JP3836593B2 - Electronic endoscope device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic endoscope apparatus, and more particularly to a configuration of an electronic endoscope apparatus that forms a still image by using an all-pixel reading method that reads all pixels accumulated in an image sensor.
[0002]
[Prior art]
In an electronic endoscope device, for example, a CCD (Charge Coupled Device) is used as a solid-state imaging device. In this CCD, an image signal (video signal) is read out by reading out charges accumulated in units of pixels by a photoelectric conversion device. Is configured to be obtained. For example, in a simultaneous electronic endoscope apparatus, a color filter is arranged on a pixel unit on the upper surface of the CCD, thereby obtaining a color image.
[0003]
FIG. 5 shows an arrangement state of the above-described color filters. As shown in the figure, on the imaging surface of the CCD 1, for example, Mg (magenta), Cy (cyan) pixels on even lines, and odd lines on odd lines. G (green) and Ye (yellow) pixels are arranged. In the CCD 1, accumulated charges (pixel signals) in units of pixels are obtained through these color filters.
[0004]
Then, according to the conventional color difference line sequential mixed readout method, the accumulated charges of the pixels on the upper and lower lines are added and mixed and read out. For example, an odd field video signal such as a mixed signal of 0 line and 1 line at the first exposure, a mixed signal of 2 lines and 3 lines,... An even field video signal such as a mixed signal of 2 lines, a mixed signal of 3 lines and 4 lines,... Is read out. Therefore, the mixed signal of the two lines of the CCD 1 becomes a signal of one line of the field image, and one field data of odd number or even number can be obtained by one exposure.
[0005]
FIG. 6 shows the operation of the signal read from the CCD 1. In the electronic endoscope apparatus, as shown in FIG. 6A, O (Odd) every 1/60 seconds (vertical synchronization period). ) / E (Even) signal (field signal) to form odd and even fields. For this reason, as shown in FIG. 2B, signal accumulation is performed by the accumulation (exposure) time T of the electronic shutter during the 1/60 second period, and the accumulated mixed signal is obtained during the next 1/60 second period. Is read out. As a result, as shown in FIG. 5C, odd (Odd) field signals and even (Even) field signals are obtained. For example, the (n−1) th odd field signal is shown on the left side of FIG. (0 + 1) line, (2 + 3) line, (4 + 5) line, etc., and the nth even field signal is the mixed signal of (1 + 2) line, (3 + 4) line, etc. shown on the right side of FIG. Become.
[0006]
The odd field signal and the even field signal are interlaced and formed as an image of one frame, and this image is displayed on the monitor as a moving image. In the endoscope apparatus, a freeze switch is arranged in the operation unit. When the freeze switch is pressed, a still image at that time is formed and displayed.
[0007]
[Problems to be solved by the invention]
However, in the above-described simultaneous electronic endoscope apparatus, as shown in FIG. 6C, 1/60 seconds are provided between the odd field image and the even field image for forming one frame image. There is a problem that the image quality (resolution, color misalignment, etc.) is reduced when displaying a still image if the endoscope itself shakes or the object moves during this time. That is, in the case of a moving image, it is often better to faithfully reproduce the subject's movement or the like by the above-described mixed readout method in the CCD 1, but in the case of a still image, the resolution is lowered.
[0008]
In addition, electronic endoscope apparatuses often employ an electronic shutter function that changes the signal accumulation time. According to this, the image quality can be improved by shortening the accumulation time in a bright place at a short distance. it can. However, as shown in FIG. 6, there is a time lag of 1/60 seconds between the two accumulations (exposure) for forming a one-frame image, and the effect of shortening the accumulation time in a still image. However, there is an inconvenience that cannot be fully enjoyed.
[0009]
The present invention has been made in view of the above problems, and its purpose is to read out all the pixels obtained by the imaging device by one exposure to form a high-quality still image, and to faithfully move the moving image. It is an object of the present invention to provide an electronic endoscope apparatus that can be reproduced.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an image sensor in which a plurality of color filters are arranged in units of pixels, and a pixel signal for a predetermined period is not accumulated in the image sensor when a freeze switch is operated. In this way, the light shielding means for blocking the illumination light, the pixel mixture at the time of image sensor output that outputs the pixel signals accumulated in the image sensor mixed between the upper and lower lines, and the image sensor accumulated in one exposure This image pickup is performed by performing both-type drive control of the all-pixel readout method in which the signals of all the pixels that have been read are sequentially read into the odd-numbered lines and the even-numbered lines using the light-shielding period set by the light-shielding means and the next field period. A control circuit that forms a moving image by the pixel mixed readout method at the time of element output and forms a still image by the other all-pixel readout method, and an image obtained from the image sensor at the time of executing the above-mentioned all-pixel readout method. A memory for storing an image signal and an image signal of the even lines of the odd lines, during the execution of the all-pixel reading mode, only one field period one image signal of the odd or even lines previously stored in the memory delaying and adding the phase adjustment memory for aligning the image signal and the same phase of the other lines, the pixel signals to each other in the odd lines and the even lines at the same exposure read out in the same phase from each memory of the A mixing circuit that forms a still image signal of odd and even fields by mixing and a moving image signal of a pixel mixed readout method output from the image sensor is directly input, and the moving image signal and the still image output from the mixing circuit And an image switching circuit for switching a signal based on an operation of a freeze switch.
