Measuring Endoscope

(A) Field of the Invention

The present invention relates to an endoscope arranged to be able to perform a three-dimensional measurement by utilizing Moire topography.

(B) Description of the Prior Art

In case Moire topography is performed, it is in general necessary to provide a lattice for both the illumination optical system and the observation optical system. When it is intended to make an ordinary topographic observation by using these same optical systems, such a lattice hinders the observation. Especially, in case of a small-sized optical instrument such as endoscope, it is practically impossible to detachably mount a lattice within the foremost end portion of the instrument, and thus the prior known endoscope have the drawback that, for performing a Moire topography and an ordinary endoscopic observation, two separate endoscopic instruments (each being designed for a different specific purpose) have to be used. Also, there has been placed on the market an endoscopic instrument in which the lattice for observation optical system is omitted because the image of an object is scanned by using a photomultiplier. In such an instrument, it has been impossible to house a photomultiplier within the small space at the foremost end portion of the instrument because the size thereof is too large.

It is, therefore, the primary object of the present invention to provide an endoscope which allows measurements including three-dimensional measurement by Moire topography without the use of a special lattice and without affecting ordinary endoscopic observation in any way.

This object is achieved according to the present invention by the arrangement comprising: an illumination light supply consisting of a plurality of fine illuminating members which are disposed regularly; illumination optical system for projecting the beam of light of said light supply onto an object under study; a focusing optical system for forming the image of the object; image pickup means consisting of a plurality of picture elements regularly disposed at the position of the object image formed by the focusing optical system; and controlling means for controlling the illumination of the respective fine illuminating members to insure that the illumination light supply will illuminate in the form of lattice so that, by this lattice-form illumination given by the illumination light supply, there are performed measurements of the object including a three-dimensional measurement thereof.

According to a preferred formation of the present invention, the illumination light supply comprises a light guide which is formed by placing together a large number of optical fibers into a bundle and whose light-incidence end is bifurcated into two portions. It should be noted that those optical fibers in these two light-incidence end portions are arranged, at the single light-emission end of this light guide, in such a pattern that the optical fibers in one of the incidence end portion and those in the other incidence end portion Between the light supply and the light-incidence ends of the light guide, there is provided a rotary filter having a red light transmitting sector, a green light transmitting sector, a blue light transmitting sector and an infrared light transmitting sector. The infrared light transmitting sector is constructed so as to insure that the infrared light beam impinges onto only one of the two light-incidence ends of the light guide whereby allowing the illumination light supply to emit light with a lattice pattern.

According to another preferred formation of the present invention, the illumination light supply is constructed as an array of successively arranged LEDs emitting a red light, a green light, a blue light and an infrared light, respectively.

According to still another preferred formation of the present invention, one of the two light-incedince end portions of the light guide is covered with an infrared light cutting filter, and an incandescent light is used as the light supply. In this case, striped filters for separating colors are provided in the foreground of the image pickup device.

According to the present invention, it will be noted that, at the time of an ordinary endoscopic observation, it is possible to perform a three-dimansional measurement of an object under observation by Moire topography without providing any visually obstructive lattice. It is also possible to indicate on a color display a compound image consisting of the image of the object under examination and a contour image formed by Moire fringes superposed on the image of the object. Thus, it is possible to present, with an improved reality, the concavo-convex, i.e. uneven, pattern of the surface of the object under observation. Moreover, the system as a whole can be constructed in a compact size, so that the resulting endoscopic instrument can be used very conveniently.

These and other objects of the present invention will become more apparent during the course of the following description and appended claims.

FIG. 1 is a diagrammatic general illustration of an embodiment of the endoscope according to the present invention.

FIG. 2 is a diagrammatic detailed illustration of a light guide employed in the embodiment of FIG. 1.

FIG. 3 is a diagrammatic front view of a rotary filter of FIG. 1.

FIGS. 4 and 5 are illustrations for explaining the principle for allowing the observer to know the unevenness of the surface of an object by utilizing Moire fringes.

FIG. 6 is a diagrammatic illustration showing the unevenness of the surface of an object which is to be shown on the display.

FIG. 7 is a diagrammatic illustration showing the signal readout section of a solid-state image sensor.

