The present invention relates generally to imaging devices, and specifically to the construction of an imaging device such as an endoscope.
Many imaging devices, such as endoscopes, are inherently limited in size, and in many cases a small imaging device is advantageous. In the case of an endoscope, the smaller the dimensions of the endoscope, the less the impact on a patient being investigated. Consequently, any system which enables an endoscope to operate efficiently, while maintaining its small dimensions, would be beneficial.
In the fabrication of a pixel-based imaging device, there may typically be one or more “bad” pixels, or other factors such as the presence of fixed pattern noise, which affect the quality of operation of the device. Such factors may typically be compensated for by calibrating the device.
U.S. Pat. No. 6,417,885, to Suzuki et al., whose disclosure is incorporated herein by reference, describes a solid-state image pickup device with a separable circuit board. The disclosure states that an image pickup section incorporates a solid-state image pickup element chip, and that electronic parts for driving or controlling the image pickup section are mounted on a circuit board.
U.S. Patent Application 2009/0292169, to Mitani et al., whose disclosure is incorporated herein by reference, describes an electronic endoscope apparatus. The apparatus is stated to include an image pickup apparatus mounted at a distal end portion of an insertion portion, and an operation portion provided “consecutively” at the insertion portion.
Japanese Patent Publication 07-327923, to Saito et al., whose disclosure is incorporated herein by reference, describes an endoscope system. The system is stated to be easy to assemble and to be safe for medical use. The disclosure further states that these qualities are accomplished by assuring the cleanliness of an endoscope side connector arranged on a clean area side of a junction cable.
Japanese Patent Publication 05-154098, to Matsumoto, whose disclosure is incorporated herein by reference, describes a signal processing circuit for an electronic endoscope apparatus. The apparatus is claimed to achieve a simplification of circuitry and as well as ease of handling by using a “correlation double sampling circuit.” The circuit is stated to operate effectively, without converting operation timing, even when an electronic endoscope with a varied length is used.
Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.
An embodiment of the present invention provides an endoscope, including:
an image sensor which is configured to generate an image signal;
a control circuit which is mounted on the endoscope, wherein the control circuit is configured to drive the image sensor based on a control signal from a processor; and
a connector which is connected to the image sensor and which is configured to detachably connect to the control circuit, wherein the connector includes a memory storing calibration data with respect to the image sensor,
wherein the control circuit adjusts the image signal, based on the calibration data stored in the memory, to form a calibrated image signal, and transmits the calibrated image signal to the processor.
Typically, the endoscope includes a handle portion, and the control circuit is mounted on the handle portion.
An insertion portion may extend from the handle portion, the image sensor may be mounted on a distal end of the insertion portion, and the connector may be connected through the insertion portion to the control circuit.
Typically, the insertion portion detachably connects to the handle portion.
In a disclosed embodiment the calibration data corrects for a defective pixel of the image sensor.
In a further disclosed embodiment the calibration data corrects a color signal generated by the image sensor.
There is further provided, according to an embodiment of the present invention, an imaging apparatus including:
an image processor;
an endoscope connecting to the image processor, wherein the endoscope includes:
an image sensor which is configured to generate an image signal;
a control circuit which is mounted on the endoscope, wherein the control circuit is configured to drive the image sensor based on a control signal from the image processor; and
a connector which extends from the image sensor and which is configured to detachably connect to the control circuit, wherein the connector includes a memory storing calibration data with respect to the image sensor,
wherein the control circuit adjusts the image signal based on the calibration data stored in the memory to generate a calibrated image signal, and transmits the calibrated image signal to the image processor.
There is further provided, according to an embodiment of the present invention, a method of fabricating an endoscope including:
calibrating an image sensor so as to generate calibration data;
storing the calibration data in a memory mounted on a connector which is connected to the image sensor by a cable;
fitting the image sensor into a distal end of a tubular insertion portion configured to be inserted into a body cavity, the tubular insertion portion including a proximal end;
positioning the connector at the proximal end of the tubular insertion portion by passing the cable through the tubular insertion portion;
connecting the connector to a control circuit; and,
fitting the control circuit into a handle portion of the endoscope.
The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:
In an embodiment of the present invention an endoscope comprises an uncalibrated image sensor, typically in the form of a rectangular array of sensor elements or pixels. The endoscope also comprises a control circuit which is mounted on or in the endoscope, and the control circuit is configured to drive the image sensor, based on a control signal from a processor. The processor is typically incorporated into an endoscope control unit which operates the endoscope.
A connector is connected to the image sensor, typically via a cable, the connector, the cable, and the sensor forming a sensor assembly which is a stand-alone unit. The connector comprises a memory which stores calibration data for the image sensor. The calibration data typically comprises respective correction factors for each of the pixels of the image sensor, and the correction factors may be determined in a calibration process implemented for the sensor assembly.
During operation of the endoscope, the control circuit adjusts the uncalibrated signals from the image sensor, based on the calibration data stored in the memory of the connector, to form a calibrated image signal. The control circuit then transmits the calibrated image signal to the processor, which typically uses the calibrated signal to generate a display on a screen.
