JP2003009000A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an endoscope provided with a solid-state image pickup means having an electric charge multiplier section for multiplying electric charges with a multiplication factor on the basis of a multiplication factor control signal that can measure the multiplication factor of electric charges. SOLUTION: A CMD(Charge Multiplying Detector)-CCD image pickup element 106 mounted on a tip of an endoscope picks up a living body observing section. In this case, a reference output signal value is stored on the basis of signal charges of an image picked up at a shade area 32 and multiplied by an electric charge multiplication section 24 to which a multiplication factor control signal denoting about 1 as the multiplication factor is applied. Further, a reference output signal value is stored on the basis of signal charges of an image picked up at the shade area 32 and multiplied by the electric charge multiplication section 24 to which a multiplication factor control signal denoting N as the multiplication factor is applied under a reference temperature environment. By dividing the output signal value by the reference output signal value, an actual multiplication factor N' of the electric charge multiplication section 24 is calculated. The multiplication factor can be measured again by controlling the voltage of the multiplication factor control signal so that the multiplication factor N' approaches the multiplication factor N. The measurement of the multiplication factor and the voltage adjustment are repeated to realize the multiplication factor N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device for picking up an image of a subject, and more particularly to a solid-state image pickup means having a charge multiplication section for multiplying an imaged signal charge with a multiplication factor based on a multiplication factor control signal. The present invention relates to an image pickup device that performs image pickup using the image pickup device.

[0002]

2. Description of the Related Art Conventionally, there has been known an image pickup apparatus for picking up an optical image of an observation section using a solid-state image pickup element such as a CCD for converting an optical image into an electric signal. In recent years, JP-A 7-1767
A solid-state imaging device having charge multiplication means for multiplying an imaged signal charge with a multiplication factor based on a multiplication factor control signal as described in Japanese Patent No. 21 has been developed, and the solid-state imaging device should be mounted. As a result, the imaging sensitivity of the imaging device can be improved and the imaging sensitivity can be controlled. That is, even when the light amount of the optical image is insufficient to be picked up by using the conventional image pickup device, if the image pickup is performed by using this solid-state image pickup device, it can be displayed as a visible image. Also, the imaging sensitivity can be appropriately controlled according to the imaging conditions. The image pickup device provided with the charge multiplying means is a CMD (Charge).
MultiplyingDetector) -CCD is used to collide an electric conductor and an atom in an electric field region of high intensity and multiply the signal charge by the charge multiplication effect caused by this ionization to improve the image pickup sensitivity of the image pickup device.

Since the charge multiplying means multiplies the signal charges in a stage prior to the charge detection part which sequentially converts the signal charges into a signal voltage and takes out as an output signal, the read noise generated in the charge detection part can be multiplied. Therefore, the S / N ratio of the output signal can be improved, and the S / N ratio of the output signal can be improved in the imaging device which may perform imaging in an environment where the light amount of the optical image is insufficient. Further, since the multiplication factor of the signal charge in the solid-state image pickup device can be changed by the multiplication factor control signal, the image pickup sensitivity can be controlled in the image pickup apparatus equipped with these charge multiplication type solid-state image pickup devices.

Further, conventionally, an endoscope apparatus equipped with a solid-state image pickup device has been widely used. These endoscopic devices are
By displaying the image captured by the solid-state image sensor on a monitor, etc., it has the advantage that multiple people can observe it at the same time. Also, by performing various image processing before displaying the captured image, the naked eye Organizational changes that cannot be recognized by can also be displayed on the monitor, greatly contributing to medical development.

In recent years, the diameter of endoscopes has been reduced, and it is applied not only to the conventional digestive system but also to the bronchus, otolaryngology, joints and the like. However, as the diameter of the endoscope becomes smaller, the number of light guides that transmit the illumination light is also limited. Therefore, it may not be possible to irradiate the illumination light sufficiently, and an apparatus capable of imaging with a desired imaging sensitivity. Was desired to be developed. Further, in addition to normal observation in which illumination light is irradiated for observation, fluorescence observation in which excitation light is irradiated and fluorescence emitted from living tissue is observed is also performed. Since the fluorescence emitted by living tissue is weak and sometimes the image cannot be captured, the development of a device capable of capturing an image with a desired imaging sensitivity has been awaited. In order to solve these problems, a device in which the above charge multiplication type solid-state imaging device is mounted on an endoscope device is disclosed in Japanese Patent Laid-Open No. 2001-29313, and its configuration and sensitivity control method are described. There is.

[0006]

However, the charge multiplication means incorporated in the above-mentioned charge multiplication type solid-state image pickup device is capable of converting the imaged signal charge by a multiplication factor based on the inputted multiplication factor control signal. Since multiplication is performed, even if there is a slight change in the signal characteristic of the multiplication factor control signal, the multiplication factor will change. In particular, in the case of multiplying charges by the charge multiplying unit that simultaneously transfers and multiplies charges, the transfer and multiplication of charges may be repeated several hundred times to obtain a desired multiplication factor. For example, even if the voltage of the multiplication factor control signal is only 1% higher than the predetermined voltage, the final multiplication factor will increase to several times. For example, when the distance from the drive element that generates the multiplication factor control signal to the image pickup element is long, the voltage of the multiplication factor control signal that reaches the image pickup element slightly differs from the desired voltage due to the influence of the drive line that connects the two. Therefore, the multiplication factor may differ from the desired multiplication factor.
In addition, if the temperature of the image pickup device changes, the multiplication factor of the charge multiplying unit may change. Therefore, in order to obtain an imaging device capable of imaging with a desired imaging sensitivity,
Compensation means for comparing the set multiplication factor and the actual multiplication factor to correct the multiplied output signal, or the signal characteristic of the multiplication factor control signal based on the set multiplication factor and the actual multiplication factor. It is necessary to provide a control means or the like for controlling the gain and maintaining the multiplication factor at the set value. When performing these corrections or controls, it is necessary to first measure the multiplication factor, but the imaging devices described in the above-mentioned JP-A-7-767721 and 2001-29313 have a specific There is no description about a means of measuring the multiplication factor.

