Patent Publication Number: US-2009225219-A1

Title: Image pickup system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image pickup system that is constituted of an image pickup device with a solid-state image sensor and a processor device detachably connected to the image pickup device. 
     2. Description Related to the Prior Art 
     An image pickup system, e.g. an endoscope system is constituted of an electronic endoscope (image pickup device) and a processor device detachably connected to each other. The electronic endoscope has a solid-state image sensor for capturing an image of a human body cavity. The processor device receives an image signal from the solid-state image sensor and produces an image, while controlling the actuation of the solid-state image sensor. As the solid-state image sensor of the electronic endoscope, a CCD (charge-coupled device) image sensor (hereinafter simply called CCD) is widely used. 
     The CCD is categorized in two, that is, an interlace scan CCD and a progressive scan CCD according to difference in a scan method. Conventionally, the processor device is designed compatibly with the scan method of the CCD that the connected electronic endoscope is equipped with. Thus, for example, an electronic endoscope with a progressive scan CCD is not connectable to an interlace scan processor device such as NTSC. 
     Accordingly, JPA 2000-287203 discloses an endoscope system having a processor device that is compatible with any electronic endoscope with a progressive scan CCD or an interlace scan CCD. The processor device is provided with a signal processing circuit including two image processing circuits compatible with each scan method. 
     In the foregoing endoscope system, however, the processor device retrieves the scan method of the CCD that the electronic endoscope is equipped with, and switches between the two image processing circuits in accordance with retrieval result. Therefore, this endoscope system requires the signal processing circuit of large size and high costs. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an image pickup system having a processor device that is a simple construction, while it is compatible with any of a progressive scan image sensor and an interlace scan image sensor. 
     To achieve the above object, a processor device composing an image pickup system according to the present invention comprises a scan method detector, an interlace-to-progressive converter and an image processing circuit. The scan method detector detects which of a progressive scan image sensor and an interlace scan image sensor a solid-state image sensor is. When the solid-state image sensor is the interlace scan image sensor, the interlace-to-progressive converter converts an interlace signal outputted from the solid-state image sensor into a first progressive signal. The image processing circuit carries out image processing on the first progressive signal converted by the interlace-to-progressive converter or a second progressive signal outputted from the progressive scan image sensor. 
     It is preferable that the image processing circuit carries out edge enhancement processing and color enhancement processing. 
     The processor device may further comprise an image memory for storing an output signal from the image processing circuit as image data, an image reader for reading the image data out of the image memory by progressive scanning or interlace scanning, and an output section for outputting the image data read by the image reader to the outside. 
     According to the image pickup system of the present invention, when the solid-state image sensor is the interlace scan image sensor, the interlace-to-progressive converter converts the interlace signal outputted from the solid-state image sensor into the progressive signal, and then the image processing circuit performs image processing on the progressive signal. Therefore, the image processing circuit that applies the image processing on any type of image signals irrespective of the type of the solid-state image sensor facilitates reduction in circuit size and costs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For more complete understanding of the present invention, and the advantage thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view of an endoscope system; 
         FIG. 2  is a front view showing a tip of an electronic endoscope; 
         FIG. 3  is a block diagram showing the structure of the endoscope system; 
         FIG. 4  is an explanatory view of a progressive scan method; 
         FIG. 5A  is an explanatory view of an interlace scan method of an odd field; 
         FIG. 5B  is an explanatory view of an interlace scan method of an even field; and 
         FIG. 6  is an explanatory view of an I/P conversion method. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , an endoscope system  2  consists of an electronic endoscope  10 , a processor device  11  and a light source device  12 . The electronic endoscope  10  is provided with a flexible insert section  13  that is introduced into a human body cavity, an operation section  14  that is joined to a base end of the insert section  13 , and a universal cord  15  that is connected to the processor device  11  and the light source device  12 . 
     At an end of the insert section  13  is provided a distal portion  16  that contains a solid-state image sensor (CCD)  40  for capturing an optical image of a target body part to inspect. Behind the distal portion  16 , a bending portion  17  consisting of a number of linked ring-like segments is provided. By operating an angle knob  18  on the operation section  14 , a number of wires extending in the insert section  13  are pulled and pushed to flexibly bend the bending portion  17  from side to side and up and down. Thus, the distal portion  16  is directed to the target body part. The processor device  11  is electrically connected to the light source device  12  via the connector  19 , and has control over the electronic endoscope  10  and the light source device  12 . The light source device  12  supplies illumination light to the electronic endoscope  10 . 
     A base end of the universal cord  15  is coupled to a multi-connector  19 . The electronic endoscope  10  is connected to the processor device  11  and the light source device  12  via the connector  19 . 
