Patent Publication Number: US-2022229156-A1

Title: Optical apparatus, and in-vehicle system and moving apparatus each including the same

Description:
BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to an optical apparatus that receives reflected light from an illuminated target object to detect the target object. 
     Description of the Related Art 
     As a distance measuring apparatus that measures the distance to a target object, there is known an apparatus that scans a target object by deflecting illumination light from a light source by using a deflection unit, and calculates the distance to the target object based on the time taken before receiving the reflected light from the target object and the phase of the reflected light. 
     Japanese Patent Application Laid-Open No. 2019-113408 discusses a distance measuring apparatus in which the diameter of each of illumination light and reflected light can be changed by an optical system disposed closer to a target object than a deflection unit. 
     In the distance measuring apparatus discussed in Japanese Patent Application Laid-Open No. 2019-113408, a lens array is employed in the optical system to improve the distance measurement accuracy. However, in a case where a lens array is used as in Japanese Patent Application Laid-Open No. 2019-113408, the configuration of an optical system is complicated and a placement error of each member easily occurs, and therefore, the difficulty of manufacturing a distance measuring apparatus increases. 
     SUMMARY 
     According to an aspect of the present invention, an optical apparatus includes a deflection unit configured to deflect illumination light from a light source to scan an object and to deflect reflected light from the object, a light guiding unit configured to guide the illumination light from the light source to the deflection unit and to guide the reflected light from the deflection unit to a light receiving element, and an optical system configured to guide the illumination light from the deflection unit to the object and to guide the reflected light from the object to the deflection unit, wherein the optical system includes a front lens unit configured to form an intermediate image of the object and to consist of lenses located closer to the object than the intermediate image and a rear lens unit configured to consist of lenses located closer to the deflection unit than the intermediate image, and wherein the rear lens unit consists of three or more and five or less positive lenses. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a main portion of an optical apparatus according to an exemplary embodiment. 
         FIG. 2  is a diagram illustrating a condition under which unnecessary light is generated on a lens surface. 
         FIG. 3  is a cross-sectional diagram of an optical system according to a first embodiment. 
         FIG. 4  is a cross-sectional diagram of an optical system according to a second embodiment. 
         FIG. 5  is a cross-sectional diagram of an optical system according to a third embodiment. 
         FIG. 6  is a cross-sectional diagram of an optical system according to a fourth embodiment. 
         FIG. 7  is a functional block diagram of an in-vehicle system according to the exemplary embodiment. 
         FIG. 8  is a schematic diagram of a vehicle (moving apparatus) according to the exemplary embodiment. 
         FIG. 9  is a flowchart illustrating an operation example of the in-vehicle system according to the exemplary embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An exemplary embodiment of the present invention will be described below with reference to the drawings. The drawings may each be illustrated in a scale different from the actual scale for the purpose of illustration. In the drawings, the same members are indicated by the same reference numbers, and the description thereof will not be repeated. 
       FIG. 1  is a schematic diagram of a main portion of an optical apparatus  1  in a cross-section (YZ cross-section) including an optical axis, according to an exemplary embodiment of the present invention. The optical apparatus  1  includes a light source unit  10 , a light guiding unit (splitting unit)  20 , a deflection unit  30 , an optical system  40 , a light receiving unit  50 , and a control unit  60 . In  FIG. 1 , an optical path (an illumination optical path) of illumination light from the light source unit  10  toward a target object (object)  100  is indicated by a solid line, and an optical path (light receiving optical path) of reflected light from the target object  100  toward the light receiving unit  50  is indicated by a broken line. 
     The optical apparatus  1  can be used as a detection apparatus (image pickup apparatus) that detects (images) the target object  100 , or a distance measuring apparatus that acquires the distance (distance information) to the target object  100 , by receiving the reflected light from the target object  100 . The optical apparatus  1  according to the present exemplary embodiment uses a technique called LiDAR (Light Detection and Ranging) to calculate the distance to the target object  100 , based on the time taken before receiving the reflected light from the target object  100  and the phase of the reflected light. 
     The light source unit  10  includes a light source  11 , an optical element  12 , and a diaphragm  13 . A laser such as a semiconductor laser having high energy concentration and high directivity can be used as the light source  11 . For example, in a case where the optical apparatus  1  is applied to an in-vehicle system to be described below, a human being can be included in the target object  100 . Therefore, desirably, a device that emits infrared light less affecting human eyes is adopted as the light source  11 . The wavelength of the illumination light emitted by the light source  11  according to the present exemplary embodiment is 905 nm included in the near infrared region. 
     The optical element  12  has a function of changing the convergence of the illumination light emitted from the light source  11 . 
     The optical element  12  according to the present exemplary embodiment is a collimator lens (light-condensing element) that converts (collimates) a divergent light beam emitted from the light source  11  into a parallel light beam. The parallel light beam here includes not only a strict parallel light beam, but also approximately parallel light beams such as a slightly divergent light beam and a weak convergent light beam. 
     The diaphragm  13  is a light shielding member provided with an aperture, and determines the light beam diameter (light beam width) of the illumination light from the optical element  12  by limiting the illumination light. The shape of the aperture of the diaphragm  13  according to the present exemplary embodiment is an oval to match the shape of the illumination light, but may be a shape other than the oval as needed. The diameter of the aperture of the diaphragm  13  according to the present exemplary embodiment is 1.60 mm in an X-direction (long axis direction) and 1.30 mm in a Z-direction (short axis direction). 
     The light guiding unit  20  is a member for splitting the optical path into an illumination optical path and a light receiving optical path, in order to guide the illumination light from the light source unit  10  to the deflection unit  30 , and guide the reflected light from the deflection unit  30  to the light receiving unit  50 . The light guiding unit  20  according to the present exemplary embodiment includes a light transmission member  21 , a perforated (pierced) mirror  22 , and a light-source light receiving element  23 . The light transmission member  21  is provided to reflect a part of the illumination light passing through the aperture of the diaphragm  13  and guide the part to the light-source light receiving element  23 . For example, a glass substrate can be used for the light transmission member  21 . 
     The perforated mirror  22  is a reflection member provided with an opening (hole) for allowing the illumination light from the light source unit  10  to pass therethrough, and reflects the reflected light from the deflection unit  30  toward the light receiving unit  50  by a reflection region (reflection portion) excluding the opening. The opening of the perforated mirror  22  according to the present exemplary embodiment is an empty hele as illustrated in  FIG. 1 , but the opening may be provided with a light transmission member. Further, as the light-guiding member (splitting member) for splitting the light into the illumination light and the reflected light, not only the perforated mirror, but also a beam splitter, a prism, a half mirror, or the like may be used. 
     The light-source light receiving element  23  is an element for photoelectrically converting the illumination light from the light source unit  10  and outputting a signal, and, for example, a sensor similar to a light receiving element  53  to be described below in the light receiving unit  50  can be used. The signal output from the light-source light receiving element  23  is used when the control unit  60  to be described below controls the light source unit  10 . An optical element (such as a filter or a lens) for guiding the light from the light transmission member  21  to the light receiving surface of the light-source light receiving element  23  may be disposed between the light transmission member  21  and the light-source light receiving element  23 , as needed. 
     The deflection unit  30  is a member for deflecting the illumination light from the light guiding unit  20  to scan the target object  100 , and for deflecting the reflected light from the target object  100  and guiding the deflected light to the light guiding unit  20 . The deflection unit  30  according to the present exemplary embodiment consists of a return mirror  31  (first deflection element) and a drive mirror  32  (movable mirror, or second deflection element). 
     It is desirable that the drive mirror  32  be swingable about at least two axes (be a 2-axis drive mirror) so that the target object  100  can be two-dimensionally scanned. For example, a galvanometer mirror or a Micro Electro Mechanical System (MEMS) mirror can be adopted as the drive mirror  32 . The drive mirror  32  according to the present exemplary embodiment is a MEMS mirror with a swinging angle (deflection angle) of approximately ±7.5 degrees around an X-axis, a swinging angle of approximately ±15.0 degrees around a Y-axis, and a swinging frequency of approximately 1 kHz. The swinging angle of the drive mirror  32  around the X-axis corresponds to an angle of field (scanning field angle) in the YZ cross-section, and the swinging angle of the drive mirror  32  around the Y-axis corresponds to an angle of field in a ZX cross-section. 
     The optical system  40  is a member for guiding the illumination light from the deflection unit  30  to the target object  100 , and also guiding the reflected light from the target object  100  to the deflection unit  30 . The optical system  40  according to the present exemplary embodiment is an optical system consisting of a plurality of lenses having refractive power (power), and having no refractive power as a whole (an afocal system). Specifically, the optical system  40  is a telescope that increases the diameter of the illumination light from the deflection unit  30  by β times, and reduces the diameter of the reflected light from the target object  100  by 1/β times. 
     The optical system  40  according to the present exemplary embodiment includes a front lens unit  41  having a plurality of lenses, and a rear lens unit  42  having a plurality of lenses, disposed in order from the target object  100  side (the object side) to the deflection unit  30  side (the deflection unit side). The front lens unit  41  is configured to condense the reflected light from the target object  100  to form an intermediate image  43  of the target object  100 . The rear lens unit  42  is configured to convert the reflected light from the front lens unit  41  into a parallel light beam to be incident on the drive mirror  32 . This configuration enables the optical system  40  to convert the diameter of each of the illumination light from the deflection unit  30  and the reflected light from the target object  100 . The optical system  40  may include other members such as a diaphragm, a filter, and a cover glass other than the front lens unit  41  and the rear lens unit  42 . 
     The deflection surface of the drive mirror  32  according to the present exemplary embodiment is located at a position conjugated with an entrance pupil of the optical system  40  when the target object  100  side is the incident side. In other words, the deflection surface of the drive mirror  32  is located at the position of the entrance pupil of the optical system  40  when the deflection unit  30  side is the incident side. Further, the absolute value of an optical magnification (lateral magnification) β of the optical system  40  according to the present exemplary embodiment is greater than 1 (|β|&gt;1). Therefore, the deflection angle of the principal ray of the illumination light output from the optical system  40  is smaller than the deflection angle of the principal ray of the illumination light deflected by the drive mirror  32  and incident on the optical system  40 , so that the resolution in detecting the target object  100  can be improved. 
     The illumination light from the light source unit  10  is deflected by the deflection unit  30  via the light guiding unit  20 , and enlarged by the optical system  40  based on the optical magnification β to illuminate the target object  100 . Further, the reflected light from the target object  100  is reduced by the optical system  40  based on the optical magnification 1/β, deflected by the deflection unit  30 , and arrives at the light receiving unit  50 . This can further reduce the spread angle by further increasing the diameter of the illumination light, and thus sufficient illuminance and resolution can be secured even in a case where the target object  100  is at a distance. In addition, it is possible to take in more reflected light from the target object  100  by increasing the pupil diameter using the optical system  40 , so that the measurement distance and the distance measurement accuracy can be improved. 
