JPH0444246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a spot light guide provided in a light guide to transmit illumination light within a light source and irradiate it onto a subject, and a non-photosensitive part is provided to absorb this reflected light. A focus detection device for an endoscope that can detect a focused point by detecting it with a light receiving element, and a focus detection device for an endoscope that automatically moves and sets a photographing lens to the focused point. The present invention relates to a focus setting device for an endoscope.

In recent years, endoscopes have been widely used in the medical and industrial fields. Particularly in the medical field, in addition to directly observing and diagnosing organs within the body cavity by bringing the eye close to the endoscope eyepiece, cameras, television cameras, etc. are attached to take photographs, etc., to serve as the key to diagnosis. Recording is widely practiced.

In the above case, when observing with the naked eye, the operator can adjust his or her diopter to form a clear optical image, that is, bring it into focus (focus point), but the camera, When a photographic device such as a television camera is attached, the photographic lens must be adjusted to a focused point in order to take clear photographs.

In order to bring the photographing lens into focus, it is desirable to have a means that can clearly detect whether or not it is in focus.

The applicant first installed a focusing lamp inside the photographic adapter, and by receiving the reflected light from the subject illuminated by this lamp with a light-receiving element provided with a small opening, it is possible to determine whether or not the focal point is in focus. We have proposed a means for detecting (focus detection). In this case, the amount of lamp light tends to be relatively limited due to the space accommodated in the adapter, etc., and the amount of light input to the light receiving element is limited. Therefore, it is difficult to sufficiently increase the difference in the detection output of the light-receiving element between the in-focus point and the other cases, and there has long been a desire for a means that can easily perform more reliable focus detection with high accuracy.

The present invention has been made in view of the above-mentioned points, and is a spot light light guide that can separate a part of the light guide inserted into an endoscope from other parts, transmit illumination light, and emit it from the end face. and a light receiving element provided with a minute non-photosensitive part for receiving reflected light from the subject irradiated by the spot light light guide, and a detection device for detecting the extreme value of the output of the light receiving element. An endoscope equipped with an endoscope focus detection device that enables easy and reliable detection of a focused point, and a drive device that moves and sets the endoscope focus detection device and a photographing lens to the focused point. The object of the present invention is to provide a focusing point setting device for use in the present invention.

Hereinafter, the present invention will be specifically described with reference to the drawings.

1 to 4 relate to an embodiment of the present invention, and FIG. 1 shows an optical system of an endoscope focus setting device using an embodiment of an endoscope focus detection device,
2 and 3 are diagrams for explaining the principle of focus detection, and FIG. 4 is a block diagram showing the configuration of the electric circuit system of the focus setting device for an endoscope.

In Fig. 1, there is shown an elongated insertion section 1 that houses an objective optical system and an illumination optical system at its distal end, the distal end side is connected to the proximal end of this insertion section 1, and a light guide base is attached to the side thereof. A camera adapter 5 is removably attached to the rear end side of the eyepiece 3 of an endoscope 4, which has an eyepiece 2 and an eyepiece 3 in which an eyepiece optical system is housed. This camera adapter 5
A camera 6 or a television camera can be detachably attached to the rear end side.

The camera adapter 5 houses a focus setting device for an endoscope that can automatically move and set the photographic lens to a focused point using the focus detection device (for an endoscope) according to the present invention.

That is, on the optical axis 7 when the endoscope 4 is attached, there is a movable back and forth (on the optical axis 7) at a rear position facing the eyepiece system of the endoscope 4 as shown by the arrow. A photographic lens 8 is disposed, and on the optical axis 7 behind the photographic lens 8 is a focusing mirror 9 formed of a semi-transparent mirror and inclined (for example, 45 degrees inclined) with respect to the optical axis 7.
is installed.

A re-imaging lens 10 and a photoelectric element 11 are sequentially disposed on the reflected optical axis (in the upper position in FIG. 1) where the light incident along the optical axis 7 is reflected by the focusing mirror 9. With respect to the optical axis 7, the focusing mirror 9
A lamp lens 13 and a focus indicator lamp 14 for indicating focus are sequentially disposed on the reflected optical axis on the back surface side (lower position in FIG. 1).

The photoelectric element 11 has a pinhole 1 in the center.
5, or has a disk shape (of course, it may be square or rectangular) with a non-photosensitive part such as a slit-shaped square hole, and the front surface of this disk can be used for devices that are sensitive to light, such as photodiodes, phototransistors, etc. The photocathode 17 is formed of an element whose current characteristics change depending on light, an element which generates a photovoltaic force such as a solar cell, an element whose resistance value changes such as a CDS, and the like.

On the other hand, in the camera 6 attached from the rear of the camera adapter 5, a return mirror 21 is arranged on the optical axis 7 behind the focusing mirror 9 and is inclined with respect to the optical axis 7 (for example, a 45-degree inclined surface). Further, a photographic film 22 is disposed behind it.

A pentaprism 23 is disposed on the reflection optical axis of the return mirror 21 (in the upper direction in the figure), and the pentaprism 23 is horizontally inverted and returned to an erect image.
A finder lens 24 is disposed on the optical axis passing through the viewfinder lens 24, and the viewfinder lens 24 is configured so that an optical image equivalent to that formed on the film 22 can be observed by bringing the eye close to the rear thereof. The return mirror 21 is retracted during photographing, and the incident light is directed to the film 22.
It is configured to be imaged onto a surface.

The position of the photocathode 17 of the photoelectric element 11 is arranged to be conjugate with the position of the surface of the film 22.

That is, the optical path length when the light passing through the photographic lens 8 is imaged on the rear film 22 surface, and the optical path length when the light is reflected by the focusing mirror 9, passes through the re-imaging lens 10, and forms an image on the photocathode 17 of the photoelectric element 11. The optical path lengths are set to be equal when images are formed.

On the other hand, in the light guide 31 inserted into the insertion section 1 of the endoscope 4, this light guide 3
The light guide fiber inserted on the optical axis 7 or closest to the optical axis 7 among the light guide fibers constituting the light guide 31a is the spot light guide 31a.
The illumination light from the light source 33 is transmitted through the universal cord 32 at the light guide base portion 2 which is the end portion of the light guide 31 . Universal code 32 above
In the light guide fiber constituting the light guide fiber, the portion connected to the spot light guide 31a at the light guide base portion 2 is a spot light guide 32a, which is connected to the spot light guide 32a by (adjusting) the aperture 34 close to the light source 33. The illumination light is supplied only to the end face of the spot light guide 32a, and this light is irradiated from the distal end face toward the subject 25 by the spot light guide 31a inserted through the insertion portion 1. has been done.

Regarding the focus detection function of the camera adapter 5 that accommodates the focus detection device for an endoscope having the optical system arranged in this way and the focus setting device for an endoscope using this device, firstly, it is The principle will be explained with reference to Figure 2, which is a simplified optical system.
After that, the operations of the endoscope focus detection device and the endoscope focus setting device will be explained.

As shown in FIG. 1, the illumination light from the light source 33 is supplied only to the spot light guide 32a through the diaphragm 34, and this light is transmitted to the spot light guide 31a inside the insertion section 1. Light is projected toward the subject 25 from the tip. The light that is projected and reflected by the subject 25 passes through the photographic lens 8 and returns to the photoelectric element 11 side.
is in focus when the lens is at the position indicated by the symbol b, and the positions when it is too close or too far away are indicated by the symbols a and c, respectively.

In the above case, the light reflected at the position b passes through the photographing lens 8 and becomes the convergence point (image formation point) at the position of the pinhole 15.
No light reaches the photocathode 17 around the photocathode 5. on the other hand,
The light reflected at the position a has a convergence point at the rear position of the pinhole 15, so the light reaches the photocathode 17 on the outer periphery of the pinhole 15 as shown in the figure.
A signal corresponding to this light is output. Similarly, code c
The light reflected at the position already becomes a convergence point at the position in front of the pinhole 15 and then spreads out, so that the light reaches the photocathode 17 and the photoelectric element 11 outputs a signal for this light.

In the above description, the light from the light source 33 is emitted along the vicinity of the optical axis 7, and in reality, some reflected light is also incident from a position shifted from the vicinity of the optical axis 7, so that the light of the photoelectric element 11 is The output signal is increased by the output level due to the above-mentioned external light, and becomes as shown in FIG. Here, the horizontal axis indicates the position of the subject 25, and the vertical axis indicates an example of the detection output level of the photoelectric element 11.

That is, the position where the subject 25 is in focus, that is, the position b
The output level Pb of the photoelectric element 11 at the position is the minimum, and the signal output levels Pa and Pc increase even if the position is closer or further away. In this way, the position where the signal output is minimum (depending on the photoelectric element, it may be maximum) is in focus, so for the subject 25 at any distance,
The photographic lens 8 is moved and the position of the photographic lens 8 where the output of the photoelectric element 11 is minimum becomes the focus.
If you take a photograph or the like at that position, you can take a clear photograph. When moving this photographic lens 8, the direction in which the output level becomes smaller than before moving indicates that it is getting closer to focus.
The photographic lens 8 may be moved in this direction manually or automatically. When setting automatically, if the movement of the photographic lens 8 is stopped at a point where the output level starts to increase or stops changing, the photographic lens 8 can be set at the in-focus position for the subject 25 at an arbitrary distance. It can be installed in

The above-mentioned principle is that the re-imaging lens 10 and the focusing mirror 9 are disposed between the photoelectric element 11 at the rear of the photographic lens 8, and the object 25 in front of the photographic lens 8 is
The optical system within the camera adapter 5 shown in FIG. 1 can be applied in exactly the same manner, except that the endoscope 4 is disposed between the ends.

In the camera adapter 5 shown in FIG. 1, when the camera is in focus, the focus indicator lamp 1
4 lights up, this light is focused by the lamp lens 13, reflected by the focusing mirror 9, travels toward the rear of the optical axis 7, and then passes through the return mirror 21 and the pentaprism 2.
3 Furthermore, since the light enters the observer's eyes through the finder lens 24, a clear photograph can be taken if the photograph is taken when the focus indicator lamp 14 is lit.

The illumination light for focus detection described above can be supplied from an external light source 33 via the universal cord 32, so a lamp with a sufficient amount of light can be used without being limited by space etc., and the irradiation beam can be made sufficiently strong for detection. Sensitivity and signal-to-noise ratio (SN ratio)
This means that it is possible to improve the

FIG. 4 shows, using electric circuit blocks, an endoscope focus setting device for moving and setting the photographing lens 8 to a focused point using the above-described focus detection device, and an automatic exposure device.

That is, this focus setting device 41 for an endoscope uses a focusing lamp (a light source 3 narrowed down by an aperture 34) on a subject 25.
Corresponds to 3. ) 42 and a light emitting circuit 43 that emits light, and a signal output detected by the photoelectric element 11 provided with a non-photosensitive part such as a pinhole 15 for reflecting light from the subject 25 is amplified to determine whether or not it is in focus. A focus detection circuit 44 for detecting focus, an indicator 45 (corresponding to the focus display lamp 14) that displays when in focus,
A (taking lens) drive device 4 that moves the taking lens 8 in order to set the taking lens 8 to the in-focus position.
6 and more.

The light emitting circuit 43 is, for example, a release button 4.
By pressing 7, switch SW ₁ is turned on from off (switch SW ₂ is also kept on during this time), and power is supplied from power source (indicated by a battery) 48 to aperture the light from light source 33. 34, that is, the spot light guides 32a, 3
Illumination light is transmitted only to 1a, and the object 25 is illuminated by this light. The focus detection circuit 44 includes an amplifier 49 that amplifies the output signal of the photoelectric element 11, and a comparison detection circuit 50. For example, the drive device 46 moves the photographic lens 8 back and forth at a constant speed. When the sensor is moved, the detection signals (amplified by the amplifier 49) are sequentially inputted at appropriate intervals, and the previously inputted signal value is compared with the subsequently inputted signal value. outputting a detection signal to stop the driving device 46 when the later input signal is equal to or larger than the previously input signal;
While moving the photographic lens 8 in the opposite direction, the detection signal is integrated by setting an appropriate time constant, and the integral output (or the number of detection signals input within a certain period of time is measured, and the measured number is ) is above a certain value, the indicator 45 is turned on and the operation of the drive device 46 is stopped.

On the other hand, when the release button 47 is further pressed, the third switch SW ₃ is turned on from off (the second switch SW ₂ is turned off and the endoscope focus setting device 41 does not operate), and the following occurs. The automatic exposure (EE) device 51 described in 1 is configured to operate.

That is, this EE device 51 includes an amplifier 54 that is supplied with power from a power source 52 when the switch SW ₃ is turned on and amplifies a detection signal of a photosensitive photoelectric element 53, and an EE shutter 55 that uses this amplified signal. Each controls a light amount control circuit 56 that controls the shutter speed and the light amount of the light source 33 for photographing.
Consists of the EE control circuit 57 and the above switch SW ₃
By turning on the EE control circuit 57, the shutter speed and amount of light are adjusted to an appropriate level.

The endoscope focus setting device 41 configured as described above moves and sets the photographing lens 8 to the in-focus position by the following operations.

That is, when the release button 47 is pressed with a finger or the like,
When the switch SW ₁ is turned on, the light emitting circuit 43 is turned on with the light source 33 narrowed down by the aperture 34, and this light is transmitted through the spot light guide 32a in the universal cord 32 and the spot light passed through the insertion section 1. The light is projected onto the subject 25 in a spot-like manner through the light guide 31a.

The light reflected by the object 25 passes through the photographic lens 8, is reflected by the focusing mirror 9, and travels to the photoelectric element 11 provided with the pinhole 15. When the photographic lens 8 is in a focused position with respect to the subject 25, the output level of the photoelectric element 11 becomes minimum. Therefore, in this case, when the driving device 46 moves the photographic lens 8 forward, for example, the output level increases, so the forward movement is immediately stopped, and the comparison detection circuit 50 outputs a detection signal, and at the same time, The drive device 46 moves the photographing lens 8 in the opposite direction. In this case as well, the output level increases, so a detection signal is output, the photographic lens 8 is stopped from moving backward, and is moved in the opposite direction (i.e., forward), so that the photographic lens 8 is focused. It vibrates minutely on the optical axis 7 of the position.
In this case, since a detection signal is output from the comparison detection circuit 50, when the signal is passed through an integrating circuit or a counting circuit having an appropriate time constant, the output becomes a certain value or more, and the above-mentioned micro-vibration operation is stopped.

On the other hand, when the photographic lens 8 is deviated from the in-focus position, when the drive device 46 first moves the photographic lens 8 in the direction opposite to the in-focus position, the photoelectric element 1
The output level of 1 increases (gradually), so
The comparison detection circuit 50 controls the drive device 46 to move the photographing lens 8 in the opposite direction in the same manner as described above. When the photographic lens 8 passes the in-focus position, the same minute vibration operation as described above is repeated, and the photographic lens 8 is placed at the in-focus position.

When the photographic lens 8 is placed in the focused position in this way, the indicator 45 such as the focus indicator lamp 14 lights up, so the observer visually confirms this and then presses the release button 47 more firmly. Then, the diaphragm 34 is opened and the EE device 51 is activated to take a photograph. In this case, the EE devices 51 can be operated simultaneously or sequentially. Moreover, the above-mentioned display 45
Alternatively, a buzzer or the like may be operated instead of lighting a lamp.

In the embodiment described above, the camera adapter 5 (such as a camera or a television camera) attached to the endoscope 4 is provided with an endoscope focus detection device and an endoscope focus setting device 41. It goes without saying that the camera adapter 5 and camera 6 can be provided in an integrated device.

Further, the photoelectric element 11 in the above-described embodiment may not have an opening such as a pinhole 15, and the portion corresponding to the opening may be a non-photosensitive portion 15a that is not exposed to light, for example, as shown in FIG. .

Note that the output of the photoelectric element 11 (combined with the electronic circuit) may become large, contrary to the fact that it becomes small when no light is incident on the element or circuit, as described above. When is in focus, the output level of the photoelectric element 11 reaches its maximum value.

Furthermore, if the aperture 34 is configured with a filter, that is, if light of a specific wavelength is supplied only to the spot light ride guide 32a, the SN ratio can be improved even if illumination light is supplied to other light guide parts. Therefore, observation and focus detection can be performed simultaneously.

As described above, according to the focus detection device for an endoscope of the present invention, illumination light from a light source having a sufficient amount of light is projected onto the subject in a spot-like manner, and the light reflected by the subject is transmitted to the non-exposed area. Since the image is formed on the photoelectric element having a It is possible to irradiate the subject with a sufficient amount of illumination light for focus detection without increasing the volume and weight of the camera, enabling accurate focus detection without sacrificing operational functionality in endoscopes with dark optical systems. It has the effect of making it possible.

Further, the focus setting device for an endoscope is configured to move the photographing lens and set the focus point using the focus detection device for the endoscope, which enables the above-mentioned highly accurate focus detection. Therefore, the photographing lens can be set to a focal point with high accuracy without impairing operational functionality, and this has the effect of enabling clear photography.

[Brief explanation of drawings]

1 to 5 are related to the present invention,
FIG. 1 shows the optical system of an endoscope focus setting device using the endoscope focus detection device according to the present invention, which is housed in a camera adapter that is inserted when a camera is attached to an endoscope. An explanatory diagram showing the system. Figure 2 is a schematic diagram showing the focus detection operation of the optical system in Figure 1 converted to a linear optical system. Figure 3 is a diagram showing the focus detection operation of the optical system in Figure 2. A characteristic diagram showing the output characteristics of the photoelectric element when the position is changed, and FIG. 4 is a focus setting device and automatic exposure device for an endoscope that moves and sets the photographing lens to the in-focus position using an electric circuit block. FIG. 5 is a front view showing another example of the shape of the photoelectric element. 1...Insertion section, 2...Light guide cap section, 3
...Eyepiece, 4...Endoscope, 5...Camera adapter, 6...Camera, 7...Optical axis, 8...Photographing lens, 9...Focusing mirror, 10...Reimaging lens, 11... photoelectric element, 13... lamp lens,
14... Focus indicator lamp, 15... Pinhole,
17...Photocathode, 21...Return mirror, 22
...Film, 23...Pentaprism, 31...
...Light guide, 31a, 32a...Spot light light guide, 32...Universal cord, 3
3...Light source, 34...Aperture, 41...Endoscope focus setting device, 42...Focusing lamp, 43...Light emitting circuit, 44...Focus detection circuit, 45...Display device, 46... Drive device, 47... Release button, 51... Automatic exposure device.

Claims (1)

[Scope of Claims] 1. Illumination light from a light source is projected onto a subject via a light guide within an endoscope, and the light reflected from the subject is reflected by a light source attached to the eyepiece of the endoscope and movable inside. In an endoscope photographing device that forms an image on an image forming surface such as a film through a photographing lens that can be photographed, a non-light sensitive device is disposed at a position optically conjugate with the image forming surface and receives reflected light from the subject. An endoscope comprising: a light-receiving element having a section; a means for detecting a maximum value or a minimum value of the output of the light-receiving element; and a light guide for transmitting spot illumination light within the endoscope. Focus detection device for mirrors. 2. Illumination light from a light source is projected onto a subject via a light guide within the endoscope, and the light reflected from the subject is transmitted via a photographic lens attached to the endoscope eyepiece and movable inside. In an endoscope photographing device that forms an image on an image forming surface such as a film, a light receiving element is provided at a position optically conjugate with the image forming surface and has a non-photosensitive part that receives reflected light from a subject. , a means for detecting a local maximum value or a local minimum value of the output of the light receiving element, and a means for moving and setting the photographing lens so that the output of the light receiving element becomes the local maximum value or the local minimum value; A focus setting device for an endoscope, characterized in that a light guide for transmitting spot illumination light is provided therein.