JP2002369796A - Electronic endoscopic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently utilize a memory and to obtain an image good in color reproducibility regardless of zooming by controlling the γ correction factor of a γ correction circuit in electronic endoscopic equipment. SOLUTION: An image pickup sensor 14 is provided to the leading end of a scope 10 and the image pickup signal obtained from the image pickup sensor 14 is outputted to a processor 100. The processor 100 forms a video signal on the basis of the obtained image pickup signal. The processor 100 reads the γ correction factor from a memory 122B for second γ correction when zooming is performed and reads the γ correction factor from a memory 122A for first γcorrection when no zooming is performed to perform γ correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention obtains a video signal corresponding to a subject image from a distal end portion of a flexible tube of a scope, performs video signal processing by a processor, and reproduces the subject image based on the video signal by a monitor device. The present invention relates to an electronic endoscope device.

[0002]

2. Description of the Related Art In such an electronic endoscope apparatus,
A CCD image sensor is provided at the tip of the scope, and this CCD image sensor is combined with an objective lens system. A light guide composed of a bundle of optical fibers is inserted into the scope, and illumination light is supplied from the light source lamp in the processor connected to the proximal end of the scope to the distal end of the scope via the light guide. . When the scope is inserted into the patient's body cavity, the front of the objective lens system is illuminated by the illumination light emitted from the distal end face of the light guide, and an optical image is formed on the light receiving surface of the CCD image sensor, where it is photoelectrically converted. And output as an image pickup signal. The image signal is sent to a video signal processing circuit of the processor, and a video signal is generated based on the image signal.
Further, the video signal is output to the monitor device, where the subject image is reproduced on the monitor screen.

Normally, in order to maintain good color reproduction characteristics and luminance gradation characteristics on a monitor screen, a gamma correction process is performed on an image pickup signal. In recent years, a digital signal processing circuit has been used in place of a conventional analog signal processing circuit as the γ processing circuit. For example, a DSP (Digital Signal Processor) or a programmable PLD (Programmable Logic Dev
γ correction coefficient data is stored in a built-in memory in an integrated circuit such as ice) or a look-up table memory, and γ corresponding to 8 to 10-bit digital luminance values obtained by A / D conversion of an image pickup signal. The gamma correction is performed by reading out the correction coefficient from the memory and multiplying it.

In general, when a photograph is taken while advancing inside a cylindrical part such as a digestive organ or the like, an image having a high contrast in which the center is dark and the periphery is bright is obtained. For this reason, it is necessary to store a γ correction coefficient corresponding to a wide range of luminance values in the memory. However, for an image in which the luminance difference within one frame is relatively small, such as when the subject is enlarged and displayed by zooming, only a part of the above γ correction coefficient data is used and other γ correction coefficients are used. It is often wasted because it cannot be used. In particular, when storing a plurality of sets of γ correction data having different characteristics according to the preference of the operator, there is a problem that the device efficiency is deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to efficiently use a memory for storing a gamma correction coefficient and to obtain an image with good color reproducibility. And

[0006]

According to the present invention, there is provided an electronic endoscope apparatus comprising: a scope having a solid-state imaging device; a photographing optical system having a variable focal length; and zoom means for controlling the focal length of the photographing optical system. A gamma correction circuit that multiplies a luminance value of an imaging signal output from the solid-state imaging device by a predetermined gamma correction coefficient to improve gradation characteristics, a storage unit that stores a plurality of sets of gamma correction coefficient data, and zooming. A detecting means for detecting, a coefficient switching means for switching γ correction coefficient data of the γ correction circuit according to a detection result by the detecting means, and a video signal generating means for generating a video signal based on the γ corrected imaging signal A processor is provided, and a monitor device that reproduces a subject image on a screen based on a video signal output by the processor is provided.

In the electronic endoscope apparatus, specifically, the storage means includes a first γ correction coefficient memory for storing a plurality of sets of γ correction coefficient data corresponding to the entire range of the luminance value selected when the zooming setting is released. And a second γ correction coefficient memory for storing a plurality of sets of γ correction coefficient data selected at the time of setting zooming and corresponding only to a predetermined range of luminance values.