Forming a sensor assembly from an uncalibrated image sensor, and incorporating calibration data into a memory separated from the image sensor but which is within the sensor assembly, is an efficient and cost-effective technique for producing a calibrated sensor assembly. Such an assembly generates calibrated image signals from an uncalibrated sensor.
In contrast to prior art sensors, sensor assemblies, as exemplified in embodiments of the present invention, separate the connector, which has a memory with sensor calibration data stored therein, from the sensor itself. The separation enables the size of the sensor to be minimized, while maintaining the association of the sensor calibration data with the sensor. Minimization of the sensor size is a critical advantage, enabling the section of the endoscope wherein the sensor operates to have a considerably reduced size compared to prior art systems.
Endoscope 10 comprises a tubular insertion portion 12, which is formed as a small diameter tubular member 14 connected to a tubular member receptacle 16. Tubular member 14 is implemented to have an external diameter allowing it to be inserted into a body cavity, such as an abdomen, of a patient. A typical external diameter of member 14 is approximately 5 mm, and a typical internal diameter of the member is less than 5 mm. Typically, receptacle 16 has external dimensions significantly larger than the external diameter of member 14, and comprises one or more controls 18 for the endoscope. The insertion of member 14 may be via a trocar, normally used during an investigative procedure on the patient. For simplicity, neither the trocar nor the patient are shown in
An image sensor 20, components of which are shown in more detail in an inset 22, is mounted at the distal end of tubular member 14. Typically, sensor 20 is approximately cylindrical or is in the form of a rectangular parallelepiped, having a largest dimension smaller than the internal diameter of member 14. Image sensor 20 is uncalibrated, and comprises an optical assembly 24, typically formed of one or more lenses, which focuses light incident on the assembly from a scene being viewed by the sensor. Assembly 24 focuses the incident light (typically light returning from light that has been projected onto the abdomen wall) onto an array of sensing elements 28, which are also referred to herein as pixels 28. Array 26 typically comprises CCD (charge coupled device) and/or CMOS (complementary metal oxide semiconductor) pixels 28 arranged on a die in a rectangular grid.
Image sensor 20 is connected by a sensor cable 30 to a sensor connector 32. Cable 30 transfers signals, including video, control, timing, and power signals, between the sensor connector and the image sensor. Typically, cable 30 comprises one or more electrical conductors for transferring the signals, although in some embodiments at least some of the signals may be transferred using one or more optical fibers located within the cable. In one embodiment sensor connector 32 is formed as a printed circuit board (PCB) having a thickness of approximately 0.3 mm.
Sensor connector 32 is configured to connect to an endoscope control circuit 34. In one embodiment, the sensor connector comprises a tongue 36, and control circuit 34 comprises a first connector element 38 which is configured as a zero insertion force (ZIF) socket mating with the tongue. In a disclosed embodiment control circuit 34, described in more detail below, is mounted on a PCB 40.
PCB 40, together with the control circuit mounted on the PCB, is configured to fit into a handle portion 42 of the endoscope, and the PCB is also referred to herein as handle board 40. Control circuit 34 includes a second connector element 44 which is configured to mate with a first termination 46 of an endoscope control cable 48. A second termination 50 connects to an endoscope control unit, described in more detail below.
Unit 52 comprises a processor 54 communicating with a memory 56, and software for operation of the endoscope is stored in the memory. Results of operations performed by processor 54 may be presented to the operator of system 10 on a screen 58, which typically displays an image of the scene being imaged by sensor 20. The software used by processor 54 may be downloaded to the processor in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.
In one embodiment circuit 34 comprises a field programmable gate array (FPGA) 80, a non-volatile memory 82, and an electronic sub-circuit 84. FPGA 80 may be configured to convert data from sensor 20 to a format suitable for endoscope control unit 52, for example by converting serial data to parallel data or to a low voltage differential signaling (LVDS) format. FPGA 80 may also be configured to transfer communications, such as I2C communications, between endoscope control unit 52, sensor 20, and buttons or other controls on handle portion 42 that may be used by an operator of endoscope in controlling the endoscope. Non-volatile memory 82 may store data enabling endoscope control unit 52 to recognize which particular type of endoscope is being used. Typically, the FPGA receives an uncalibrated image signal from sensor 20, generates a calibrated signal using calibration data stored in memory 60, and transfers the calibrated signal to the control unit. The calibration data stored in memory 60 is described in more detail below. Electronic sub-circuit 84 facilitates the transfer of data to and from FPGA 80.
Calibration setup 100 is operated in the factory by a calibration control unit 102, which typically presents details of the calibration process to a professional performing the calibration on a display unit. Herein, by way of example, it is assumed that endoscope control unit 52 has been configured as calibration control unit 102, so that processor 54 of the endoscope control unit acts together with memory 56 as an overall controller for the calibration, including presenting calibration details on screen 58.
