JP2007313166A - Endoscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and high-definition endoscope equipped with a synchronous primary color imaging unit and an objective optical system that are perfect for a high-definition endoscope. <P>SOLUTION: The endoscope 1 comprises the objective optical system 4 with a focus adjustability, and a solid-state image sensing device to read out all pixels of a primary color single panel with 300,000 or more valid pixels, which satisfies a conditional expression (1) below: 1.95<Fno/Pv<2.4 (1) Pv: a vertical pixel pitch (μm), Fno: F number of the objective optical system 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an endoscope, and more particularly to an endoscope suitable for a surgical operation.

  In the so-called video scope in which a solid-state imaging device is mounted at the distal end of the endoscope insertion portion, commercialization of a system that outputs a high-definition video signal of HDTV standard or PC format is in full swing in the digestive field. In the digestive field, it can be used even with a frame frequency of 30 Hz or less, and high-definition and high-quality images can be easily promoted by using a primary color imaging system such as a frame sequential method or an all-pixel readout primary color single-plate color solid-state imaging device.

  On the other hand, in a surgical videoscope that requires a field frequency of 50 Hz or more for treatment work, the restrictions on the high-frequency circuit at the leading edge are severe, and conventionally only a field readout type complementary color CCD, which is inferior in image quality to the primary color imaging system. There was no choice. Among rigid endoscope camera systems that compete with videoscopes in the field of endoscopic surgery, the three-plate camera system is the system with the highest image quality, and videoscopes are mainly used in procedures that require a tip bending mechanism. In this technique, the rigid endoscope camera system is used as a standard with priority on image quality.

  As described above, in order to use the video scope with a tip bending mechanism, which is highly functionally useful, in general surgery, improvement of image quality is the biggest problem. However, with the recent development of solid-state image sensors, drive circuits, and processing systems for digital home appliances, it has become possible to construct high-definition simultaneous primary color imaging units (primary color CCDs, multi-plate imaging units) with high display frequencies. Endoscope tip mounting is becoming technically possible. Since the simultaneous primary color imaging unit requires the objective optical system to have an image forming performance higher than that of the conventional complementary color system, more attention than before is required with respect to contrast due to diffraction, false color, depth of field, and the like.

The following is known as a prior art referring to the objective optical system and the solid-state imaging device specifications in the endoscope.
JP-A-6-194582 JP 2000-267002 A JP 2002-28126 A JP 2005-323874 A

However, although the specification data of the solid-state imaging device and the objective optical system are described in the embodiments of these documents, it is not a preferable specification setting for combining with a high-definition simultaneous primary color imaging unit that can be mounted on an endoscope. .
The present invention has been made in view of such circumstances, and provides a small-sized and high-quality endoscope by including a simultaneous primary color imaging unit and an objective optical system that are optimal for a high-quality endoscope. The purpose is to do.

In order to solve the above problems, the present invention employs the following means.
The present invention has an objective optical system having a focus adjustment function, and a primary color single-plate color all-pixel readout solid-state imaging device having 300,000 or more effective pixels,
Conditional expression (1) 1.95 <Fno / Pv <2.4
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: An endoscope that satisfies the F number of the objective optical system is provided.

The present invention also includes an objective optical system having a focus adjustment function and a two-plate imaging unit, and the two-plate imaging unit includes a solid-state imaging device G having 600,000 or more effective pixels for imaging green light, A solid-state imaging device RB having 600,000 or more effective pixels for imaging red light and blue light,
Conditional expression (1) 1.95 <Fno / Pv <2.4
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: An endoscope that satisfies the F number of the objective optical system is provided.

The present invention also includes an objective optical system having a focus adjustment function and a two-plate imaging unit, and the two-plate imaging unit has an all-pixel readout solid-state imaging device having 150,000 or more effective pixels for imaging green light. G, red light, and blue light are imaged, and an all-pixel readout solid-state image pickup device RB having 150,000 or more effective pixels arranged by shifting the solid-state image pickup device G by about 1/2 pitch pixel in both horizontal and vertical directions. And
Conditional expression (2) 1.95 <Fno / (Pv / 2) <2.4
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: An endoscope that satisfies the F number of the objective optical system is provided.