FIG. 8 is a block diagram showing a signal readout circuit of the solid-state image sensor.

FIG. 9 is a diagrammatic illustration showing the structure of an interline transfer type solid-state image sensor.

FIGS. 10A and 10B are diagrammatic illustrations showing the entirety and a part, respectively, of an illuminating lens moving mechanism.

FIGS. 11A and 11B are diagrammatic illustrations, respectively, for explaining a second embodiment of the present invention.

FIGS. 12A, 12B and 12C are diagrammatic illustrations for explaining a third embodiment of the present invention.

FIG. 13 is a block diagram of the electric circuit portion which is applied to the third embodiment.

The present invention will hereunder be described with respect to the embodiments illustrated in the accompanying drawings.

In FIG. 1, reference numeral 1 represents a light supply lamp; 2 a light guide having bifurcated light-incidence ends 2a and 2b and having one light-emission end 2c where respective optical fibers are regularly arranged as shown in FIG. 2 in such a way that the optical fibers in the two light-incidence end portions 2a and 2b are arranged at the light-emission end in alternate rows of fibers relative to each other; 3 a rotary filter disposed between the light supply lamp 1 and the light-incidence ends of the light guide 2, and which is divided into four sectors consisting of a red light transmitting sector 3a, a green light transmitting sector 3b, a blue light transmitting sector 3c and an infrared light transmitting sector 3d as shown in FIG. 3. Furthermore, the infrared light transmitting sector 3d is constructed to have an opaque region 3d' to face the sector 2b of the light incidence end of the light guide 2 when the sector 3d is placed in a light path; 4 an illumination lens for projecting onto the object 5 under observation the light-emission end of the light guide 2 as being the illumination light supply which consists of a plurality of fine light-emitting members; 6 an objective lens of the observation optical system for forming the image of the object 5 under observation; and 7 a solid-state image sensor disposed at the focusing position of the objective lens 6. Numeral 8 represents a synchronizing circuit; 9 a motor driving circuit for driving a motor M which rotates the rotary filter 3 in accordance with a control signal delivered from the synchronous circuit 8; 10 a driving circuit for actuating the solid-state image sensor 7 based on a control signal delivered from the synchronous circuit 8; 11 a preamplifier for amplifying an output signal delivered from the solid-state image sensor 7; 12 a processing circuit; 13 an A/D converter circuit; 14 a multiplexer; 15 to 18 memories for being inputted with signals allotted, respectively, by the multiplexer 14 to correspond to the illuminations of red light, green light, blue light or infrared light emitting in synchronism with the rotation of the rotary filter 3; 20, 21 and 22 D/A converter circuits, respectively; 23 a color encoder; 24 a mixing circuit; 25 a color display; 26 a measuring and processing circuit for processing various data such as determination or identification of the frequency of Moire fringes, removal of unwanted fringes, and so forth, and for performing image processing; 27 a D/A converter circuit; 28 a projection image processing circuit for converting that output of the measuring and processing circuit 26 which has already been converted by the D/A converter circuit 27 to an analog signal into a compound projection image signal; and 29 a color display for indicating a contour image of the object 5 under observation as depicted by Moire fringes in accordance with the signal coming from the projection image processing circuit 28. The forward end portion of the light guide 2, the illuminating lens 4, the objective lens 6 and the solid-state image sensor 7 are housed especially in the foremost end portion of the main body E of the endoscope.

