JP2004294788A - Electronic endoscope device provided with automatic focusing function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an accurate focusing state even when halation is caused. <P>SOLUTION: A microcomputer 42 is provided with a halation determination part 42A and a passive AF control part 42B. The halation judgment part 42A determines whether signal levels of a plurality of divided range finding areas in an image pickup area are a halation level or not, and in determining the existence of a range finding area of the halation level, the passive AF control part 42B performs focus evaluation operation by a high frequency signal outputted from a BPF part 40 in the range finding areas other than the range finding area of the halation level and performs passive automatic focusing by mountain climbing operation on the basis of the focus evaluation value. Consequently a focused and clear enlarged image or the like can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic endoscope apparatus having an autofocus function, and more particularly to an electronic endoscope apparatus that performs an autofocus control while capturing an image of an object to be observed optically enlarged by a movable lens provided in an objective optical system. Regarding the configuration.
[0002]
[Prior art]
The electronic endoscope device mounts a CCD (Charge Coupled Device) or the like, which is a solid-state imaging device, at the tip of an electronic endoscope (electronic scope), and illuminates light from a light source device to image the inside of an object to be observed. In addition, an image pickup signal of the CCD obtained by the electronic endoscope is output to a processor device, and the processor device performs image processing to display an image of the object to be observed on a monitor.
[0003]
FIG. 6 shows a configuration of a distal end portion of an endoscope with an objective lens moving mechanism as disclosed in Japanese Patent Application Laid-Open No. 2001-100114 in this type of electronic endoscope. In FIG. 6, an observation window lens 3 is provided on the distal end surface of the support portion 2 of the endoscope distal end portion 1. On the rear side of the optical path of the observation window lens 3, a solid A CCD 6 serving as an image sensor is arranged. The CCD 6 is connected to a signal line 8 via a circuit board 7, and a signal captured by the CCD 6 via the signal line 8 is supplied to a processor device.
[0004]
A first movable lens 10 and a second movable lens 11 constituting an objective optical system are arranged between the observation window lens 3 and the prism 4, and a holding frame 12 of the first movable lens 10 and a second movable lens The 11 holding frame 13 is attached to the camshaft 14 by fitting the engagement holes 12A and 13A to the outer periphery of the cylindrical camshaft 14. A cam pin 16 projects from the engaging hole 12A, and a cam pin 17 projects from the engaging hole 13A. Cam grooves 18, 19 having different inclination angles with respect to the axis of the cam shaft 14 are formed. The cam pin 16 engages with the cam groove 18 and the cam pin 17 engages with the cam groove 19.
[0005]
The shaft 20Z of the motor 20 is attached to the camshaft 14. Therefore, if the cam shaft 14 is rotated by controlling the rotation of the motor 20, the first movable lens 10 and the second movable lens 11 are moved back and forth in the optical axis direction by the engagement of the cam grooves 18, 19 with the cam pins 16, 17. (A different amount of movement), thereby performing optical scaling (magnification) and the like.
[0006]
In recent years, as shown in Japanese Patent Application Laid-Open No. 2002-263058, a device having an autofocus mechanism has been manufactured. According to this autofocus mechanism and control, focusing can be performed more precisely than in the past. In addition, it is possible to display and observe a detailed enlarged image or the like on a monitor.
[0007]
[Patent Document 1]
JP 2001-100114 A [Patent Document 2]
JP-A-2002-263058
[Problems to be solved by the invention]
However, when autofocus control is performed in a conventional electronic endoscope apparatus, when halation occurs due to light reflected on the mucous membrane in the body to be observed, there is a problem that the accuracy of the focus control is reduced. That is, in general, in an electronic endoscope apparatus, since a digestive organ or the like covered with a mucous membrane is to be imaged, light illuminated from the tip of the electronic endoscope is reflected on the mucous membrane, and halation occurs on a monitor screen. Since a signal for evaluating the in-focus state (focus) cannot be obtained from the video signal of the portion where the halation has occurred, auto-focus control cannot be performed with high accuracy.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electronic endoscope device having an auto-focus function capable of obtaining an accurate focusing state even when halation occurs. It is in.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an objective optical system having a movable lens that moves in the optical axis direction and varies the focal length, and a solid-state imaging device that captures an image of an object to be observed via the objective optical system. A high-frequency signal extraction circuit for extracting a high-frequency signal for evaluating a focusing state of the movable lens from the video signal, the electronic endoscope device comprising: A determination circuit for determining whether or not a signal level of each area obtained by dividing (setting) an imaging area into a plurality of areas based on a signal is at a halation level; and a passive auto based on a high-frequency signal output from the high-frequency signal extraction circuit. When the focus control is performed and the determination circuit determines the presence of the divided area at the halation level, the divided area at the halation level is determined. A passive autofocus control unit for a passive autofocus control based on the high frequency signal has been removed area, characterized in that the provided.