The present invention further includes an objective optical system having a focus adjustment function and a three-plate imaging unit, and the three-plate imaging unit has an all-pixel readout solid-state imaging device having 150,000 or more effective pixels for imaging green light. G, a red light image, an all-pixel readout solid-state image pickup element R having 150,000 or more effective pixels arranged by shifting about 1/2 pitch pixel in both horizontal and vertical directions with respect to the solid-state image pickup element G, and blue light And an all-pixel readout solid-state image pickup element B having 150,000 or more effective pixels arranged so as to substantially match the pixel arrangement of the solid-state image pickup element R,
Conditional expression (2) 1.95 <Fno / (Pv / 2) <2.4
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: An endoscope that satisfies the F number of the objective optical system is provided.

  According to the present invention, the simultaneous primary color imaging unit and the objective optical system that reduce the false color and suppress the deterioration of the luminance reproducibility without depending on the point separation type optical low pass filter are provided. There is an effect that the image quality can be improved.

[First Embodiment]
Hereinafter, an endoscope 1 according to a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the endoscope 1 according to the present embodiment includes an imaging unit 3 and an objective optical system 4 at the distal end of the insertion portion 2. The imaging unit 3 is a single-plate color solid-state imaging device having an all-pixel readout type and primary color Bayer type filter array, and the effective pixel number of this solid-state imaging device is 691200, which is the same as an input image described later.
Moreover, the endoscope 1 according to the present embodiment satisfies the following conditional expression (1).
1.95 <Fno / Pv <2.4 (1)
However,
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: F number of the objective optical system Note that the interpolation calculation of the filter array uses a simple average in both the horizontal and vertical directions.

Here, the principle of image quality evaluation in the present invention will be described below with reference to FIGS.
3, 4, and 6, the vertical axis represents the reproducibility error rate (“Error ratio” in the figure) of the luminance component Y, the color difference component RY, and the color difference component BY of the imaging unit, The axis indicates Fno of the objective optical system.

The objective optical system 4 and the imaging unit 3 can be regarded as an image conversion filter between the input image and the output image, and can be classified into the following two types of logical operations.
Calculation C: Convolution calculation of optical system point image intensity distribution Calculation P: Process calculation specific to imaging unit Input / output characteristics are determined by the calculation C / calculation P. Therefore, the fluctuation of the output image relative to the input image can be regarded as a reproducibility error. Thus, it is possible to quantitatively evaluate image quality fluctuations.

In FIG. 3, FIG. 4, and FIG. 6, each error component of Y, RY, and BY is obtained by the following equations.
Y reproducibility error rate [%]: Σ | Yout−Yin | / Σ | Yin |
RY reproducibility error rate [%]: Σ | (Rout−Yout) − (Rin−Yin) | / Σ | Rin−Yin |
BY reproducibility error rate [%]: Σ | (Bout−Yout) − (Bin−Yin) | / Σ | Bin−Yin |
In the above definition, the subscript “in” means the input image, and the subscript “out” means the output image. In addition, the calculation within Σ is performed for each pixel, and Σ means that all pixels in the effective range are integrated.

In the present invention, accurate reproduction of an input image is regarded as good image quality.
Further, the low Y reproducibility error rate leads to the luminance being maintained including the spatial frequency characteristics, and it can be considered that the resolution degradation, contrast degradation, and false resolution are small. Further, the reproducibility error rate of RY and BY leads to the color reproducibility being maintained including the spatial frequency characteristics, and is mainly useful as a false color evaluation scale. This is because a pixel in which false color is strongly generated has a large variation in color difference component, and the reproducibility error rate of RY and BY based on the sum indicates the number of false colors.

In addition, the color difference processing of the above calculation P does not affect the color reproducibility of the entire image, so that unnecessary tuning such as a color matrix or gamma that affects color variation from the low spatial frequency region is performed. There is no premise.
Note that when both the calculation C and the calculation P are unprocessed, the input image and the output image are equal, so the reproducibility error rate is 0% for all three types, and the image quality is the best.

  Further, when the objective optical system 4 is assumed to be an ideal lens having no aberration, the point image intensity distribution is determined by diffraction for each wavelength, and therefore the lens design is performed by using the point image intensity distribution at the best focus position of the ideal lens as the calculation C. The parameter that can predict the image quality before and changes the point image intensity distribution is Fno.

