JP4336166B2 - Electronic endoscope device with autofocus function - Google Patents

Description

  The present invention relates to an electronic endoscope apparatus having an autofocus function, and more particularly to an electronic endoscope apparatus that captures an optically enlarged object image by a movable lens provided in an objective optical system and performs autofocus control. Concerning configuration.

  An electronic endoscope device mounts a CCD (Charge Coupled Device) or the like, which is a solid-state image sensor, on the tip of an electronic endoscope (electronic scope), and illuminates light from the light source device to image the object to be observed. In addition, a CCD image signal obtained by the electronic endoscope is output to a processor device, and an image of the object to be observed is displayed on a monitor by performing image processing on the processor device.

  FIG. 7 shows the configuration of the 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. 7, an observation window (lens) 3 is provided on the distal end surface of the support portion 2 of the endoscope distal end portion 1, and a prism 4 and a cover glass 5 are disposed behind the optical path of the observation window 3. A CCD 6 that is a solid-state image sensor is disposed. The CCD 6 is connected to a signal line 8 via a circuit board 7, and a signal imaged by the CCD 6 via the signal line 8 is supplied to the processor device.

  A first movable lens 10 and a second movable lens 11 constituting an objective optical system are disposed between the observation window 3 and the prism 4, and the holding frame 12 and the second movable lens 11 of the first movable lens 10. The holding frame 13 is attached to the camshaft 14 by engaging the engagement holes 12A and 13A with the outer periphery of the cylindrical camshaft 14. A cam pin 16 protrudes from the engagement hole 12A, and a cam pin 17 protrudes from the engagement hole 13A. Cam grooves 18 and 19 having different inclination angles with respect to the axis of the cam shaft 14 are formed. Thus, the cam pin 16 is engaged with the cam groove 18, and the cam pin 17 is engaged with the cam groove 19.

  A shaft 20Z of the motor 20 is attached to the cam shaft 14. Therefore, if the cam shaft 14 is rotated by rotation control 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 and 19 and the cam pins 16 and 17 ( A different amount of movement) is performed, and optical scaling (enlargement) is performed.

In recent years, as shown in Japanese Patent Laid-Open No. 2002-263058, an endoscope having an autofocus mechanism has been manufactured, and according to this autofocus mechanism and control, it is more than conventional. It is possible to display and observe an enlarged image or the like on which the focus is adjusted precisely and in detail on the monitor.
Japanese Patent Laid-Open No. 2001-100114 JP 2002-263058 A JP-A-8-334678

  However, as the autofocus control of the conventional electronic endoscope apparatus, passive autofocus control for driving the movable lenses 10 and 11 based on the focus evaluation signal extracted from the video signal is performed. In this passive method, It takes time to extract the focus evaluation signal, and there is a problem in that it is not possible to perform quick control that follows movement, particularly in an enlarged image. That is, since the video signal is formed in units of fields, the focus evaluation signal is also extracted every 1 field period (vertical scanning period) of, for example, 1/60 seconds, and the video has a high magnification rate. As the influence of the movement increases, for example, in the case of an observation object that moves at the timing of pulsation, an image that follows the movement cannot be obtained.

  On the other hand, active focus control that performs distance measurement (triangular side method) by receiving the reflected light of the projected light is performed as focus control for cameras and the like, not endoscopes. In order to measure a far distance in focus distance measurement, it is necessary to increase the width of the light receiving sensor in the base line length direction, and in order to increase the distance measurement resolution, the light receiving sensor itself is increased in size. However, when the light projecting portion and the light receiving portion are arranged at the distal end portion of the endoscope to be reduced in diameter, the arrangement space is limited, and if a wide light receiving sensor is mounted, the reduction in diameter is impaired. There is a problem of being.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to perform quick autofocus control following movement such as pulsation in an enlarged image. An object of the present invention is to provide an electronic endoscope apparatus having an autofocus function that does not impair the reduction in diameter.

  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 makes the observation magnification variable, and a solid-state imaging device that images an object to be observed through the objective optical system. A high-frequency signal for focusing evaluation is extracted from the video signal, and the movable lens is driven and controlled based on the signal. Passive autofocus control circuit, distance measuring means for measuring the distance to the object to be observed by an active method, and active autofocus control for driving and controlling the movable lens based on distance measurement information output from the distance measuring means The passive autofocus control circuit is executed up to a predetermined minimum magnification set by the circuit and the movable lens. A switching control circuit to perform the I Bed autofocus control circuit, characterized in that the provided.

