Abstract:
A system for generating images of a specimen comprises: means for generating a signal representation of a shadow image of the specimen; means for increasing a resolution of the shadow image; magnifying means for generating a signal representation of an image of a scanning area of the specimen; display means for providing simultaneous displays of the images; and means for identifying the scanning area on the display of the shadow image.

Description:
RELATED APPLICATIONS  
       [0001]     This patent application is related to U.S. Pat. No. 4,777,525 issued to Kendall Preston, Jr. on Oct. 11, 1988 and is hereby incorporated by reference. The present U.S. patent application Ser. No. and the related Patent are commonly owned.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention:  
         [0003]     This invention relates generally to electro-optical scanning systems and, more particularly, to scanning systems that involve indirect viewing (via a television intermediary) of an image field at a plurality of magnifications wherein resolution of a shadow image is greatly enhanced.  
         [0004]     2. Description of the Prior Art:  
         [0005]     Automatic systems for scanning and analyzing microscope field images have been previously developed, the most notable being the automatic scanning and examination of blood cells. However, the interpretive ability of visual examination by a human observer is still generally required for accurate analysis, particularly with respect to, for example, histological specimens. Typical microscopic examination of a specimen involves the examination of the specimen by direct viewing through oculars using various objective elements to provide a plurality of magnifications. Different magnifications can be accomplished by selectively positioning the various objective lenses located in a turret immediately over the specimen. By rotation of the turret, objective lenses of different magnifications can be used to examine the specimen. The general procedure is to scan a specimen at relatively low magnification and then to use higher magnification to examine selected specimen areas in detail.  
         [0006]     The direct viewing process, through widely utilized, has several disadvantages. First, the microscope field images at a plurality of magnifications cannot be viewed simultaneously. In addition, the manual positioning of the turret containing the plurality of lenses frequently makes more detailed examination of a selected specimen region ambiguous. This is due to the lack of knowledge of the precise spatial relationship between the fields viewed at different magnifications. Furthermore, viewing of a specimen through an ocular for a long period of time can be tiring. Finally, photography and storage of images can require a separate operation, frequently disturbing the examination routine.  
         [0007]     Similar problems can be found in examination of images recorded on high-resolution photographic emulsions such as those used in aerial photography and in the storage of documents on microfiche. Typically, a search for certain selected information is conducted at relatively low magnification. Examination of areas of the low magnification image in which the selected information may be present can then be performed at a higher magnification until the presence of the selected information is confirmed or rejected.  
         [0008]     U.S. Pat. No. 4,777,525 discloses a microscope scanning system that can view and present to the user images of a specimen under a plurality of magnifications simultaneously, can accurately determine the spatial relationships between the plurality of images and can conveniently store and retrieve the images for future examination and for comparison purposes. However, the line scan diode array sensor disclosed only provides a low magnification non-optical image of a specimen commonly called a shadow image.  
         [0009]     Therefore, a need existed to provide an improved microscope scanning system that can view and present to the user images of a specimen under a plurality of magnifications simultaneously, that can accurately determine the spatial relationships between the plurality of images and can conveniently store and retrieve the images for future examination and for comparison purposes. The improved microscope scanning system will increase the magnification of the non-optical image of a specimen.  
       SUMMARY OF THE INVENTION  
       [0010]     In accordance with one embodiment of the present invention, it is an object of the present invention to provide an improved optical scanning system.  
         [0011]     It is another object of the present invention to provide an improved optical scanning system that will increase the resolution of the non-optical image of a specimen (i.e., shadow image).  
       BRIEF DESCRIPTION OF THE EMBODIMENTS  
       [0012]     In accordance with one embodiment of the present invention, a system for generating images of a specimen is disclosed. The system comprises: means for generating a signal representation of a shadow image of the specimen; means for increasing the resolution of the shadow image; magnifying means for generating a signal representation of an image of a scanning area of the specimen; display means for providing simultaneous displays of the images; and means for identifying the scanning area on the display of the shadow image.  