     The processor device  11  feeds power to the electronic endoscope  10  through a transmission cable extending in the universal cord  15 , and controls the actuation of the CCD  40 . The processor device  11  receives an image signal outputted from the CCD  40 , and subjects the image signal to various kinds of signal processing to form image data. The processor device  11  converts an image data format suitably for connected external equipment such as a monitor and a recorder, and outputs the image data thereto. 
     As shown in  FIG. 2 , a front face  16   a  of the distal portion  16  is provided with an image capturing window  30 , lighting windows  31 , a medical instrument outlet  32  and an airing/watering nozzle  33 . The image capturing window  30  is disposed in the upper middle of the front face  16   a . Behind the image capturing window  30 , the CCD  40  is disposed through an objective lens system  43  and a prism  44  (refer to  FIG. 3 ). 
     The two lighting windows  31  symmetric with respect to the image capturing window  30  projects illumination light that is guided from the light source device  12  through a light guide  70  (refer to  FIG. 3 ) to the human body cavity. The medical instrument outlet  32  is connected to a medical instrument inlet  20  (refer to  FIG. 1 ) through a channel extending in the insert section  13 . A medical instrument with a needle, a diathermy knife or the like at its tip is inserted into the instrument inlet  20  in order to protrude the tip of the instrument from the instrument outlet  32  to the target body part. 
     The airing/watering nozzle  33  ejects water or air to the target body part in response to an operation on a airing/watering button  21  (refer to  FIG. 1 ) on the operation section  14 . 
     In  FIG. 3 , the endoscope  10  has the CCD  40  mounted in the distal portion  16 , and an AFE (analog front end processor device)  41  and a memory  42  in the operation section  14 . The CCD  40  is either a progressive scan CCD or an interlace scan CCD. The CCD  40  is so disposed that object light passing through the objective lens system  43  and the prism  44  is incident upon its light receiving surface. The light receiving surface is provided with a color filter including a plurality of color segments (for example, primary-colors filter of Bayer arrangement). 
     The AFE  41  includes a correlated double sampling circuit (CDS)  45 , an automatic gain controller (AGC)  46  and an analog-to-digital converter (A/D)  47 . The CDS  45  subjects the image signal outputted from the CCD  40  to correlated double sampling processing to remove reset noise and amplifier noise. Then, the AGC  46  amplifies the image signal by gain that the processor device  11  has designated. The A/D converter  47  converts the amplified image signal into a digital signal of a predetermined bit number, and inputs it to the processor device  11  through the connector  19 . 
     The memory  42  stores distinction data for distinguishing the scan method of the CCD  40 , that is, which of the progressive scan CCD and the interlace scan CCD the CCD  40  is. No sooner is the electronic endoscope  10  connected to the processor device  11 , than the processor device  11  reads out the distinction data (identity data). 
     The processor device  11  includes a CPU  48 , a timing generator (TG)  49 , an isolation device (ID)  50 , another CPU  51 , a digital signal processing circuit (DSP)  52 , an image memory  53 , a memory controller (MC)  54  as an image reader and an output circuit  55 . The CPU  48  controls the operation of the electric endoscope  10 . The TG  49  generates various timing pulses. The ID  50  electrically separates the electric endoscope  10  from the processor device  11 . The CPU  51  controls the operation of the processor device  11 . The DSP  52  subjects the image signal to signal processing. The image memory  53  stores image data. The MC  54  controls the actuation of the image memory  53 . The output circuit  55  converts the format of the image data stored on the image memory  53  suitably for external equipment and outputs. 
     Upon connecting the electric endoscope  10  to the processor device  11 , the CPU  48  that functions as a scan method detector for detecting the scan method of the CCD  40  reads the distinction data stored on the memory  42 . The CPU  48  drives the TG  49  on the basis of the detected scan method. The TG  49  generates drive pulses (a vertical/horizontal scanning pulse, a reset pulse and the like) for the CCD  40  and a synchronization pulse for the AFE  41  under the control of the CPU  48 , and inputs them into the electric endoscope  10  through the connector  19 . 
     When the CCD  40  is the progressive scan CCD, as shown in  FIG. 4 , the TG  49  inputs the drive pulses to the CCD  40  for successively reading the whole horizontal lines ( 1 ,  2 ,  3  . . . ) of a single picture frame out of a pixel area  40   a  of the CCD  40 . When the CCD  40  is the interlace scan CCD, on the other hand, the TG  49  inputs the drive pulses to the CCD  40  for alternately reading horizontal lines ( 1 ,  3 ,  5  . . . ) in an odd field shown in  FIG. 5A  and horizontal lines ( 2 ,  4 ,  6  . . . ) in an even field shown in  FIG. 5B  out of the pixel area  40   a.    