In the invention according to claim 2, as the distance measuring means, a light projecting unit that projects distance measuring light toward the object to be observed, and reflected light from the object to be observed based on the light projection of the light projecting unit. A light receiving unit that receives light and outputs distance measurement information.
According to a third aspect of the present invention, there is provided an ultrasonic transmission / reception unit that transmits ultrasonic waves toward the object to be observed and receives reflected waves of the transmitted ultrasonic waves to obtain distance measurement information as the distance measuring means. It is characterized by that.

  According to the above configuration, for example, when the optical magnification ratio is a, the passive autofocus control is performed when the magnification is lower than this. In this passive autofocus, the focus is set by the high frequency signal of the video signal. Evaluation is performed (or contrast is evaluated), and the movable lens is hill-climbed in a direction in which the focus evaluation value is maximized, thereby obtaining an in-focus state (in-focus state). When the enlargement ratio is low, the influence of motion is small in video display, and passive autofocus control is sufficient as in the conventional case.

  On the other hand, when the magnification is higher than a times, active autofocus control is performed. In this active autofocus control, the reflected light of the projected light is received (or the reflected wave of the transmitted ultrasonic wave is received), The distance of the object to be observed is obtained from the light receiving position (reception state), and the movable lens is driven based on the distance measurement information. When the enlargement ratio is high, the influence of motion is large in video display, but the autofocus operation is performed in an extremely short time than one field period. A good (in-focus) image can be obtained.

  According to the electronic endoscope apparatus of the present invention, as described above, since rapid active autofocus control is performed in a region where the optical magnification ratio is high, a good image following movement such as pulsation can be obtained even during magnification. In addition, the light receiving unit used in active autofocus can use a small sensor in a region with a high enlargement ratio, and the diameter reduction of the endoscope is not impaired. In the magnification changing mechanism of the endoscope, when the magnification is increased, the focus position is shifted to the near distance side. That is, since the observation distance (distance from the scope tip to the object to be observed) is shortened, a small light receiving sensor that performs distance measurement on the short distance side is sufficient in an area where a high magnification is set.

  The present invention can be applied not only to performing distance measurement by light projection and reception as in the first embodiment, but also to active autofocus in which distance measurement is performed by transmitting and receiving ultrasonic waves as in the second embodiment.

  FIG. 1 shows the configuration of an electronic endoscope apparatus having an autofocus function according to the first embodiment. In FIG. 1, the endoscope distal end portion 21 has a first movable lens (or group) 23 and a second movable lens (or the rear side of the observation window 22) and the second movable lens (or Group) 24, and a CCD 25, which is a solid-state imaging device, is arranged behind the second movable lens 24. A signal picked up by the CCD 25 is supplied to a processor device via a circuit board and a signal line.

  The first movable lens 23 and the second movable lens 24 are attached to respective actuators 26A and 26B. As these actuators 26A and 26B, linear actuators such as piezoelectric actuators and electrostatic actuators, The cam mechanism shown in the figure is disposed in each of the movable lenses 23 and 24, and the cam shaft is driven by a motor or a linear transmission member. The actuators 26A and 26B cause the first and second movable lenses 23 and 24 to move back and forth relatively in the optical axis direction. The first movable lens 23 mainly serves as an autofocus (focusing). The second movable lens 24 is configured to serve as an optical scaling (observation distance, observation depth, focal length, etc. are variable).

  The tip 21 receives a light projecting unit 27B that projects distance measuring light (infrared light or the like) from the light projecting window 27A and a reflected light from the object to be observed for active autofocus control. A light receiving unit (light receiving sensor) 28B that receives light through the window 28A is provided. The sensor of the light receiving unit 28B may be a small sensor that can measure a short object distance (for example, 15 mm or less).

  The apparatus also includes a timing generator (TG) 30 for driving the above-described CCD 25, and a CDS (correlated double sampling) / input of the output signal of the CCD 25 to perform correlated double sampling operation and automatic gain control. An AGC (automatic gain control) circuit 31 is provided, and at the subsequent stage of the CDS / AGC circuit 31, an A / D converter 32, a DSP (digital signal processor) 33 for performing various video processes, and one frame of video A video memory 34 for storing data, a D / A converter 35, and a monitor 36 connected to the processor device are arranged. Further, an actuator drive circuit 38 for driving the actuators 26A and 26B arranged at the tip portion 21 is provided. The above-described circuits from the CDS / AGC circuit 31 to the actuator drive circuit 38 are allocated to either an electronic endoscope or a processor device.