     The light receiving unit (light receiving unit for distance measurement)  50  includes an optical filter  51 , a light condenser  52 , and the light receiving element (light receiving element for distance measurement)  53 . The optical filter  51  is a member for transmitting only desired light, and blocking (absorbing) unnecessary light, i.e., light except the desired light. The optical filter  51  according to the present exemplary embodiment is a bandpass filter that passes only light in a wavelength band corresponding to the illumination light emitted from the light source  11 . The light condenser  52  is a member for condensing the light that has passed through the optical filter  51  on the light receiving surface of the light receiving element  53 , and consists of a single optical element (condenser lens) in the present exemplary embodiment. 
     The configuration of each of the optical filter  51  and the light condenser  52  is not limited to that of the present exemplary embodiment, and the members may be replaced with each other in the placement order or may each be disposed as a plurality of members as needed. For example, the light condenser  52  may consist of a plurality of condenser lenses. 
     The light receiving element (light receiving element for distance measurement)  53  is an element (sensor) for receiving light from the light condenser  52  and photoelectrically converting the received light to output a signal. An element consisting of a photodiode (PD), an avalanche photodiode (APD), or a single photon avalanche diode (SPAD) can be adopted as the light receiving element  53 . The reflected light from the target object  100  illuminated by the illumination light is deflected by the deflection unit  30  and reflected by the perforated mirror  22  to be incident on the light receiving element  53  via the optical filter  51  and the light condenser  52 . 
     The control unit  60  controls the light source  11 , the light-source light receiving element  23 , the drive mirror  32 , and the light receiving element  53 . The control unit  60  is, for example, a processing device (processor) such as a central processing unit (CPU), or an arithmetic device (computer) provided with the processing device. The control unit  60  drives each of the light source  11  and the drive mirror  32  at a predetermined drive voltage or a predetermined drive frequency, and controls the output (the amount of the illumination light) of the light source  11  based on a signal from the light-source light receiving element  23 . The control unit  60  can also, for example, change the illumination light to pulsed light by controlling the light source  11 , and generate signal light by modulating the intensity of the illumination light. 
     Further, the control unit  60  can acquire the distance information of the target object  100 , based on the time from when the illumination light is emitted from the light source  11  (light emission timing) to when the reflected light from the target object  100  is received by the light receiving element  53  (light receiving timing). At this moment, the control unit  60  may acquire a signal from the light receiving element  53  at a specific frequency. The control unit  60  may acquire the distance information based on the phase of the reflected light from the target object  100 , instead of the time taken before receiving the reflected light from the target object  100 . Specifically, the control unit  60  may acquire the distance information of the target object  100  by determining the difference (phase difference) between the phase of the signal of the light source  11  and the phase of the signal output from the light receiving element  53 , and multiplying this phase difference by the velocity of light. 
     The optical apparatus  1  as such a distance measuring apparatus using LiDAR is suitable for an in-vehicle system that distinguishes the target object  100  such as a vehicle, a pedestrian, or an obstacle, and controls the own vehicle based on the distance information of the target object  100 . In a case where LiDAR is used, it is possible to adopt a coaxial system in which the optical axis of the light source unit  10  and the optical axis of the light receiving unit  50  partially coincide with each other, or a non-coaxial system in which the optical axes do not coincide with each other. The optical apparatus  1  according to the present exemplary embodiment includes the light guiding unit  20 , thereby implementing the coaxial system while downsizing the entire apparatus. 
     In an in-vehicle system or the like, it is desired to detect a range of objects from an object at a short distance (about 1 m) to an object at a long distance (about 300 m) from the optical apparatus  1 , as the target objects  100 . However, the intensity of the reflected light (signal light) from the target object  100  is very feeble, for example, about 10 −7  to 10 −8  when the power of the illumination light emitted from the light source  11  is 1. In addition, the intensity of the reflected light from the target object  100  is lower as the distance from the optical apparatus  1  to the target object  100  is longer. For example, in a case where the distance from the optical apparatus  1  to the target object  100  increases 10 times, the intensity of the reflected light received by the optical apparatus  1  decreases to about 1/100. 
     Here, if reflected light (scattering light) unintentionally generated in each member inside the optical apparatus  1  arrives at the light receiving element  53  as unnecessary light (stray light), this greatly affects the distance measurement accuracy. For example, if the ratio of the unnecessary light to the signal light received by the light receiving element  53  increases, the signal to noise (S/N) ratio decreases, thereby making it difficult to distinguish between the signal light and the unnecessary light, so that the distance measurement accuracy decreases to a great extent. A method of increasing the amount of the illumination light (the output of the light source  11 ) based on an increase in the distance to the target object  100  is conceivable, but this method is not desirable because the influence on the eyes of a person as the target object  100  is large. 
     Such unnecessary light is easily generated, in particular, on the lens surface located subsequent to the light guiding unit  20 . 
     In the present exemplary embodiment, because the optical system  40  disposed closer to the target object  100  than the light guiding unit  20  includes the plurality of lenses, there is a possibility that the illumination light becomes the unnecessary light when reflected (scattered) by each of the lens surfaces. Therefore, to suppress the generation of the unnecessary light on each of the lens surfaces of the optical system  40 , it is desirable to design the optical apparatus  1  in such a manner that a ray (illumination ray) included in the illumination light is not perpendicularly incident on each of the lens surfaces. This will be described with reference to  FIG. 2 . 
       FIG. 2  is a schematic diagram illustrating the illumination light incident on a lens surface  4  disposed closer to the target object  100  than the deflection unit  30 . The illumination light deflected by swinging of the drive mirror  32  is incident on the lens surface  4 . In other words, the illumination light is incident on the lens surface  4  at various incident angles. An illumination ray A indicated by a solid line is a part of the illumination light and passes through the curvature center C of the lens surface  4 , and therefore, the ray A is perpendicularly incident on the lens surface  4 . In this case, the ray A is reflected by the lens surface  4  and travels on the reflection optical path opposite to the illumination optical path, and therefore, the ray A can be incident on the light receiving element  53  together with the reflected ray from the target object  100 , as the unnecessary light. Even if an anti-reflection film having a reflectance ratio of about 0.1% is disposed on the lens surface  4 , a part of the ray can be such unnecessary light. 
     On the other hand, an illumination ray B indicated by a dotted line does not pass through the curvature center C, and is therefore incident on the lens surface  4  at an incident angle to some extent. In other words, a normal line D and the illumination ray B at the incident point of the illumination ray B on the lens surface  4  are not parallel to each other (do not overlap each other). Therefore, even if the illumination ray B is reflected by the lens surface  4 , the illumination ray B travels on an optical path different from the reflection optical path, so that the unnecessary light is not generated. Therefore, to suppress the generation of the unnecessary light in the optical system  40 , the deflection unit  30  and the optical system  40  may be disposed in such a manner that each of the illumination rays incident on each of the lens surfaces does not pass through the curvature center of each of the lens surfaces (is not perpendicularly incident on each of the lens surfaces). 
     Specifically, it is desirable to design each of the lenses in the optical system  40  in such a manner that the normal line at the incident point of the illumination ray on each of the lens surfaces of the optical system  40  and the illumination ray are not parallel to each other, in other words, each of the illumination rays is not perpendicularly incident on each of the lens surfaces. For example, it is possible to prevent the illumination ray from being perpendicularly incident on each of the lens surfaces, by designing each of the lenses while confirming the incident angle of each of the illumination rays with respect to each of the lens surfaces in the optical system  40 , using known optical simulation software or the like. Design parameters for each of the lenses are a curvature (curvature radius), a thickness (a thickness in an optical-axis direction), a surface shape, and a position in a direction perpendicular to an optical axis (decentering), but are not limited thereto. The shape of each of the lens surfaces may be aspherical, but is, desirably, spherical considering the easiness of molding. 
     The deflection unit  30  and the optical system  40  may be disposed at positions displaced (shifted) with respect to each other in a Y-direction, in order to reduce the illumination rays perpendicularly incident on each of the lens surfaces. To realize this configuration, the deflection unit  30  may be disposed in such a manner that the optical path of the principal ray of the illumination light at a central field angle in the scan range of the drive mirror  32  and the optical axis of the optical system  40  do not coincide with each other, in a cross-section (the YZ cross-section) including the illumination optical path and the reflection optical path. It is possible to obtain a similar effect by setting (tilting) the scan range of the deflection unit  30  asymmetrically with respect to the optical axis of the optical system  40 , instead of shifting the deflection unit  30  and the optical system  40  with respect to each other. The tilting may be combined with the shifting. Further, at least one of the shifting and the tilting may be combined with the above-described design of each of the lenses. 
     Here, in a case where the configuration for suppressing the generation of the unnecessary light is adopted as described above, the freedom of the design of the optical system  40  decreases in comparison with a case where this configuration is not adopted. In particular, in the rear lens unit  42  on which the illumination light from the deflection unit  30  is incident first, the freedom of the design including the shape and the location of each of the lenses decreases to a great extent. Therefore, in order to achieve both of the downsizing and the satisfactory optical performance of the optical system  40 , it may be desirable to design in such a manner that the number of lenses forming the rear lens unit  42  and the sign of the refractive power of each of the lenses are appropriate. 
     As a result of trial and error, the present inventor has found that both of the downsizing of the entire system and the satisfactory optical performance of the optical system  40  can be realized by having the rear lens unit  42  consisting of three or more and five or less positive lenses. According to the optical system  40  of the present exemplary embodiment, it is possible to correct aberrations successfully while downsizing the optical system  40 , by using the rear lens unit  42  consisting of only the positive lenses. In a case where a negative lens is added to the rear lens unit  42 , the size of the rear lens unit  42  is increased to correct aberrations successfully, in comparison with the case where the rear lens unit  42  consists of only the positive lenses. 
     Further, it is possible to suppress the generation of the unnecessary light while downsizing the optical system  40 , by having the rear lens unit  42  consisting of three or more and five or less positive lenses. In a case where the number of the positive lenses is two or less, the overall focal length of the rear lens unit  42  is too long, so that it is difficult to downsize the optical system  40 . In addition, it is difficult to prevent each of the rays incident on each of the lens surfaces in the rear lens unit  42  and the normal line at the incident point on each of the lens surfaces from being parallel, and it is therefore difficult to reduce the unnecessary light sufficiently. 
     Meanwhile, in a case where the number of the positive lenses is six or more, the overall focal length of the rear lens unit  42  is short, so that the intermediate image  43  is too close to the lens surface of the rear lens unit  42 . In this case, the rays are concentrated near the intermediate image  43 , so that the influence of scratches and dust on the lens surface is large, making it difficult to obtain satisfactory optical performance. In addition, as the number of the positive lenses increases, it is more difficult to design the rear lens unit  42  to prevent the intermediate image  43  from interfering with the lens surface. 
     The number of the positive lenses forming the rear lens unit  42  may be selected depending on which one of the downsizing of the optical system  40  and the reduction of the unnecessary light is given priority. For example, to further downsize the optical system  40 , the number of the positive lenses forming the rear lens unit  42  is, desirably, four or five. In addition, to achieve the optimum balance between the downsizing of the optical system  40  and the reduction of the unnecessary light, the number of the positive lenses forming the rear lens unit  42  is, desirably, four. 
     It is desirable that the optical system  40  satisfy the following conditional expression (1), where the focal length of the front lens unit  41  is ff, and the focal length of the rear lens unit  42  is fr. 
     
