in the measured object is needed to distinguish the measured object in more detail. That is, a small number of the slits  12   b  is necessary. Conversely, when the distance between the candidate object necessary for driving assistance and the vehicle C is long, the time required to perform driving assistance for the object also becomes substantially long. Thus, high spatial resolution in the measured object is needed to distinguish measured object more simply. That is, a large number of the slits  12   b  is necessary. 
     In the spectrum measuring apparatus  10  of the above structure, as the distance between the measuring part and the slit group  12 G becomes longer, the number of measuring parts of the measured object  20  increases. Thus, when the distance between the candidate object necessary for driving assistance and the vehicle C is longer, spatial resolution in the measured object becomes high. Conversely, when the distance between the candidate object necessary for driving assistance and the vehicle C is shorter, the resolution of the wavelength component in the measured object becomes high. Accordingly, since the spatial resolution and the resolution of the wavelength component in the measured object  20  are set to match the timing of driving assistance, the assistance accuracy in driving assistance can be improved. 
     When the number of measuring parts of the measured object  20  is small, the number of slits  12   b  corresponding to the measuring parts is also small. Thus, the light receiving area of the measuring unit  15  becomes small. When the number of measuring parts of the measured object  20  is large, the number of slits  12   b  corresponding to the measuring parts increases. Thus, the light receiving area of the measuring unit  15  becomes large in correspondence with the number of slits  12   b.    
     In the spectrum measuring apparatus  10  of the above-mentioned structure, as the number of slits  12   b  becomes larger, the distance between the spectroscope  14  and the measuring unit  15  becomes shorter. Conversely, as the number of slits  12   b  becomes smaller, the distance between the spectroscope  14  and the measuring unit  15  becomes longer. Further, as described above, the number of the light receiving elements receiving dispersed light, that is, data amount of the measuring result, becomes larger as the measuring unit  15  moves away from the spectroscope  14  and, conversely, becomes smaller as the measuring unit  15  moves closer to the spectroscope  14 . Thus, when the number of slits  12   b  is large, the amount of the spectrum data is suppressed toward a certain amount and, conversely, when the number of slits  12   b  is small, the amount of the spectrum data is increased toward the certain amount. Therefore, since the amount of measured data can be set to a generally fixed amount in correspondence with the slit group  12 G used for measuring, an operation such as eliminating parts of the spectrum data or interpolating part of the spectrum data with dummy data becomes unnecessary. Thus, spectrum measurement including time for analyzing the spectrum data can be easily achieved in real time. 
     When the spectrum data is generated, the control unit  26  determines again whether the ignition is turned on or off based on the detection result of the ignition sensor (step S 6 ). When it is determined that the ignition is turned off, the control unit  26  finishes the spectrum measuring processing. When it is determined that the ignition is turned on, the control unit  26  outputs the spectrum data to the spectrum data analyzing unit  33 . Then, the control unit  26  allows the spectrum data analyzing unit  33  to generate the identification data indicating the identification result of the candidate object necessary for driving assistance, allows each unit performing driving assistance to output the identification data, and allows each unit to perform driving assistance, thereby repeating the above-mentioned processing (step S 7 ). 
     As described above, the spectrum measuring apparatus  10  in the fifth embodiment has the advantages listed below in addition to the advantages of the above embodiments. 
     (14) The control unit  26  of the spectrum measuring apparatus  10  determines the number of measuring parts  20   a  as the attribute of the measuring parts based on the distance between the measured object  20  and the slit group  12 G. Thus, the switching aspect of the slit group  12 G for measuring can be controlled based on the distance between the measured object  20  and the slit group  12 G. As a result, for example, when the distance between the spectrum measuring apparatus  10  and the measured object  20  is short, the number of slits  12   b  can be decreased thereby decreasing the spatial resolution of the measured object  20 . Further, for example, when the distance between the spectrum measuring apparatus  10  and the measured object  20  is long, the number of slits  12   b  can be increased thereby increasing the spatial resolution of the measured object  20 . Therefore, spectrum measurement effectively using the range of the measured object  20  can be achieved in real time. 
