JPS63271308A - Optical system for endoscope - Google Patents

Abstract

PURPOSE:To reduce size and electric power consumption and to speed up wavelength band conversion by disposing a transmittance characteristic varying element of an electric control type to at least either of an image pickup system and illuminating system. CONSTITUTION:The transmittance characteristic varying element 6 of the electric control type is disposed to at least either of the image pickup system and illuminating system so that the transmittance characteristic varying element 6 is acted as a band change filter, color filter for face sequential color illumination or image pickup, band change cut filter, color temp. change filter, etc. For example, the transmittance characteristic varying element 6 is disposed between an objective lens 4 and a solid-state image pickup element 5. Then, the image pickup by colors is executable when the transmission wavelength bands of the element 6 are changed to B, G, R, B,... and the signals from the solid-state image pickup element 5 are read out in synchronization therewith at the time of observing a subject or luminous object illuminated by white illumination light or external light. The size and electric power consumption are thereby reduced and the wavelength band change is speeded up.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an endoscope optical system for medical and industrial use.

[Prior art and problems to be solved by the invention] Various filters are used in endoscope optical systems, including band conversion filters, color filters for frame-sequential color illumination or imaging, Both band conversion cut filters and color temperature conversion filters convert the wavelength band of transmitted light or non-transmitted light when necessary or in a time-sharing manner, but conventionally, multiple filters with different wavelength bands are prepared and these are converted. Wavelength band conversion was performed by replacing the wavelength band in a removable or rotating manner. Therefore, since a tm/mechanical drive device is required, there are problems in that the entire endoscope optical system becomes large, that it is difficult to increase the wavelength band conversion speed, and that power consumption is large. In addition, it is impossible to install a removable X-ray rotary filter at the end of the endoscope because it inevitably increases the size of the entire optical system.
This was unsuitable for electronic endoscopes in which the lift system is concentrated at the end of the endoscope.

In view of the above problems, the present invention can reduce the size of the entire optical system, increase the speed of wavelength band conversion, reduce power consumption, and
A further object of the present invention is to provide an endoscope optical system suitable for electronic endoscopes.

[Means and effects for solving the problem] The endoscope optical system according to the present invention includes an electrically controlled variable transmittance characteristic element disposed in at least one of the imaging system and the illumination system to adjust the i3 transmittance characteristic. Variable elements can be used as band conversion filters, color filters for field sequential color illumination or continuous images, and band conversion cant filters.

It is designed to function as a color temperature conversion filter or the like.

〔Example〕

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.

FIG. 1 shows a first embodiment, in which numeral 1 indicates a rigid portion at the tip of the endoscope. 2 is a light guide whose input end is connected to a light source (not shown); 3 is an illumination lens disposed on the output end side of the light guide 2; these constitute an illumination system. 4 is an objective lens arranged in parallel with the illumination lens 3; 5 is a solid-state image pickup device placed at a position where an object image is formed by the objective lens 4; and 6 is placed between the objective lens 4 and the solid-state image pickup device 5. This is a transmittance characteristic variable element with one electrical control.

FIG. 2 shows an example of the transmittance characteristic variable element 6, and 7
8 is a plurality of ring-shaped laminated piezoelectric actuator elements connecting the outer peripheries of adjacent transparent films 7, and the distance between the transparent films 7 is are all equal, and the lengths in the axial direction of the piezoelectric actuator element 8, that is, the intervals between the attachment positions of the transparent film 7 to the piezoelectric actuator element 8 are all equal. Reference numeral 9 denotes a plurality of variable voltage power supplies for applying voltage to each piezoelectric actuator element, and the piezoelectric actuator element 8 extends in the vertical direction, that is, in the axial direction in FIG. 2, approximately in proportion to the applied voltage. . It is assumed that all the transparent films 7 have the same thickness and are made of the same material.

In the transmittance characteristic variable element 6, the transparent film 7
When there is an air gap d between them, light interference occurs at λ, and a transmittance characteristic having a transmittance peak at a wavelength of d=- is generated. For example, in order to produce a transmittance peak at a wavelength of 0.6μ belonging to the visible light region as shown in FIG. 3, the distances between the transparent films 7 should be d, d, d.

If each power source 9 is controlled so that d4 are all different, the transmittance characteristics due to each interval d, dt, d, d are shown in Fig. 4 (A
), the wavelengths λ1. λ2゜λ1. It has a peak at λ4, and the transmittance characteristic of the element 6 as a whole is a combination of the above transmittance characteristics, that is, it has a relatively wide transmission wavelength band as shown in FIG. 4(B). Furthermore, the difference between adjacent intervals dt d+
, dzdz and da dx are made equal, the difference λ2-λ1 . between adjacent wavelengths in FIG. 4(A). λ.

-λ7. Since λ4−λ is also equal, balanced transmittance characteristics can be obtained.

Moreover, when a voltage is applied to each piezoelectric actuator element 8 by each power supply 9 and the voltage is changed, the distances d, d, d, , d4 between each transparent film 7 change, and the transmission wavelength band due to each distance changes. moves, but the difference between adjacent intervals d, −
d,,d,-dt.