In view of the above circumstances, the present invention provides an image pickup apparatus including a solid-state image pickup means having a charge multiplication section for multiplying an imaged signal charge with a multiplication factor based on a multiplication factor control signal. An object of the present invention is to provide an imaging device equipped with a specific measuring unit for measuring the magnification.

[0008]

An image pickup device according to the present invention is a solid-state image pickup device having a charge multiplication section for multiplying an imaged signal charge by a predetermined multiplication factor based on an applied multiplication factor control signal. And a multiplication factor control signal output unit for outputting the multiplication factor control signal, wherein the multiplication factor control signal output unit outputs a first multiplication factor control signal for setting the multiplication factor to approximately 1. , A second multiplication factor control signal for setting the multiplication factor to a value greater than 1 can be switched and output, and an image is picked up by a predetermined light-shielded pixel of the solid-state image pickup means to obtain the first multiplication factor. The signal charge multiplied by the charge multiplying unit to which the magnification control signal is applied and the charge multiplication to which the second light multiplication control signal is applied by being imaged by the predetermined light-shielded pixel of the solid-state imaging unit. The second charge based on the signal charge multiplied by Those having a charge multiplication factor measuring means for calculating the multiplication factor in the charge multiplying unit when the multiplication factor control signal is applied.

The charge multiplication factor measuring means converts the signal charge which is picked up by a predetermined light-shielded pixel of the solid-state image pickup means and multiplied by the charge multiplication part to which the first multiplication factor control signal is applied. A second output based on a first output signal value based on the signal charge and a signal charge imaged by a predetermined light-shielded pixel of the solid-state imaging unit and multiplied by a charge multiplication unit to which the second multiplication control signal is applied. It may be provided with storage means for storing the output signal value and multiplication factor calculating means for calculating the multiplication factor by dividing the second output signal value by the first output signal value.

Here, as the "predetermined light-shielded pixel", an optical black pixel provided in a light receiving portion for measuring a dark current, a pixel light-shielded by a physical shutter, or an image pickup means If it is provided on a mirror or the like, it means a pixel or the like that is brought into the same state as light blocking by turning off the illumination. The signal charge multiplied by the first multiplication factor control signal and the signal charge multiplied by the second multiplication factor control signal may be picked up by the same pixel, or substantially the same charge. May be captured by different pixels as long as they can be regarded as being output.

Another image pickup device according to the present invention is a solid-state image pickup means having a charge multiplication section for multiplying an imaged signal charge by a predetermined multiplication factor based on an applied multiplication factor control signal; In an imaging apparatus provided with a multiplication factor control signal output means for outputting a multiplication factor control signal, the multiplication factor control signal output means has a first multiplication factor control signal for setting the multiplication factor to approximately 1, and the multiplication factor. Is output by switching between the second multiplication factor control signal having a value greater than about 1 by means of charge injection means for injecting a predetermined signal charge before the charge multiplication part, and the charge injection means. The signal charge that has been injected and multiplied by the charge multiplication unit to which the first multiplication factor control signal has been applied, and the charge multiplication that has been injected by the charge injection unit and has the second multiplication factor control signal applied. Based on the signal charge multiplied by , Those having a charge multiplication factor measuring means for calculating the multiplication factor in the charge multiplying unit when the second multiplication factor control signal is applied. Here, “before the charge multiplying section” means the stage before the charge multiplying section and the charge multiplying section. Further, the charge injecting means injects the same amount of signal charges as the amount of signal charges injected in the first charge injection when performing the second charge injection.

The charge multiplication factor measuring means has a first output signal value based on the signal charge injected by the charge injection means and multiplied by the charge multiplication section to which the first multiplication factor control signal is applied. And storage means for storing a second output signal value based on the signal charge injected by the charge injection means and multiplied by the charge multiplication section to which the second multiplication factor control signal is applied, and the second storage means. And a multiplication factor calculating means for calculating a multiplication factor by dividing the output signal value of 1 by the first output signal value.

Further, the image pickup apparatus of the present invention controls the signal characteristic of the charge multiplication rate control signal output from the multiplication rate control signal output means based on the multiplication rate calculated by the charge multiplication rate measuring means. It may be provided with a multiplication factor control means. Further, the solid-state image pickup means may be incorporated in an endoscope device.

[0014]

In the image pickup device according to the present invention, the solid-state image pickup means performs the image pickup with the predetermined light-shielded pixels, and the charge multiplication section to which the first multiplication factor control signal having the multiplication factor of about 1 is applied. In the charge multiplying section to which the multiplied signal charge and the second multiplication factor control signal which makes the multiplication factor a value greater than 1 are imaged by the predetermined light-shielded pixel of the solid-state image pickup means. It is possible to provide a specific multiplication factor measuring means for calculating the multiplication factor in the charge multiplication unit when the second multiplication factor control signal is applied based on the multiplied signal charge.

Further, as the charge multiplication factor measuring means, the first based on the signal charge imaged by a predetermined light-shielded pixel and multiplied by the charge multiplication unit to which the first multiplication control signal is applied. And the second output signal value based on the signal charge multiplied by the charge multiplication unit to which the second multiplication factor control signal is applied and which is imaged by the predetermined pixel shielded from the If a storage unit and a multiplication factor calculation unit that calculates the multiplication factor by dividing the second output signal value by the first output signal value are used, increase by simple signal processing. The magnification can be calculated.