  In addition, the calculation P has a certain amount of logical interpolation calculation method for each imaging unit type, and ignores parameters related to image tuning such as gamma, pedestal, knee, white balance, color matrix, enhancement, etc. The logical image quality degradation can be evaluated.

  Further, the reproducibility error rate by the calculation C and the calculation P varies depending on the frequency component and color component of the input image. For example, black and white and gray scale charts frequently used in laboratory evaluations do not have color difference components, and thus are not suitable for evaluating color difference reproducibility error rates as practical image quality. Therefore, the input images at the time of calculation in FIGS. 3, 4 and 6 are digitally recorded in-vivo images containing moderate to high-frequency components such as blood vessels.

The digital image is premised on obtaining an output image having the same conditions as the input image, using 691200 square pixels (horizontal 960 pixels / vertical 720 pixels) and RGB 8-bit gradation. The output image can be displayed almost at full size on a PC monitor with XGA resolution (horizontal 1024 pixels / vertical 768 pixels), and can be regarded as higher resolution than NTSC / PAL. As a condition related to the calculation C of the optical system, it is assumed that the horizontal and vertical pixel pitch of the input image is 2.1 μm, and the convolution is 7 × 7.
3, 4, and 6, the reproducibility error rate is plotted in increments of 0.5 in the range of Fno from 3 to 10.

Hereinafter, Reference Example 1 and Reference Example 2 will be described with reference to FIGS. 4 to 6 for comparison with the present invention.
(Reference Example 1)
The reference example 1 is provided with a solid-state image pickup device that reads all pixels and has no pixel shift by using a three-image pickup unit as an ideal image pickup unit. In Reference Example 1, the number of effective pixels of each solid-state imaging device corresponds to 691200, which is the same as that of the input image. In this system, since the calculation P by the imaging unit can be regarded as no processing, only the influence of diffraction by the calculation C is graphed.

In the imaging unit according to Reference Example 1, as shown in FIG. 4, the reproducibility error rate of both the luminance component Y, the color difference component RY, and the color difference component BY is monotonically increasing with respect to Fno. As the blur increases greatly, the reproducibility of brightness and color difference both deteriorates.
In addition, when Fno is 3.0, the reproducibility error rates of the luminance component Y, the color difference component RY, and the color difference component BY are almost 0%, respectively, and image quality does not deteriorate if aberrations are removed at Fno 3.0 or less. It can be seen that, for the present imaging unit, the brighter objective optical system having a smaller Fno has better image quality.

  Moreover, it can be said that the focus function of the objective optical system is indispensable as a countermeasure against a decrease in the depth of field due to the low Fno. In order to obtain a frame frequency of 60 Hz with this imaging unit specification, since the solid-state imaging device driving frequency exceeds 41 MHz with single-line readout, it is inevitable that heat generation will become a problem when the three-plate unit is mounted with high density.

  As described above, the reference example 1 is desirably combined with the objective optical system with a focus function that has a bright aberration and has excellent image quality as an imaging unit, but it is extremely difficult to implement in a video scope and is not practical.

(Reference Example 2)
The reference example 2 includes an interlace complementary single-plate color solid-state imaging device as an imaging unit. Cy, Ye, Mg, and G in FIG. 5 mean cyan, yellow, magenta, and green, respectively. In Reference Example 2, the number of effective pixels of the solid-state imaging device corresponds to 691200, which is the same as the input image.

  The imaging unit according to Reference Example 2 has a significantly different tendency from that of Reference Example 1. As shown in FIG. 6, the reproducibility error rate of the luminance component Y is less changed with respect to Fno, and the reproducibility error rate of color difference is Fno. The larger the is, the better. Further, the absolute value of each reproducibility error rate is much higher than that in FIG.

  This tendency indicates that the complementary color single plate method generates luminance information by adding four peripheral pixels and thus has low resolving power, and generates false color information by adding and subtracting eight peripheral pixels. The luminance reproducibility does not increase even if the blur due to the diffraction becomes small, and the false color decreases as the blur due to the diffraction increases.

  From FIG. 6, it can be seen that it is desirable to set Fno to be larger when the complementary color single plate method is not used. In addition, since the depth of field can be increased in the present imaging unit in which Fno can be set large, the focus function is not essential.

As described above, Reference Example 2 has a low image quality as an imaging unit and is desirable for combining with a pan-focus objective optical system in an endoscope that does not require a high image quality. It is not desirable as an imaging unit for use.
As described above, in Reference Example 1 and Reference Example 2, it is difficult to achieve both image quality and mounting.