       
         
           
             
               
                 
                   
                     1 
                     . 
                     8 
                   
                   &lt; 
                   
                     ff 
                     / 
                     fr 
                   
                   &lt; 
                   8.0 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     The target object  100  can be accurately detected even in a case where the target object  100  is at a long distance, by satisfying the conditional expression (1). If the ratio exceeds the upper limit of the conditional expression (1), the optical magnification of the optical system  40  is too large, so that the size of the entire system increases and the unnecessary light is easily generated, and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (1), the optical magnification of the optical system  40  is too small, so that the reflected light from the target object  100  at a long distance is not easily received, and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (1a), and it is more desirable to satisfy the following conditional expression (1b), and it is yet more desirable to satisfy the following conditional expression (1c). 
     
       
         
           
             
               
                 
                   
                     2 
                     . 
                     0 
                   
                   &lt; 
                   
                     ff 
                     / 
                     fr 
                   
                   &lt; 
                   7.0 
                 
               
               
                 
                   ( 
                   
                     1 
                     ⁢ 
                     c 
                   
                   ) 
                 
               
             
             
               
                 
                   2.5 
                   &lt; 
                   
                     ff 
                     / 
                     fr 
                   
                   &lt; 
                   6.0 
                 
               
               
                 
                   ( 
                   
                     1 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
             
               
                 
                   3.0 
                   &lt; 
                   
                     ff 
                     / 
                     fr 
                   
                   &lt; 
                   5.0 
                 
               
               
                 
                   ( 
                   
                     1 
                     ⁢ 
                     c 
                   
                   ) 
                 
               
             
           
         
       
     
     In addition, it is desirable that the optical system  40  satisfy the following conditional expression (2), where, for the lens closest to the deflection unit in the rear lens unit  42 , the curvature radius of the lens surface on the object side is R1B1, and the curvature radius of the lens surface on the deflection unit side is R2B1. 
     
       
         
           
             
               
                 
                   
                     
                       - 
                       1 
                     
                     ⁢ 
                     
                       2 
                       . 
                       0 
                     
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     2.0 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     The conditional expression (2) is an expression about the shape factor of the lens closest to the deflection unit among the positive lenses forming the rear lens unit  42 . It is possible to make this lens have an appropriate meniscus shape, and to suppress the generation of the unnecessary light while making it easy to manufacture this lens, by satisfying the conditional expression (2). If the ratio exceeds the upper limit of the conditional expression (2), the shape of this lens becomes closer to a planoconvex shape or biconvex shape. In this case, to prevent the direction of the normal line and the direction of the ray on the lens surface on the deflection unit side from coinciding with each other, it may be desirable to refract the ray at an extremely large angle on this lens surface, so that it is difficult to correct an aberration, and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (2), the curvature of each of the lens surfaces is too large, so that it is difficult to manufacture this lens, and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (2a), and it is more desirable to satisfy the following conditional expression (2b). 
     