If d and -d are changed while being kept constant, the transmission wavelength band shifts with a constant width as shown in FIG. 5(A)→(B)-(C). Therefore, as shown in FIG. 6, the applied voltages are V+, V+', V+'; Vz.

Vz', V! "iVi, V3', V3
';Va.

When v, ', v, '', the transmitted light becomes B (blue) and 'G (
V+, Vz so that it becomes (green), R (red).

V,,V, are selected, and the applied voltage is these potentials ■1v1
′・Vl′；Vz・v2′・Vt′；Vgo・
v, ′, v, “; Va , Va ′,
If Va " is set to repeatedly change stepwise (for convenience of drawing, illustration of v, , V, +, V is omitted), element 6 can be used as a color filter for frame-sequential color imaging. can.

Since this embodiment is configured as described above, when observing a subject or a luminescent object illuminated with white illumination light or external light, the transmission wavelength band of the element 6 is set as described above, that is, B, G, R.
, B, . . . and read out signals from the solid-state imaging device 5 in synchronization with this change, color imaging can be performed. In that case, compared to an example using a mosaic filter, this embodiment has better resolution because signals of each color are extracted from all pixels of the solid-state image sensor 5. Since no mechanism is required, the entire imaging system can be miniaturized. Furthermore, this is preferable for electronic endoscopes in which the imaging system is concentrated at the distal end of the endoscope. Further, for the same reason, there are advantages in that the transmission wavelength band conversion speed can be increased and power consumption can be reduced.

The color filter for field sequential color imaging is shown in Figure 5 (A
), (B), and (C), and the conversion time is short, it is convenient because it allows more time to accumulate the R, G, and B signals in the solid-state image sensor. Since the element 6 responds in several milliseconds, it is sufficiently usable.

Further, even if the elongation of the voltage actuator element 8 is not proportional to the applied voltage, it is possible to obtain the necessary characteristics by appropriately controlling the applied voltage or appropriately arranging the transparent film 7.

Next, a second example will be described. This has the same basic structure as the first embodiment, so its explanation will be omitted. However, in this case, as shown in FIG.
Each power supply 9 is controlled so that +, dx, dz, and da all almost match. Therefore, the transmittance characteristic of the element 6 as a whole is a combination of multiple transmittance characteristics shown in FIG. 3, that is, a characteristic with a sharp peak (characteristic with a narrow transmission wavelength band) as shown in FIG. Become. Then, each power source 9 is controlled to change the intervals d, d, d, , d while keeping them consistent, so that the transmittance characteristic of the entire element 6 is the same as the 9th one.
As shown in the figure, the narrow transmission wavelength band shifts. Therefore, according to this embodiment, by using the element 6 as a spectroscopic band conversion filter, it is possible to know the spectral characteristics of the characteristic reflected light and emitted light of the subject.
It is possible to perform analyzes with high precision that cannot be obtained by mere observation.

FIG. 10 shows a third embodiment, where 10 is a light source, 11 is a light source, and 11 is a light source.
is a condensing lens that condenses the light from the light source 10 onto the incident end surface of the light guide 2, and between the light source 10 and the condensing lens 11 is provided the element 6 of the first embodiment (with the characteristics shown in FIG. 5). ) is arranged. Therefore, by using the element 6 as a color filter for field-sequential color illumination,
Similar to the first embodiment described above, color imaging can be performed. In this case, it is possible to construct an illumination optical system that is simpler and more compact than the conventional one using a rotary filter.

FIG. 11 shows a fourth embodiment, in which reference numeral 12 denotes a rotary filter arranged between the condenser lens 11 and the incident end surface of the light guide 12 and rotated by a motor 13. As shown in FIG. 12, the rotating filter 12 consists of three filters arranged around the circumference: a B (blue) filter, a G (green) filter, and an R (red) + NIR (near infrared) filter. , their transmittance characteristics are as shown in FIGS. A rate characteristic variable element 6 is arranged.1
4 processes the signal from the solid-state imaging element 5 and displays it on a monitor TV.
15 is an image signal processing circuit for displaying an image; 16 is an element driving circuit for driving the element 6 with a signal from the image signal processing circuit 14;

The element 6 is normally an NIR cut filter as shown in Fig. 14 (A), but when necessary, it is
) is controlled by the element drive circuit 14 to form an R-cut filter. This is based on the following principle.

That is, by setting the distance d between the transparent films in the element 6 to λ d =-, it is possible to set the wavelength band where the reflectance is maximum. And the intervals d+, dt,
dx, da is relatively wide and the difference between adjacent intervals d
By increasing z d+ , dz -dx , da -d3, a wide non-transmissive wavelength region can be obtained on the long wavelength side as shown in FIG. 14(A), and the intervals d, d2 . d,,d4
relatively narrow (and the difference between adjacent intervals dz d+
, di dz , da-d, a narrow non-transparent wavelength region can be obtained on the short wavelength side as shown in FIG. 14(B).

Thus, element 6 has characteristics as a band translation cut filter.

Since this embodiment is constructed as described above, if the characteristics of the element 6 are set as shown in FIG. 14(A), the result is B.