The embodiment of the present invention is construction as described above. Therefore, the beam of light emitting from the light supply lamp 1 is successively converted to a red light, a green light, a blue light and an infrared light along with the rotation of the rotary filter 3 driven by the motor M, to illuminate the object 5 of observation via the light guide 2 and the illuminating lens 4. It should be noted. however, that the beam of infrared light which is transmitted through the rotary filter 3 when the infrared light transmitting sector 3d of the rotary filter 3 is inserted in the path of light will enter into the light guide 2 only through the light-incidence end 2a thereof. Therefore, the infrared light beam will emit at the light-emission end of the light guide 2 through every other row of optical fibers. Thus, the object 5 under survey will be illuminated with stripes or fringes. On the other hand, when either one of the other light-transmitting sectors of the rotary filter 3, i.e. either the red light transmitting sector 3a, the green light transmitting sector 3b or the blue light transmitting sector 3c, is inserted in the path of light beam, it will be noted that the red light, the green light or the blue light which has transmitted through the rotary filter 3 will enter the light guide 2 through both of the light-incidence ends 2a and 2b of the light guide 2, and as a result the light beam will emit through the entire output region of the light-emission end 2c of the light guide 2. Accordingly, the object 5 under observation is illuminated uniformly. The light reflected from the illuminated object 5 under survey is thus focused on the solid-state image sensor 7 by the focusing lens 6. This solid-state image sensor 7 is actuated by the driving circuit 10 in synchronism with the rotation of the rotary filter 3 based on a control signal delivered from the synchronous circuit 8, and output signals of the image of the object produced by the red light, the green light, the blue light and the infrared light, successively. These signals which are outputted are amplified by the preamplifier 11 and are processed by the processing circuit 12, and they are converted to digital signals by the A/D converter 13, and these digital signals are allotted to respective memories 15 to 18, respectively, by the multiplexer 14. That is, the image signal produced by the red light is inputted to the memory 15; the image signal developed by the green light is inputted to the memory 16; the image signal formed by the blue light is inputted to the memory 17; and the image signal caused by the infrared light is inputted to the memory 18, respectively. Those image signals due to the red light, the green light and the blue light which have been stored in the memories 15, 16 and 17, respectively, are read out simultaneously by the timing signal coming from the synchronous circuit 8, and are converted to analog signals by the D/A converter circuits 20, 21 and 22, respectively, and are supplied to the color encoder 23, where video signals are produced. These video signals are supplied further to the mixing circuit 24 where they are added with a synchronous signal delivered from the synchronous circuit 8 to thereby become a compound projection image signal to be displayed on the color display 25. Also, the image signal due to the infrared light, which has been stored in the memory 19, is first processed by the measuring and processing circuit 26, and thereafter it is converted to an analog signal by the D/A converter circuit 27, and is supplied to the projection image processing circuit 28 where the signal is provided with a synchronous signal coming from a synchronous circuit 8. It should be noted here that, in case there is the need to superpose an ordinary image onto the image which may, for example, be of a contour pattern obtained from the measuring and processing circuit 26, said signal is made into a compound projection image signal which is produced by mixing the image signal with a signal coming from the color encoder 23, and this compound projection image signal is displayed by the color display 29 such as CRT.

The method of obtaining a contour image by processing image data stored in the memory 18 has already been put to practice and is known from, for example, Yatagai et al's Opt. Eng. 21 (1982) 901, and 21 (1982) 432 of same and also 23 (1984) 401 of same, and accordingly, its detailed explanation is omitted.

Now a brief description will be provided of the principle that the concavo-convex (i.e. uneven) surface of the object can be ascertained by Moire fringes or stripes. The method employed in the present invention is called the projection method. As shown in FIG. 4, lattice P.sub.1 is projected onto an object O through a lens L.sub.1 to form the image of the object O by a lens L.sub.2, so that this object image is observed through a lattice P.sub.2. The image of the lattice P.sub.1 projected onto the object O deforms in accordance with the concavo-convex (uneven) pattern of the surface of the object O, and Moire fringes are formed between the image of this deformed lattice P.sub.1 and the lattice P.sub.2. To make the explanation simple, let us here suppose that the projection lens L.sub.1 is the same as the focusing lens L.sub.2, and that the lattice P.sub.1 is same as the lattice P.sub.2, respectively. Then, as shown in FIG. 5, it is assumed that the distance between the lattice and the principal point of the lens facing the lattice is assumed to be a, the distance between the principal point of the lens and the reference point (to be determined appropriately) at the surface of the object O to be l, the distance between the principal points of the respective lenses to be d, the focal distance of respective lenses to be f, the pitches of the respective lattices to be S, and the frequency of Moire fringes to be N. Then, the depth of the N-th Moire fringe as counted from the reference point will be given by: ##EQU1## In this way, it is possible to know the concavo-convex (uneven) appearance of a given surface by utilizing Moire fringes. The above-mentioned calculation is performed by the measuring and processing circuit 26. Furthermore, by means of the microcomputer which is contained in this measuring and processing circuit, there is performed the processing of the signals necessary for the depiction, on the display 29, of such a diagram pattern as shown in FIG. 6. As will be understood from the above explanation, the light-emitting end face of the light guide 2 in, for example, the embodiment of FIG. 1 corresponds to the lattice P.sub.1, and the light-receiving face of the solid-state image sensor 7 corresponds to the lattice P.sub.2. Also, an arrangement may be made so that the signals delivered from the measuring and processing circuit 26 are outputted to various data terminal devices such as a magnetic disc memory, or to an X-Y plotter. It should be noted here that the arrangement is provided such that, at the time of observation utilizing infrared light, there is read out a signal from picture elements of every other row (see FIG. 7) or every other column of the solid-state image sensor 7. Accordingly, there is obtained a contour image formed by Moire fringes in the same way as that obtained when the object 5 under survey is observed via the lattice having a pitch representing the width or distance between the rows of picture elements of the solid-state image sensor 7. For this reason, either by providing a gating circuit 30 at the output portion of the solid-state image sensor 7 as shown in FIG. 8, and by alternately switching this circuit 30 to "on" and "off" in synchronism with the driving pulses of the driving circuit 10 of the solid-state image sensor 7, or by reading out signals from the memory 18 in correspondence to the outputs of the image elements of every other row or column of the solid-state image sensor 7, or by performing image processing by the measuring and processing circuit 26, there are read out signals delivered from the picture elements of every other row or column of the solid-state image sensor 7. Furthermore, in the case of the solid-state image sensor of the interlacing type, it is possible to easily read out signals of every other row or column by deriving signals of only the first field or the second field. Also, from the fact that the picture elements themselves of the solid-state image sensor are arranged in the form of a lattice, it will be understood that especially in the case of an interline transfer type solid-state image sensor (see FIG. 9) wherein vertical transfer registers 32, 32', 32", . . . are arranged between light-sensitive sections 31, 31', 31", . . . forming non-sensitive zones, it is also possible to obtain a contour image due to Moire fringes by the output signals from all the picture elements instead of by the signals from every other row or column.

FIGS. 10A and 10B show a mechanism for moving an illuminating lens 4 in such a way that, only when the infrared light transmitting sector 3d of the rotary filter 3 is inserted in the path of light beam in synchronism with the rotation of the rotary filter 3, the light-emission end of the light guide 2 is focused on the object 5 under observation, and that when the other light-transmitting sectors 3a, 3b or 3c of the rotary filter 3 are inserted in the path of light, the light-emission end of the light guide 2 is projected as a blurred image onto the object 5 under observation. Numeral 33 represents a lens frame for supporting the illuminating lens 4 advanceably and retreatably in the direction of the optical axis; 34 a spring having its one end fixed to the lens frame 33 for pulling the lens frame 33 in the direction of the arrow; 35 a cam plate provided on a shaft 36 which is arranged to be brought, by such means as a worm gear, into engagement with the shaft of the motor M which is assigned to rotate the rotary filter 3 and which makes one revolution during one rotation of the rotary filter 3. One end of a rod 37 having its other end fixed to the lens frame 33 abuts, by means of the spring force of a spring 34, a cam face 35a of the cam plate 35. The cam face 35a is constructed to have a shape such that, when the infrared light transmitting sector 3d of the rotary filter 3 is inserted in the path of light, the rod 37 is brought into contact with the larger-diameter portion 35a' extending through about 90 degrees of the cam face 35a of the cam plate 35, and that when the other light-transmitting sector 3a, 3b or 3c is inserted in the path of light, said rod 37 is in contact with the remainder smaller-diameter portion 35a" of the cam face 35a of the cam plate 35. It should be understood that, when the rod 37 is in contact with the larger-diameter portion 35a' of the cam face 35a, the illuminating lens 4 is at a position of focusing the light-emission end of the light guide 2 on the object 5 under observation. In case, however, the rod 37 is abutting the smaller-diameter portion 35a" of the cam face 35a, the illuminating lens 4 is located at a position closer to the light-emission end of the light guide 2, so that the light-emission end of this light guide 2 is projected, as a blurred image, onto the object 5 under observation. Thus, in case of illumination by red light, green light or blue light, it will be noted that, among the core and clad which constitute the individual optical fibers of the light guide 2, only the core will illuminate, so that the mesh-like illumination which can be produced when the light-emission end of the light guide 2 is focused on the object 5 under survey is eliminated due to blurring. In case of illumination by infrared light, however, the light-emission end of the light guide 2 is clearly focused in a stripe pattern on the object 5 under examination.