In another image pickup device according to the present invention, the signal charge injected by the charge injection means and multiplied by the charge multiplication section to which the first multiplication factor control signal having a multiplication factor of about 1 is applied. , A second multiplication factor control based on the signal charges multiplied by the charge multiplication section to which the second multiplication factor control signal is applied, which is injected by the charge injecting means and has a multiplication factor greater than about 1. It is possible to provide a concrete charge multiplication factor measuring means for calculating the multiplication factor in the charge multiplication unit when a signal is applied. Further, when calculating the multiplication factor, since the signal charge imaged by the light-shielded pixel is unnecessary, the measurement of the multiplication factor is not affected by the quality of the light-shielded state, and the reliability of the measurement result is improved. .

Further, as the charge multiplication factor measuring means, a first output based on a signal charge injected by the charge injecting means and multiplied by the charge multiplying section to which the first multiplication factor control signal is applied. Storage means for storing a signal value and a second output signal value based on the signal charge injected by the charge injection means and multiplied by the charge multiplication section to which the second multiplication factor control signal is applied; The second output signal value is the first
If a unit having a multiplication factor calculation means for calculating the multiplication factor by dividing by the output signal value of 1 is used, the multiplication factor can be obtained by simple signal processing.

If the multiplication factor control means for controlling the signal characteristic of the multiplication factor control signal output from the charge multiplication factor control signal output means based on the multiplication factor calculated by the charge multiplication factor measurement means is provided, The multiplication factor can be easily controlled to a desired value.

When the solid-state image pickup means is incorporated in the endoscope apparatus, the endoscope is inserted into the body cavity, the environmental temperature of the solid-state image pickup element is changed, and the increase in the charge multiplication section is performed. Even when the magnification changes, the multiplication factor can be measured.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, with reference to FIGS. 1 and 2, an endoscope apparatus as a first specific embodiment to which an image pickup apparatus according to the present invention is applied will be described. Figure 1
2 is a schematic configuration diagram of the endoscope apparatus, and FIG. 2 is a schematic view of a CMD-CCD image pickup element as a solid-state image pickup means mounted in the present endoscope apparatus. This endoscopic device,
Illumination light R light (red light) Lr, G light (green light) L
g, B light (blue light) Lb is sequentially irradiated, and the CMD- is provided with a charge multiplication unit that multiplies the reflected light reflected by the observation unit with the multiplication factor based on the multiplication control signal. This is a field-sequential endoscopic device that captures an image with a CCD image sensor and displays the image of the observation unit as a color image on a monitor.

The endoscope apparatus according to the first embodiment of the present invention comprises a CMD-CCD image pickup device having a charge multiplication means at the tip thereof, and a scope portion inserted into a suspected lesion of a patient. 100, an illumination unit 110 including a light source that emits illumination light, and C for controlling the operation of the CMD-CCD image sensor
A CD control unit 120, an image processing unit 130 for performing image processing for displaying a captured image signal as a color image,
A controller 140 that is connected to each part and controls the drive timing and the like, and a monitor 150 that displays the captured image 11
It consists of

The scope section 100 includes a light guide 101 and a CCD cable 102 which extend to the tip inside. At the tip of the light guide 101 and the CCD cable 102, that is, the tip of the scope section 100, an illumination lens 104 is provided.
And an objective lens 105. CCD cable 10
A CMD-CCD image pickup element 106 having a charge multiplication section is connected to the tip of the CMD 2.
A prism 107 is attached to the.

The CMD-CCD image pickup device 106 is a frame transfer type CCD image pickup device as shown in FIG. 2, and has a light receiving portion 21 for converting a picked-up optical image into a signal charge.
A storage unit 22 that temporarily stores and transfers signal charges, a horizontal transfer path 23 that horizontally transfers signal charges, a connection path 26 and a connection path 26 that sequentially transfer the signal charges transferred from the horizontal transfer path 23.
A charge multiplication unit 24 that multiplies the signal charge transferred from the output unit 25, and an output unit 25 that converts the signal charge into a signal voltage, amplifies the signal charge, and outputs the signal voltage from the output terminal 27 to the image processing unit 130.

The light receiving section 21 is composed of vertical transfer CCDs 30 for performing photoelectric conversion and vertical transfer of signal charges, arranged in the vertical direction and in the horizontal direction. For the sake of simplicity, FIG. 2 shows the light receiving unit 21 composed of four vertical and five horizontal vertical transfer CCDs 30, but an actual CMD-CCD image pickup device.
The vertical / horizontal 106 includes several hundreds of vertical transfer CCDs 30. The light receiving section 21 is composed of a light receiving area 31 for performing normal light reception and a light shielding area 32 light shielded by a thin metal film or the like for use in dark output correction and the like. Normally, a plurality of vertical transfer CCDs 30 are provided in the light-blocking area 32.
Are provided (only one is shown in FIG. 2 for the sake of simplicity), and these are OPBs (Optical Blaces).
k) It is called a pixel. Note that the charge signal is read from the vertical transfer CCD 30 provided in the light receiving region 31 and the light shielding region 32 by a normal reading operation.

The storage section 22 is composed of a vertical transfer CCD 33 which is light-shielded by a thin metal film or the like and temporarily stores signal charges and performs vertical transfer. The horizontal transfer path 23 is composed of a horizontal transfer CCD 35, and the connection path 26 is composed of a transfer CCD 39.

The charge multiplication section 24 is composed of a large number of charge multiplication cells 36. The charge multiplying cell 36 is for multiplying and inputting the input charge using the charge multiplying effect caused by ionization by causing electrons and atoms to collide with each other in a strong charge region. In FIG. 2, the storage unit 2
2, the horizontal transfer path 23, the connection path 26, and the charge multiplication section 24 are also simplified and described like the light receiving section 21.