Observation using three colors of G and R is possible, and by switching the characteristics of the element 6 as shown in FIG. 14 (B), B and G can be observed.

Observation using IR's three-color reconnaissance system becomes possible.

In addition, 11060n YAG laser is used for medical endoscopes.
Although an infrared laser (infrared laser) is used for processing, the reflected light of this laser is so strong that it enters the solid-state image sensor 5 and causes smearing. Therefore, conventionally, an interference filter that removes 11060n light was placed in the optical path as a transmission prevention film, but while this does not interfere with near-infrared observation, it creates a ripple in the normal observation wavelength range, which becomes an obstacle. There was a problem.

On the other hand, in this embodiment, two spacing groups having different non-transparent wavelength bands are formed in the element 6, and by overlapping these, the transmittance characteristics as shown in FIG. 15 are created, and only when necessary. One non-transparent wavelength band can be exposed. Therefore, element 6 has YA
If the YAG laser non-transmissive characteristic occurs only during G laser irradiation, there is an advantage that no trouble will occur during observation.

FIG. 16 shows a fifth embodiment, in which 17 is an image guide and 18 is an eyepiece. Reference numeral 19 denotes an imaging section of a television camera or electronic still camera connected to the eyepiece section, in which a variable transmittance characteristic element 6 is disposed between the photographic lens 20 and the solid-state image sensor 5.

In the element 6, a transparent film 7 is formed as shown in FIG. 17(A).
As the distance between comrades increases, the difference d between adjacent comrades
When t −d+ , ds di, and da dx are made small, the peaks of each transmittance become denser on the longer wavelength side as shown in FIG. 18(A), so the transmittance characteristic of the entire element becomes It will look like the solid line a in Figure 19. Also, Figure 17 (
As shown in B), as the distance between the transparent films 7 becomes smaller, the difference between the adjacent distances d4-d, d, -d, d, -d
, is made small, the peaks of each transmittance become denser on the short wavelength side as shown in FIG. 18(B), and the transmittance characteristic becomes as shown by the dotted line in FIG. 19.

Therefore, each variable voltage power supply 9 provides each interval d,,d.

By controlling d, , d as described above, the element 6 can be used as a color temperature conversion filter.

Therefore, according to this embodiment, the white balance can be easily adjusted.

It goes without saying that the element 6 may be placed between the objective lens 4 and the incident end of the image guide 17.

〔Effect of the invention〕

The endoscope optical system according to the present invention can miniaturize the entire optical system, increase the wavelength band conversion speed, and reduce power consumption.
Moreover, it has the important practical advantage of being suitable for electronic endoscopes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of an endoscope optical system according to the present invention, FIG. 2 is a cross-sectional view of a transmittance characteristic variable element used in the first embodiment, and FIG. Figure 4 is a diagram showing the transmittance characteristics depending on the spacing, Figure 4 is a diagram showing the transmittance characteristics in Figure 3 superimposed with the peaks shifted, and Figure 5 is a diagram showing the transmittance characteristics in Figure 4 when the applied voltage is changed. A diagram showing the transmittance characteristics, FIG. 6 is a diagram showing the change characteristics of the applied voltage corresponding to FIG. Figure 8 shows the characteristics obtained by superimposing the transmittance characteristics so that the peaks match, corresponding to Figure 7, and Figure 9 shows the transmission when the applied voltage is changed in Figure 8. 10 is a sectional view of the third embodiment, FIG. 11 is a sectional view of the fourth embodiment, and FIGS. 12 and 13 are front views and front views of the rotary filter of the fourth embodiment, respectively. 14 is a diagram showing the characteristics of the variable transmittance element used in the fourth embodiment, FIG. 15 is a diagram showing different characteristics set for the above element, and FIG. 16 is a diagram showing the characteristics of the variable transmittance element used in the fourth embodiment.
A cross-sectional view of the embodiment, FIG. 17 is a diagram showing the change characteristics of each interval of the variable transmittance characteristic element used in the fifth embodiment, FIG. 18 is a diagram showing the transmittance characteristics corresponding to FIG. 17, and FIG. The figure is a diagram showing transmittance characteristics that are a combination of the characteristics shown in FIG. 18. 1... Endoscope tip rigid part, 2... Light guide, 3... Illumination lens, 4... Objective lens, 5...
... solid-state image sensor, 6... variable transmittance characteristic element,
7.,... Transparent film, 8...Piezoelectric actuator element, 9...
- Variable voltage power supply, 10... Light source, 11... Condensing lens, 12... Rotating filter, 13... Motor, 14... Image signal processing circuit, 15... -Monitor TV, 16...Element drive circuit 17...Image guide, 181. ...Eyepiece, 19...1.
Imaging unit, 20... photographing lens. Figure 11 Figure 2 "17 Figure 3 Figure 4 (A) CB) 5a length off factor 18 Figure 18 9 cause Figure 10 112 Figure 113 Figure 18 (A) (B) Figure 19 Mi skin l

Claims (1)

[Claims] An endoscope optical system comprising an electrically controlled transmittance characteristic variable element disposed in at least one of an imaging system and an illumination system.