[0011]
According to the above configuration, for example, it is determined whether or not there is halation in the eight divided A to H ranging areas. For example, when it is determined that halation has occurred in the ranging area H, this determination is performed. Passive autofocus is performed based on high-frequency signals in areas A to G excluding area H. In this passive autofocus, the focus is evaluated (or the contrast is evaluated) by a high-frequency signal of a video signal, and a focused state is obtained by a hill-climbing operation. That is, the focus evaluation calculation based on the high-frequency signal determines the direction of hill-climbing (the direction in which the evaluation is improved), that is, whether the direction is a short distance from a long distance (近) or a short distance to a long distance. The movable lens is moved. Then, by stopping the movable lens when the value of the focus evaluation becomes maximum in the hill-climbing operation, a good in-focus state can be obtained.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 illustrates a configuration of an electronic endoscope apparatus having an autofocus function according to the embodiment. In FIG. 1, a first movable lens (or group) 25 and a second movable lens (a group) constituting an objective optical system are provided behind an observation window lens 24 in the endoscope distal end portion 22 similarly to the configuration of FIG. Or a group) 26, and a CCD 27, which is a solid-state image sensor, is disposed behind the second movable lens 26 via a cover glass or the like. The signal imaged by the CCD 27 is supplied to the processor via a circuit board and signal lines.
[0013]
The first movable lens 25 and the second movable lens 26 are attached to actuators 28A and 28B, respectively. These actuators 28A and 28B include linear actuators such as piezoelectric actuators and electrostatic actuators, and FIG. A cam mechanism indicated by 6 is disposed on each of the movable lenses 25 and 26, and the cam shaft is driven by a motor or a linear transmission member. The actuators 28A and 28B cause the first and second movable lenses 25 and 26 to relatively move back and forth in the optical axis direction, and the first movable lens 25 mainly performs a function of autofocus (focusing). The second movable lens 26 is configured to serve as an optical zoom (variable focal length).
[0014]
The apparatus further includes a timing generator (TG) 30 for driving the above-described CCD 27, a CDS (correlated double sampling) / CDS (correlation double sampling) for inputting an output signal of the CCD 27 and performing automatic gain control. An AGC (automatic gain control) circuit 31 is provided. An A / D converter 32, a DSP (digital signal processor) 33 for performing various kinds of image processing, and an image of one frame are provided after the CDS / AGC circuit 31. A video memory 34 for storing data, a D / A converter 35, and a monitor 36 connected to the processor device are arranged.
[0015]
Further, an actuator drive circuit 38 for driving the actuators 28A and 28B disposed at the distal end portion 22 is provided. The circuits from the CDS / AGC circuit 31 to the actuator drive circuit 38 are distributed to one of the electronic endoscope and the processor device.
[0016]
In such an electronic endoscope device, a BPF (band-pass filter) unit 40 is provided, which receives an output video signal of the A / D converter 32 and extracts a high-frequency component of the video signal (luminance signal or the like). The BPF section 40 extracts two types of high-frequency components (first and second high-frequency detection signals) for evaluating the focus (or contrast) by using two BPFs having different pass bands (center frequencies). Further, a microcomputer 42 for controlling the overall control of the electronic endoscope or the processor device is provided, and a halation determination unit 42A and a passive autofocus (AF) control unit 42B are provided in the microcomputer 42.
[0017]
The halation determination unit 42A detects and determines a halation state in an imaging area (area) based on an output from the BPF unit 40 (or an output from the A / D converter 32). That is, as shown in FIG. 2, in the embodiment has set the 8 divided areas A to H of the imaging area (display area) E ₁ as a distance measurement area, in each of the ranging areas A to H, It is determined whether a halation state occurs by comparing whether the level of the output signal from the BPF unit 40 corresponding to the luminance signal is smaller than a preset threshold value a (level ≦ a). . When no halation has occurred based on the output of the halation determination unit 42A, the passive AF control unit 42B, for example, performs a focus evaluation calculation (focus voltage calculation or contrast calculation) from the high-frequency signals of all the distance measurement areas A to H. For example, if halation occurs in the distance measurement area H, focus evaluation calculation is performed from the high-frequency signals of the distance measurement areas A to G, and passive autofocus is performed by a hill-climbing operation.
[0018]
FIG. 3 shows a hill-climbing operation of the auto-focus control. In this control, the hill-climbing direction is determined from the calculated focus evaluation value (focal voltage). ) moving the position of the movable lens 25 and 26 toward the close distance from, by the lens position to grasp when the focus evaluation value and moves to P ₃ is lowered from P _2, a lens 25 within the depth of focus F, 26 is moved.