The output section 25 includes a charge detection section 37 for converting the signal charge into a signal voltage (output signal) and an output amplifier 38 for amplifying the output signal.

The light guide 101 is connected to the lighting unit 110. CCD cable 102 is CMD-CC
A drive line 103a to which a drive signal for the D image sensor 106 is transmitted
And an output line 103b for reading out signal charges from the CMD-CCD image pickup device 106 are combined, one end of the drive line 103a is connected to the CCD control unit 120, and one end of the output line 103b is connected to the image processing unit 130. There is.

The illumination unit 110 is a white light source 111 consisting of a xenon lamp that emits white light, a light source power source 112 electrically connected to the white light source 111, and a white light emitted from the white light source. The condenser lens 113, a switching filter 114 for sequentially separating white light into R light, G light, and B light, and a filter rotating unit 115 for rotating the switching filter 114.

As shown in FIG. 3, the switching filter 114 has an R filter 114a which transmits R light and a G filter which transmits G light.
It is composed of a filter 114b, a B filter 114c that transmits B light, and a mask portion 114d having a light blocking function. While the illumination light (R light, G light, or B light) is not applied by the mask portion 114d, in the CMD-CCD image pickup device 106, signal charges are transferred from the light receiving portion 21 to the storage portion 22.

The CCD control unit 120 outputs a normal CCD drive signal and a multiplication factor control signal for controlling the multiplication factor in the charge multiplication unit 24, and a predetermined signal value used when measuring the multiplication factor. Storage means 12 for storing
2, a multiplication factor calculation means 124 for calculating a multiplication factor, and a multiplication factor control means 125 for outputting a control signal for controlling the multiplication factor to a desired value based on the multiplication factor calculated by the multiplication factor calculation means 124. And a D / A conversion circuit 126 for converting the control signal output from the multiplication factor control means 125 into an analog signal and outputting the analog signal to the CCD driver.

The storage means 122 is a memory for storing a reference signal value picked up by an OPB pixel and multiplied by a multiplication factor of 1.
123a and a memory 123b for storing the signal value picked up by the OPB and multiplied by a predetermined multiplication factor. The multiplication factor calculating means 124 calculates the multiplication factor in the charge multiplication unit 24 by dividing the signal value stored in the memory 123b by the signal value stored in the memory 123a. The multiplication factor control means 125 feedback-controls the value of the multiplication factor control signal output from the CCD driver 121 so that the multiplication factor calculated by the multiplication factor calculation means 124 matches the multiplication factor set by the controller 140. To do. The details of this feedback control will be described later.

The image processing unit 130 is a CMD-CCD.
A signal processing circuit 131 that performs a process process of a signal captured by the image sensor 106, an A / D conversion circuit 132 that digitizes the image signal obtained by the signal processing circuit 131, and a digitized image signal for each color. An image memory 133 for saving, and a video signal processing circuit for converting the image signals of the three colors simultaneously output from the image memory 133 into a video signal and outputting the video signal.
It has 134. The A / D conversion circuit 132 stores a part of the digitized signal in the storage means 122 as necessary.
Is output to. The controller 140 is connected to each part and controls the operation timing. The storage unit 122, the multiplication factor calculation unit 124, the multiplication factor control unit 125, and the CCD driver 121 constitute the charge multiplication factor measurement unit of the present invention. In particular, the multiplication control unit 125 and the CCD driver 121 are multiplication control units. It constitutes a signal output means.

The operation of the endoscope apparatus according to the first embodiment of the present invention will be described below. Prior to imaging, the observer inserts the scope section 100 into the body cavity of the subject, and guides the tip of the scope section 100 to the vicinity of the observation section 10.

In order to simplify the explanation, the operation at the time of performing normal image pickup will be described first, and then the multiplication operation control operation will be described. However, in reality, the image pickup operation and the multiplication operation control operation are performed. Are done in parallel.

First, the operation when acquiring the R image of the RGB image will be described. The light source power source 112 is driven based on a signal from the controller 140, and white light is emitted from the white light source 111. The white light is condensed by the condenser lens 113 and passes through the switching filter 114. Switching filter 114
Then, based on the signal from the controller 140, the R filter 114a is arranged on the optical path. Therefore, the white light becomes R light Lr when passing through the switching filter 114. R
The light Lr is incident on the light guide 101, and the scope unit 10
After the light is guided to the tip of 0, from the illumination lens 104 to the observation unit 1
Irradiate to 0.

The reflected light of the R light Lr reflected by the observation unit 10 is condensed by the condenser lens 105, reflected by the prism 107, and reflected by the R light reflected image Z on the CMD-CCD image pickup device 106.
It is imaged as r.

In the CMD-CCD image pickup device 106, the light receiving section
In the vertical transfer CCD 30 of 21, the R light reflection image Zr is received, photoelectrically converted, and converted into an electric signal according to the intensity of light.

When a predetermined time has passed, the switching filter 114
Then, the mask unit 44 is arranged on the optical path based on the signal from the controller 140. For this reason the light guide 101
There is a period in which no light is incident on. During this time, the signal charges accumulated in the vertical transfer CCD 30 are transferred to the vertical transfer CCD 33 in the storage section 22.

The signal charges transferred to the vertical transfer CCD 33 of the storage unit 22 are vertically transferred in parallel and sequentially sent to the horizontal transfer CCD 35 of the horizontal transfer path 23. In the horizontal transfer path 23,
When the signal charges of the pixels on one horizontal line enter, the signal charges are transferred in the horizontal direction, and sequentially via the connecting path 26, the charge multiplying unit.
Transferred to 24 charge multiplication cells 36. In the charge multiplication cell 36, the signal charges are sequentially transferred while being multiplied based on the multiplication control signal. The signal charge output from the final charge multiplication cell 36 to the output section 25 provided at the right end is converted into a signal voltage by the charge detection section 37, amplified by the output amplifier 38, and output from the output terminal 27 as an output signal. Is output. After that, the signal charges of the next horizontal 1 line are transferred from the storage unit 22 to the horizontal transfer path 23. By repeating such operations, the signal charges are sequentially read out from the lower left pixel of the light receiving unit 21 in the right direction, and when the signal charges of the horizontal 1 line are read out, the signal charges of the horizontal 1 line above it are next read out. Are read out, and the signals are sequentially moved to read out all the signal charges forming the R image. As for the output signals read from the second and subsequent stages from the bottom, as shown in FIG. 4, first, the signal imaged in the light-shielding area 32 of the CMD-CCD 106 is output, and then the light-receiving area 31.
The signal imaged in is output.

While the signal charge accumulated in the accumulating section 22 is being read out, the G light Lg is emitted from the illumination unit 110, is reflected by the observing section 10, and is condensed by the condenser lens 105. The light is condensed and reflected by the prism 107, and as a G light reflection image Zg, the CMD-CCD image pickup device 106
Is received by. In addition, the CMD-CCD image sensor 106
The image pickup operation in (1) is executed based on the operation control signal input from the CCD driver 120.

The output signal of the R image output from the CMD-CCD image pickup device 106 is processed as a R image signal by the signal processing circuit 131 of the image processing unit 130, and is output by the A / D conversion circuit 132. It is converted into a digital signal and stored in the storage area of the R image signal of the image memory 133.

Thereafter, the G image signal and the B image signal are acquired by the same operation, and the G image signal and the B image signal of the image memory 133 are respectively acquired.
The image data is stored in the image signal storage area and the B image signal storage area.

When the image signals of three colors are stored in the image memory 133, they are synchronized with each other at the display timing and outputted, and converted into a video signal by the video signal processing circuit 134 and outputted to the monitor 150. It is displayed as a color image 11.

Next, the multiplication factor control operation for controlling the multiplication factor of the charge multiplying section 24 will be described. Normally, the charge multiplication characteristic of the charge multiplication unit 24 changes with temperature.
For example, if the scope section 100 that was stored at room temperature is
When it is inserted into the body of a patient and the temperature rises, its multiplication characteristic changes from the solid line shown in FIG. 5 to the broken line. Therefore, even if the voltage of the multiplication factor control signal is constant, the multiplication factor changes. In addition, there are individual differences in the body temperature, and it is difficult to predict the body temperature and set the voltage of the multiplication factor control signal in advance. Furthermore, even though the multiplication characteristics at room temperature are known, the rate of change of the multiplication characteristics due to the effect of temperature changes differs depending on the individual charge multiplication section, so the temperature is measured and the voltage of the multiplication control signal is corrected. After all it is difficult to do.

As another factor causing the multiplication factor to deviate from the predetermined value, the influence of the voltage drop in the CCD drive line connecting the CCD driver 121 and the CCD image pickup device can be considered. The distance between the CCD driver 121 and the CCD image pickup element varies depending on each endoscope. Even if the CCD driver outputs a multiplication factor control signal of a predetermined voltage, the multiplication factor control signal is generated by the voltage drop in the CCD drive line. There may be a case where the voltage of is shifted. The rate of change of the gain with respect to the change of the voltage of the gain control signal is shown in FIG.
As shown in (3), it becomes large when the multiplication is performed by a high multiplication factor, and the error of the multiplication factor becomes large due to the influence of the voltage drop.

In order to solve this problem, in this embodiment, the multiplication factor is measured and the voltage of the multiplication factor control signal is feedback-controlled so that a desired multiplication factor can be obtained. That is, as shown in FIG. 5, a1 is set as the original multiplication factor, and therefore b1 is supplied as the voltage of the multiplication factor control signal. However, since the body temperature is high, the actual multiplication factor is If it is deviated to a2, by lowering the voltage of the multiplication factor control signal to b2, a1 can be realized as the multiplication factor. On the contrary, when the voltage of the multiplication factor control signal is lowered due to the influence of the voltage drop of the CCD drive line and the multiplication factor is shifted to the lower side, the voltage of the multiplication factor control signal is increased. A desired multiplication factor can be realized. In order to perform this feedback control, it is first necessary to measure the actual multiplication factor. Details of the multiplication factor measurement operation and control operation will be described below with reference to the flowchart shown in FIG.

In step 101, an image is first picked up. In step 102, the multiplication factor control means 125 outputs a control signal S for outputting a multiplication factor control signal in which the multiplication factor becomes approximately 1.
Is output to the CCD driver 121 via the D / A conversion circuit 126. The CCD driver 121 does not perform multiplication as shown in (a) of FIG. 7 as a multiplication factor control signal and simply executes transfer, that is, outputs a pulse signal having a multiplication factor of about 1 as a multiplication factor control signal voltage. To do.

In step 103, first, the horizontal direction of the light receiving section 21 is set.
The signal charge of the vertical transfer CCD 30 for the column is read. That is, the CMD-CCD image pickup is performed without multiplying the signal charges picked up by the vertical transfer CCD 30 in the horizontal row at the bottom of the light receiving portion 21 of the CCD image pickup element 106 (that is, by multiplying by 1). Read from element 106. The read output signal is subjected to signal processing by the signal processing circuit 131, and the A / D conversion circuit 132
After being digitized by, it is output to the storage means 133. When the digitized signal is output from the A / D conversion circuit 132, the multiplication factor is measured for the signal value a picked up by a pixel in the light shielding area 32 of the light receiving unit 21, that is, one of OPB pixels. It is output to the storage means 122 as a reference value for the storage and stored in the memory 123a.

In step 104, multiplication factor control means
125 has a multiplication factor of 140
The control signal S for outputting the multiplication factor control signal which becomes the target multiplication factor N inputted from the C is inputted via the D / A conversion circuit 126 to the C signal.
Output to the CD driver 121. CCD driver 121
As a multiplication factor control signal, as shown in FIG. 7B, under the reference temperature, the charge multiplying section 24 outputs a pulse signal of a voltage at which multiplication is performed with a multiplication factor N >> 1.

At step 105, the signal charges of the vertical transfer CCD 30 for one horizontal row of the light receiving portion 21 are read. That is,
If this step is executed for the first time, the CCD image sensor 10
Vertical transfer CCD in the second horizontal row from the bottom of 6 light receiving section 21
The signal charge imaged in 30 is multiplied and read out from the CMD-CCD image sensor 106, and if it is the nth time, it is imaged by the vertical transfer CCD 30 in the n + 1th horizontal row from the bottom of the light receiving portion 21 of the CCD image sensor 106. The signal charge generated by CMD-C
The data is read from the CD image sensor 106. The read output signal is subjected to signal processing by the signal processing circuit 131, digitized by the A / D conversion circuit 132, and then output to the storage means 133. When the digitized signal is output from the A / D conversion circuit 132, the signal value b captured by one of the OPB pixels is output to the storage unit 122 and stored in the memory 123b.

In step 106, the multiplication factor calculation means 124
, The signal value b stored in the memory 123b is stored in the memory 12
The charge multiplication unit 24 is divided by the signal value a stored in 3a.
The actual multiplication factor N ′ = a / b in the above equation is calculated and output to the multiplication factor control means 125.

In step 107, multiplication factor control means
125 compares the actual multiplication factor N ′ with the target multiplication factor N, and if they match, the adjustment of the multiplication factor control signal is ended. At this point, the multiplication factor control signal output from the CCD driver 121 is Output continuously. If the multiplication factor N'is larger than the target multiplication factor N, the routine proceeds to step 108, where the multiplication factor is made slightly smaller than the previous multiplication factor (that is, the multiplication factor control signal is reduced by α). A new control signal S is set and the process returns to step 105. If the multiplication factor N'is smaller than the target multiplication factor N, the routine proceeds to step 109, where the multiplication factor is slightly larger than the previous multiplication factor (that is, the multiplication factor control signal is increased by α). ), The control signal S is changed, and the process returns to step 105.

By performing the above-described control, the multiplication factor can be measured in steps 101 to 107. Based on the measured multiplication factor, the multiplication factor control signal of the multiplication factor control signal is calculated in steps 105 to 109. By adjusting the gain
The desired multiplication factor set by 0 can be matched. Such control may be performed once, for example, when the endoscope is inserted into the body cavity, or may be performed every time one frame is imaged. Even if the actual multiplication factor N ′ and the target multiplication factor N match in step 107, if the step is changed to return to step 105 without ending the operation, the light receiving unit 21 The fine adjustment can be repeated for each horizontal line (vertical transfer CCD 30 for one horizontal row).

Although the signal value detected by one of the OPB pixels is stored in the memories 123a and 123b in this embodiment, a plurality of OPB pixels provided in each horizontal line are stored. Storing the average signal value of improves the measurement accuracy of the multiplication factor.

Further, the signal charge of a predetermined OPB pixel in the first imaged frame is read with a multiplication factor of 1, the signal value is stored in the memory 123a, and the signal of the same OPB pixel of the next imaged frame is read. The value can be stored in the memory 123b and the multiplication factor can be controlled for each frame sequentially. In this case, it takes several frames for the actual gain to reach the target gain, but the same OPB
Since the multiplication factor is measured using pixels, the multiplication factor can be accurately measured even if the dark noise included in the signal value of the OPB pixel differs for each OPB pixel.

Further, the signal charges of a predetermined plurality of OPB pixels in the first imaged frame are read with a multiplication factor of 1, the average value of the signal values is stored in the memory 123a, and the signal of the next imaged frame is read. It is also possible to store the average value of the signal values of the same plurality of OPB pixels in the memory 123b and sequentially control the multiplication factor for each frame. By using the average value of the signal values of a plurality of OPB pixels, it is less likely to be affected by noise and the measurement accuracy of the multiplication factor is improved. The multiplication factor may be measured using the average value of the signal values of all OPB pixels in each frame.

If the multiplication factor is measured using the signal charge of the OPB pixel shielded by the metal film as in this embodiment, the illumination may be turned on or off, but the illumination is turned off. With this, it is possible to read out the signal charges in a more surely shielded state. Further, if the multiplication factor is measured only in a state where the illumination is off or the light receiving portion 21 is shielded by a shutter or the like, the multiplication factor is limited to OPB pixels and the pixels in the light receiving region 31 are used. You can also

Next, with reference to FIGS. 1 and 8, an endoscope apparatus according to a second specific embodiment of the present invention will be described. Since the schematic configuration of the endoscope apparatus according to the second specific embodiment is almost the same as that of the endoscope apparatus according to the first embodiment shown in FIG. 1, only numbers are given to FIG.
FIG. 8 is a schematic view of a CMD-CCD image pickup device as a solid-state image pickup means mounted on the present endoscope apparatus. Note that, in FIG. 8, elements that are the same as the elements in FIG. 2 are given the same numbers, and descriptions thereof will be omitted unless necessary.

The endoscope apparatus according to the second embodiment of the present invention includes a CMD-CCD image pickup device having a charge multiplication means at the tip thereof, and a scope portion inserted into a suspected lesion of a patient. 200, an illumination unit 110 having a light source for emitting illumination light, C for controlling the operation of the CMD-CCD image sensor
A CD control unit 210, an image processing unit 130 that performs image processing for displaying a captured image signal as a color image,
It is composed of a controller 220 which is connected to each part and controls the drive timing and the like, and a monitor 150 which displays a captured image.

The scope section 200 is the scope section shown in FIG.
C instead of CMD-CCD image sensor 106 in 100
An MD-CCD image pickup device 201 is provided. Other configurations are similar to those of the scope unit 100.

The CMD-CCD image pickup device 201 is a frame transfer type CCD image pickup device as shown in FIG. 8, and a connecting passage 40 is provided between the horizontal transfer passage 23 and the charge multiplying section 24. A charge injection unit 41 is connected to the.
As shown in FIG. 9, the charge injection unit 41 is composed of a capacitor 42, a transistor 43 and a transistor 44. The charge injection unit 41 is used only when measuring the multiplication factor, and by applying a reset pulse synchronized with the transfer clock shown in (a) of FIG. The charge is accumulated in 42. Further, by applying an injection pulse to the gate of the transistor 44 at the timing shown in FIG. 10B, the charge accumulated in the capacitor 42 is injected into the connection path 40. The injection of these charges is performed immediately before the signal charges of the OPB pixel are transferred to the connection path 40. CMD
As for the output signal read from the output terminal 27 of the CCD image pickup device 201, the signal of the connection path 40 is first read for each horizontal line, and then the light shield area 32 (OP
The signal imaged in the B pixel) is read out, and the signal imaged in the light receiving area 31 is finally read out. Therefore, the signal read out from the connection path 40 contains the signal of the injected charges.

The CCD control unit 210 outputs a normal CCD drive signal, a multiplication factor control signal for controlling the multiplication factor in the charge multiplication unit 24, and a reset driver and an injection pulse for measuring the multiplication factor. It is equipped with 211.

When measuring the multiplication factor, the multiplication factor control means
The 125 outputs a control signal S for outputting a multiplication factor control signal with a multiplication factor of 1 to the CCD driver 211 via the D / A conversion circuit 126. The CCD driver 211 outputs, as a multiplication factor control signal, a pulse signal of a voltage for executing only transfer without performing multiplication, and at the same time, outputs a reset pulse and an injection pulse at the timing shown in FIG.
A predetermined charge is injected into the connection path 40.

These injected charges and signal charges are not multiplied (that is, multiplied by a multiplication factor of 1) and CMD-CC.
The signal is read from the D image pickup device 201, subjected to signal processing by the signal processing circuit 131, digitized by the A / D conversion circuit 132, and then output to the storage unit 133. Note that when the digitized signal is output from the A / D conversion circuit 132, the signal value corresponding to the injected charge is output to the storage unit 122,
It is stored in the memory 123a as a reference value when measuring the multiplication factor. Further, as in the first embodiment, when the next horizontal line is read out, the CCD driver 211, if under the reference temperature, changes the voltage of the voltage multiplied by the multiplication factor N in the charge multiplication unit 24. The pulse signal is output as a multiplication factor control signal. At this time as well, at the same time, at the timing shown in FIG. 11, a reset pulse and an injection pulse are output to inject a predetermined charge into the connection path 40.

These injected charges and signal charges are multiplied by the charge multiplying unit 24, read out from the CMD-CCD image pickup device 201, subjected to signal processing by the signal processing circuit 131, and then A / D converted.
After being digitized by the conversion circuit 132, it is output to the storage means 133. When the digitized signal is output from the A / D conversion circuit 132, the signal value corresponding to the injected charge is output to the storage unit 122 and stored in the memory 123b.
Thereafter, similarly to the first embodiment, the multiplication factor can be calculated by dividing the signal value stored in the memory 123b by the signal value stored in the memory 123a. Further, the multiplication factor control signal can be finely adjusted so that the multiplication factor in the charge multiplying section 24 matches the desired multiplication factor N. Further, since the signal charge imaged by the light-shielded pixel is not used when calculating the multiplication factor, the measurement of the multiplication factor is not affected by the quality of the light-shielded state, and the reliability of the measurement result is improved. .

In each embodiment, CMD-
The multiplication factor was measured from the value obtained by converting the signal read out from the CCD image sensor into a digital signal. As a modified example, for example, the output waveform of the analog signal output from the signal processing unit 131 is output from the OPB pixel. It is also conceivable to store the obtained signal portion and obtain the multiplication factor from the ratio. From the signal processing unit 131, when the multiplication factor is 1,
When the signal as shown in FIG. 12A is output and the multiplication factor is N ′, the signal as shown in FIG. 12B is output, so that FIG. The multiplication factor can be obtained by dividing b in (1) by a in (a) of FIG.

Although a CCD image pickup device capable of two-dimensional image pickup is used as the solid-state image pickup means in each of the above embodiments, a line CCD can also be used as the solid-state image pickup means. In this case, the first imaged signal charge is read with a multiplication factor of 1, the reference signal value is stored based on the signal value in that OPB pixel, and the signal in the OPB pixel in the next imaged signal charge is stored. The value may be stored and the multiplication factors may be calculated sequentially. The solid-state image pickup means is not limited to the CCD image pickup element, and any solid-state image pickup means capable of multiplying the signal charges by the charge multiplying section may be used.

As a modified example of the present invention, it is also possible to directly transfer the signal charge from the connection path to the charge detection section and use the output signal value thereof as the above-mentioned reference value. In this case, the output signal corresponds to the “first output signal value based on the signal charge multiplied by the charge multiplication unit to which the first multiplication factor control signal having the multiplication factor of about 1 is applied”. .

Furthermore, as another modification, the charge multiplication section 24
It is also conceivable that the multiplication factor is measured based on the signal charge itself (that has not been converted into a voltage) multiplied by and output. Further, the signal charge output from the connection path can be used similarly to the above-mentioned reference value.
In this case, the signal charge corresponds to “the signal charge multiplied by the charge multiplication unit to which the first multiplication factor control signal having the multiplication factor of about 1 is applied”. In particular, if the charge injection part is provided and the injection charge amount is known, the charge amount of the injection charge is kept as it is and the “multiplication factor is approximately 1”
The signal charge multiplied by the charge multiplication section to which the multiplication control signal is applied.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an endoscope apparatus according to a first specific embodiment of the present invention.

FIG. 2 is a schematic diagram of a CCD image sensor used in the endoscope apparatus according to the first specific embodiment.

FIG. 3 is a schematic configuration diagram of a rotary filter.

FIG. 4 is a waveform diagram of an output signal

FIG. 5 is a graph illustrating a relationship between a voltage value of a multiplication factor control signal, a multiplication factor, and temperature.

FIG. 6 is a flowchart illustrating a flow of multiplication factor measurement and control operation.

FIG. 7 is an explanatory diagram of a multiplication factor control signal.

FIG. 8 is a schematic diagram of a CCD image sensor used in the endoscope apparatus according to the second specific embodiment.

FIG. 9 is a circuit diagram of a charge injection unit.

FIG. 10 is an explanatory diagram of a reset pulse and an injection pulse.

FIG. 11 is an explanatory diagram of an injection charge signal.

FIG. 12 is a waveform diagram of an output signal imaged in a light-shielded area.

[Explanation of symbols]

11 images 21 Receiver 22 Storage 23 Horizontal transfer path 24 Charge multiplier 25 Output section 26,40 connections 30,33 Vertical transfer CCD 31 Light receiving area 32 shaded area 35 Horizontal transfer CCD 36 charge multiplication cell 41 Charge injection part 100,200 scope section 106,201 CMD-CCD image sensor 110 lighting unit 120,210 CCD control unit 121,211 CCD driver 122 storage means 123a, 123b memory 124 Gain calculation means 125 Gain control means 130 Image processing unit 140,220 controller 150 monitor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 29/762 F term (reference) 4C061 AA01 AA07 AA11 AA12 AA13 AA25 BB02 CC06 DD00 LL02 NN01 SS03 4M118 AA10 AB01 BA12 DA16 DA40 FA06 GD03 GD07 GD13 HA23 5C024 BX02 CY44 EX52 GY03 GY44 GZ36 HX55

Claims (6)

[Claims] 1. A solid-state image pickup means having a charge multiplication section for multiplying an imaged signal charge by a predetermined multiplication factor based on an applied multiplication factor control signal, and outputting the multiplication factor control signal. In an imaging apparatus provided with a multiplication factor control signal output means, the multiplication factor control signal output means sets a first multiplication factor control signal for setting the multiplication factor to about 1 and a value greater than about 1 for the multiplication factor. And a second multiplication factor control signal that can be output by switching, and is imaged by a predetermined light-shielded pixel of the solid-state imaging means,
The signal charge multiplied by the charge multiplication unit to which the first multiplication factor control signal is applied and an image of a predetermined pixel shielded by the solid-state image pickup unit are imaged, and the second multiplication factor control signal is applied. And a charge multiplication factor measuring means for calculating a multiplication factor in the charge multiplication unit when the second multiplication factor control signal is applied, based on the signal charge multiplied in the charge multiplication unit. An imaging device characterized by the above. 2. A signal multiplied by a charge multiplication unit to which the first multiplication factor control signal is applied, wherein the charge multiplication factor measuring unit takes an image with a predetermined light-shielded pixel of the solid-state image pickup unit. Based on a first output signal value based on electric charge and a signal electric charge which is imaged by a predetermined light-shielded pixel of the solid-state imaging means and multiplied by a charge multiplication section to which the second multiplication factor control signal is applied. Storage means for storing the second output signal value,
The image pickup apparatus according to claim 1, further comprising: a multiplication factor calculation unit that calculates a multiplication factor by dividing the second output signal value by the first output signal value. 3. A solid-state image pickup means having a charge multiplying unit for multiplying the imaged signal charge by a predetermined multiplication factor based on the applied multiplication factor control signal, and outputting the multiplication factor control signal. In an imaging apparatus provided with a multiplication factor control signal output means, the multiplication factor control signal output means sets a first multiplication factor control signal for setting the multiplication factor to about 1 and a value greater than about 1 for the multiplication factor. And a second injection control signal for switching the output, and a charge injection unit for injecting a predetermined signal charge before the charge multiplication unit; The signal charges multiplied by the charge multiplying part to which the multiplication factor control signal is applied and injected by the charge injecting means and multiplied by the charge multiplying part to which the second multiplication factor control signal is applied. A second multiplication factor control signal based on the signal charge and An image pickup apparatus, comprising: a charge multiplication factor measuring means for calculating a multiplication factor in the charge multiplication unit when is applied. 4. The charge multiplication factor measuring means based on a signal charge injected by the charge injection means and multiplied by a charge multiplying part to which the first multiplication factor control signal is applied.
Is injected by the output signal value and the charge injection means,
Storage means for storing a second output signal value based on the signal charge multiplied by the charge multiplication section to which the second multiplication control signal is applied, and the second output signal value for the first output signal value. 4. The image pickup apparatus according to claim 3, further comprising a multiplication factor calculation means for calculating a multiplication factor by dividing the output signal value. 5. A multiplication factor control means for controlling the signal characteristic of the multiplication factor control signal output from said multiplication factor control signal output means based on the multiplication factor calculated by said charge multiplication factor measuring means. The imaging device according to any one of claims 1 to 4, wherein: 6. The image pickup apparatus according to claim 1, wherein the solid-state image pickup means is incorporated in an endoscope apparatus.