       
         
           
             
               
                 
                   
                     
                       - 
                       1 
                     
                     ⁢ 
                     
                       0 
                       . 
                       0 
                     
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     4.0 
                   
                 
               
               
                 
                   ( 
                   
                     2 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     - 
                     8.0 
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     6.0 
                   
                 
               
               
                 
                   ( 
                   
                     2 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     In addition, it is desirable that the optical system  40  satisfy the following conditional expression (3), where, for the lens adjacent to the lens closest to the deflection unit in the rear lens unit  42 , the curvature radius of the lens surface on the object side is R1B2, and the curvature radius of the lens surface on the deflection unit side is R2B2. 
     
       
         
           
             
               
                 
                   
                     - 
                     
                       6 
                       . 
                       0 
                     
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     0.5 
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     The conditional expression (3) is an expression about the shape factor of the lens second from the deflection unit side among the positive lenses forming the rear lens unit  42 . It is possible to make this lens have an appropriate meniscus shape, and to suppress the generation of the unnecessary light while making it easy to manufacture this lens, by satisfying the conditional expression (3). If the ratio exceeds the upper limit of the conditional expression (3), the shape of this lens becomes closer to a biconvex shape, so that it is difficult to correct a spherical aberration occurring on each of the lens surfaces, and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (3), it is difficult to design the lens to prevent the direction of the normal line and the direction of the ray on each of the lens surfaces from coinciding with each other and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (3a), and it is more desirable to satisfy the following conditional expression (3b). 
     
       
         
           
             
               
                 
                   
                     - 
                     
                       5 
                       . 
                       0 
                     
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     1.0 
                   
                 
               
               
                 
                   ( 
                   
                     3 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     - 
                     4.0 
                   
                   &lt; 
                   
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         + 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                     / 
                     
                       ( 
                       
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         - 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                           ⁢ 
                           B 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                   
                   &lt; 
                   
                     - 
                     2.0 
                   
                 
               
               
                 
                   ( 
                   
                     3 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     In addition, it is desirable that the optical system  40  satisfy the following conditional expression (4), where the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the deflection unit in the rear lens unit  42  is Lr, and the distance on the optical axis from the lens surface closest to the deflection unit in the front lens unit  41  to the lens surface closest to the object in the rear lens unit  42  is Li. 
     
       
         
           
             
               
                 
                   
                     0 
                     . 
                     1 
                   
                   &lt; 
                   
                     L 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     i 
                   
                   &lt; 
                   4.0 
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     It is possible to reduce the full length of the optical system  40  while keeping the distance between the front lens unit  41  and the rear lens unit  42  appropriately, by satisfying the conditional expression (4). If the ratio exceeds the upper limit of the conditional expression (4), the distance between the front lens unit  41  and the rear lens unit  42  is short and the intermediate image  43  is too close to each of the lens surfaces, so that the influence of scratches and dust on each of the lens surfaces is large, which makes it difficult to obtain satisfactory optical performance, and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (4), the rear lens unit  42  and the front lens unit  41  are too far away from each other, so that the full length of the optical system  40  is long. This reduces the degree of freedom of the location of each of the lenses, and also leads to an increase in manufacturing cost because of an increase in the size of a barrel holding each of the lenses, and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (4a), and it is more desirable to satisfy the following conditional expression (4b). 
     
       
         
           
             
               
                 
                   
                     
                       0 
                       . 
                       1 
                     
                     ⁢ 
                     5 
                   
                   &lt; 
                   
                     L 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     i 
                   
                   &lt; 
                   
                     3 
                     ⁢ 
                     .00 
                   
                 
               
               
                 
                   ( 
                   
                     4 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   0.2 
                   &lt; 
                   
                     L 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     i 
                   
                   &lt; 
                   2.0 
                 
               
               
                 
                   ( 
                   
                     4 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     In addition, it is desirable that the optical system  40  satisfy the following conditional expression (5), where the average value in terms of the refractive index with respect to the d-line of the positive lens in the optical system  40  is NPave, and the average value in terms of the refractive index with respect to the d-line of the negative lens in the optical system  40  is NNave. 
     
       
         
           
             
               
                 
                   
                     1 
                     . 
                     2 
                   
                   &lt; 
                   
                     NPave 
                     / 
                     NNave 
                   
                   &lt; 
                   1.5 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     In the present exemplary embodiment, the wavelength of the illumination light is not particularly limited. However, in particular, in a case where the optical apparatus  1  is used as a distance measuring apparatus, it is desired to use infrared light less affecting a human body as the illumination light and narrow the wavelength band of the illumination light to increase the directivity. Therefore, it is desirable to select the material of each of the lenses forming the optical system  40 , considering the correction of the Petzval sum in preference to the correction of the chromatic aberration. Specifically, it is desirable that a material having a high refractive index be adopted for the positive lens, and a material having a low refractive index be adopted for the negative lens. 
     It is possible to correct the Petzval sum of the optical system  40  successfully and suppress the occurrence of the field curvature and the astigmatic difference, by satisfying the conditional expression (5). If the ratio exceeds the upper limit of the conditional expression (5), the degree of freedom in the selection of the material of each of the lenses decreases, so that an increase in the difficulty of manufacturing each of the lenses or a decrease in the internal transmittance can occur, and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (5), the Petzval sum of the optical system  40  increases, and it is difficult to correct the field curvature and the astigmatic difference, and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (5a), and it is more desirable to satisfy the following conditional expression (5b). 
     
       
         
           
             
               
                 
                   
                     
                       1 
                       . 
                       2 
                     
                     ⁢ 
                     5 
                   
                   &lt; 
                   
                     NPave 
                     / 
                     NNave 
                   
                   &lt; 
                   1.45 
                 
               
               
                 
                   ( 
                   
                     5 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   1.3 
                   &lt; 
                   
                     NPave 
                     / 
                     NNave 
                   
                   &lt; 
                   1.4 
                 
               
               
                 
                   ( 
                   
                     5 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     Desirably, the front lens unit  41  according to the present exemplary embodiment consists of one or more positive lenses and one or more negative lenses. According to this configuration, it is easy to correct the Petzval sum and the spherical aberration successfully in the front lens unit  41 . Further, desirably, the front lens unit  41  consists of two or more positive lenses and two or more negative lenses. According to this configuration, each of the positive refractive power and the negative refractive power can be shared by the plurality of lenses, so that the curvature of each of the lens surfaces can be reduced, making it easy to manufacture each of the lenses. In addition, the incident position of the light beam varies according to the lens, so that the plurality of aberrations are shared by the lenses and can be thereby easily corrected. 
     In a case where the front lens unit  41  includes a plurality of positive lenses and a plurality of negative lenses, it is desirable to alternately dispose at least one positive lens and at least one negative lens. For example, desirably, the front lens unit  41  consists of at least one positive lens, at least one negative lens, at least one positive lens, and at least one negative lens disposed in order from the object side. 
     In this case, the front lens unit  41  has a configuration in which the negative lens is located on the deflection unit side of a lens unit (a triplet unit) having a function similar to that of a triplet, and therefore, the spherical aberration and the astigmatic difference can be corrected successfully. 
     The number of the positive lenses and the negative lenses in the front lens unit  41  is not particularly limited, but, desirably, the front lens unit  41  consists of two positive lenses and two negative lenses to achieve both of the simplification and the satisfactory aberration correction of the front lens unit  41 . More desirably, the front lens unit  41  consists of the positive lens, the negative lens, the positive lens, and the negative lens disposed in order from the object side to the deflection unit side. 
     Here, it is desirable that the optical system  40  satisfy the following conditional expression (6), where, in a case where the front lens unit  41  includes one or more positive lenses and one or more negative lenses, the average value in terms of the focal length of the positive lens in the front lens unit  41  is ffPave, and the average value in terms of the focal length of the negative lens in the front lens unit  41  is ffNave. 
     
       
         
           
             
               
                 
                   
                     - 
                     
                       1 
                       . 
                       0 
                     
                   
                   &lt; 
                   
                     ffPave 
                     / 
                     ffNave 
                   
                   &lt; 
                   
                     
                       - 
                       0 
                     
                     ⁢ 
                     .2 
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     The relationship between the refractive power of the positive lens and the refractive power of the negative lens forming the front lens unit  41  can be made appropriate, and the aberration occurring in the positive lens can be corrected successfully by the negative lens, by satisfying the conditional expression (6). If the ratio exceeds the upper limit of the conditional expression (6), the negative refractive power in the front lens unit  41  is too large, and the focal length of the front lens unit  41  increases, making it difficult to downsize the optical system  40 , and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (6), the positive refractive power in the front lens unit  41  is too large, so that it is difficult to correct the spherical aberration occurring in the front lens unit  41  and various aberrations occurring in the rear lens unit  42 , and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (6a), and it is more desirable to satisfy the following conditional expression (6b). 
     