  In such an electronic endoscope apparatus, a BPF (band pass filter) unit 40 is provided which inputs 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. In addition, a microcomputer 42 that controls the entire control of the electronic endoscope or the processor device is provided. In the microcomputer 42, a passive autofocus (AF) control unit 42A, an active autofocus (AF) control unit 42B, and a switching are provided. A control unit 42C is provided.

  The passive AF control unit 42A performs focus evaluation calculation from the two high-frequency signals extracted from the video signal and output from the BPF unit 40, and moves the movable lenses 23 and 24 to the maximum evaluation point (maximum focus voltage). Perform hill-climbing movements. On the other hand, the active AF control unit 42B outputs infrared light from the light projecting element of the light projecting unit 27B, and detects the detection signal of the position of light received by the light receiving unit 28B (position at the sensor). To control the movement of the movable lenses 23 and 24. A magnification switch 44 for a magnification operation is provided in an operation unit or the like of the electronic endoscope, and this operation signal is supplied to the microcomputer 42.

FIG. 2 shows the hill-climbing operation of the passive autofocus control. In this control, the hill-climbing direction is determined based on a focus evaluation value (focal voltage) calculated from two high-frequency signals. By moving the positions of the movable lenses 23 and 24 from a long distance (∞) to a close distance as in C, and grasping when the lens position moves from P ₂ to P ₃ and the focus evaluation value decreases, etc. The movable lenses 23 and 24 are moved within the focal depth F.

  FIG. 3 shows the relationship between the magnification and the distance of the best focus, the front depth of field (front focus position), and the rear depth of field (rear focus position) in Example 1. In the operation of the movable lenses 23 and 24, as the magnification is increased, the best focus position and the focused range shift to the front side (short distance side). In such an operation to change the observation distance, in the embodiment, when the magnification is a times or less (when the observation distance is on the far side) with a (for example, 75) times as a boundary, passive autofocus control is performed. When the magnification is larger than a times (when the observation distance is on the short distance side), active autofocus control is performed.

  The first embodiment has the above configuration, and its operation will be described with reference to FIG. First, in the electronic endoscope apparatus of this example, the inside of the observation object is imaged by the CCD 25 in FIG. 1, and after image processing by the circuits of the subsequent CDS / AGC circuits 31 to D / A converter 35, An image of the object to be observed is displayed on the screen of the monitor 36. When the zoom switch 44 is operated, the movable lenses 23 and 24 are driven to the zoom position and the focused position, and the optically enlarged object image is picked up by the CCD 25, and the monitor An enlarged image of the observed object is displayed on the screen 36.

  Then, as shown in Step 101 of FIG. 4, when the microcomputer 42 receives an autofocus operation instruction, in Step 102, the position data of the movable lenses 23 and 24 is read, and in the next Step 103, the currently set magnification is set. It is determined whether it is higher than a times. Here, when the magnification is a or less (≦ a) [N (NO)], the passive AF control unit 42A is executed, and in the next Step 104, the video signal is input to the BPF 40, and the first high-frequency signal is detected. (Step 105) and detection of the second high-frequency signal (Step 106) are performed, and in the next Step 107, focus evaluation calculation based on the two high-frequency signals is performed.

  Next, in Step 108, it is determined whether or not the subject is in focus based on the focus evaluation value obtained by the above-described focus evaluation calculation. When Y (YES), the process returns to the original state. An operation direction is determined and a lens operation is executed (Step 110). 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 23 and 24 are moved toward the determined direction. Move to step 102. By repeating such an operation, the movable lenses 23 and 24 finally move to the in-focus position, and as a result, a normal or enlarged image that is well focused on the object to be observed is displayed on the monitor 36. Is done.

  On the other hand, when the magnification is higher than a (> a) in Step 103 (Y), the active AF control unit 42B is executed, and the light projection by the light projecting unit 27B is performed in Step 111. Thus, the reflected light is received by the light receiving unit 28B. When the light receiving position output from the light receiving unit 28B is input to the control unit 42B (Step 113), after ranging is performed in Step 114, the movable lenses 23 and 24 are driven (Step 115), thereby focusing. Is done.