The processor of the electronic endoscope apparatus according to the present invention is connected to a scope having a solid-state imaging device and a photographic optical system having a variable focal length, and zoom means for controlling the focal length of the photographic optical system. A gamma correction circuit that multiplies a luminance value of an imaging signal output from the solid-state imaging device by a predetermined gamma correction coefficient to improve gradation characteristics, a storage unit that stores a plurality of sets of gamma correction coefficient data, and zooming. Detecting means for detecting, and γ of the γ correction circuit according to the detection result by the detecting means.
It is characterized by having coefficient switching control means for switching correction coefficient data, and video signal generation means for generating a video signal based on the γ-corrected imaging signal.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an electronic endoscope apparatus according to the present invention. The electronic endoscope apparatus includes a scope 10 having a flexible tube, a processor 100 detachable from the scope 10, and a monitor device 200 connected to the processor 100. A light guide member 12 composed of an optical fiber bundle is provided on the scope 10.
The proximal end of the light guide member 12 is attached to the processor 1 when the scope 10 is mounted on the processor 100.
00 is optically connected to a light source 102. Thus, the illumination light from the light source 102 is
Is guided to the scope distal end portion 10a to illuminate a subject in front, for example, the internal organ X.

An image sensor 14 comprising a solid-state image sensor, for example, a CCD, is provided at the distal end portion 10a of the scope. The image sensor 14 includes an objective lens system 16 combined with the CCD. The scope 10 has a zoom function and an autofocus function. More specifically, the objective lens system 16 includes a plurality of lenses, and the movable lens included therein is driven by the zoom / focus control circuit 114 of the processor 100 to change the relative position in the optical axis direction, thereby changing the focus. The position and the image magnification are changed. The scope 10 is provided with a zoom dial 18 for performing zooming.
It is electrically connected to the focus control circuit 114.

In the present embodiment, a simultaneous method is employed to reproduce a color image, and an optical image of a subject illuminated by white illumination light is formed on a light receiving surface of a CCD by an objective lens system 16. The optical subject image formed on the CCD is photoelectrically converted into an analog image signal for one frame by the image sensor 14, and is sequentially read from the image sensor 14 by a drive / process circuit 22 built in the connector unit 20 of the scope 10. It is.

The analog image signal read from the image sensor 14 is processed in the drive / process circuit 22 in accordance with the characteristics of the image sensor 14 and the optical characteristics of the scope 10, such as a clamp process, a sample hold process, and γ.
A correction process, a white balance correction process, an amplification process, and the like are performed, converted into a component digital signal including a luminance signal and a color difference signal, and sequentially output to the video signal processing circuit 104 of the processor 100.

A read-only memory (ROM) 26 provided in the connector section 20 stores information on optical characteristics unique to the scope 10. Since the scope 10 is composed of high-precision parts, even a small mechanical error greatly affects the optical characteristics of each scope 10. For this reason, the scope 10 is provided with data,
The configuration is such that there is no need to perform an adjustment operation in accordance with the optical characteristics of each scope 10 on the processor 100 side when replacing.

The video signal processing circuit 10 of the processor 100
4, the luminance signal component has γ according to the operator's preference.
The γ correction process is performed again to perform the correction, and the color difference signal and the decoded synchronization signal are multiplexed on the γ corrected luminance signal.
An analog color video signal such as a TSC composite video signal is generated.

The analog color video signal is supplied to the processor 1
00 to the recording device 30 such as the monitor device 200 or VCR
Output to 0. The monitor device 200 reproduces a subject image on a screen based on the analog color video signal, and the recording device 300 records the analog color video signal as a still image or a moving image. A keyboard 400 is connected to the processor 100, and character information such as a patient name input from the keyboard 400 and observation date and time obtained from a timer circuit (not shown) is transmitted to the system control circuit 1.
The signal is converted into a character pattern signal by 06 and output to the video signal processing circuit 104, where it is added to the component digital signal. Thus, the character information is displayed on the screen of the monitor device 200 together with the reproduced image of the optical subject image.