  On the other hand, in the endoscope 1 according to the first embodiment, as shown in FIG. 3, the reproducibility error rate of the luminance component Y with respect to the increase in Fno in the low Fno region by the imaging unit 3. Tends to increase, and the color difference reproducibility error rate tends to decrease, and the tendency is different from those of Reference Example 1 and Reference Example 2. As described above, regardless of the reproducibility error rate of either luminance or color difference, the imaging unit 3 has a higher error rate and inferior image quality than the imaging unit according to Reference Example 1, but the error is lower than that of the imaging unit according to Reference Example 2. It can be seen that the rate is low and the image quality is excellent.

  Further, the color difference reproducibility error rate curve is caused by generating false colors by interpolation with surrounding pixels as in Reference Example 2, and the low Fno side is related to the low-pass effect due to increased blur due to diffraction. As the number of false colors increases, the false colors are reduced and saturated on the high Fno side. Further, unlike the reference example 1 and the reference example 2, in the endoscope 1, as shown in FIG. 3, the reproducibility error rate of luminance / color difference is in a trade-off relationship with respect to Fno. Appropriate Fno exists in the middle zone.

  When the luminance reproducibility and false color are balanced with Fno without using an optical low-pass filter, Fno is about 4.0 if priority is given to luminance reproducibility, Fno is about 5.5 if priority is given to reduction of false color, and Fno 4.0. ˜5.5 is a range corresponding to the necessary conditions. Furthermore, the most desirable range for the balance between luminance reproducibility and false color is Fno 4.5 to 5.0, which is a sufficient condition.

The Fno / Pv normalized by the two Fno ranges and the vertical pixel pitch Pv (2.1 μm) are collectively shown below including the equation (1).

Fno / Pv is a parameter for maintaining the correlation with the reproducibility error rate even when the pixel pitch is changed. If Fno / Pv is constant, the amount of blur due to diffraction also decreases proportionally when Pv is reduced. The error rate can be maintained.
The reason why the vertical pixel pitch is used instead of the horizontal pixel pitch is that the number of scanning lines is regarded as important as a reference for the image format.

The above formula (1) sets a range between the necessary condition and the sufficient condition. If Fno / Pv is less than 1.95, false colors increase, which is not preferable, and if it exceeds 2.4, luminance reproducibility deteriorates.
Since the imaging unit 3 is a single plate of about 1/7 inch, it has a size that can be sufficiently mounted on the distal end of the endoscope 1. Further, in order to obtain a frame frequency of 60 Hz, a single-line readout drive frequency of 41 MHz or more is required. However, since the imaging unit 3 is a single plate, the problem of heat generation can be reduced and measures can be taken.

As described above, the imaging unit 3 is more suitable for high image quality than the complementary color type imaging unit of Reference Example 2, and does not have a fatal mounting problem like the imaging unit of Reference Example 1.
Therefore, according to the endoscope 1 according to the present embodiment, the simultaneous primary color imaging unit 3 and the objective that reduce the false color and suppress the deterioration of the luminance reproducibility without depending on the point separation type optical low-pass filter. By providing the optical system 4, it is possible to achieve a small size and high image quality.

[Second Embodiment]
Next, an endoscope according to a second embodiment of the present invention will be described below with reference to FIGS.
The endoscope according to the present embodiment corresponds to an array obtained by rotating a primary color Bayer array as an imaging unit by 45 ° instead of the single-plate color solid-state image sensor of the endoscope 1 according to the first embodiment. A single-plate color solid-state imaging device having a honeycomb array is provided.

  The effective number of pixels of this solid-state imaging device is regarded as 345600, which is half of the input image, as a real pixel, and interpolation processing widely known as honeycomb arrangement or pixel shift processing is applied to virtual pixels that are blank in FIG. Specifically, RGB low-frequency image data and high-frequency image data of a luminance signal using a phase difference for each color are generated separately and added at a ratio of 1: 1.

In this imaging unit, the adjacent array direction of pixels is 45 °, and the pixel pitch in the adjacent array direction is 2.97 μm (2.1 μm * √2). Therefore, 2.1 μm which is the vertical pixel pitch of the input image is used.
Further, as shown in FIG. 8, the graph of the reproducibility error rate of this imaging unit has the same tendency as that of the primary color Bayer type, and the reason is the same as in the case of the primary color Bayer. In addition, the desirable Fno range in this imaging unit may be the same as in the first embodiment. Therefore, the desired Fno / Pv range is not problematic as the above equation (1), as in the first embodiment.