     In the case of the progressive scan CCD, the frequency of the drive pulses is so set as to output the image signals of 60 frames per second. In the case of the interlace scan CCD, the frequency of the drive pulses is so set as to output the image signals of 60 fields per second. 
     The TG  49  also feeds a synchronization pulse for signal processing to the DSP  52  and the CPU  51  through the ID  50 . The ID  50  is an isolator made of a photocoupler and the like. The image signal is inputted from the AFE  41  to the DSP  52  through the ID  50 . 
     The DSP  52  includes a digital video processing circuit for the progressive scan CCD (hereinafter called DVP for PRG)  56 , a digital video processing circuit for the interlace scan CCD (hereinafter called DVP for IL)  57 , a selector  58  for selecting one of the DVP for PRG  56  and the DVP for IL  57 , an interlace-to-progressive (I/P) converter  59  disposed subsequently to the DVP for IL  57 , and an image processing circuit  60 . The I/P converter  59  converts an interlace signal outputted from the DVP for IL  57  into a progressive signal. The image processing circuit  60  applies enhancement processing on the progressive signal, which is outputted from the DVP for PRG  56  or the I/P converter  59 . 
     The image signal from the AFE  41  is inputted into the selector  58  through the ID  50 . The CPU  51  communicates with the CPU  48  via the ID  50 , and judges the scan method of the CCD  40 . When the CCD  40  is the progressive scan CCD, the CPU  51  controls the selector  58  to input the image signal to the DVP for PRG  56 . When the CCD  40  is the interlace scan CCD, on the other hand, the image signal is inputted into the DVP for IL  57 . 
     The DVP for PRG  56  subjects the inputted progressive image signal to color separation, color interpolation, gain correction, white balance correction, gamma correction and the like, and converts the image signal into a YC signal consisting of a luminance signal (Y) and a chrominance signal (C). The DVP for IL  57 , in a like manner, subjects the inputted interlace image signal to color separation, color interpolation, gain correction, white balance correction, gamma correction and the like, and converts the image signal into a YC signal. 
     Of field signals (O 1 , E 1 , O 2 , E 2  . . . ) outputted every 1/60 second from the DVP for IL  57 , as shown in  FIG. 6 , the I/P converter  59  carries out interpolation processing on a pair of an odd field  80  and an even field  81  composing a single frame to generate an interpolation field  82 . To be more specific, for example, subjecting the horizontal line (scanning line) No.  1  of the odd field  80  and the horizontal line (scanning line) No.  2  of the even field  81  to the interpolation processing generates a first horizontal line of the interpolation field  82 . In the interpolation processing, the average of corresponding two pixels on the two horizontal lines Nos.  1  and  2  is obtained. Thus, the odd field signal O 1  and the even field signal E 1  form the interpolation field signal IN 1 , and the odd field signal O 2  and the even field signal O 2  form the interpolation field signal IN 2 . 
     Then, the odd field signal O 1  and the interpolation field signal IN 1  are combined to generate a frame signal F 1  with a period of 1/60 second. Combining the even field signal E 1  and the interpolation field signal IN 1  generates a frame signal F 2 . Frame signals F 3 , F 4  . . . are generated in a like manner. 
     In this combination processing, the interpolation field  82  is treated as the even field  81  when being combined with the odd field  80 . The interpolation field  82  is treated as the odd field  80 , when being combined with the even field  81 . Accordingly, the output signals (frame signals) F 1 , F 2  . . . from the I/P converter  59  have a progressive form, just as with the output signal from the DVP for PRG  56 . 
     To the image processing circuit  60 , the output signal from the DVP for PRG  56  or the output signal from the I/P converter  59  is inputted. Both of the signals are in the progressive form. The image processing circuit  60  subjects the signal to the enhancement processing such as edge enhancement and color enhancement, and successively inputs the enhanced frame signals into the image memory  53  as the image data. 
     The MC  54  controls image readout operation from the image memory  53 . The MC  54  reads the image data out of the image memory  53  on the basis of a command of the CPU  51  by progressing scanning shown in  FIG. 4  or interlace scanning shown in  FIGS. 5A and 5B . 
     The output circuit  55  includes a progressive digital-to-analog converter (hereinafter called PRG D/A)  61 , an interlace digital-to-analog converter (hereinafter called IL D/A)  62 , and a selector for choosing between the PRG D/A  61  and the IL D/A  62 . 
     The selector  63  chooses the PRG D/A  61  or the IL D/A  62  based on a command from the CPU  51 . The CPU  51  controls the selector  63  to successively input the progressive signals (frame signals), which are read out of the image memory  53  by the progressive scanning, to the PRG D/A  61 . The CPU  51  instead controls the selector  63  to successively input the interlace signals (field signals), which are readout of the image memory  53  by the interlace scanning, to the IL D/A  62 . 