The system control circuit 106 is a microcomputer for controlling all operations of the processor 100, and includes a CPU, a ROM for storing programs and parameters for executing various routines, and a RAM for temporarily storing data and the like. .

The processor 100 has an automatic dimming function. Specifically, the processor 100 calculates an average luminance level of one frame of the imaging signal output from the video signal processing circuit 104, and based on the average luminance level,
The aperture of the stop 112 provided between the light source 102 and the incident end face of the light guide member 12 is adjusted to an appropriate degree. Thereby, the light amount is automatically adjusted.

The processor 100 is provided with a contrast type autofocus function. Specifically, the movable lens is moved by the zoom / focus control circuit 114, and the focus detection circuit 108 detects the amount of change in the amplitude of the specific frequency component from the image signal output from the video signal processing circuit 104. The system control circuit 106 determines that focus is achieved when the signal amplitude takes the maximum value based on the detection result of the focus detection circuit 108.

The auto focus function and the automatic light control function are set or canceled by a panel switch 110 provided on the surface of the processor 100.

FIG. 2 is a block diagram showing details of the video signal processing circuit 104. 1 input from scope 10
The digital luminance signal for the frame is γ-corrected by the γ correction circuit 120 and then stored in a luminance signal memory (Y memory) 1.
40. The corresponding digital color difference signal for one frame is a color difference signal memory (RY / BY memory) 1
42. The luminance signal and the chrominance signal stored in both memories 140 and 142 are simultaneously transmitted to the encoder 14.
4 where the synchronization signal is added and the NTSC
Converted to a composite video signal.

The gamma correction circuit 120 stores the first gamma correction memory 12 for storing three sets of gamma correction coefficient data for standard magnification.
2A and a second gamma correction memory 122B for storing only four sets of zoomed gamma correction coefficient data for zooming.
Switches 124 and 126 for switching the input and output of a luminance signal to and from these memories 122A and 122B;
A selection information adding circuit 128 for adding information for selecting only one correction coefficient data to the luminance signal in advance.

The switches 124 and 126 are switched in accordance with the setting or cancellation of the zooming function.
Alternatively, which set of γ correction coefficient data to use in the second γ correction memories 122A and 122B is arbitrarily selected by operating the panel switch 110, and the selection information adding circuit 128 is inputted according to the selection result. 8
2-bit data indicating the selected γ correction coefficient data is added to the header portion of the digital luminance signal of the bit data,
Output as 10-bit data. The first or second γ correction memories 122A and 122B decode the 10-bit data to obtain a luminance value represented by 256 gradations, and perform γ correction by multiplying the luminance value by a γ correction coefficient corresponding to the luminance value. Output to the Y memory 140 via the switch 126.

FIG. 3 shows the first and second gamma correction memories 12.
It is a graph which shows input-output characteristics of 2A and 122B. FIG.
Explaining the input / output characteristics of the first γ correction memory 122A shown in (a), the first to third γ correction coefficient data are as follows.
This is a data group of 256 γ correction coefficients corresponding to luminance values 0 to 255, respectively.
A is sequentially stored in A. A curve C1 shows input / output characteristics when the first γ correction coefficient data is used, and curves C2 and C
Reference numeral 3 denotes input / output characteristics when the second and third γ correction coefficient data are used, respectively.

When zooming is not performed and the first γ correction coefficient data is selected, when the data of the luminance value Xa is input, the output value becomes Ya1 on the curve C1. Here, when the data is switched to the second γ correction coefficient data,
Even if the same luminance value Xa is input, the output is Ya on the curve C2.
2 (Ya2 <Ya1), and when the data is switched to the third γ correction coefficient data, the output becomes Ya3 (Ya2 <Ya3 <Ya1) on the curve C3 in response to the input of the luminance value Xa. Thus, color reproducibility and gradation characteristics can be changed.

In general, zooming is not performed when the distal end portion 10a of the scope 10 advances and retreats inside a cylindrical inner wall of a digestive organ or the like, and a high contrast image is displayed on the screen of the monitor device 200 with a dark center and a bright periphery. Is done. In other words, the luminance difference within one frame is large. Therefore, the first to third γ correction coefficient data have a luminance value of 0 to 25.
It is preferable to have a γ correction coefficient corresponding to each of S.5 and S.5. Thereby, an image having a large difference in luminance can be appropriately gamma-corrected, and an image whose color reproducibility and gradation characteristics match the operator's preference can be displayed on the monitor 200.