       
         
           
             
               
                 
                   
                     - 
                     
                       0 
                       . 
                       8 
                     
                   
                   &lt; 
                   
                     ffPave 
                     / 
                     ffNave 
                   
                   &lt; 
                   
                     - 
                     0.3 
                   
                 
               
               
                 
                   ( 
                   
                     6 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   
                     - 
                     0.75 
                   
                   &lt; 
                   
                     ffPave 
                     / 
                     ffNave 
                   
                   &lt; 
                   
                     
                       - 
                       
                         0 
                         . 
                         4 
                       
                     
                     ⁢ 
                     0 
                   
                 
               
               
                 
                   ( 
                   
                     6 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     In addition, it is desirable that the optical system  40  satisfy the following conditional expression (7). 
     
       
         
           
             
               
                 
                   
                     
                       0 
                       . 
                       6 
                     
                     ⁢ 
                     5 
                   
                   &lt; 
                   
                     f 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     r 
                   
                   &lt; 
                   
                     
                       2 
                       . 
                       2 
                     
                     ⁢ 
                     0 
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
     It is possible to reduce the full length of the optical system  40  while keeping the distance between the front lens unit  41  and the rear lens unit  42  appropriately, by satisfying the conditional expression (7). If the ratio exceeds the upper limit of the conditional expression (7), the focal length of the rear lens unit  42  is too long, making it difficult to downsize the optical system  40 , and therefore, such a ratio is not desirable. If the ratio falls below the lower limit of the conditional expression (7), the distance between the front lens unit  41  and the rear lens unit  42  is short and the intermediate image  43  is too close to each of the lens surfaces, so that the influence of scratches and dust on each of the lens surfaces is large, making it difficult to obtain satisfactory optical performance, and therefore, such a ratio is not desirable. 
     Further, it is desirable to satisfy the following conditional expression (7a), and it is more desirable to satisfy the following conditional expression (7b). 
     
       
         
           
             
               
                 
                   
                     
                       0 
                       . 
                       7 
                     
                     ⁢ 
                     0 
                   
                   &lt; 
                   
                     f 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     r 
                   
                   &lt; 
                   
                     2 
                     ⁢ 
                     .00 
                   
                 
               
               
                 
                   ( 
                   
                     7 
                     ⁢ 
                     a 
                   
                   ) 
                 
               
             
             
               
                 
                   0.85 
                   &lt; 
                   
                     f 
                     ⁢ 
                     
                       r 
                       / 
                       L 
                     
                     ⁢ 
                     r 
                   
                   &lt; 
                   
                     
                       1 
                       . 
                       5 
                     
                     ⁢ 
                     0 
                   
                 
               
               
                 
                   ( 
                   
                     7 
                     ⁢ 
                     b 
                   
                   ) 
                 
               
             
           
         
       
     
     Desirably, all the lenses forming the optical system  40  are spaced apart from each other in the optical-axis direction. In other words, desirably, the optical system  40  does not include a cemented lens, and all the lenses in the optical system  40  are single lens elements. In a case where the optical system  40  includes a cemented lens, each of the lenses forming this cemented lens can be detached or decentered by a temperature change. Therefore, the optical system  40  is configured using only the single lens elements, so that the satisfactory optical performance can be maintained even in a case where a temperature change occurs. This effect is apparent in a case where the optical system  40  is placed in an environment where the temperature frequently changes, in particular, in a case where the optical system  40  is mounted in an in-vehicle system. 
     As described above, in the optical apparatus  1  according to the present exemplary embodiment, both of the downsizing of the optical system  40  and the reduction of the unnecessary light can be achieved, and satisfactory optical performance can be obtained by a simple configuration. This can realize satisfactory distance measurement accuracy in a case where the optical apparatus  1  is applied to a distance measuring apparatus. 
     The optical system  40  according to a first embodiment of the present invention will be described below. The present embodiment corresponds to Numerical Embodiment 1 to be described below. For the optical system  40  according to the present embodiment, the description will be omitted for a configuration similar to that of the optical system  40  according to the above-described exemplary embodiment. 
       FIG. 3  is a diagram illustrating a cross-section (the YZ cross-section) including an optical axis OAL of the optical system  40  according to the present embodiment. In  FIG. 3 , the object side (the +Z side) is the left side, the deflection unit side (the −Z side) is the right side, and a plurality of reflection optical paths corresponding to a plurality of angles of the drive mirror  32  is illustrated. The optical system  40  according to the present embodiment is a telescope consisting of a plurality of lenses L 111  to L 118  having refractive power, and having no refractive power as a whole. In the present embodiment, each of all the lens surfaces of the lenses L 111  to L 118  is a spherical surface, so that it is easy to manufacture each of the lenses. In addition, in the present embodiment, each of all the lenses L 111  to L 118  is a single lens element, so that the satisfactory environment resistance of the optical system  40  is realized. 
     As illustrated in  FIG. 3 , in the present embodiment, the drive mirror  32  is shifted in the Y-direction in such a manner that a central axis OAM of the drive mirror  32  and the optical axis OAL of the optical system  40  do not coincide with each other. The central axis OAM here coincides with the optical path of a principal ray Rc (not illustrated) at the central field angle in the scan range among the illumination light immediately after deflected by the drive mirror  32 . In other words, the drive mirror  32  is disposed in such a manner that the incident point (the intersection between the deflection surface and the optical path of the principal ray Rc) of the principal ray Rc on the deflection surface and the optical axis OAL are spaced apart from each other. Further, the scan range of the drive mirror  32  is set in such a manner that the central axis OAM inclines toward (is not parallel to) the optical axis OAL. These configurations prevent the principal ray Rc from being perpendicularly incident on each of the lens surfaces, so that unnecessary light can be reduced. Further, in the present embodiment, the unnecessary light can be further reduced by designing each of the lenses to also prevent the illumination rays other than the principal ray Rc from being perpendicularly incident on each of the lens surfaces. 
     The front lens unit  41  according to the present embodiment consists of the positive lens L 111 , the negative lens L 112 , the positive lens L 113 , and the negative lens L 114  disposed in order from the object side to the deflection unit side. This configuration makes it possible to correct the spherical aberration and the astigmatic difference successfully while simplifying the front lens unit  41 . Specifically, a triplet group consisting of the lenses L 111  to L 113  for transmitting a light beam having a relatively large diameter mainly corrects the spherical aberration, and the negative lens L 114  having a relatively large difference (degree of beam separation) in the transmission position of a light beam corresponding to an angle of view mainly corrects the astigmatic difference. 
     The rear lens unit  42  according to the present embodiment consists of the positive lens L 115 , the positive lens L 116 , the positive lens L 117 , and the positive lens L 118  disposed in order from the object side to the deflection unit side. In other words, the rear lens unit  42  consists of four positive lenses. This configuration realizes both of the downsizing of the entire system and the satisfactory optical performance of the optical system  40 . 
     The optical system  40  according to a second embodiment of the present invention will be described below. The present embodiment corresponds to Numerical Embodiment 2 to be described below. For the optical system  40  according to the present embodiment, the description will be omitted for a configuration similar to that of the optical system  40  according to the above-described first embodiment. 
       FIG. 4  is a diagram illustrating a cross-section including the optical axis OAL of the optical system  40  according to the present embodiment. The optical system  40  according to the present embodiment is a telescope consisting of lenses L 121  to L 129 , and having no refractive power as a whole. The optical system  40  according to the present embodiment is designed to prevent each of the illumination rays from being perpendicularly incident on each of the lens surfaces as in the first embodiment. 
     The front lens unit  41  according to the present embodiment consists of the positive lens L 121 , the negative lens L 122 , the positive lens L 123 , and the negative lens L 124  disposed in order from the object side to the deflection unit side. The rear lens unit  42  according to the present embodiment consists of the positive lens L 125 , the positive lens L 126 , the positive lens L 127 , the positive lens L 128 , and the positive lens L 129  disposed in order from the object side to the deflection unit side. In other words, the rear lens unit  42  consists of five positive lenses. The number of the positive lenses in the rear lens unit  42  according to the present embodiment is larger than that of the first embodiment by one, which can increase the positive refractive power of the rear lens unit  42 , and also increase the positive refractive power of the front lens unit  41  accordingly, so that the optical system  40  can be further downsized. 
     The optical system  40  according to a third embodiment of the present invention will be described below. The present embodiment corresponds to Numerical Embodiment 3 to be described below. For the optical system  40  according to the present embodiment, the description will be omitted for a configuration similar to that of the optical system  40  according to the above-described first embodiment. 
       FIG. 5  is a diagram illustrating a cross-section including the optical axis OAL of the optical system  40  according to the present embodiment. The optical system  40  according to the present embodiment is a telescope consisting of lenses L 131  to L 137 , and having no refractive power as a whole. The optical system  40  according to the present embodiment is designed to prevent each of the illumination rays from being perpendicularly incident on each of the lens surfaces as in the first embodiment. 
     The front lens unit  41  according to the present embodiment consists of the positive lens L 131 , the negative lens L 132 , the positive lens L 133 , and the negative lens L 134  disposed in order from the object side to the deflection unit side. The rear lens unit  42  according to the present embodiment consists of the positive lens L 135 , the positive lens L 136 , and the positive lens L 137  disposed in order from the object side to the deflection unit side. In other words, the rear lens unit  42  consists of three positive lenses. The number of the positive lenses in the rear lens unit  42  according to the present embodiment is smaller than that of the first embodiment by one, and therefore, the rear lens unit  42  can be further simplified, and the distance between the intermediate image  43  and each of the lens surfaces in front of and behind the intermediate image  43  can be sufficiently secured by increasing the distance between the front lens unit  41  and the rear lens unit  42 . 
     The optical system  40  according to a fourth embodiment of the present invention will be described below. The present embodiment corresponds to Numerical Embodiment 4 to be described below. For the optical system  40  according to the present embodiment, the description will be omitted for a configuration similar to that of the optical system  40  according to the above-described first embodiment. 
       FIG. 6  is a diagram illustrating a cross-section including the optical axis OAL of the optical system  40  according to the present embodiment. The optical system  40  according to the present embodiment is a telescope consisting of lenses L 141  to L 149 , and having no refractive power as a whole. The optical system  40  according to the present embodiment is designed to prevent each of the illumination rays from being perpendicularly incident on each of the lens surfaces as in the first embodiment. 
     The front lens unit  41  according to the present embodiment consists of the positive lens L 141 , the negative lens L 142 , the positive lens L 143 , the positive lens L 144 , and the negative lens L 145  disposed in order from the object side to the deflection unit side. 
     The rear lens unit  42  according to the present embodiment consists of the positive lens L 146 , the positive lens L 147 , the positive lens L 148 , and the positive lens L 149  disposed in order from the object side to the deflection unit side. In other words, the rear lens unit  42  consists of four positive lenses. 
     The optical magnification (β=2.0) of the optical system  40  according to the present embodiment is lower than the optical magnification (β≥3.5) of the optical system  40  according to each of the first to third embodiments. Therefore, the optical system  40  according to the present embodiment is suitable for the detection of the target object  100  at a short distance in comparison with the optical system  40  according to each of the first to third embodiments. In such a configuration as well, both of the downsizing and the satisfactory optical performance of the optical system  40  can be achieved by appropriately designing the rear lens unit  42 . 
     Numerical Embodiments 
     Numerical Embodiments 1 to 4 of the optical system  40  corresponding to the first to fourth embodiments described above will be described below. In surface data, the surface number indicates the position of the lens surface in the order when counted from the object side, r indicates the curvature radius [mm] of the lens surface, and d indicates the distance [mm] on the optical axis between the adjacent lens surfaces. Further, nd indicates the refractive index with respect to the d-line (a wavelength of 587.6 nm) of a medium between the adjacent lens surfaces, and vd indicates the Abbe number based on the d-line of the medium between the adjacent lens surfaces. 
     In various kinds of data, the optical magnification 13 indicates the magnification (at the time of illumination) of the optical system  40 , and the entrance pupil diameter indicates the diameter [mm] of the entrance pupil of the optical system  40  when the target object  100  side is the incident side (at the time of light receiving). Further, the shift amount indicates the distance [mm] between the central axis OAM and the optical axis OAL in the YZ cross-section, and the tilt amount indicates the angle [degree] formed by the central axis OAM and the optical axis OAL in the YZ cross-section. 
     The ray angle data indicates the angle [degree] between the optical axis OAL and each of the principal ray (central ray) and the marginal rays (upper and lower rays) among the reflected light from the target object  100  illuminated by the illumination light at the central field angle in the scan range of the drive mirror  32 . Here, the indicated data includes the angle of each ray immediately before being incident on the lens surface closest to the object in the optical system  40 , the angle of each ray immediately after being output from the lens surface closest to the deflection unit in the optical system  40 , and the difference between these angles. 
     