  FIG. 5 shows a diagram comparing the video output and the operation of the sensor (photodiode) used in the light receiving unit 28B. A video signal of one field can be obtained in 1/60 second (vertical scanning period). On the other hand, the light receiving unit 28B receives the reflected light in 1/400 seconds. Further, the lens operation from the distance measurement calculation in the active autofocus control is performed in a short time compared to the lens operation from the focus evaluation calculation in the passive autofocus control. Therefore, even when the object to be observed moves at the timing of the pulsation in a state where the image is magnified at a magnification higher than a times (an area where the observation distance is near), it is possible to capture the movement. There is an advantage that a picture is taken. On the other hand, in the case of a times or less (the region where the observation distance is on the far side), a good image similar to the conventional one can be obtained by passive autofocus control.

  FIG. 6 shows the configuration of the second embodiment. This second embodiment applies an active method for transmitting and receiving ultrasonic waves as a distance measuring means. As shown in FIG. 6, in the second embodiment, an ultrasonic transducer 46 and a transmission / reception unit 47 for converting an ultrasonic wave and a signal are provided at the endoscope distal end portion 21 as active distance measuring means. When an ultrasonic pulse is transmitted from the ultrasonic transducer 46 based on the transmission signal output from the transmission / reception unit 47, the reception signal of the reflected wave reflected from the observation object is received by the transmission / reception unit 47 via the ultrasonic transducer 46. Is done. In the transmitter / receiver 47, distance information of the object to be observed is obtained from the difference between the transmission time and the reception time of the ultrasonic wave. Then, this distance information is supplied to the above-described active AF control unit 42B in the microcomputer 42, thereby performing active autofocus control when the magnification ratio is higher than a times as in the first embodiment.

1 is a circuit block diagram showing a configuration of an electronic endoscope apparatus having an autofocus function according to Embodiment 1 of the present invention. It is a figure which shows the mountain climbing operation | movement in the passive autofocus control of an Example. It is a figure which shows the relationship between the magnification set in an Example, and observation distance, and the operation | movement range of passive autofocus control and active autofocus control. It is a flowchart which shows the operation | movement with the microcomputer of an Example. It is a figure which shows the image | video output of an Example, and the operation | movement of the sensor of a light-receiving part. FIG. 10 is a block diagram illustrating a configuration of a distal end portion of an electronic endoscope apparatus having an autofocus function according to a second embodiment. It is sectional drawing which shows the structure of the conventional electronic endoscope front-end | tip part.

Explanation of symbols

1, 21 ... End of endoscope,
10, 23 ... 1st movable lens,
11, 24 ... second movable lens,
26A, 26B ... Actuator,
27B: Light projecting unit, 28B: Light receiving unit,
31 ... CDS / AGC circuit, 33 ... DSP,
38 ... Actuator drive circuit,
40 ... BPF part, 42 ... microcomputer,
42A: Passive AF control unit,
42B ... Active AF control unit,
42C ... switching control unit,
46: Ultrasonic transducer, 47: Transmission / reception unit.

Claims (3)

An objective optical system having a movable lens that moves in the optical axis direction and makes the observation magnification variable, and a solid-state imaging device that images the object to be observed through the objective optical system, and outputs an image signal from the output of the solid-state imaging device In an electronic endoscope device forming
A passive autofocus control circuit that extracts a high-frequency signal for focusing evaluation from the video signal and controls the driving of the movable lens based on the signal;
Distance measuring means for measuring the distance to the object to be observed by an active method;
An active autofocus control circuit that drives and controls the movable lens based on distance measurement information output from the distance measurement means;
A switching control circuit that executes the passive autofocus control circuit up to a predetermined minimum magnification set by the movable lens and executes the active autofocus control circuit when higher than the minimum magnification; An electronic endoscope apparatus equipped with an autofocus function.   As the distance measuring means, a light projecting unit for projecting distance measuring light toward the object to be observed, and a reflected light from the object to be observed based on the light projection of the light projecting unit are received, and distance measurement information is output. 2. The electronic endoscope apparatus according to claim 1, further comprising a light receiving unit that performs the operation.   The ultrasonic transmission / reception unit that transmits ultrasonic waves toward the object to be observed and receives reflected waves of the transmitted ultrasonic waves to obtain distance measurement information is provided as the distance measuring means. The electronic endoscope apparatus according to 1.

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