[0019]
The embodiment has the above configuration, and its operation will be described with reference to FIG. First, in the electronic endoscope apparatus of this example, an image of the inside of the object to be observed can be taken by the CCD 27 of FIG. 1, and image processing is performed by the CDS / AGC circuits 31 to D / A converter 35 in the subsequent stage. The image of the object to be observed is displayed on the screen of the monitor 36. When a zooming switch (zoom switch) (not shown) is operated, the movable lenses 25 and 26 are driven to the zooming position and the in-focus position, and the optically enlarged observation target image is captured by the CCD 27. Thereby, the enlarged image of the observed object is displayed on the screen of the monitor 36.
[0020]
Then, as shown in Step 101 of FIG. 5, when the microcomputer 42 receives an autofocus operation instruction, the position data of the movable lenses 25 and 26 is read in Step 102, and the first high-frequency detection signal is received in the next Steps 103 and 104. And the second high-frequency detection signal. Next, in Step 105, it is determined whether or not the signal level of the first high-frequency detection signal in the distance measurement areas A to H in FIG. 3 is smaller than a threshold value (set value) a. It is determined whether or not the signal levels of the ranging areas A to H of the high-frequency detection signal are smaller than a threshold value a. When it is determined that the value is equal to or larger than the threshold value a (level <a), the process proceeds to Steps 108 and 109.
[0021]
In the above Step 107, the focus evaluation calculation is performed in all the distance measurement areas A to H (in this case, it is possible to change not only all but also only the areas E to H in the center, for example), and the above Step 108 , 109, focus evaluation calculation is performed in a state excluding the area where halation has occurred. For example, as shown in FIG. 4, when the halation occurs in the portion of Ha on the screen of the monitor 36 and it is determined that the area of D and H is equal to or larger than the threshold a as shown in FIG. 2, The focus evaluation calculation is performed using the remaining ranging areas A to C and EG.
[0022]
Next, in Step 110, it is determined whether or not the subject is in focus based on the focus evaluation value obtained by the above focus evaluation calculation. If Y (YES), the process returns to the original state, and if N (NO), the process returns to the original state. The hill-climbing operation direction is determined in Step 111, and the lens operation is performed in the next Step 112. That is, the direction in which the focus evaluation value is improved is determined in either the direction from the long distance (∞) to the close distance or the direction from the close distance to the long distance, and the movable lenses 25 and 26 are moved in the determined direction. Move and return to Step 102. By repeating such an operation, the movable lenses 25 and 26 are finally moved to the in-focus position. As a result, an image or an enlarged image that is in good focus on the object to be observed is displayed on the monitor 36. Can be displayed.
[0023]
In this way, in this embodiment, the autofocus control is performed in the ranging area, excluding the halation portion where the high frequency component does not exist and the focus cannot be evaluated. Therefore, the autofocus control is performed with high accuracy. In addition, there is an advantage that hunting of the focusing operation near the top of the hill climbing operation (the maximum value of the focus evaluation) is not induced.
[0024]
【The invention's effect】
As described above, according to the present invention, it is determined whether or not the signal levels of the plurality of divided areas in the imaging area are at the halation level, and when the presence of the divided area at the halation level is determined, the Since passive autofocus control is performed based on the high-frequency signal in the area excluding the divided area, a precise focusing state can be obtained even when halation occurs, and especially the enlarged image of the electronic endoscope In this case, there is an effect that a clear and focused object image can be displayed and observed.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram illustrating a configuration of an electronic endoscope apparatus having an autofocus function according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a divided ranging area set in an imaging area according to an embodiment.
FIG. 3 is a diagram illustrating a hill-climbing operation in autofocus according to the embodiment.
FIG. 4 is a diagram showing a halation portion on a monitor screen according to the embodiment.
FIG. 5 is a flowchart illustrating an operation of the microcomputer according to the embodiment.
FIG. 6 is a cross-sectional view showing a configuration of a conventional electronic endoscope distal end portion.
[Explanation of symbols]
1,22 ... Endoscope tip
10, 25 ... first movable lens,
11, 26 ... second movable lens,
28A, 28B ... actuator,
31: CDS / AGC circuit, 33: DSP,
38 ... actuator drive circuit,
40: BPF unit, 42: microcomputer,
42A: halation determination unit,
42B ... Passive AF control unit,
A to H: divided ranging areas.

Claims (1)

An objective optical system having a movable lens that moves in the direction of the optical axis to change the focal length, and a solid-state imaging device that captures an image of an object to be observed via the objective optical system, and a video signal is output from an output of the solid-state imaging device In the electronic endoscope apparatus forming
A high-frequency signal extraction circuit for extracting a high-frequency signal for evaluating the focus state of the movable lens from the video signal,
Based on the video signal, a determination circuit that determines whether the signal level of each area obtained by dividing the imaging area into a plurality is at a halation level,
When passive autofocus control is performed based on the high-frequency signal output from the high-frequency signal extraction circuit, and when the determination circuit determines the presence of the divided area at the halation level, the area excluding the divided area at the halation level is excluded. An electronic endoscope device having an autofocus function, comprising: a passive autofocus control unit that performs passive autofocus control based on the high-frequency signal.

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