     (15) The control unit  26  of the spectrum measuring apparatus  10  controls changes in the distance between the spectroscope  14  and the measuring unit  15  with the distance varying unit  24  based on the number of slits  12   b  serving as the attribute of the slit group  12 G. Thus, since the distance between the spectroscope  14  and the measuring unit  15  can be controlled based on the number of slits  12   b  used for measuring, for example, when the number of slits  12   b  used for measuring is large, the data amount can be suppressed to a substantially fixed amount by decreasing the resolution of the wavelength component in the spectrum while increasing the spatial resolution. Conversely, when the number of slits  12   b  used for measuring is small, the data amount can become closer to the fixed amount by increasing the resolution of the wavelength component while decreasing the spatial resolution. Accordingly, even when the slit groups  12 G having different attributes, for example, different number of slits  12   b , are applied as the slit group  12 G used for measuring, as described above, the data amount or the resolution of the wavelength component can be adjusted while adjusting the spatial resolution. 
     The above embodiments may be modified as described below. 
     In the fifth embodiment, the spectrum measuring apparatus  10  is mounted on the vehicle C serving as the mobile body but not limited in such a manner, and the switching of the slit switch  22  may be controlled according to the control value corresponding to the attribute of the measuring parts  20   a . Even when the spectrum measuring apparatus  10  is not mounted on a mobile body, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the spectrum measuring apparatus  10  is mounted on the vehicle C serving as the mobile body but not limited in such a manner, and the distance between the spectroscope  14  and the measuring unit  15  changed by the distance varying unit  24  may be controlled according to the control value corresponding to the attribute of the slit group  12 G. Even when the spectrum measuring apparatus  10  is not mounted on a mobile body, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In fifth embodiment, the switching of the slit switch  22  is controlled based on the control value corresponding to the attribute of the measuring parts  20   a , and the distance between the spectroscope  14  and the measuring unit  15  changed by the distance varying unit  24  is controlled based on the control value corresponding to the attribute of the slit group  12 G. However, for example, the distance between the spectroscope  14  and the measuring unit  15  may be fixed and only the switching aspect of the slit switch  22  may be controlled based on the attribute of the measuring parts  20   a . Even in such a structure, the same advantages as advantage (14) of the fifth embodiment can be obtained. Alternatively, the slit group  12 G may be fixed and only the distance between the spectroscope  14  and the measuring unit  15  changed by the distance varying unit  24  may be controlled based on the attribute of the slit group  12 G. Even in such a structure, the same advantages as advantage (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the spectrum measuring apparatus  10  includes the shielding unit  12  and the slit switch  22 , which are described in the second embodiment, and the distance varying unit  24 , which is described in the third embodiment. Further, the two or more different slit groups  12 G of the shielding unit  12  are different from each other in the attribute such as the number of slits  12   b . However, the present invention is not limited in such a manner. For example, the slit group  12 G in which the three slits  12   b  are eccentrically arranged around the center in the width direction Dw, which is the arrangement direction of the slits  12   b , as described in the fourth embodiment may be one of two or more different slit groups  12 G. Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the attribute of the measuring part  20   a  is embodied as the number of measuring parts  20   a  but not limited in such a manner. The attribute of the measuring parts  20   a  may be embodied as size of the measuring parts  20   a  and position of the measuring parts  20   a  in the measured object. Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the control unit  26  determines the attribute of the measuring parts  20   a  based on the distance between the measured object  20  and the slit group  12 G. However, the present invention is not limited in such a manner and, for example, the suitable attribute of the measuring parts  20   a , such as position, number, and size of the measuring parts  20   a  in the measured object  20  may be determined based on driving state such as the surrounding environment of the measured object  20  or behavior of the vehicle C. Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the attribute of the measuring parts  20   a  is embodied as the number of measuring parts  20   a  but not limited in such a manner. The attribute of the slit group  12 G may be embodied as the interval between adjacent slits  12   b  or position of the eccentric slits  12   b . Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, as the distance between the measuring part  20   a  and the slit group  12 G becomes shorter, the number of measuring parts  20   a  of the measured object  20  becomes smaller. However, for example, as the distance between the measuring part  20   a  and the slit group  12 G becomes shorter, the number of measuring parts  20   a  of the measured object  20  may become larger. In such a structure, as the measured object  20  moves closer to the spectrum measuring apparatus  10 , the spatial resolution can be increased. 