       
         
           
               
             
               
                   
               
               
                 (Numerical Embodiment 1) 
               
               
                   
               
             
            
               
                 Surface data 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface  
                   
                   
                   
                   
               
               
                 Lens 
                 number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 L111 
                 1 
                 41.107 
                 6.30 
                 2.001 
                 29.139 
               
               
                   
                 2 
                 119.720 
                 10.91 
                   
                   
               
               
                 L112 
                 3 
                 −60.247 
                 2.00 
                 1.516 
                 64.141 
               
               
                   
                 4 
                 1918.293 
                 25.88 
                   
                   
               
               
                 L113 
                 5 
                 −654.854 
                 3.20 
                 2.001 
                 29.139 
               
               
                   
                 6 
                 −55.770 
                 15.63 
                   
                   
               
               
                 L114 
                 7 
                 −17.579 
                 1.30 
                 1.516 
                 64.141 
               
               
                   
                 8 
                 −46.620 
                 28.47 
                   
                   
               
               
                 L115 
                 9 
                 −495.348 
                 3.10 
                 2.001 
                 29.139 
               
               
                   
                 10 
                 −68.368 
                 4.50 
                   
                   
               
               
                 L116 
                 11 
                 82.093 
                 3.50 
                 2.001 
                 29.139 
               
               
                   
                 12 
                 −1551.590 
                 0.30 
                   
                   
               
               
                 L117 
                 13 
                 35.125 
                 4.10 
                 2.001 
                 29.139 
               
               
                   
                 14 
                 67.954 
                 0.30 
                   
                   
               
               
                 L118 
                 15 
                 23.198 
                 3.80 
                 2.001 
                 29.139 
               
               
                   
                 16 
                 31.108 
               
               
                   
               
            
           
           
               
            
               
                 Various kinds of data 
               
            
           
           
               
               
            
               
                 Optical magnification β 
                 3.8 
               
               
                 Entrance pupil diameter [mm] 
                 14.8 
               
               
                 Shift amount [mm] 
                 4.1 
               
               
                 Tilt amount [degree] 
                 9.6 
               
               
                   
               
            
           
           
               
            
               
                 Ray angle data 
               
            
           
           
               
               
               
               
            
               
                   
                 Object side 
                 Deflection unit side 
                 Difference 
               
               
                   
               
               
                 Upper  
                 0.041 
                 0.050 
                 0.009 
               
               
                 ray 
                   
                   
                   
               
               
                 Principal  
                 0.035 
                 0.000 
                 −0.035 
               
               
                 ray 
                   
                   
                   
               
               
                 Lower  
                 0.028 
                 −0.052 
                 −0.080 
               
               
                 ray 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                   
               
               
                 (Numerical Embodiment 2) 
               
               
                   
               
             
            
               
                 Surface data 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface 
                   
                   
                   
                   
               
               
                 Lens 
                 number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 L121 
                 1 
                 39.383 
                 7.25 
                 2.001 
                 29.139 
               
               
                   
                 2 
                 202.116 
                 9.86 
                   
                   
               
               
                 L122 
                 3 
                 −52.981 
                 2.00 
                 1.516 
                 64.141 
               
               
                   
                 4 
                 −401.197 
                 24.46 
                   
                   
               
               
                 L123 
                 5 
                 −228.481 
                 3.16 
                 2.001 
                 29.139 
               
               
                   
                 6 
                 −40.023 
                 10.55 
                   
                   
               
               
                 L124 
                 7 
                 −13.435 
                 1.30 
                 1.516 
                 64.141 
               
               
                   
                 8 
                 363.802 
                 13.05 
                   
                   
               
               
                 L125 
                 9 
                 −28.664 
                 2.80 
                 2.001 
                 29.139 
               
               
                   
                 10 
                 −26.765 
                 5.12 
                   
                   
               
               
                 L126 
                 11 
                 −343.608 
                 3.38 
                 2.001 
                 29.139 
               
               
                   
                 12 
                 −63.244 
                 0.30 
                   
                   
               
               
                 L127 
                 13 
                 85.978 
                 3.54 
                 2.001 
                 29.139 
               
               
                   
                 14 
                 −523.346 
                 0.30 
                   
                   
               