On the other hand, when zooming is performed by operating the zoom dial 18, the subject is enlarged and displayed, and a bright image having a relatively small depth is obtained. That is, the luminance difference in one frame is small, and only a part of the γ correction coefficient data, particularly, only the high luminance side is used, and the γ correction coefficient on the low luminance side is not used, so that it is often wasted.

In consideration of such a usage state of the scope, the γ correction coefficient data stored in the second γ correction memory 122B stores only the γ correction coefficient to be used, and instead, the number of sets of γ correction coefficient data is changed. Is increasing. As a result, various gamma corrections can be performed with the same memory capacity as before, and an image with good color reproducibility can always be reproduced.

The gamma correction circuit 120 may be a circuit that holds the gamma correction coefficient as lookup table data, a DSP (Digital Signal Processor), or an integrated circuit that allows the operator to freely change the gamma characteristics, such as a PLD.
(Programmable Logic Device) or other integrated circuits.

The second gamma correction memory 12 shown in FIG.
Explaining the input / output characteristics of 2B, the fourth to seventh γ correction coefficient data are a data group of (256−Bo) γ correction coefficients corresponding to luminance values Bo (Bo> 0) to 255, respectively. The γ correction coefficients are sequentially stored in the memory 122B. The straight line C4 shows the input / output characteristics when the second γ correction coefficient data is used, and the curves C5, C6 and C7 show the input / output characteristics when the fifth, sixth and seventh γ correction coefficient data are used, respectively. .

When zooming is performed, when the data of the luminance value Xb is input, the output value becomes the selected γ.
Each differs according to the correction coefficient data. When the fourth γ correction coefficient data is selected, the output Yb1 and the fifth γ
When the correction coefficient data is selected, the output Yb2,
When the sixth γ correction coefficient data is selected, the output Y
b3, the output is Yb4 when the seventh γ correction coefficient data is selected.

In the present embodiment, there are seven sets of γ correction coefficient data, but the number is not limited to this number.
Of course, there may be more than one pair.

FIG. 4 is a flowchart showing a gamma correction processing routine executed in the system control circuit 106 of the processor 100.

In step S102, the panel switch 11
At 0, it is determined whether the zoom function and the autofocus function are set, and whether or not zooming is instructed by the zoom dial 18 to display an enlarged image.
If it is determined that the enlarged display has been selected, step S10
In step 4, the zoom / focus control circuit 114 starts the zooming and autofocus operations, and the focus detection circuit 108 detects the in-focus state. In step S106, it is determined whether or not the camera is in focus.
106 is repeatedly executed, and if it is determined that the subject is in focus, the process proceeds to step S108, where the first γ correction memory 12
Switches 124 and 126 are switched to connect the selection information adding circuit 128 and the Y memory 140 to 2A.

In the next steps S110 to S122, information indicating which of the fourth to seventh γ correction coefficient data is selected is added to the luminance signal. To elaborate,
In step S110, it is determined whether or not the fourth γ correction data has been selected.
At 112, a signal indicating information that the fourth γ correction data is selected is sent to the selection information adding circuit 128, and
If no correction data has been selected, step S1 is performed.
At 14, it is determined whether the fifth γ correction data has been selected. If the fifth γ correction data has been selected, a signal indicating this is sent to the selection information adding circuit 128 in step S116, and if the fifth γ correction data has not been selected, the sixth γ correction data is further selected in step S118. Is determined. 6th γ
If the correction data has been selected, a signal indicating this is sent to the selection information adding circuit 128 in step S120, and if the sixth γ correction data has not been selected, it is considered that the last seventh γ correction data has been selected. Then, in step S122, a signal indicating this is sent to the selection information adding circuit 128.

When any of steps S112, S116, S120 and S122 is completed, step S124 is executed.
To drive the video signal processing circuit 104 to display the enlarged image on the monitor device 200, and then return to step S102.