     In the fifth embodiment, the spectrum measuring apparatus  10  includes the control unit  26 . This structure may be changed so that the vehicle C includes the control unit  26 . Further, although the vehicle C includes the spectrum data analyzing unit  33 , this structure may be changed so that the spectrum measuring apparatus  10  includes the spectrum data analyzing unit  33 . Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fifth embodiment, the slit group  12 G is switched based on the distance between the measured object  20  and the slit group  12 G, and the distance between the spectroscope  14  and the measuring unit  15  is adjusted based on the attribute of the switched slit group  12 G. However, the present invention is not limited in such a manner and, for example, the position, size, or number of the measuring parts  20   a  suitable for the driving state, including the surrounding environment such as day or night, rain or shine, and driving place (urban area or farm area), the analysis result of the spectrum measuring apparatus  10 , and the behavior of the vehicle C of the spectrum measuring apparatus  10  may be used as the attribute of the measuring parts  20   a  used for switching the slit group  12 G. Even in such a structure, the same advantages as advantages (14) and (15) of the fifth embodiment can be obtained. 
     In the fourth embodiment, the wavelength band that allows the band-pass filter  13  to pass therethrough differs according to the interval between adjacent slits  12   b , and the spread of each wavelength component dispersed from the spectroscope  14  varies according to the interval between adjacent slits  12   b . However, the present invention is not limited in such a manner, and the wavelength band that allows the band-pass filter  13  to pass therethrough may be the same irrespective of the interval between adjacent slits  12   b , and the spread of each wavelength component dispersed from the spectroscope may differ according to the interval between adjacent slits  12   b . For example, in the fourth embodiment, such a structure may be obtained by a one band-pass filter  13  and two types of different spectroscopes  14  in which the spread of each wavelength component differs according to the interval between adjacent slits  12   b . Even in such a structure, the same advantages as the fourth embodiment may be obtained. 
     In the third and fifth embodiments, the distance between the spectroscope  14  and the measuring unit  15  is changed by the movement of the measuring unit  15 . However, the present invention is not limited in such a manner, and the spectroscope  14  may be moved. Alternatively, the spectroscope  14  and the measuring unit  15  may both be moved. In such structures, to increase the resolution of the wavelength component there is no need for a margin of movement for the measuring unit  15 . In other words, the spectrum measuring apparatus  10  can be miniaturized. This increases the degree of freedom in design of the vehicle C, which serves as the mobile body in which the miniaturized spectrum measuring apparatus  10  is arranged. 
     The shielding unit  12  and the band-pass filter  13 , which includes two types of band-pass filters, of the fourth embodiment can be applied to the one of the two or more slit groups  12 G and the corresponding band-pass filter  13  of the second embodiment. This obtains the same advantages as the second embodiment. 
     The shielding unit  12  and the band-pass filter  13 , which includes the two types of band-pass filters, of the fourth embodiment can be applied to the shielding unit  12  and the band-pass filter  13  of the third embodiment. This obtains the same advantages as the third embodiment. 