A calibration enclosure 104 is configured to receive sensor 20, so that the sensor is fixedly mounted to the unit. Enclosure 104 is configured to allow preset displays to be presented to sensor 20 on a screen 106, so that the sensor is able to acquire test images of the displays for calibration. Screen 106 may comprise a luminescent monitor, such as a flat screen LCD video monitor. Alternatively, screen 106 may be passive, and displays on the screen may be formed on the screen from illuminators 108 in enclosure 104. Further alternatively, the displays may be in the form of a target such as a Gretag-Macbeth color chart or a uniform grayscale chart, which could be paper or backlit. The displays presented on screen 106, i.e., the intensities and colors, or RGB (red, green, blue) levels, of individual regions of the screen, are under overall management of control unit 102.
In setup 100 connector 32 is inserted into first connector element 38 of control circuit 34, and the circuit is connected to calibration control unit 102 by cable 48. It will be appreciated that the arrangement of electronic components in setup 100 is substantially the same as the arrangement of the components internally in endoscope 10, so that in some embodiments, rather than assembly 70 being calibrated separately from its endoscope, the assembly may be calibrated while it is in its endoscope. In this case, tubular member 14, rather than sensor 20, is inserted into calibration enclosure 104.
In an initial step 150, sensor 20 of the sensor assembly is inserted into calibration enclosure 104, and the assembly is connected, as illustrated in
In a scene generation step 152, the calibration control unit creates a display on screen 106. Typically, the display generated comprises a single color with equal intensities being emitted from each area of the whole screen.
In an image acquisition step 154, the calibration control unit operates sensor 20, via a control signal transmitted to control circuit 34, which in turn drives the sensor. The sensor acquires an image of the scene displayed on screen 106 by scanning signals generated by pixels 28 of the sensor, and the image of the scanned signals returns to the control unit via control circuit 34. The returned image, i.e., the image received by the control unit, comprises respective uncalibrated signals originating from respective pixels 28 of array 26.
In a tabulation step 156, the processor of calibration control unit 102 tabulates, on a pixel by pixel basis, the uncalibrated signal from each pixel 28 together with an expected pixel signal. The expected pixel signal comprises levels that the control unit expects to receive back from the display created by the unit on screen 106. The expected pixel signal typically comprises an expected intensity level and an expected color value. Similarly, the uncalibrated pixel signal comprises an actual measured intensity level and an actual measured color value. Typically, in order to cancel out random noise effects, such as thermal noise, the measured intensity level and the measured color value (for each pixel) are acquired for a number of scans of sensor 20 over time, and the measured levels are averaged.
For each pixel, the tabulation, i.e., the measured and expected intensity levels and the measured and expected color values, may be stored in the memory of calibration control unit 102.
As illustrated by a line 158, the calibration control unit reiterates steps 152, 154, and 156. In each reiteration, in step 152 the control unit creates a different display on screen 106, and in step 156, the values of the measured and expected intensity levels and the measured and expected color values are stored in memory.
A number of iterations, N, required for a satisfactory calibration of sensor assembly 70, and the different displays generated on screen 106 for each iteration, may be determined by an operator of the calibration process without undue experimentation. In one embodiment, three different intensity levels, for each of nine different colors (red, green, blue, magenta, cyan, yellow, white, black, grey), i.e., a total of 27 displays, are created on screen 106. Larger numbers of displays typically provide greater accuracy for the calibration.
In a correction factor step 160, the calibration control unit uses the tabulation generated in step 156 to generate a correction factor for each pixel 28 of array 26. Typically, for each pixel the correction factor is incorporated into a look-up table for the pixel.
In a memory storage step 162, the correction factors for each pixel 28, typically corresponding to a look-up table as illustrated in
In the above description the correction factors for each pixel 28 have been assumed to be in the form of a look-up table. As necessary, during operation of endoscope 10 with sensor assembly 70 (after calibration as described with reference to the flowchart of
In some embodiments the correction factors for a given pixel are dependent on signals received by neighboring pixels, including nearest neighbor pixels, next-neighbor pixels, and/or pixels further these neighboring pixels from the given pixel. Such correction factors may be generated, mutatis mutandis, using the flowchart of
In some embodiments, one or more pixels 28 may be defective, giving substantially no response when illuminated. Such defective pixels are also termed “bad” pixels. A correction factor for a defective pixel may also be generated using the flowchart of
Once the correction factors have been stored as described above, sensor assembly 70 may be incorporated into endoscope 10, and endoscope control unit 52 may be configured to use the corrected values generated by the factors in generating the display on screen 58.
It will be understood that implementation of sensor assembly 70, as described above, may be performed using a sensor 20 having pixels 28. Production of sensor assembly with a sensor, as described hereinabove, allows for the use of a significantly smaller sensor (compared to prior art systems) in endoscope 10, with no reduction of efficiency of operation of the endoscope. Embodiments of the present invention enable sensor 20 to be smaller than prior art systems by incorporating calibration data for the sensor into memory 60 of sensor connector 32.
It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.