As described above, in this imaging unit, the driving frequency of the solid-state imaging device is half that of the imaging unit 3 of the first embodiment, and there is no critical mounting problem. In addition, since the image pickup unit has a pixel pitch in the adjacent arrangement direction larger than that of the image pickup unit 3, it is easy to improve sensitivity by increasing the pixel aperture.
Therefore, according to the endoscope according to the present embodiment, similarly to the endoscope 1 according to the first embodiment, the false color is reduced without depending on the point separation type optical low-pass filter, and the luminance reproduction is performed. By providing the simultaneous primary color imaging unit and the objective optical system that suppress the deterioration of the property, it is possible to achieve a small size and high image quality.

[Third Embodiment]
Hereinafter, an endoscope according to a third embodiment of the present invention will be described with reference to FIGS.
The endoscope according to the present embodiment is an imaging unit that captures an all-pixel readout solid-state imaging device in which an oblique pixel shift is performed by a two-plate imaging unit instead of the imaging unit 3 of the endoscope according to the first embodiment. A unit 5 is provided. The imaging unit 5 includes, for example, two solid-state imaging devices 6 and a color separation prism 7 as shown in FIG.

  In FIG. 10, (a) corresponds to the solid-state imaging device G. In addition, since green light is separated by the color separation prism, it is not essential to install an on-chip filter on the solid-state imaging device G. Further, (b) corresponds to the solid-state imaging device RB, and an on-chip filter for imaging red light and blue light for each pixel is arranged, and the filter arrangement is a checkered pattern.

  Note that the blank pixels in FIGS. 10A and 10B are left for the sake of convenience in order to express the phase shift of horizontal / vertical 1/2 pitch of the pixel shift, and the logical synthesis result of these pixel arrays is It becomes FIG.10 (c), and becomes completely the same as FIG. Therefore, the operation P is logically the same as that of the second embodiment, and the reproducibility error rate graph of FIG. 8 can also be applied to this embodiment.

In the present embodiment, the number of effective pixels of each solid-state image sensor on two plates is 172800, which is ¼ of the input image, and the vertical pixel pitch Pv of each solid-state image sensor is 2 of 2.1 μm. It is 4.2 μm, which is double. In this case, the preferable Fno range is the same as that of the imaging units of the first and second embodiments, but the expression (2) is used because the vertical pixel pitch expression of the solid-state imaging device changes.
In addition, (2) Formula only replaces Pv of the above Formula (1) with (Pv / 2), and there is no change in the range to be satisfied.

  In addition, since the imaging unit 5 requires a drive frequency of the solid-state imaging device to be ¼ that of the imaging unit 3 of the first embodiment and ½ that of the imaging unit according to the second embodiment, there is room for further improvement in image quality. There is. For example, by setting the number of effective pixels of each of the two solid-state imaging devices to 960 horizontal × vertical 540, a full standard HD image (horizontal 1920 × vertical 1080) can be generated.

In this state, the single-line readout drive frequency at a frame frequency of 60 Hz is 31 MHz, and there is room for higher definition than the imaging unit 3. Moreover, since the imaging unit 5 can take a pixel pitch larger than the imaging unit of 1st Embodiment and 2nd Embodiment, it is easy to improve a sensitivity by enlarging a pixel opening. Further, the two-plate imaging unit can be made smaller than the three-plate imaging unit.
As described above, according to the endoscope according to the present embodiment, it is possible to achieve a smaller size and higher image quality than the endoscopes according to the first embodiment and the second embodiment.

[Fourth Embodiment]
Next, an endoscope according to a fourth embodiment of the present invention will be described below with reference to FIGS. 11 and 12.
The endoscope according to the present embodiment includes an interlaced readout solid-state image sensor as a two-plate imaging unit instead of the imaging unit 3 of the endoscope according to the first embodiment as an imaging unit. In FIG. 11, (a) corresponds to the solid-state imaging device G. As in the third embodiment, it is not essential to install an on-chip filter on the solid-state image sensor G.