     The shielding plate  12   a  forming the shielding unit  12  is disk-shaped in the second embodiment. However, the present invention is not limited in such a manner. For example, as shown in  FIG. 9 , the shielding plate  12   a  may have the shape of a hexagonal tube as long as it has the two or more different slit groups  12 G. Further, the shielding plate  12   a  may have the shape of a flat polygonal plate or a polygonal tube instead of the shape of a flat polygonal plate or hexagonal tube. This increases the degree of freedom in design of the shielding unit  12 . 
     Each of the slits  12   b  includes the optical element  12   c  in each of the above embodiments. However, the present invention is not limited to such a structure. For example, a collimator shared by each of the slits  12   b  may be arranged between the shielding unit  12  and the spectroscope  14 . Alternatively, each of the slits  12   b  may be arranged so that light from the slits  12   b  do not interfere with each other. In such a structure, the optical elements  12   c  may be eliminated thereby facilitating the manufacturing of the shielding unit  12 . 
     In the above embodiments, the band-pass filter  13  that passes only light in the measuring band is arranged in the spectrum measuring apparatus  10 . However, the band-pass filter  13  may be eliminated as long as the wavelength components dispersed by the spectroscope  14  do not interfere with each other. This simplifies the structure of the spectrum measuring apparatus  10  and facilitates the manufacturing of the spectrum measuring apparatus  10 . 
     In the above embodiments, the band-pass filter  13  is arranged between the shielding unit  12  and the spectroscope  14 . However, the arrangement of the band-pass filter  13  is not limited in such a manner as long as the band-pass filter  13  is arranged in the preceding stage of the measuring unit  15 . In other words, as long as light in the measuring band enters the light receiving elements of the measuring unit  15 , the band-pass filter  13  may be arranged at any position. This increases the degree of freedom in design of the spectrum measuring apparatus  10 . 
     In the above embodiments, the slits  12   b  are formed as apertures extending in the longitudinal direction Dm, that is, in the direction perpendicular to the planes of  FIGS. 1 ,  3 ,  4  and  5 . However, the present invention is not limited in such a manner. More specifically, as long as light from the slits  12   b  do not interfere with each other, the slits  12   b , which are apertures, can be formed in any direction. For example, instead of being parallel to the direction perpendicular to the planes of  FIGS. 1 ,  3 ,  4  and  5 , the direction of the slits  12   b , which are apertures, may be diagonal relative to that direction. In addition, the slits  12   b , which are apertures, may have any length and those with long lengths and those with short lengths may be mixed. Even in such a structure, the same advantages as the above embodiments are obtained. In particular, in the fourth embodiment, the shielding unit  12  may include the slit group  12 G that measures the part of which the spectrum can be measured with the high spatial resolution and the part of which the spectrum can be measured with the high resolution of the wavelength component in further detail. 
     In the above embodiments, the two or more slits  12   b  are arranged in the width direction Dw. However, the two or more slits  12   b  may be arranged in two or more different directions and an optical system may be provided for each row. Even in such a structure, the same advantages as the above embodiments can be achieved. In particular, in the fourth embodiment, the shielding unit  12  may include the slit group  12 G that measure the part of which the spectrum can be measured with the high spatial resolution and the part of which the spectrum can be measured with the high resolution of the wavelength component in further detail. 
     DESCRIPTION OF REFERENCE NUMERALS 
       10 : spectrum measuring apparatus,  11 : condenser,  12 : shielding unit,  12   a : shielding plate,  12   b : slit,  12   c : optical element,  12 G: slit group,  13 : band-pass filter,  13   a : first band-pass filter,  13   b : second band-pass filter,  14 : spectroscope,  15 : measuring unit,  20 : measured object,  20   a : measuring part,  22 : slit switch,  23 : matching unit,  24 : distance varying unit,  100 : hyper spectrum sensor,  111 : inlet,  112 : mirror,  113 : collimator,  114 : shielding plate,  114   a : single slit,  115 : collimator,  116 : spectroscope,  117 : imager,  118 : measuring unit,  118   a : light receiving element,  118   b : light receiving element,  120 : object,  120   a : measuring part.