Patent Publication Number: US-2003234869-A1

Title: Camera for measuring distance to object

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of Invention  
       [0002] The invention relates to a camera for measuring the distance to an object and, in particular, to a camera that incorporates a laser range-measuring device.  
       [0003] 2. Related Art  
       [0004] The conventional digital camera has a CCD (Charge-Coupled Device) and a lens. An object forms an image on the CCD through the lens.  
       [0005] The conventional digital camera, however, can only be used to take images but is unable to measure the distance between the digital camera and the object.  
       SUMMARY OF THE INVENTION  
       [0006] In view of the foregoing, it is an objective of the invention to provide a camera for measuring the distance to an object. It includes a camera body and a laser range-measuring device, with which the distance to the object is measured.  
       [0007] Pursuant to the above objective, the disclosed camera includes a lens, a beam splitting device, an image detector, a microprocessor, a display, and a laser range-measuring device. The laser range-measuring device uses the beam splitting device and the lens to obtain the distance to the object. Furthermore, using the focal length, the width and height of the image on the image detector, and the distance between the camera and the object, the invention can compute the width and height of the object according to the geometrical optics.  
       [0008] The invention is featured in the combination of the beam splitting device that makes the combination of the camera and the laser range-measuring device possible.  
       [0009] The invention is also featured in that it can compute the width and height of the object according to the geometrical optics with the help of the distance to the object measured by the laser range-measuring device.  
       [0010] According to the above-mentioned features, the invention can further obtain the moving speed of the object.  
       [0011] One advantage of the invention is that the distance between the camera and an object can be obtained along with the object&#39;s image at the same time.  
       [0012] Another advantage of the invention is that the width and height of the object can be obtained according to the geometrical optics and, therefore, the moving speed of the object can be computed. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] The invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:  
     [0014]FIG. 1 schematically shows the disclosed digital camera;  
     [0015]FIG. 2 is a flowchart which schematically demonstrates how the microprocessor computes the distance between the camera and an object;  
     [0016]FIGS. 3A through 3C schematically show how the disclosed digital camera can be used to measure the size of the object on a plane perpendicular to the optical axis of the lens; and  
     [0017]FIGS. 4A to  4 C are a series of diagrams illustrating the relation between the image moving speed and the object moving speed. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0018] With reference to FIG. 1, the disclosed digital camera includes a zoom lens  2 , an image detector  10 , a microprocessor  5 , a beam splitting device  4 , a light emitter  6 , and a light receiver  7 . The beam splitting device  4  includes a first beam splitter  4   a  and a second beam splitter  4   b . The microprocessor  5  includes an image processor  11 , a range signal processor  8  and a CPU (Central Processing Unit)  12 .  
     [0019] As shown in the drawing, the light emitter  6 , such as a semiconductor light emitter, is controlled by the CPU  12  to send out a single-wavelength beam. This single-wavelength beam is reflected by the first beam splitter  4   a  and projected by the zoom lens  2  on an object (not shown). The object then reflects the single-wavelength beam through the zoom lens  2 , the first beam splitter  4   a  and the second beam splitter  4   b . The light signal is finally received by the light receiver  7 , e.g. an avalanche photodiode receiver. The light receiver converts the single-wavelength beam into an electric signal, which is then sent to the microprocessor  5 . In the microprocessor  5  the range signal processor  8  filters out noisy diffusive light. The extracted light signal is then used by the CPU  12  to compute the distance between the camera and the object.  
     [0020]FIG. 2 schematically demonstrates how the microprocessor computes the distance between the camera and the object. In step  1 , the CPU makes the light emitter to send out a single-wavelength beam at time t1. In step  2 , the light receiver receives the single-wavelength beam and converts it into an electric signal for the microprocessor to use. The single-wavelength beam includes that reflected from the object and those produced by other objects in the external environment. Therefore, the electric signal at the moment contains the range signal from the object and noisy diffusive light signals. In step  3 , the range signal processor is employed to filter out the noisy diffusive signals and sends the range signal produced at time t2 to the CPU. In step  4 , the CPU computes the distance D between the camera and the object using the formula D=C×(t2−t1)/2, where C is the speed of light.  
     [0021] With further reference to FIG. 1, after the CPU  12  obtains the distance between the camera and the object, the distance is shown on an image display  9 , such as an LCD (Liquid Crystal Display), via the image processor  11 . In addition, the image of the object is formed on the image detector  10 , e.g. a CCD , with the help of the zoom lens  2 . The light passing through the zoom lens  2  is reflected by the second beam splitter  4   b  and forms an image on the image detector  10 . The image detector converts the image into an image signal, which is directly sent to the image display  9  or first to the image processor  11  and then the image display  9 .  
     [0022] The disclosed digital camera further contains a motor  13  and an adjustable aperture  3 . The microprocessor  5  controls the motor  13  to adjust the focal length of the zoom lens  2  and the adjustable aperture to change the exposure.  
     [0023] Please refer to FIGS. 3A through 3C. As shown in FIG. 3A, the object  60  is placed at a front focal position D of the zoom lens  2 . Therefore, it forms an image  70  at a rear focal position f of the zoom lens  2 ; that is, the image is formed on the image detector  10 . With simultaneous reference to FIGS. 3A and 3B, the object  60  has a height H on the plane S perpendicular to the optical axis OA of the lens  2 . Its image on the image detector  10  has a height h, which can be determined from the product of the pixel height and the number of pixels occupied by the image in the corresponding direction on the image detector  10 . After the distance D between the camera and the object is obtained by the camera, the height H of the object can be computed by the CPU using the formula H=D×h/f. With reference to FIGS. 3A and 3C, if the object  60  has a width L on the plane D perpendicular to the optical axis OA of the lens  2 , it forms an image  70  with a width  1  on the image detector  10 . The width  1  can be determined from the product of the pixel width and the number of pixels occupied by the image in the corresponding direction on the image detector  10 . After the distance D between the camera and the object is obtained by the camera, the height L of the object can be computed by the CPU using the formula L=D×1/f.  
     [0024] With reference to FIG. 4A, at time t1 the image  70  is formed at a first position p1 on the image detector  10 . In FIG. 4B, the image  70  is at a second position p2 at time t2. Thus, the microprocessor computes the speed of the image between time t1 and time t2. When the object  60  moves at an unknown speed V on the plane perpendicular to the optical axis of the lens  2 , the image  70  moves at a speed v on the image detector  10 . Since the speed v of the image is already obtained by the number of pixels the image  70  crosses divided by the time interval, the CPU further calculates the speed V of the object on the plane S by multiplying the image speed v by the magnification power M of the zoom lens, where M=D/f. In other words, after obtaining the distance between the camera and the object, the camera can further figure out the object speed V.  
     [0025] While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.