               
                 L128 
                 15 
                 34.916 
                 4.10 
                 2.001 
                 29.139 
               
               
                   
                 16 
                 70.744 
                 0.30 
                   
                   
               
               
                 L129 
                 17 
                 23.759 
                 3.72 
                 2.001 
                 29.139 
               
               
                   
                 18 
                 32.157 
               
               
                   
               
            
           
           
               
            
               
                 Various kinds of data 
               
            
           
           
               
               
            
               
                 Optical magnification β 
                 3.5 
               
               
                 Entrance pupil diameter [mm] 
                 14.8 
               
               
                 Shift amount [mm] 
                 4.3 
               
               
                 Tilt amount [degree] 
                 9.4 
               
               
                   
               
            
           
           
               
            
               
                 Ray angle data 
               
            
           
           
               
               
               
               
            
               
                   
                 Object side 
                 Deflection unit side 
                 Difference 
               
               
                   
               
               
                 Upper ray 
                 0.039 
                 0.069 
                 0.030 
               
               
                 Principal ray 
                 0.033 
                 0.000 
                 −0.033 
               
               
                 Lower ray 
                 0.028 
                 0.103 
                 0.075 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                   
               
               
                 (Numerical Embodiment 3) 
               
               
                   
               
             
            
               
                 Surface data 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface  
                   
                   
                   
                   
               
               
                 Lens 
                 number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 L131 
                 1 
                 55.792 
                 4.65 
                 2.001 
                 29.139 
               
               
                   
                 2 
                 199.307 
                 8.49 
                   
                   
               
               
                 L132 
                 3 
                 −110.557 
                 2.00 
                 1.516 
                 64.141 
               
               
                   
                 4 
                 2336.958 
                 63.19 
                   
                   
               
               
                 L133 
                 5 
                 −717.748 
                 2.60 
                 2.001 
                 29.139 
               
               
                   
                 6 
                 −57.176 
                 3.76 
                   
                   
               
               
                 L134 
                 7 
                 −27.455 
                 1.30 
                 1.516 
                 64.141 
               
               
                   
                 8 
                 −46.650 
                 44.86 
                   
                   
               
               
                 L135 
                 11 
                 73.363 
                 3.67 
                 2.001 
                 29.139 
               
               
                   
                 12 
                 10121.070 
                 0.30 
                   
                   
               
               
                 L136 
                 13 
                 34.226 
                 4.19 
                 2.001 
                 29.139 
               
               
                   
                 14 
                 64.311 
                 0.30 
                   
                   
               
               
                 L137 
                 15 
                 24.042 
                 3.75 
                 2.001 
                 29.139 
               
               
                   
                 16 
                 31.557 
               
               
                   
               
            
           
           
               
            
               
                 Various kinds of data 
               
            
           
           
               
               
            
               
                 Optical magnification β 
                 3.5 
               
               
                 Entrance pupil diameter [mm] 
                 14.8 
               
               
                 Shift amount [mm] 
                 4.1 
               
               
                 Tilt amount [degree] 
                 9.5 
               
               
                   
               
            
           
           
               
            
               
                 Ray angle data 
               
            
           
           
               
               
               
               
            
               
                   
                 Object side 
                 Deflection unit side 
                 Difference 
               
               
                   
               
               
                 Upper  
                 0.038 
                 −0.014 
                 −0.052 
               
               
                 ray 
                   
                   
                   
               
               
                 Principal  
                 0.032 
                 0.000 
                 −0.032 
               
               
                 ray 
                   
                   
                   
               
               
                 Lower  
                 0.026 
                 0.068 
                 0.042 
               
               
                 ray 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                   
               
               
                 (Numerical Embodiment 4) 
               
               
                   
               
             
            
               
                 Surface data 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Surface  
                   
                   
                   
                   
               
               
                 Lens 
                 number 
                 r 
                 d 
                 nd 
                 vd 
               
               
                   
               
               
                 L141 
                 1 
                 34.971 
                 5.10 
                 2.001 
                 29.139 
               
               
                   
                 2 
                 153.153 
                 9.60 
                   
                   
               
               
                 L142 
                 3 
                 −31.435 
                 3.50 
                 1.516 
                 64.141 
               
               
                   
                 4 
                 −157.459 
                 12.40 
                   
                   
               
               
                 L143 
                 5 
                 −131.553 
                 4.60 
                 1.516 
                 64.141 
               
               
                   
                 6 
                 −32.263 
                 1.70 
                   
                   
               
               
                 L144 
                 7 
                 179.847 
                 3.30 
                 2.001 
                 29.139 
               
               
                   
                 8 
                 −85.115 
                 8.30 
                   
                   
               
               
                 L145 
                 9 
                 −19.306 
                 6.50 
                 1.516 
                 64.141 
               
               
                   
                 10 
                 31.578 
                 21.60 
                   
                   
               
               
                 L146 
                 11 
                 −290.125 
                 3.40 
                 2.001 
                 29.139 
               
               
                   
                 12 
                 −69.894 
                 5.00 
                   
                   
               
               
                 L147 
                 13 
                 133.185 
                 3.60 
                 2.001 
                 29.139 
               
               
                   
                 14 
                 −361.726 
                 0.30 
                   
                   
               
               
                 L148 
                 15 
                 50.144 
                 4.20 
                 2.001 
                 29.139 
               
               
                   
                 16 
                 112.513 
                 0.30 
                   
                   
               
               
                 L149 
                 17 
                 25.536 
                 5.00 
                 2.001 
                 29.139 
               
               
                   
                 18 
                 36.897 
               
               
                   
               
            
           
           
               
            
               
                 Various kinds of data 
               
            
           
           
               
               
            
               
                 Optical magnification β 
                 2.0 
               
               
                 Entrance pupil diameter [mm] 
                 14.8 
               
               
                 Shift amount [mm] 
                 6.0 
               
               
                 Tilt amount [degree] 
                 15.6 
               
               
                   
               
            
           
           
               
            
               
                 Ray angle data 
               
            
           
           
               
               
               
               
            
               
                   
                 Object side 
                 Deflection unit side 
                 Difference 
               
               
                   
               
               
                 Upper  
                 0.080 
                 0.138 
                 0.058 
               
               
                 ray 
                   
                   
                   
               
               
                 Principal  
                 0.073 
                 0.000 
                 −0.073 
               
               
                 ray 
                   
                   
                   
               
               
                 Lower  
                 0.066 
                 −0.226 
                 −0.292 
               
               
                 ray 
               
               
                   
               
            
           
         
       
     
     Various numerical values in Numerical Embodiments 1 to 4 are indicated in Table 1. As indicated in Table 1, the optical system  40  according to any of Numerical Embodiments 1 to 4 satisfies the above-described conditional expressions (1) to (7). 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 First 
                 Second 
                 Third 
                 Fourth 
               
               
                   
                   
                 embod- 
                 embod- 
                 embod- 
                 embod- 
               
               
                   
                   
                 iment 
                 iment 
                 iment 
                 iment 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 ff [mm] 
                 74.936 
                 59.738 
                 89.411 
                 44.766 
               
               
                   
                 fr [mm] 
                 19.935 
                 17.000 
                 25.329 
                 22.532 
               
               
                   
                 R1B1  
                 23.198 
                 23.759 
                 24.042 
                 25.536 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                   
                 R2B1  
                 31.108 
                 32.157 
                 31.557 
                 36.897 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                   
                 R1B2  
                 35.125 
                 34.916 
                 34.226 
                 50.144 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                   
                 R2B2  
                 67.954 
                 70.744 
                 64.311 
                 112.513 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                   
                 Lr [mm] 
                 19.600 
                 23.566 
                 12.206 
                 21.800 
               
               
                   
                 Li [mm] 
                 28.470 
                 13.048 
                 44.858 
                 21.600 
               
               
                   
                 NPave 
                 2.001 
                 2.001 
                 2.001 
                 2.001 
               
               
                   
                 NNave 
                 1.516 
                 1.516 
                 1.516 
                 1.516 
               
               
                   
                 ffPave  
                 62.271 
                 49.389 
                 71.144 
                 64.231 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                   
                 ffNave  
                 −85.616 
                 −72.885 
                 −170.964 
                 −98.477 
               
               
                   
                 [mm] 
                   
                   
                   
                   
               
               
                 Conditional 
                 ff/fr 
                 3.759 
                 3.514 
                 3.530 
                 1.987 
               
               
                 expression  
                   
                   
                   
                   
                   
               
               
                 (1) 
                   
                   
                   
                   
                   
               
               