The invention according to claim 2 is characterized in that the control circuit executes an electronic shutter function for controlling a charge accumulation time of the image pickup device for exposure amount adjustment.
[0011]
According to the above configuration, for example, the pixel mixture readout method at the time of output of the image sensor is normally selected, and the pixel mixture signal read from the image sensor is supplied directly to the image switching circuit as in the conventional case. The pixel mixture signal output through the image switching circuit is subjected to signal processing for a moving image. Then, when the freeze switch is pressed, the mode is switched to the all-pixel readout method, thereby forming a still image.
[0012]
For example, the charge accumulated by exposure (exposure time is arbitrary) within a predetermined (first) 1/60 second period (vertical synchronization period) is imaged in the second period (1/60 second). The odd lines of the element (CCD) are read out (read from the transfer line) and stored in a predetermined memory, and the remaining even lines are read out during the third period (at the time of the next exposure). Remembered. The light source light in the second period is shielded by the light shielding means so that the even lines can be read.
[0013]
That is, if the charges for the next exposure are accumulated in the second period for sequentially reading out the accumulated charges of the odd lines, the remaining even lines cannot be read. Therefore, in the present invention, the light output in the second period is eliminated, and the accumulated charges in the even lines are read out in the third period. Thereby, the signal for all the pixels of the image sensor obtained by one exposure can be read out.
[0014]
Next, for example, the odd line video signal first stored in the above memory is further stored in the phase adjustment memory and delayed by 1/60 second, and then the odd line and even line are mixed by the mixing circuit. Pixel mixing processing is performed with the data. That is, as a result, this pixel mixing process forms a signal equivalent to the pixel mixing readout method at the time of image sensor output performed at the time of signal output from the image sensor, but the pixel based on the information obtained by one exposure. This is distinguished from the pixel mixture readout method at the time of image sensor output in that mixing is performed.
[0015]
Then, odd-numbered field and even-numbered field video signals are formed by this pixel mixed signal, and a still image is displayed based on these video signals. Therefore, the still image is formed based on the signals of all the pixels obtained by one exposure, resulting in a high quality image.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a circuit configuration of an electronic endoscope apparatus as an example of the embodiment. This electronic endoscope apparatus includes a scope (electronic endoscope) 10 and a processor apparatus having an image processing circuit. It becomes the structure connected to the light source device (or device which integrated these devices) provided with the light source. The scope 10 is provided with a CCD 12 having a color filter similar to that described with reference to FIG. 5 at the distal end thereof, and a light guide 15 for guiding the light from the light source 14 to the distal end portion. The operation unit of the scope 10 is provided with a freeze switch 16 for displaying a still image.
[0017]
A CCD drive circuit 18 for driving the CCD 12 is connected to the CCD 12, and a timing generator 19 and a microcomputer (microcomputer) 20 are connected to the drive circuit 18, and the microcomputer 20 is connected to the freeze switch 16. An operation signal is input. The CCD drive circuit 18 receives a timing signal based on the control of the microcomputer 20 and performs drive control of a CCD mixed pixel reading method for moving images and an all pixel reading method for still images.
[0018]
For example, in the case of this all-pixel reading method, two types for reading out the accumulated data for all the pixels accumulated in the CCD 12 in one exposure into an odd line and an even line (shifted in time). Are supplied from the CCD drive circuit 18, and based on this, control is performed to sequentially read out the odd line signal and the even line signal from the CCD 12 separately. In the CCD mixed pixel readout method, one type of readout pulse is given to each line.