     The PRG D/A  61  converts the frame signal into an analog progressive signal. The IL D/A  62 , on the other hand, converts the field signal into an analog interlace signal (NTSC or the like) To output terminals of the PRG D/A  61  and the IL D/A  62 , external equipment such as a monitor and a recorder compatible with its signal form is connected. 
     The light source device  12  is composed of a light source  64  such as a xenon lamp and a halogen lamp, a light source driver  65  for driving the light source  64 , an aperture stop mechanism  66  for adjusting the amount of light emitted from the light source  64 , a condenser lens  67  disposed in front of the aperture stop mechanism  66 , and a CPU  68  for controlling the light source driver  65  and the aperture stop mechanism  66  by communicating with the CPU  51 . The condense lens  67  condenses light passing through the aperture stop mechanism  66 , and leads it to an entry of the light guide  70 . The light propagates through the light guide  70 , and illuminates the target body part from the lighting windows  31  through a lens  71 , as described above. 
     In observing the target body part by the endoscope system  2 , the electronic endoscope  10  is first connected to the processor device  11  and the light source device  12  through the connector  19 , and the processor device  11  and the light source device  12  are turned on. Then, a doctor inserts the insert section  13  of the electronic endoscope  10  into the human body cavity. The CCD  40  captures images of the target body part, while the light illuminates there through the lighting windows  31 . Thus, the doctor observes the target body part with the monitor connected to the processor device  11 . 
     Upon connecting the electronic endoscope  10  to the processor device  11 , the CPU  48  of the processor device  11  reads the distinction data out of the memory  42  of the electronic endoscope  10  in order to detect which of the progressive scan CCD and the interlace scan CCD the electronic endoscope  10  is equipped with. The CPU  48  controls the TG  49  on the basis of the detected scan method and drives the CCD  40 . 
     An image signal outputted from the CCD  40  is subjected to analog signal processing, and converted into a digital signal in the AFE  41 . Then, the digital image signal is inputted into the processor device  11  through the connector  19 . In the processor device  11 , the image signal is inputted to the DSP  52 , and to the DVP for PRG  56  or the DVP for IL  57  in accordance with the scan method detected by the CPU  48 . In other words, the progressive image signal is inputted to the DVP for PRG  56 , and the interlace image signal is inputted to the DVP for IL  57 . 
     The image signal inputted to the DVP for PRG  56  is subjected to predetermined signal processing such as color separation, color interpolation, gain correction, white balance correction, gamma correction and the like. The image signal is then inputted to the image processing circuit  60  as a progressive YC signal. On the other hand, the image signal inputted to the DVP for IL  57  is also subjected to the predetermined signal processing such as color separation, color interpolation, gain correction, white balance correction, gamma correction and the like. The image signal is then inputted to the I/P converter  59  as an interlace YC signal. The I/P converter  59  converts the interlace YC signal into a progressive YC signal and inputs it to the image processing circuit  60 . As a result, the progressive YC signal is inputted to the image processing circuit  60  irrespective of the type of the CCD  40 . 
     The progressive YC signal is subjected to the enhancement processing in the image processing circuit  60 , and is stored frame-by-frame on the image memory  53  as image data. The CPU  51  controls the MC  54  in accordance with the type of the external equipment connected to the processor device  11 , and reads the image data out of the image memory  53  by the progressive scanning or the interlace scanning. The image data from the image memory  53  is inputted to the output circuit  55 . The image data is converted into an analog progressive signal or interlace signal in the output circuit  55 , and outputted to the external equipment. 
     According to the endoscope system  2 , as described above, when the CCD  40  is the interlace scan CCD, the processor device  11  first converts the interlace image signal from the CCD  40  into a progressive form, and carries out the image processing by the image processing circuit  60 . Therefore, obviating the need to provide a plurality of image processing circuits in accordance with the scan methods reduces circuit size and costs. 
     In the foregoing embodiment, the image processing circuit  60  subjects the progressive signal to enhancement processing. However, the present invention is not limited to it, the image processing circuit  60  may carry out characteristic extraction processing (text recognition) and the like in addition to the enhancement processing. 
     An I/P conversion method by the I/P converter  59  described above is just an example, and other methods are available. 
     The present invention has been explained by taking the endoscope system as an example of an image pickup system. The present invention, however, is applicable to any image pickup system such as an ultrasonic endoscope system which combines an electronic endoscope and an ultrasonic probe, a digital camera in which a lens barrel with image capturing function is detachable from a camera body having a display device such as a LCD, and a Web camera system which consists of a camera and a personal computer, as log as the image pickup system includes an image pickup device with a CCD and a processor device that are detachably connected to each other. 
     Although the present invention has been fully described by the way of the preferred embodiment thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein.