JP2003298956A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high frame rate and an image showing a smooth motion of an object to be observed even though an image sensor having many pixels is employed. <P>SOLUTION: A first shield area OB<SB>1</SB>is set to the left end and a second shield area OB<SB>2</SB>is set to the right end of the image screen of a CCD 10 by using a shield mask, and a signal is read in a timing that a pixel ahead by the number of pixels of the first shield area OB<SB>1</SB>(third area I<SB>3</SB>) when counted from the second shield area OB<SB>2</SB>of a preceding horizontal line signal (a-3) is almost coincident with the top pixel of the first shield area OB<SB>1</SB>of a succeeding horizontal line signal (b). Thus the read of the horizontal line signal is accelerated by the sum of the first shield area OB<SB>1</SB>and the second shield area OB<SB>2</SB>, thereby increasing the frame rate. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image pickup apparatus, particularly an electronic endoscope apparatus and the like, reads out an image pickup signal accumulated in an image pickup element such as a CCD and forms an image of an object to be observed based on the image pickup signal. The present invention relates to the configuration of an image pickup device that displays a monitor.

[0002]

2. Description of the Related Art An image pickup device is used, for example, in an electronic endoscopic device. This electronic endoscopic device is a CCD (Charge).
A solid-state image sensor such as a Coupled Device)
By observing the signal of the object to be observed imaged by the CD by the image pickup element drive circuit and subjecting the imaged signal to predetermined image processing, the object to be observed such as inside the body cavity can be displayed on the monitor.

In recent years, due to the promotion of the increase in the number of pixels of the CCD, the conventional CCD having 270,000 pixels or 410,000 pixels is used.
Have produced CCDs with 850,000 pixels and 1.25 million pixels, and have achieved high image quality even in electronic endoscope devices used in the medical field.

[0004]

However, in the conventional image pickup device equipped with a CCD having a large number of pixels, the CCD
There is a problem in that a sufficient frame rate cannot be obtained due to the limit of increasing the clock frequency for reading the pixel signal from. That is, in the above-described conventional 410,000-pixel CCD, 30 frames per second (frame rate: 30 frames / second) are formed by using a clock frequency of 14.318 MHz, while in contrast, a CC of 850,000 pixels is used.
In D, 20 frames (frame rate: 20 frames / second) are formed per second using the clock frequency of 20 MHz, and when the number of pixels is increased, the number of frames formed per second is reduced. There is an inconvenience to do. Then, such a decrease in the frame rate causes a decrease in the smooth movement of the observed object image.

Further, even if the CCD is not particularly composed of a large number of pixels, in the field sequential system for forming three images based on the three color lights of R (red), G (green) and B (blue), the simultaneous system is used. Compared with the above, since the image data is reduced to 1/3, the phenomenon of color breakage has been a problem from the past. Therefore, in this case, color breakup can be improved by increasing the frame rate.

Further, in an electronic endoscope or the like, the aspect ratio of a display image is often set to a value other than 4: 3, so C
The left and right edge areas of the imaging surface are wasted without using the full size of the CD, but in order to increase the frame rate,
It is also conceivable to manufacture a CCD of a dedicated size (for example, an aspect ratio, 1: 1 etc.) in which the left and right end areas of the imaging surface which are not used are cut. However, in this case, the general-purpose C
There is an inconvenience that the CD cannot be used and the manufacturing cost of the CCD is high.

The present invention has been made in view of the above problems, and an object thereof is to increase the frame rate and to obtain an image of an object to be observed with a smooth motion in an image pickup device having a large number of pixels. Another object of the present invention is to provide an image pickup apparatus capable of reducing the color breakup phenomenon in the frame sequential method and further reducing the cost without manufacturing a dedicated image pickup element.

[0008]

In order to achieve the above object, the invention according to claim 1 is an image pickup device for picking up an image of an object to be observed, and a first pixel portion for a predetermined pixel at the left end of the image pickup surface of the image pickup device. 1 left-side light-shielding mask that shields 1 light-shielding area, right-side light-shielding mask that shields a second light-shielding area for a predetermined number of pixels at the right end of the image pickup surface, and the above-described horizontal line signal that is read first in order to increase the frame rate. An image pickup element drive circuit for reading out each horizontal line signal at a timing at which a pixel ahead of the second light-shielding area by the pixel of the first light-shielding area substantially coincides with a leading edge pixel of the first light-shielding area of the horizontal line signal to be read out next. It is characterized by having. Claim 2
According to another aspect of the invention, there is provided an oscillator that generates a clock frequency higher than a standard clock frequency according to the number of pixels of the image pickup device, and the image pickup device drive circuit reads a pixel signal at the high clock frequency. And

According to the above arrangement, the pixels in the next horizontal line are not read out after all the pixels in the previous horizontal line have been read out. The first light-shielding area and the second light-shielding area between the line signals are read out so as to overlap the effective pixel area. That is, the effective pixel region corresponding to the pixels of the first light-shielding region existing before (second in time) the second light-shielding region is the third region, and the effective pixel region of the second light-shielding region existing after the first light-shielding region is The fourth effective pixel area corresponding to the number of pixels
In the case of the area, the third area of the previous horizontal line signal and the first light shielding area of the next horizontal line signal overlap, and the second light shielding area of the previous horizontal line signal and the fourth area of the next horizontal line signal overlap. Each signal is read in the state.

According to this, the horizontal line signal can be read faster by the number of pixels obtained by adding the first light-shielding region and the second light-shielding region, and as a result, the frame rate can be increased. Especially, the aspect ratio of the screen is not always 4: 3.
When it is not necessary to use the full size of the image sensor, the frame rate can be increased without increasing the clock frequency by using only the necessary area.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of an entire electronic endoscope apparatus as an image pickup apparatus according to an embodiment. In this electronic endoscope apparatus, a solid state is provided at a distal end portion of a scope. CCD (Charge Coupled Device) 1 which is an image sensor
0 is provided together with the objective optical system, and as the CCD 10, for example, those having 410,000 pixels, 850,000 pixels, and 1.25 million pixels are used. Further, a light guide 12 that supplies light to the distal end portion of the scope is arranged, and this light guide 12 is connected to the light source device 14 through the inside of the scope. That is, the light supplied from the light source device 14 through the light guide 12 is emitted from the tip of the scope to the object to be observed, whereby the object to be observed is imaged by the CCD 10.

The CCD 10 includes a CCD drive circuit 16
Is connected to an oscillator 17 having a clock frequency. For example, when the CCD 10 has 850,000 pixels, a clock frequency of 20 MHz is used, and when the CCD 10 has 410,000 pixels, a clock frequency of 14.318 MHz is used. To be Further, in this example, when the clock frequency is increased by 410,000 pixels or the like, 17.9 MHz, 21.
A device that generates a clock frequency such as 5 MHz is used. Then, the CCD drive circuit 16 forms drive signals for horizontal transfer and vertical transfer based on such a clock signal, and the CCD 10 is driven by this drive signal.
The image pickup signal is read from.

On the other hand, in the subsequent stage of the CCD 10, the CCD
C for correlated double sampling and gain control of the output signal
DS (Correlated Double Sampling) / AGC (Automa
ticGain Control) circuit 18, A / D converter 19, signal processing circuit 2 for performing various signal processing for color image formation
0, a D / A converter 21, etc. are provided, and the output of this D / A converter 21 is supplied to the monitor. Further, a microcomputer 22 that integrally controls the above circuits in the electronic endoscope is provided.

FIG. 2 shows the structure of the image pickup area of the CCD 10. The CCD 10 is provided, for example, with photodiodes 25 arranged in pixel units, and arranged along a vertical column of the photodiodes 25, and a gate 26. A vertical transfer CCD (line) 27 connected via the horizontal transfer CCD (line) 28, a horizontal transfer CCD (line) 28 for inputting a horizontal line signal sent from the vertical transfer CCD 27, and the horizontal transfer CCD 2
It is composed of an amplifier 29 and the like for outputting the 8 signals to the outside.
Then, in the present invention, a predetermined range on the left and right ends of the CCD 10 is shielded from light.

FIG. 3 shows a light-shielding area in the image pickup area of the CCD 10. In the case of 850,000 pixels, if 768 pixels (pixels) are formed in the vertical direction and 1067 pixels are formed in the horizontal direction, for example. Conventionally, a 3-pixel area (optical black area) OB ₇ is provided on the left side and a 4-pixel area is provided on the right side.
Although the 0 pixel area OB ₈ is shielded, in this example,
In addition to this, the first light-shielding region (optical black region) OB ₁ and the second light-shielding region OB ₂ each having 128 pixels are shielded on the left and right. This light shielding area is set by disposing a mask (mechanical structural mask) on the image pickup surface side of the CCD 10. Therefore, the effective pixel in this case is 768.
(= 1024-256).

FIG. 4 shows horizontal line signals read from the CCD 10 under the control of the CCD drive circuit 16. As shown, first the CCD
A horizontal line signal a-1 is output from the horizontal transfer CCD (line) 28 described in FIG. 2 of FIG. 10, and in this horizontal line signal, as described above, the signal of the first light shielding area OB ₁ and the second light shielding region OB _1. The signal of the area OB ₂ is included. This a-1
The horizontal line signal of (b) is sequentially read via the amplifier 29 (FIG. 2) like a-2 with the lapse of time, and the signal of the next horizontal line of b is read at the time of a-3.

That is, the second light shielding area OB of the horizontal line signal
_TwoIn front of (128 pixels), the first light shielding area OB₁Pixel
To the effective pixel area corresponding to the third area I_Three(128 strokes
The first light-blocking area OB₁(128 strokes
After the blank), the second light-shielding area OB _TwoCorresponding to the number of pixels
The effective pixel area is the fourth area I._FourThink as (128 pixels)
And the second light shielding area OB of the horizontal line signal (a-3)_TwoOr
3rd area I_ThreeThe previous pixel p is the next horizontal line signal
(B) First light shielding area OB₁Ties that match the top pixel of
This horizontal line signal (b) is read by the ming.

According to this, the horizontal line signal (a-
3) in the third region I ₃ and the first in the next horizontal line signal (b)
The light-shielded area OB ₁ overlaps, and the second light-shielded area OB ₂ of the previous horizontal line signal (a-3) and the fourth area I ₄ of the next horizontal line signal (b) overlap, I ₃ + OB ₂ = OB ₁
Since + I ₄ = 256 pixels, the horizontal line signal is 2
This makes it possible to read 56 pixels faster.

The embodiment has the above-mentioned structure, and the operation of each embodiment shown in FIGS. 6 and 7 will be described. In the first embodiment of FIG. 6, a CCD 10 having 850,000 pixels is used, and the clock frequency is the same as that of the conventional 20 MHz, which is compared with the conventional signal. That is, in contrast to the horizontal synchronizing signal (HD) of FIG. 6 (A), conventionally, the blanking signal of FIG. 6 (B) and 20 MHz of FIG. 6 (C) are used.
As a result of using the clock signal of 1, the effective pixel becomes 1024 pixels as shown in FIG.
A horizontal line signal (CCD output) is obtained. That is, in the related art, since the first light-shielding region OB ₁ and the second light-shielding region OB ₂ are not set as described above, the horizontal direction is 1024.
An image signal that becomes a pixel is obtained.

On the other hand, in the first embodiment, as shown in FIG.
If the horizontal sync signal (HD) with an early timing is used
The horizontal synchronization signal t₁At the timing of
The horizontal line signal is read out, and the blanking line of FIG.
6G and the clock signal in FIG. 6G are similar.
And the horizontal line signal shown in FIG.
Is output from. However, this CCD output of FIG. 6 (H)
In the first light shielding area OB₁And the second shaded area OB_Two
Is set, so the effective pixels are 768 pixels. 1
The signal of the horizontal line is obtained. And the water of FIG. 6 (E)
Flat sync signal t _TwoSignal of the next horizontal line at the timing of
Is read out, the blanking signal of FIG.
6 (J) clock signal, CCD 10
A horizontal line signal of 6 (K) is output. This horizontal lie
Signal is also the first shaded area OB₁And the second shaded area OB_TwoSet up
By definition, the number of effective pixels becomes 768 pixels.

Here, the water shown in FIGS. 6 (H) and 6 (K) is used.
When comparing the flat line signals, the effective pixels are shielded by the first
Area OB₁And the second shaded area OB_TwoThe signal is
It is understood that the data is read without waste. That is, the figure
6 (H) and FIG. 6 (K), the horizontal line signal is explained in FIG.
As is clear, the third region (I_Three) And the first shading area OB ₁
Overlaps with each other, and the second light-shielding area OB_TwoAnd the fourth area
(I_Four) Are overlapped, the images of the third and fourth areas are
The elementary signal is read well.

According to the first embodiment, as shown in FIG. 6 (G), in one horizontal line of 1270 clocks, reading can be speeded up by 256 clocks,
It is possible to increase the frame rate by 1.25 times. That is, 20 frames per second can be obtained with a clock frequency of 20 MHz in the past, whereas in the first embodiment, 2 frames per second with the same clock frequency of 20 MHz.
Five frames will be obtained.

The second embodiment shown in FIG.
The clock frequency of the conventional 14.
This is 1.25 times higher than 318 MHz. That is, in contrast to the horizontal synchronizing signal (HD) of FIG. 7 (A), conventionally, the blanking signal of FIG. 7 (B) and 1 of FIG. 7 (C) are used.
As a result of using the clock signal of 4.318 MHz, a signal of one horizontal line (CCD output) having 768 effective pixels (pixels) is obtained as shown in FIG. 7D.

On the other hand, in the second embodiment, the horizontal synchronizing signal shown in FIG. 7 (E) is used, and the blanking signal in FIG. 7 (F) and 17.9 MHz (= 1 in FIG. 7G) are used.
A clock signal of 4.318 × 1.25) is used.
If the first horizontal line signal is read out at the timing of t ₁ in the horizontal synchronizing signal, a horizontal line signal of 576 pixels shown in FIG. 7H is output from the CCD 10. That is, in this example, the first light-shielding region OB ₁ and the second light-shielding region OB ₂ for 96 pixels are set, and a signal of one horizontal line in which the number of effective pixels is 576 (= 768-192) is obtained.

Then, t ₂ of the horizontal synchronizing signal of FIG.
When the signal of the next horizontal line is read at the timing of, the horizontal line signal of FIG. 7 (K) is output from the CCD 10 by the blanking signal of FIG. 7 (I) and the clock signal of FIG. 7 (J). . This horizontal line signal also has 576 effective pixels depending on the settings of the first light-shielding region OB ₁ and the second light-shielding region OB ₂ . Therefore, also in the case of the second embodiment, as shown in FIG.
In the horizontal line signal of (K), the third region (I ₃ ) overlaps the first light-shielding region OB _1, and the second light-shielding region OB also overlaps.
By overlapping ₂ and the fourth region (I ₄ ), the pixels in the third region and the fourth region are read well.

According to the second embodiment, the clock frequency can be multiplied by 1.25 and reading can be accelerated by 192 clocks in one horizontal line of 728 clocks, and the frame rate can be increased by 1.5 times. It becomes possible. That is, 30 frames per second can be obtained with a clock frequency of 14.318 MHz in the past, whereas in the second embodiment, 1 with a clock frequency of 17.9 MHz.
Forty-five frames will be obtained per second.

The number of effective pixels and the clock frequency set in the first light-shielding region OB ₁ and the second light-shielding region OB ₂ in the first or second embodiment are examples, and these are the required frames. It can be changed and set as appropriate according to the rate.

FIG. 5 shows the configuration of the third embodiment.
In the third embodiment, the light shielding area is provided in the vertical direction as well.
Of. That is, for example, a CCD 10 with 1,250,000 pixels is used
If there is, the first light-shielding area O of 256 pixels is formed on both the left and right ends.
B_ThreeAnd the second shaded area OB_FourAnd both upper and lower ends
96 pixel upper light-shielding area OB₅And lower shading area OB ₆
Is set by a mask. According to this third embodiment,
It is common to reduce the number of effective pixels in the horizontal direction from 1280 to 768.
And reduce the effective pixels in the vertical direction from 960 to 768,
Also, by adjusting the clock frequency, etc.
You can improve your performance.

Although the electronic endoscope apparatus has been described in this example, the present invention can be applied to other image pickup apparatuses such as video cameras.

[0030]

As described above, according to the present invention,
The light-shielding mask shields the first light-shielding region and the second light-shielding region for a predetermined number of pixels on the left and right edges of the image pickup surface of the image sensor, and the pixel ahead of the second light-shielding region of the previous horizontal line by the pixel of the first light-shielding region is Since the horizontal line signal is read at a timing substantially coincident with the leading edge pixel of the first light-shielding region of the next horizontal line, the pixel for which the first light-shielding region and the second light-shielding region are added in the reading of the horizontal line signal, It can be faster, which allows higher frame rates. As a result, it is possible to obtain an image of the object to be observed with a smooth motion in the image pickup device having a large number of pixels, and to reduce the color breakup phenomenon in the frame sequential method.

In particular, the aspect ratio of the screen is always 4:
3 is not necessary, and when the full size of the image sensor is not used, there is an advantage that the frame rate can be increased without increasing the clock frequency by using only the necessary area. Also, when increasing the frame rate with an aspect ratio other than 4: 3,
Since a general-purpose image sensor can be used without manufacturing an image sensor of a dedicated size, cost reduction can be achieved.

Further, according to the second aspect of the invention, the image pickup device is driven at a clock frequency higher than the standard clock frequency according to the number of pixels of the image pickup device, so that the image pickup device is originally set. Without reducing the number of effective pixels
The frame rate can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an image pickup area of a CCD according to an embodiment.

FIG. 3 is a diagram showing a light-shielding region on an image pickup surface of an 850,000-pixel CCD in an embodiment example (first example).

FIG. 4 is a diagram showing a read timing of a horizontal line signal read from the CCD of the embodiment.

FIG. 5 is a diagram showing a light shielding area on an image pickup surface of a 1.25 million pixel CCD according to a third embodiment.

FIG. 6 is a waveform diagram showing the processing of the horizontal line signal of the first embodiment in comparison with the related art.

FIG. 7 is a waveform diagram showing the processing of the horizontal line signal of the second embodiment in comparison with the related art.

[Explanation of symbols]

10 ... CCD, 16 ... CCD drive circuit, 17 ... Oscillator, 25 ... photodiode, 27 ... Vertical transfer CCD (line), 28 ... Horizontal transfer CCD (line).

Claims (2)

[Claims] 1. An image pickup device for picking up an image of an object to be observed, and a first part for a predetermined number of pixels at a left end of an image pickup surface of the image pickup device.
A left-side light-shielding mask that shields a light-shielding area, a right-side light-shielding mask that shields a second light-shielding area for a predetermined number of pixels at the right end of the image pickup surface, and the above-mentioned first horizontal line signal read out in order to increase the frame rate. An image pickup element drive circuit for reading out each horizontal line signal at a timing at which a pixel ahead of the first light-shielding area from the second light-shielding area substantially coincides with the leading edge pixel of the first light-shielding area of the horizontal line signal to be read out next. Imager equipped. 2. An oscillator for generating a clock frequency higher than a standard clock frequency according to the number of pixels of the image pickup device is provided, and the image pickup device drive circuit reads a pixel signal at the high clock frequency. The image pickup apparatus according to claim 1, wherein