On the other hand, if zooming with the zoom dial 18 is not designated in step S102, that is, if display at standard magnification is instructed, step S130 is performed.
In order to connect the selection information adding circuit 128 and the Y memory 140 to the second γ correction memory 122B,
24 and 126 are switched.

Subsequently, in step S132, it is determined whether or not the first γ correction data is selected. If it is selected, in step S134, a signal indicating the information that the first γ correction data is selected is output to the selection information adding circuit 128. If the first γ correction data is not selected, it is further determined in step S136 whether the second γ correction data is selected. If the second γ correction data has been selected, a signal indicating that fact is sent to the selection information adding circuit 128 in step S138. If the second γ correction data has not been selected, the remaining third γ correction data has been selected. In step S140, a signal indicating this is sent to the selection information adding circuit 128.

Step S134, S138 or S14
When any one of 0 is completed, the drive of the video signal processing circuit 104 is controlled in step S142 to display the image at the standard magnification on the monitor device 200, and then in step S1
Return to 02.

As described above, according to the electronic endoscope apparatus of the present embodiment, the memory for storing the γ correction coefficient can be efficiently used, and an image having good color reproducibility can be obtained.

[0041]

As described above, an object of the electronic endoscope apparatus of the present invention is to automatically obtain a high-accuracy image when zooming is performed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an electronic endoscope apparatus according to the present invention.

FIG. 2 is a block diagram illustrating details of a video signal processing circuit illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of coefficient data stored in a gamma processing memory;

FIG. 4 is a flowchart showing a gamma correction processing routine executed in a system control circuit of the processor shown in FIG. 1;

[Explanation of symbols]

 Reference Signs List 10 scope 14 imaging sensor 100 processor 104 video signal processing circuit 120 gamma correction circuit 200 monitoring device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H04N 7/18 H04N 7/18 M 5C065 9/04 9/04 Z F-term (Reference) 2H040 BA03 GA02 GA06 GA11 4C061 AA00 BB02 CC06 DD03 HH51 JJ17 JJ18 LL02 NN01 NN05 PP13 TT02 TT12 TT20 YY14 5C022 AA09 AB15 AB22 AB66 AC42 5C024 AX02 BX02 CY45 CY50 EX54 GY01 GY31 HX18 HX50 H0301 CC02 CB01A0313 AA04 BB04 BB12 BB41 CC02 CC03

Claims (3)

[Claims] 1. A scope having a solid-state image sensor, a photographing optical system having a variable focal length, zoom means for controlling a focal length of the photographing optical system, and luminance of an image signal output from the solid-state image sensor. A gamma correction circuit that multiplies a value by a predetermined gamma correction coefficient to improve gradation characteristics, a storage unit that stores a plurality of sets of gamma correction coefficient data,
Detecting means for detecting zooming, coefficient switching means for switching γ correction coefficient data of the γ correction circuit according to the detection result by the detecting means, and a video signal for generating a video signal based on the γ corrected image signal An electronic endoscope apparatus comprising: a processor having a generation unit; and a monitor device that reproduces the subject image on a screen based on the video signal output by the processor. 2. A memory for a first γ-correction coefficient which stores a plurality of sets of γ-correction coefficient data corresponding to the entire range of luminance values selected at the time of canceling the setting of zooming, and a memory selected at the time of setting of zooming. 2. The electronic endoscope apparatus according to claim 1, further comprising a second γ correction coefficient memory for storing a plurality of sets of γ correction coefficient data corresponding only to a predetermined value range. 3. A processor of an electronic endoscope apparatus to which a scope having a solid-state imaging device and a photographing optical system having a variable focal length is connected, and zoom means for controlling a focal length of the photographing optical system. A gamma correction circuit for multiplying a luminance value of an imaging signal output from the solid-state imaging device by a predetermined gamma correction coefficient to improve gradation characteristics, a storage unit for storing a plurality of sets of gamma correction coefficients, and zooming. Detecting means for detecting, coefficient switching control means for switching a γ correction coefficient of the γ correction circuit according to a detection result by the detecting means, and video signal generating means for generating a video signal based on the γ-corrected image signal And a processor for the electronic endoscope apparatus.