[0019]
Further, an A / D converter 22 for inputting the output signal of the CCD 12 is provided, and a first stage for storing the image data of the odd-numbered lines for reading out all pixels is provided at the subsequent stage of the A / D converter 22. Memory 23, second memory 24 for storing even line image data, third memory 25 for phase adjustment for storing data of first memory 23 as it is, and delaying read timing by 1/60 second, stationary An image mixing circuit 26 is provided. That is, all pixel signals obtained by the CCD 12 are temporarily stored in the respective memories 23 and 24 in a state of being divided into odd line data (video signal) and even line data. The odd line data is delayed by 1/60 second so as to have the same phase as the even line data stored in the second memory 24.
[0020]
As a result, both image data can be read simultaneously, and the mixing circuit 26 in the next stage adds and mixes the pixel data of the odd lines in the third memory 25 and the pixel data of the even lines in the second memory 24 (still image). Pixel mixing processing). Accordingly, in the case of a still image, the mixing circuit 26 forms a pixel mixed signal equivalent to the conventional color difference line sequential mixed readout method.
[0021]
FIG. 2 shows the contents of still image data formed by the circuits from the CCD 12 to the mixing circuit 26 described above. As shown in FIG. 1A, the CCD 12 is configured so that horizontal lines from 0 to N lines are provided corresponding to the number of scanning lines, and pixel data of the horizontal lines are transferred to a transfer line and read out. Is done. The data of odd lines (1, 3, 5,...) Of the CCD 12 is stored in the first memory 23 (and the third memory 25) of FIG. Is stored in the second memory 24 of FIG.
[0022]
As described above, the data in the memories 25 and 24 is subjected to pixel mixing between the lines of FIG. (B) and FIG. (C) by the mixing circuit 26, and as shown in FIG. The addition operation data of line, 2 lines + 3 lines, 4 lines + 5 lines,... Is output as odd (Odd) field data. Also, with the readout line of FIG. (C) shifted downward by one line (reading from the position of C1 in the figure), pixel mixing is performed between the lines of FIG. (B) and as shown in FIG. (E). In addition, the addition operation data of 1 line + 2 lines, 3 lines + 4 lines, 5 lines + 6 lines,... Is output as even field data. In this example, the odd lines of the CCD 12 are distinguished as ODD, even numbers as EVEN, odd numbers of fields subject to interlace scanning as Odd, and even numbers as Even.
[0023]
In FIG. 1, an image switching circuit 27 for switching between a moving image and a still image is provided at the subsequent stage of the mixing circuit 26. This image switching circuit 27 is controlled by the microcomputer 20 when the freeze switch 16 is pressed. Switch from terminal to b terminal. A DVP (digital video processor) 29 is connected to the image switching circuit 27, and the DVP 29 performs color signal processing in the same pixel mixture readout method as in the prior art, and forms, for example, a color difference signal and a luminance signal. Then, image position control, enlargement processing, and the like are also performed. Although not shown, automatic gain control, a gamma processing circuit, and the like are also arranged at appropriate positions.
[0024]
In the subsequent stage of the DVP 29, a fourth memory 30 for storing odd field data, a fifth memory 31 for storing even field data, a switching circuit 32, and a D / A converter 33 are provided. That is, the fourth memory 30 stores odd (Odd) field data obtained by converting the data of FIG. 2D into a color difference signal or the like, and the fifth memory 31 stores the data of FIG. Even field data obtained by converting into a color difference signal or the like is stored.
[0025]
On the other hand, in a light source unit (or a light source device) that supplies light to the light guide 15 disposed in the scope 10, a diaphragm 35 and a light shielding plate 36 are provided between the light source 14 and the incident end of the light guide 15. Be placed. The light shielding plate 36 is configured to rotate, for example, a semicircular plate, and a drive circuit 38 is connected to rotationally drive the light shielding plate 36. In this example, the light shielding plate 36 blocks light for a predetermined 1/60 second after the freeze switch 16 is pressed in the field O / E signal of a cycle of 1/60 second.
[0026]
A diaphragm control circuit 39 is connected to the diaphragm 35, and a lamp driving circuit 40 is connected to the lamp 14. The diaphragm control circuit 39 drives the diaphragm 35 on the basis of a luminance signal obtained by the DVP 29, and a light source. The output light quantity of 14 is adjusted.
[0027]
This example has the above-described configuration, and its operation will be described with reference to FIGS. 3 and 4 (each figure coincides with time at the point Q). As shown in FIG. 3B, as the field O (Odd) / E (Even) signal, a timing signal for forming one field image in 1/60 seconds is used as in the conventional case. First, in a normal state, it is set to execute a moving image processing, that is, a pixel mixed readout method at the time of CCD output. The light shielding plate 36 in FIG. Irradiation from the tip portion into the body to be observed is performed via the guide 15.