         [0013]     In accordance with another embodiment of the present invention, a system for generating images of a specimen is disclosed. The system comprises: means for generating a signal representation of a shadow image of the specimen; means for increasing a resolution of the shadow image; magnifying means for generating a signal representation of an image of a scanning area of the specimen; display means for providing simultaneous displays of the images; and means for identifying the scanning area on the display of the shadow image. The means for increasing a resolution of the shadow image comprises a faceplate placed over said specimen. The faceplate transfers illumination from a light source with less distortion than the prior art to generate a signal representation of a shadow image of the specimen. The faceplate is comprised of a plurality of fiber optic threads coupled together. The faceplate is tapered to increase a pixel array of the fiber optic threads.  
         [0014]     The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, as well as a preferred mode of use, and advantages thereof, will best be understood by reference to the following detailed description of illustrated embodiments when read in conjunction with the accompanying drawings.  
         [0016]      FIGS. 1   a  and  1   b  are perspective views of apparatus for generating a signal representation of a shadow image and for providing a magnified image of a scanning area thereon in accordance with the present invention.  
         [0017]      FIG. 1   c  is a perspective view of the faceplate used to increase resolution of the shadow image of a specimen.  
         [0018]      FIG. 1   d  is a side view of a fiber optic thread used in the present invention.  
         [0019]      FIG. 2  is a block diagram of the preferred embodiment of the present invention.  
         [0020]      FIG. 3   a  is a schematic block diagram of an apparatus for providing a view, with selectable resolution of the scanning area.  
         [0021]      FIG. 3   b  is a schematic block diagram of an apparatus for generating and storing a signal representation of the image of the scanning area.  
         [0022]      FIG. 3   c  is a schematic block diagram of an apparatus for providing a view, with a selectable resolution of the scanning area. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     Referring to  FIG. 1   a  and  1   b , a substrate  2  carrying, for example, a histological specimen (mounted on a microscope slide) or a high-resolution photographic emulsion mounted on an appropriate substrate, is held by clips  3  in traverse member  1  and associated apparatus which position and control the motion of the specimen  2 . When placing the specimen  2  into the traverse member  1 , the traverse member  1  is moved by motor  6  and associated gears coupled to gear rack  5  so that the specimen moves past three line-scan diode-array sensors  7 ,  8  and  9 . A lamp  18  and a collimating lens  19  provide generally parallel light to the line-scan diode arrays as the slide is moved past these sensors. The signals from the sensors  7 ,  8  and  9  are digitized and the three separate color images are provided with proper registration so that a full image can be reconstructed and displayed from the three sets of output signals. The full color image is referred to hereinafter as a shadow image. It should be understood that a lens system is not used in producing the shadow image. The shadow image is of a larger area than attainable with a lens system. The specimen  2  is then positioned by traverse member  1  and associated apparatus so that radiation from lamp  17 A passing through condensing lens  15  illuminates the specimen. An image of the specimen is relayed by objective lens  10  to a plurality of optical detectors (not shown in these figures). The optical detectors are adapted to receive a plurality of magnified images of a scanning area of the specimen. The specimen  2  can be moved relative to the optical detectors by motors  17  and  6  along with the associated gears coupled to gear racks  5  and  16  respectively. These motors, gears and associated gear racks can control the position of the specimen  2  horizontally and vertically by positioning traverse member  4  relative to support member  11  and by positioning traverse member  1  relative to traverse member  4 , respectively. Focusing can be accomplished, in part, by movement of support member  11  in a direction parallel to the optical axis using flexure mount  12  supported by post  13  coupled to an optical bench (not shown) by mount  14 .  
         [0024]     The line scan diode array disclosed above provides a low magnification non-optical image (i.e., shadow image) of the specimen. Referring now to  FIG. 1   c , to increase the resolution of the shadow image, a faceplate  2 A may be positioned over the slide. The faceplate  2 A helps to concentrate the radiation from lamp  17 A passing through condensing lens  15  to better illuminate the specimen thereby increasing the resolution.  
         [0025]     The faceplate  2 A is comprised of a plurality of threads  2 C which are bonded together. The threads  2 C help to transmit the radiation from the lamp  17 A passing through condensing lens  15  with as little degradation as possible to better illuminate the specimen. In accordance with one embodiment of the present invention, fiber optic threads are used. As shown in  FIG. 1   d , in fiber optic threads  2 B, light travels through the core by constantly reflecting from the cladding since the angle of the light is always greater than the critical angle. Because the cladding does not absorb any light from the core, the light wave can travel great distances with little degradation.  
         [0026]     In general, a rectangular shaped faceplate  2 A may be used to concentrate the radiation from lamp  17 A passing through condensing lens  15  to better illuminate the specimen. However, the pixel array formed by the bonded fiber optic threads  2 B is limited by a standard rectangular shaped faceplate  2 A. Only a certain number of fiber optic threads  2 B can be bonded together in a standard rectangular formation that covers a predefined area.  
         [0027]     In order to increase the density of the pixel array and further enhance the resolution of the shadow image, a tapered faceplate  2 A′ may be used. A tapered faceplate  2 A′ will increase the density of the pixel array so that a greater number of fiber optic threads  2 B is present in a smaller area. A tapered faceplate  2 A′ is formed by heating a larger sized rectangular shaped faceplate. Once heated, the faceplate  2 A is stretched to form a narrower tapered end section  2 A″. The narrower tapered end section  2 A″ will have the same pixel array density as the larger sized rectangular shaped faceplate but in a smaller area. By using the narrower tapered end section  2 A″, one can double the pixel array density and thereby provide greater resolution of the shadow image.  
         [0028]     Referring next to  FIG. 2 , a block diagram of the control system, image generation system, image display system and image storage/retrieval system of the apparatus for  FIG. 1  is shown. For the photosensitive arrays or diode line scanners,  24 R(ed),  24 G(reen) and  24 B(lue), a synchronous line scan driver  23  ensures that the images resulting from activation of the photosensitive arrays can be aligned horizontally with the proper spatial relationship, while pulses to the vertical motor  6  as recorded by 14 bit-counter  22 ′ and the known separation between the diode line scanners provide vertical alignment. The red, green and blue diode line scanners provide output signals that are amplified and converted to digital signals in units  25   r ,  25   g  and  25   b . A Red-Green-Blue (RGB) frame storage unit  26  can be used to acquire and align these low resolution images and the resultant full-color shadow image can be displayed on the RGB display unit  27 .  
         [0029]     In order to acquire higher resolution images of a scanning area of the specimen, optical magnifying systems, such as are described with reference to  FIG. 3   a ,  FIG. 3   b  and  FIG. 3   c  can be used. The magnified image is focused on a photodetecting device, such as a vidicon. The internal photodetector scan control (not shown in these figures) controls the photosensors scanning each color. The internal camera scan control can apply these images either to a plurality of instantaneous displays  42  and  42 ′ or to a video to RGB converter  28  for storage in the RGB frame storage unit  26  for display on RGB display unit  27 . Shadow images from line scanners  24 R,  24 G and  24 B and the higher resolution images can be transferred to an archival signal storage unit  29  for later retrieval. Vertical and horizontal position control units,  20  and  20 ′, respectively, and horizontal and vertical stepping motors,  17  and  6 , respectively, can control the viewing location of the scanning area. Counters,  22  and  22 ′, respectively, can be used to determine the location of the scanning area on the shadow image. The focus control unit  20 ″ and focus stepping motor  21  (not shown in  FIG. 1 ) control the focus of the image of the scanning area by deflection of the flexure mount  12  shown in  FIG. 1 . The vertical control, horizontal control and focus control are governed by a central control system  40 , that can respond to input signals from, for example, function keys  41 . These function keys can also be used to control transfer of images to and from the RGB store, the low and high magnification scanners, and the image storage and retrieval unit. Function keys can also control a cursor on display unit  27  for the shadow image permitting the identification thereon of the scanning area. The function keys provide signals that are processed by the control system  40  and result in appropriate signals being applied to the controlled apparatus. The control system  40  is preferably a microprocessor which has the function keys  41  programmed to move the specimen to any desired position. The contents of the 14-Bit Counters  22 ,  22 ′,  22 ″ are inputs, as shown in  FIG. 2 , (which are gated by the input from the control system  40 ) to the RGB Frame Storage Unit  26 .  
         [0030]     Referring now to  FIG. 3   a , a first mechanism for providing a plurality of magnifications is shown. Light from specimen  2  is transmitted through a zoom lens optical system  39  to provide a variable controllable magnification. The light beam transmitted by the zoom lens system  39  is reflected off a dichroic filter  31   r  so that the red portion of the beam is imaged on photodetector  35   r . A second dichroic filter reflects the remaining green components of the beam from the remaining light at dichroic filter  31   g  and this reflected light is imaged on photodetector  35   g . The remaining blue component of the light is imaged on photodetector  35   b . Each photodetector ( 35 r,  35   g  and  35   b ) can be either a Charge-Coupled Device(CCD) array, vidicon or another type of light sensitive device. The outputs of these photodetectors provide the input to the video to RGB convertor  28 . For each setting of the zoom lens, an image may be converted and stored in RGB storage unit  26 , displayed by RGB monitor  27 , and stored, if desired, in archival storage unit  29 . Simultaneously the present image may be displayed on either monitor  42  or  42 ′ thus providing the required multi-resolution display.  
         [0031]     Referring next to  FIG. 3   b , another method of providing images at a plurality of magnification is shown. The light which illuminates specimen  2  is focused by lens system  34  to generate an optical image. A portion of the beam containing the red light is reflected from dichroic mirror  31   r  onto photodetecting array  35   r , while a second portion of light containing the green information is reflected from dichroic filter  31   g  onto photodetector  35   g . The remaining portion of the beam containing the blue light is imaged on photodetector  35   b . The output signals of the photodetecting arrays  35   r ,  35   g  and  35   b  are applied to analog-to-digital converters  38   r ,  38   g  and  38   b , and thereafter stored in multi-resolution signal storage unit  38 , wherein each color component has a separate storage region. A medium resolution image can be provided to display unit  42  ( FIG. 2 ) by the address generator associated with storage unit  38 , while a high resolution image can be provided to display  42 ′ ( FIG. 2 ) by a second address generator container in storage unit  38 . The multi-resolution video storage unit  38  (see  FIG. 3   b ) is used to simultaneously provide both a medium resolution video image and a high resolution video image. The medium resolution video image is produced by an address generator that takes a sub-sample of the entire image stored in multi-resolution video storage unit  38  whereas the high resolution video image is produced by an address generator which samples each point of a sub-region within the multi-resolution video storage unit  38 . The arrays  35   r ,  35   g  and  35   b , as well as the associated storage unit  38  contain the information for both the medium and the high resolution video images.  