FIGS. 11A and 11B show a second embodiment of the present invention. Numeral 40 represents an LED array (see FIG. 11B) consisting of successively arranged rows R, G, B and I of LEDs (which may be semiconductor laser, for example) emitting red light, green light, blue light and infrared light, respectively, at the position of the light-emission end of the light guide 2, in place of the light supply lamp 1, the light guide 2 and the rotary filter 3 which are employed in the embodiment of FIG. 1. The remains arrangement of this second embodiment is similar to that of the embodiment of FIG. 1. According to this arrangement, the rows of LED array are lighted up successively in the order of R, G, B and I by a driving circuit 41 based on a control signal delivered from the synchronizing circuit 8, whereby there can be performed face-after-face type image-pickup operation. In this case also, if an arrangement is provided so as to move the illuminating lens 4 in the same way as in FIG. 10, it will be understood that, in case of illumination by red light, green light or blue light, the object 5 under observation will be illuminated substantially uniformly due to blurring. It should be noted here that an arrangement may be provided so that the signals from the solid-state image sensor are read out for example once every two rows or three rows in accordance with the time intervals of emission of light from the LEDs.

FIGS. 12A, 12B, 12C and 13 show a third embodiment of the present invention. In place of the rotary filter 3 employed in the embodiment of FIG. 1, there is disposed an infrared light cutting filter 50 (FIG. 12A) in the foreground of the light-emission end 2b of the light guide 2. Also, a color-separating stripe filter 51 (FIGS. 12B and 12C) is disposed in the foreground of the solid-state image sensor 7, so that visible light impinges onto the two light-incidence ends 2a and 2b of the light guide 2, whereby the light emits through the entire region of the light-emission end of the light guide 2 to illuminate the object 5 under survey. However, infrared light enters only through the light-incidence end 2a of the light guide 2 due to the function of the infrared light cutting filter 50, so that the light emits through the light-emission end of the light guide 2 at every other row of optical fibers to illuminate the object 5 under survey in a stripe pattern. The image of the object 5 under observation thus illuminated is focused on the solid-state image sensor 7 by the objective lens 6. The output signal of the solid-state image sensor 7 is amplified by the preamplifier 11, and it is converted to a digital signal by the A/D converter circuit 13, and thereafter it is distributed into image signals produced by red light, green light, blue light and infrared light, respectively, as allotted by the multiplexer 14, as shown in FIG. 13. After these respective signals are processed by the processing circuit 12', the image signals produced by red light, green light and blue light are converted to analog signals by the D/A converter circuits 20, 21 and 22, respectively, and they are supplied to the color encoder 23 whereby a video signal is formed. This video signal is supplied to the mixing circuit 24 to become a compound image projection signal. By this image projection signal, a color projection image is presented on the color display 25. Also, the infrared light is processed by the measuring and processing circuit 26, and thereafter it is converted to an analog signal by the D/A converter circuit 27, and then it is converted further to a compound image projection signal by the projection image processing circuit 28 to present a contour image on the color display 29. It should be understood here that the stripe filter 51 requires that the sector I intended to transmit infrared light to be of lattice form. With respect to the sectors R, G and B which transmit red light, green light and blue light, respectively, they may be formed in mosaic pattern instead of lattice form. In such a case, however, the color-separating circuit will need some modification in its arrangement.

In the above-state description, in the first and second embodiments, the observation by utilizing Moire fringes employs infrared light. It should be understood, however, that in place of infrared light, there may be used visible light such as red light, green light and blue light. Also, in the respective embodiments stated above, it is also possible to use invisible light such as ultraviolet light in place of infrared light.

In the above-mentioned description, the principle of the present invention has been stated with respect to endoscope. It should be understood, however, that this principle is not limited thereto, but it can be applied also to optical instruments which perform Moire topography.