[0028]
Due to this light irradiation, the CCD 12 at the tip captures an image in the observed body, and the CCD 12 accumulates charges corresponding to the image light. This accumulated charge is read by adding pixels between horizontal lines by the drive pulse from the CCD drive circuit 18, and the pixel mixture signal described in FIG. 5 is output. The output signal of the CCD 12 is supplied from the A / D converter 22 to the image switching circuit 27 via the through line L. At this time, the image switching circuit 27 is switched to the terminal a side by the microcomputer 20, and the CCD output signal is supplied to the DVP 29. The operation after this DVP 29 is the same as that of the prior art, and a moving image is displayed on the monitor based on the odd field signal stored in the fourth memory 30 and the even field signal stored in the fifth memory 31.
[0029]
On the other hand, when the freeze switch 16 of the scope 10 is pressed, the microcomputer 20 switches from the pixel mixed readout method to the all-pixel readout method for still images. For example, if the trigger Tr1 (or Tr2) by the freeze switch 16 is given as shown in FIG. 3 (A), as shown in FIG. 3 (C), when the next O / E signal rises ( The light shielding plate 36 blocks the optical path only for 1/60 second from t1), and light is blocked during that time [FIG. 3 (D)]. Accordingly, the image data from which all the pixels are read out is the electric charge accumulated in the CCD 12 by the exposure L in the period of 1/60 seconds before the light-shielded period. This charge is obtained by the electronic shutter pulse g1 in FIG. 3G, and the charge (data) of all the pixels is read out by the CCD drive circuit 18.
[0030]
That is, FIG. 3E shows the odd-line read pulse P1 shown in FIG. 2B, and FIG. 3F shows the even-line read pulse P2 shown in FIG. 2C. Odd (ODD) line data and even (EVEN) line data are sequentially read out from the CCD 12 by a read pulse P1 in which the pulse at t2 is eliminated and a read pulse P2 in which the pulse at t1 is eliminated. Therefore, reading of odd lines is performed during the above-described light shielding period (t1 to t2), and reading of even lines is performed during the next period (t2 to t3). As shown in FIG. 3G, the electronic shutter pulse does not exist between t1 and t2.
[0031]
The odd line data is written into the first memory 23 as shown in FIG. 4B, and the even line data is written into the second memory 24 as shown in FIG. Next, as shown in FIGS. 4D and 4E, the odd line data in the first memory 23 and the even line data in the second memory 24 are read twice, and the odd line data is 1 / Stored in the third memory 25 for phase adjustment of 60 seconds. Therefore, as can be understood from FIGS. 4E and 4F, the data of the odd lines and the even lines are aligned in the same phase (timing).
[0032]
In this way, each data read from the memories 25 and 24 is pixel-mixed by the mixing circuit 26. In this example, in order to enable this, as shown in FIG. Writing to the memory 23 and the second memory 24 is prohibited. Then, pixel mixture conversion is performed in the same period [FIG. 4 (H)]. First, the addition data of 0 line + 1 line, 2 lines + 3 lines, 4 lines + 5 lines,... Shown in FIG. This is output and stored as odd (Odd) field data in the fourth memory 30 [FIG. 4 (I)]. Next, the addition data of 1 line + 2 lines, 3 lines + 4 lines, 5 lines + 6 lines,... Shown in FIG. 2E is output and stored in the fifth memory 31 as even field data. .
[0033]
Then, at the same time when these odd-numbered field data and even-numbered field data are read, the switching circuit 32 causes the fourth memory to output each field data alternately as shown in FIGS. 30 and the fifth memory 31 are selected. These field data are output to the monitor via the D / A converter 33, and an image is displayed on the monitor by interlace scanning. As a result, a still image is displayed based on all pixel data obtained at the same exposure, and a high-quality image is obtained. Therefore, even if the endoscope itself is shaken or the object to be observed moves for 1/60 second, it is possible to observe a clear still image with little influence.
[0034]
By the way, in the above embodiment, as described above, the electronic shutter function can be used according to the brightness in the observed body. However, according to the present invention, the effect of the electronic shutter function is further enhanced. become. That is, in the conventional method, an image is formed based on the video signal obtained by the two exposures. Therefore, if there is movement and blurring between the two exposures, it affects the image quality. However, in the present invention, since a still image is formed based on the video signal obtained by one exposure, the effect of shortening the signal accumulation time directly appears in this one exposure time, and the image quality is improved. There is an advantage that appears prominently.