         [0032]     Referring next to  FIG. 3   c , a third apparatus and method for producing images with a plurality of magnifications is shown. The light which illuminates the specimen  2  is collimated by lens system  34 . The portion of the beam containing the red light is reflected off dichroic filter  31   r . The light reflected from this dichroic filter is passed through beam splitter  32  so that a portion of the light is imaged by a lens system  36  on photodetector  35   r  and the remaining portion of the light reflected by the beam splitter is imaged by lens system  37  on photodetector  35   r  ′. The light passing directly through dichroic filter  31   r  has the green component reflected by dichroic filter  31   g . The light reflected from dichroic filter  31   g  is passed through beam splitter  32 ′ so that a portion of the light is imaged by a lens system  36 ′ on photodetector  35   g , while a second portion of the light is imaged by lens system  37 ′ on photo detector  35   g ′. The light passing through filter  31   g  is passed through beam splitter  32 ″. A portion of the light that is reflected is imaged by lens system  36 ″ on photodetector array  35   b  while a second portion of the light passing through the beam splitter  32 ″ is imaged by means of lens system  37 ″ on a photodetector  35   b ′. The lenses  36 ,  36 ′ and  36 ″ and  37 ,  37 ′ and  37 ″ provide two magnifications so that medium and high resolution images can be produced simultaneously. Photodetectors  35   r  and  35   r ′,  35   g  and  35   g ′,  35   b  and  35   b ′ provide, in combination, two simultaneous images at two different magnifications which are then transmitted to monitors  42  and  42 ′. These photodetectors can be CCD arrays or vidicons as is characteristic of television systems or other optical detection systems with suitable resolution.  
       Operation of the Preferred Embodiment  
       [0033]     In the image viewing system of the instant invention, single magnification direct viewing of the specimen at a given time is not employed. Instead, images at a multiplicity of magnification, with regions at higher magnification located within the lower resolution image, can be viewed simultaneously or in sequence. Indeed, in the preferred embodiment, three images can be viewed simultaneously so that a comparison can be made of areas of interest at the different magnifications. In addition, the presence of the cursor or similar identifying electronically generated optical cue on the monitor screen permits scanning by a higher resolution image of a lower resolution image to occur in a systematic manner. This scanning process avoids the loss of orientation typical of the direct-viewing, single-magnification microscope which occurs when the turret containing the various objective lenses are rotated from one position into another position. Because the information is digitized for viewing on the RGB monitors, this information is in a format that is also convenient for digital storage. Thus a plurality of regions of interest can be stored in the archival digital signal storage apparatus and withdrawn for simultaneous examination as desired. It will of course be clear that in attempting to find certain phenomena in a particular specimen, standard images of similar specimens can also be retrieved from the archival system for comparison purposes. Similarly it will be clear that the scanning of the specimen can be observed simultaneously at a plurality of viewing stations so that more than one investigator can provide his expertise during an examination.  
         [0034]     Three methods of providing simultaneously medium and high resolution images are described. The greatest flexibility, of course, is obtained in  FIG. 3   b  where, by simply sub-sampling the high resolution image formed by high resolution CCD arrays, a lower resolution image can be generated electronically without a plurality of additional optical channels. However, better image quality can be obtained from the arrangement of  FIG. 3   c  because separate optical elements are provided for each resolution. The arrangement of  FIG. 3   a  has the advantage of the simplicity of a single optical system but the disadvantage that simultaneous multi-resolution viewing is only obtainable using a separate frame store for each resolution.  
         [0035]     In the preferred embodiment, the use of stepper motors  6 ,  17 ,  21  and associated counters  22 ,  22 ′,  22 ″ permit convenient correlation of the location of the higher resolution image with the position of marker signals on the lower resolution image indicating the location of the higher resolution image. The quantized movement of the stepper motor provides precise identification of a current image position.  
         [0036]     The scanning system of the instant invention is particularly well suited for the analysis of histological specimens. In particular, the lower magnification images can be used as a guide to determine the region requiring inspection at higher magnification. However, it will be clear that the system can also be used for any image-bearing specimen such as a photographic emulsion.  
         [0037]     The array of low resolution diode-sensors has been found to provide a resolution of approximately one thousandth inch with readily available technology. The image produced by passing the specimen in front of the sensor array(s) can be digitally stored and displayed. By the procedures described above, the image developed from the low resolution sensor arrays can also be modified and images at various magnifications provided without the requirement for additional optical apparatus.  
         [0038]     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.