FIG. 11B corresponds to the solid-state imaging device RB. An on-chip filter for imaging red light and blue light for each pixel is arranged, but the filter arrangement is a vertical stripe, and two vertical pixels are used at the time of interlace reading. Can be mixed.
In the result of logic synthesis in FIG. 11C, it is possible to acquire image information of the two primary colors GB or GR in each pixel, but for the insufficient R / B information, a simple average of horizontal adjacent real pixels is used.

In the present embodiment, the number of effective pixels of each solid-state imaging device is 691200, which is the same as that of the input image, and Pv is 2.1 μm. Further, the graph of the reproducibility error rate is almost the same as that of the primary color Bayer type of the first embodiment, and the desired range can apply the formula (1) of the first embodiment as it is.
The reason why the difference from the single-plate primary color Bayer type is small despite the increase in the total number of pixels in the two plates is that the vertical resolution is lowered by the interlaced vertical two-pixel mixture.

As described above, this imaging unit is not much different from the primary color Bayer type in terms of image quality, but by adopting interlace, the single-line readout drive frequency can be suppressed to about 21 MHz at a field frequency of 60 Hz that can be used in surgery. Therefore, if only the drive frequency is viewed, it has the capacity to increase the number of pixels and achieve higher definition. The image pickup unit has the same pixel pitch as that of the image pickup unit 3 of the first embodiment. However, since the two-pixel mixed readout is performed, the sensitivity about twice that of the image pickup unit 3 is obtained.
Therefore, according to the endoscope according to the present embodiment, the size is small, and the image quality can be further improved as compared with the endoscope 1 according to the first embodiment.

[Fifth Embodiment]
Hereinafter, an endoscope according to a fifth embodiment of the present invention will be described with reference to FIGS.
The endoscope according to the present embodiment is an all-pixel readout solid-state imaging device in which an oblique pixel shift is performed by a three-plate imaging unit instead of the imaging unit 3 of the endoscope 1 according to the first embodiment as an imaging unit. The imaging unit 8 is provided. The imaging unit 8 includes, for example, three solid-state imaging devices 6 and a color separation prism 7 as shown in FIG. In FIG. 13, a color separation prism 7 having a small radial size is used.

In FIG. 14, solid-state image pickup devices R, G, and B correspond to (a), (b), and (c), respectively, and the solid-state image pickup devices R, G, and B are separated into three colors by a color separation prism. Installation of an on-chip filter on the solid-state image sensor is not essential.
In FIG. 14, blank pixels are left for the sake of convenience in order to express a phase shift of horizontal / vertical ½ pitch of pixel shift, and the logical synthesis result of these pixel arrays is as shown in FIG.

  In this embodiment, the number of effective pixels of each solid-state image sensor is 172800, which is 1/4 of the input image, and the vertical pixel pitch Pv of each solid-state image sensor is twice the vertical pixel pitch of 2.1 μm of the input image. It becomes 4.2 μm.

  FIG. 14 (d) is very similar to FIG. 7 of the second embodiment and FIG. 10 (c) of the third embodiment. The graph of the reproducibility error rate shown in FIG. Very similar to FIG. 8 of the third embodiment. For this reason, the preferred Fno range is not different from that in the second and third embodiments, but the vertical pixel pitch expression of the solid-state image sensor changes as in the third embodiment. Use.

As described above, the image pickup unit 8 has a low driving frequency and sufficient capacity for high definition, like the image pickup unit 5 of the third embodiment. Further, like the image pickup unit 5, the pixel aperture is enlarged to improve the sensitivity.
Therefore, according to the endoscope according to the present embodiment, it is small in size and can have higher image quality than the endoscope according to the third embodiment.

  As described above, in the first to fifth embodiments, the high-definition imaging unit has considered the preferable Fno setting with priority on the image quality in the best focus state. It is inevitable that the depth of field will decrease with the improvement in image quality. Basically, the literature group mentioned above occupies an important position as a countermeasure for lowering the depth of field. As a structure for this, in the present invention, for example, it is essential to mount a focus function on the objective optical system 4 (see FIG. 1).

As the configuration of the focusing function, a type in which a part of the lens in the objective optical system 4 is moved by an actuator or a variable focus lens unit such as a liquid lens can be considered.
Note that the type in which the imaging unit 3 itself is moved is not desirable because it also involves the movement of the electrical wiring portion associated with the imaging unit 3.