                 Conditional 
                 (R1B1 +  
                 −6.865 
                 −6.658 
                 −7.398 
                 −5.495 
               
               
                 expression  
                 R2B1)/ 
                   
                   
                   
                   
               
               
                 (2) 
                 (R1B1 −  
                   
                   
                   
                   
               
               
                   
                 R2B1) 
                   
                   
                   
                   
               
               
                 Conditional 
                 (R1B2 +  
                 −3.140 
                 −2.949 
                 −3.275 
                 −2.608 
               
               
                 expression  
                 R2B2)/ 
                   
                   
                   
                   
               
               
                 (3) 
                 (R1B2 −  
                   
                   
                   
                   
               
               
                   
                 R2B2) 
                   
                   
                   
                   
               
               
                 Conditional 
                 Lr/Li 
                 0.688 
                 1.806 
                 0.272 
                 1.009 
               
               
                 expression  
                   
                   
                   
                   
                   
               
               
                 (4) 
                   
                   
                   
                   
                   
               
               
                 Conditional 
                 NPave/ 
                 1.320 
                 1.320 
                 1.320 
                 1.320 
               
               
                 expression  
                 NNave 
                   
                   
                   
                   
               
               
                 (5) 
                   
                   
                   
                   
                   
               
               
                 Conditional 
                 ffPave/ 
                 −0.727 
                 −0.678 
                 −0.416 
                 −0.652 
               
               
                 expression  
                 ffNave 
                   
                   
                   
                   
               
               
                 (6) 
                   
                   
                   
                   
                   
               
               
                 Conditional 
                 fr/Lr 
                 1.017 
                 0.721 
                 2.075 
                 1.034 
               
               
                 expression  
                   
                   
                   
                   
                   
               
               
                 (7) 
               
               
                   
               
            
           
         
       
     
     [In-Vehicle System] 
       FIG. 7  illustrates a configuration of an in-vehicle system (driving assistance apparatus)  1000  including the optical apparatus  1  according to the present exemplary embodiment. The in-vehicle system  1000  is held by a movable moving body (moving apparatus) such as an automobile (vehicle), and used to assist the driving (operation) of the vehicle, based on the distance information of a target object such as an obstacle or a pedestrian near the vehicle acquired by the optical apparatus  1 . 
       FIG. 8  is a schematic diagram of a vehicle (moving apparatus)  500  including the in-vehicle system  1000 .  FIG. 8  illustrates a case where a distance measurement range (detection range) of the optical apparatus  1  is set in front of the vehicle  500 , but the distance measurement range may be set behind or beside the vehicle  500 . 
     As illustrated in  FIG. 7 , the in-vehicle system  1000  includes the optical apparatus  1 , a vehicle information acquisition apparatus  200 , a control apparatus (electronic control unit (ECU))  300 , and a warning apparatus (warning unit)  400 . In the in-vehicle system  1000 , the control unit  60  included in the optical apparatus  1  has a function as a distance acquisition unit (acquisition unit) and a collision determination unit (determination unit). However, the distance acquisition unit and the collision determination unit may each be provided as a unit separate from the control unit  60  in the in-vehicle system  1000 , or may each be provided outside the optical apparatus  1  (e.g., inside the vehicle  500 ), as needed. Alternatively, the control apparatus  300  may be used as the control unit  60 . 
       FIG. 9  is a flowchart illustrating an example of operation of the in-vehicle system  1000  according to the present exemplary embodiment. The operation of the in-vehicle system  1000  will be described below with reference to this flowchart. 
     First, in step S 1 , the light source unit  10  of the optical apparatus  1  illuminates a target object near the vehicle, and the control unit  60  acquires the distance information of the target object, based on a signal output by the light receiving unit  50  by receiving the reflected light from the target object. In step S 2 , the vehicle information acquisition apparatus  200  acquires vehicle information including the speed, yaw rate, and steering angle of the vehicle. Subsequently, in step S 3 , the control unit  60  determines whether the distance to the target object is within the range of a preset distance, using the distance information acquired in step S 1  and the vehicle information acquired in step S 2 . 
     This makes it possible to determine whether the target object is present within the preset distance from the vehicle, and determine a possibility of a collision between the vehicle and the target object. Step S 1  and step S 2  may be performed in reverse order, or may be performed in parallel. If the target object is present within the preset distance (YES in step S 4 ), the operation proceeds to step S 4 . In step S 4 , the control unit  60  determines that “there is a possibility of a collision”. If the target object is not present within the preset distance (NO in step S 4 ), the operation proceeds to step S 5 . In step S 5 , the control unit  60  determines that “there is no possibility of a collision”. 
     Next, in the case where the control unit  60  determines that “there is a possibility of a collision”, the control unit  60  notifies (transmits) this determination result to the control apparatus  300  and the warning apparatus  400 . In this case, in step S 6 , the control apparatus  300  controls the vehicle based on the determination result from the control unit  60 , and in step S 7 , the warning apparatus  400  warns a user (driver) of the vehicle based on the determination result from the control unit  60 . The determination result may be notified at least one of the control apparatus  300  and the warning apparatus  400 . 
     The control apparatus  300  controls the vehicle, for example, to apply a brake, release the accelerator, turn a steering wheel, and suppress the output of an engine or a motor by generating a control signal for generating a braking force on each wheel. The warning apparatus  400  gives a warning to the driver by, for example issuing a warning sound, displaying warning information on a screen of a car navigation system, or vibrating a seat belt or steering wheel. 
     As described above, the in-vehicle system  1000  according to the present exemplary embodiment can detect the object and measure the distance by performing the above-described processing, so that the collision between the vehicle and the object can be avoided. In particular, the distance can be accurately measured by applying the optical apparatus  1  according to each of the above-described embodiments to the in-vehicle system  1000 , so that the target object can be accurately detected and the collision can be accurately determined. 
     In the present exemplary embodiment, the in-vehicle system  1000  is applied to the driving assistance (collision damage reduction), but is not limited thereto. The in-vehicle system  1000  may be applied to cruise control (including all vehicle speed tracking function) and automatic driving. The in-vehicle system  1000  is applicable not only to a vehicle such an automobile but also to a moving body such as a ship, an aircraft, or an industrial robot. The in-vehicle system  1000  is also applicable not only to a moving body but also to various apparatuses that use object recognition of an Intelligent Transport System (ITS), a surveillance system, or the like. 
     The in-vehicle system  1000  and the moving apparatus  500  may include a notification apparatus (notification unit) for notifying the manufacturer of the in-vehicle system  1000  and the seller (dealer) of the moving apparatus  500  of the fact that the moving apparatus  500  has collided with an obstacle in a case where this collision has occurred. For example, an apparatus that transmits information (collision information) about the collision between the moving apparatus  500  and the obstacle to a preset external destination by e-mail or the like can be adopted as the notification apparatus. 
     In this way, the configuration is adopted in which the notification apparatus automatically notifies the collision information, so that measures such as an inspection and a repair after the collision can be immediately performed. The destination of the collision information may be an arbitrary place set by a user, such as an insurance company, a medical institution, or the police. 
     The notification apparatus may be configured to notify the destination of failure information of each part and consumption information of consumables in addition to the collision information. The presence or absence of the collision may be detected using the distance information acquired based on the output from the above-described light receiving unit  50 , or may be detected using another detection unit (sensor). 
     [Modifications] 
     While the present invention has been described above with reference to the exemplary embodiment and embodiments, the present invention is not limited to these exemplary embodiment and embodiments, and various combinations, modifications, and changes can be made within the scope of the gist of the present invention. 
     For example, the optical system  40  according to each of the embodiments may be an optical system that increases the diameter of the reflected light from the target object, as needed, instead of being the telescope that reduces the diameter of the reflected light from the target object  100 . The optical system  40  may also be an optical system having refractive power as a whole, as needed, instead of being the afocal system. 
     In each of the embodiments, the members are integrated (integrally held), but may each be configured as a separate member as needed. For example, the light source unit  10  and the light receiving unit  50  may each be detachable from the light guiding unit  20  or the deflection unit  30 . In that case, holding members (housings) that hold the respective members may be provided with connection portions (coupling portions) for connecting to each other. In this case, to improve the accuracy of the positioning between the light source unit  10  and the light guiding unit  20 , the diaphragm  13  may be disposed inside the light guiding unit  20  and held by a holding member common to the light-guiding member. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Applications No. 2021-007468, filed Jan. 20, 2021, No. 2021-007469, filed Jan. 20, 2021, and No. 2021-007470, filed Jan. 20, 2021, which are hereby incorporated by reference herein in their entirety.