[0035]
In this example, the period for reading out all pixels for forming a still image is set to one frame formation period (1/30 seconds, but this may be a period of several frames), and then the above-described image switching is performed quickly. Since it is configured to switch to the moving image signal by the circuit 27, there is an advantage that the aperture control that makes the screen brightness constant works well. That is, the aperture control circuit 39 adjusts the amount of light based on the luminance signal formed by the DVP 29. When returning to a moving image after a long period of still image operation, the amount of light is adjusted based on past data. Control will be performed, halation will occur, and conversely the screen will be dark. However, in this example, after switching to the moving image signal immediately after the period of one frame, there is an advantage that the above-described problems are eliminated and an image with stable brightness can be obtained.
[0036]
Further, the present invention has an advantage that all pixels are read out without changing the structure of the CCD 12 and the clock frequency. That is, conventionally, it has also been proposed to sequentially read out all pixels within a 1/60 second period using a double transfer frequency (without distinguishing between odd lines and even lines). In this case, however, the structure of the transfer line (vertical CCD) of the CCD 1 must be formed at double density, so that the configuration becomes complicated and the clock frequency is doubled. The present invention has the advantage that all pixels can be read out without adopting such a configuration.
[0037]
【The invention's effect】
As described above, according to the present invention, a moving image is formed by an image sensor output pixel mixed readout method in which pixel signals accumulated in an image sensor are mixed and output between upper and lower lines, and illumination light is emitted for a predetermined period. While using a light-shielding means that shuts off the image, a still image is formed by an all-pixel readout method that sequentially reads out the signals of all pixels accumulated in the imaging device in one exposure divided into odd lines and even lines , and phase adjustment By adding and mixing the pixel signals of the odd and even lines at the same exposure by the memory and the mixing circuit to form a still image signal of one field, a smooth image that faithfully reproduces the motion of the moving image On the other hand, a high-quality image without blur can be obtained for a still image.
[0038]
In addition, in a still image, it is possible to obtain an effect of shortening the accumulation time by the electronic shutter, and further, there is an advantage that all pixel readout can be performed without changing the structure of the CCD and the clock frequency.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration of an electronic endoscope apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating image data read between the CCD and the mixing circuit in FIG. 1;
FIG. 3 is an explanatory diagram showing a still image forming operation in the embodiment.
FIG. 4 is an explanatory diagram illustrating a still image forming operation in the embodiment and a continuation of FIG. 3;
FIG. 5 is a diagram illustrating a configuration of a color filter and pixel mixture reading in a conventional CCD.
FIG. 6 is an explanatory diagram showing the operation of a conventional CCD.
[Explanation of symbols]
1,12 ... CCD,
10… Scope,
16 ... Freeze switch,
18 ... CCD drive circuit,
20 ... microcomputer,
23 ... 1st memory, 24 ... 2nd memory,
25 ... Phase adjustment (third) memory,
26 ... mixing circuit,
27 ... Image switching circuit,
30, 31 ... memory,
36 ... light shielding plate,
38: A light shielding plate driving circuit.

Claims (2)

An image sensor in which a plurality of color filters are arranged in units of pixels;
A light blocking means for blocking illumination light so that pixel signals for a predetermined period are not accumulated in the image sensor when a freeze switch is operated ;
An image sensor output pixel mixture readout method that mixes and outputs pixel signals accumulated in the image sensor between upper and lower lines, and signals of all pixels accumulated in the image sensor in one exposure by the light shielding means. Using the set light-shielding period and the next field period , drive control of both types of all-pixel readout method that reads sequentially into odd lines and even lines, and forms moving images with this pixel mixed readout method at the time of image sensor output A control circuit for forming a still image by the other all-pixel readout method;
A memory for storing the odd-numbered line image signal and the even-numbered line image signal obtained from the image sensor at the time of executing the all-pixel reading method;
During execution of the all-pixel reading mode, the phase adjustment for aligning the image signal and the same phase of the other line is delayed by one field period one image signal of the odd or even lines previously stored in the memory Memory,
A mixing circuit that adds and mixes the pixel signals of the odd-numbered line and the even-numbered line at the same exposure read out in the same phase from the respective memories to form still image signals of the odd-numbered and even-numbered fields;
An image switching circuit that directly inputs a moving image signal of a pixel mixed readout method output from the image sensor and switches the moving image signal and a still image signal output from the mixing circuit based on an operation of a freeze switch; An electronic endoscope apparatus.   The electronic endoscope apparatus according to claim 1, wherein the control circuit executes an electronic shutter function for controlling a charge accumulation time of the imaging device for exposure adjustment.

Images