  Further, since Fno slightly fluctuates with the focusing operation in the objective optical system 4, it is necessary that Fno satisfying the above expressions (1) and (2) exists at at least one point within the focus range. is there. Furthermore, it is more preferable to set Fno so as to satisfy the expressions (1) and (2) in all of the focus range.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

It is a figure which shows the structure arrangement | positioning of this invention. It is a figure which shows the filter arrangement | sequence of the Bayer arrangement single-plate color solid-state image sensor of the 1st Embodiment of this invention. It is a figure which shows the reproducibility error rate of the Bayer arrangement single plate color solid-state image sensor of the 1st Embodiment of this invention. It is a figure which shows the reproducibility error rate of the 3 plate imaging unit of the reference example 1. FIG. It is a figure which shows the filter arrangement | sequence of the complementary color single plate color solid-state image sensor of the reference example 2. It is a figure which shows the reproducibility error rate of the complementary color single plate color solid-state image sensor of the reference example 2. It is a figure which shows the filter arrangement | sequence of the honeycomb arrangement | sequence single plate color solid-state image sensor of the 2nd Embodiment of this invention. It is a figure which shows the reproducibility error rate of the honeycomb arrangement | sequence single plate color solid-state image sensor of the 2nd Embodiment of this invention, and the 2 plate imaging unit of 3rd Embodiment. It is a figure which shows the 2 image pick-up unit structure of the 3rd Embodiment and 4th Embodiment of this invention. It is a figure which shows the logic pixel arrangement | sequence of the 2 panel imaging unit of the 3rd Embodiment of this invention. It is a figure which shows the logic pixel arrangement | sequence of the 2 panel imaging unit of the 4th Embodiment of this invention. It is a figure which shows the reproducibility error rate of the 2 panel imaging unit of the 4th Embodiment of this invention. It is a figure which shows the 3 image pick-up unit structure of the 5th Embodiment of this invention. It is a figure which shows the logic pixel arrangement | sequence of the 3 board imaging unit of the 5th Embodiment of this invention. It is a figure which shows the reproducibility error rate of the 3 board imaging unit of the 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Endoscope 2 Insertion part 3 Imaging unit 4 Objective optical system

Claims (4)

An objective optical system having a focus adjustment function;
A primary color single-plate color all-pixel readout solid-state image sensor having more than 300,000 effective pixels,
An endoscope that satisfies the following conditional expression (1).
(1) 1.95 <Fno / Pv <2.4
However,
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: F number of the objective optical system An objective optical system having a focus adjustment function;
A two-plate imaging unit,
The two-plate imaging unit includes a solid-state imaging device G having 600,000 or more effective pixels for capturing green light, and a solid-state imaging device RB having 600,000 or more effective pixels for capturing red light and blue light.
An endoscope that satisfies the following conditional expression (1).
(1) 1.95 <Fno / Pv <2.4
However,
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: F number of the objective optical system An objective optical system having a focus adjustment function;
A two-plate imaging unit,
The two-plate image pickup unit picks up an all-pixel readout solid-state image pickup device G having 150,000 or more effective pixels for picking up green light, red light and blue light, and both horizontal and vertical directions with respect to the solid-state image pickup device G And an all-pixel readout solid-state imaging device RB having 150,000 or more effective pixels arranged with a shift of about ½ pitch pixel,
An endoscope that satisfies the following conditional expression (2).
(2) 1.95 <Fno / (Pv / 2) <2.4
However,
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: F number of the objective optical system An objective optical system having a focus adjustment function;
A three-plate imaging unit,
The three-plate imaging unit captures red light with an all-pixel readout solid-state imaging device G having 150,000 or more effective pixels for imaging green light, and approximately 1/2 in both horizontal and vertical directions with respect to the solid-state imaging device G. An all-pixel readout solid-state imaging device R having an effective pixel number of 150,000 or more arranged by shifting two pitch pixels and an image of blue light and the effective pixel number 150,000 arranged so as to substantially match the pixel arrangement of the solid-state imaging device R The above-described all-pixel readout solid-state imaging device B,
An endoscope that satisfies the following conditional expression (2).
(2) 1.95 <Fno / (Pv / 2) <2.4
However,
Pv: Vertical pixel pitch [μm] of the solid-state image sensor
Fno: F number of the objective optical system

Images