JPH06350919A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain the image pickup device by which a picture signal of an optimum level stable at all times is outputted and a picture with excellent quality is easily obtained without unevenness for every picture field. CONSTITUTION:This device is provided with an image pickup element 15 having a photoelectric conversion section applying photoelectric conversion to a light from an image pickup object and having a charge read means reading the charge obtained by said photoelectric conversion section, a lighting means 10 generating a pulsive illumination light lighting an image pickup object 13 for a predetermined time and a control mans 16 controlling the drive of a charge read means or the lighting means so as to provide at least one pulse illuminating light within one period of charge read from the photoelectric conversion section. The control means 16 controls the charge read means or the lighting means in response to the quantity of the signal charge stored in the photoelectric conversion section. Furthermore, the device is provided with a flush means flushing a photographing object 13 in place of the lighting means 10, and the control means 15 controls the drive of the charge read means or the flush means.

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.

[0002]

2. Description of the Related Art In recent years, various image pickup devices for picking up an image of a subject have been provided with the progress of semiconductor technology. On the other hand, there is a demand for taking an image in a wavelength band that cannot be picked up by a conventional light source or wavelength. Is occurring. For example,
In a microscope for observing the fine structure of living things and various substances, the shorter the wavelength of the illumination light used, the better the spatial resolution, and the finer structure can be observed. Irradiate the target metal with
The X-ray generated at that time is used as illumination light, and a resolution of 1 μm or less is currently obtained.

[0003]

However, in the X-ray microscope as described above, recording of an observation image, that is, image pickup is performed by exposing a photosensitive film for a long time. Had to be further developed after the exposure for a long time, which was very complicated. In addition, in order to process image data with a computer and improve or measure the image quality, it is necessary to read an image on a developed photograph using a scanner or the like, and there is a problem that promptness is lacking.

On the other hand, it is conceivable to use a solid-state image pickup device such as a CCD instead of the film having such a problem. However, all the conventional image pickup devices have a speed comparable to continuous light or an image pickup cycle. It is made for the purpose of recording optical information that changes with time. For example, when the imaging device is used in the X-ray microscope as described above, the following inconvenience occurs.

That is, in the above X-ray microscope,
The light emission cycle for illuminating the imaging target is about 1/10 seconds, while the imaging cycle is about 1/30 seconds. Therefore, when performing imaging using a conventional imaging device, there is Illumination light is emitted in the imaging cycle (image field),
Illumination light is not generated in a certain imaging cycle thereafter, and the brightness of the image fluctuates in each imaging cycle (image field), resulting in very poor image quality.

The present invention has been made in order to solve the problem in the conventional image pickup apparatus, and an object thereof is to provide an image pickup apparatus which can easily obtain a high quality image.

[0007]

[Means for Solving the Problems] To achieve the above object,
According to the invention of claim 1 of the present application, a photoelectric conversion unit for converting light from an image pickup object into an electric charge, and an image pickup device having a charge reading unit for reading out the electric charge obtained by the photoelectric conversion unit, and the image pickup object are fixed. Illuminating means for generating pulsed illumination light for time illumination, and the charge reading means or the illuminating means so that at least one pulse illumination light is generated within one cycle of reading out charges from the photoelectric conversion unit. The present invention relates to an image pickup apparatus including: a control unit that controls driving.

According to a second aspect of the present invention, in the first aspect of the invention, the control means controls the charge reading means or the illuminating means in accordance with the amount of signal charges accumulated in the photoelectric conversion section. The present invention relates to an imaging device.

Further, the invention of claim 3 is an image pickup device having a photoelectric conversion part for converting light from an image pickup object into an electric charge, and a charge reading means for reading out the electric charge obtained by the photoelectric conversion part; A light emitting means for emitting light for a certain period of time,
According to another aspect of the present invention, there is provided an image pickup apparatus, comprising: a control unit that controls driving of the charge reading unit or the light emitting unit so that the image pickup object emits light at least once within one cycle of reading charges from the photoelectric conversion unit. It is a thing.

According to a fourth aspect of the invention, in the third aspect of the invention, the control means controls the charge reading means or the light emitting means according to the amount of signal charges accumulated in the photoelectric conversion section. The present invention relates to an imaging device.

[0011]

In the invention of claim 1, which is configured as described above, the illuminating means outputs pulsed illumination light to the object to be imaged at the time of photographing, and the object to be imaged is illuminated by this illumination light. And the light from the imaging target (imaging light)
Is incident on the image pickup device, converted into electric charges by the photoelectric conversion unit of the image pickup device, and then outputted as an electric image signal by the electric charge reading means.

On the other hand, the charge reading means and the illuminating means of the image pickup device are arranged so that at least one of the pulsed illumination light is generated within one cycle of reading the charge from the photoelectric conversion section by the charge reading means. The drive is controlled by the control means.

As described above, in the present image pickup device, one or more pulse illuminations are always performed within one cycle of reading out charges from the photoelectric conversion unit, that is, in one image pickup cycle for obtaining one image field. There is no image field in which illumination is not performed in the image capturing, and it is possible to prevent uneven illumination in each image field.

Further, it is possible to perform a plurality of pulsed illuminations within one image pickup cycle. Therefore, the characteristics of the individual imaged objects (such as the transmittance and the thickness to be transmitted) and the illumination means are different. An image signal of an optimum level can be obtained according to the output difference. For example, when one pulse illumination cannot obtain a sufficient image signal, such as when the light source or the optical system included in the illumination unit is dark, or when the transmittance of the imaging target is poor, a plurality of image signals can be obtained within one imaging cycle. It may be controlled so as to perform the pulse illumination. That is, in the present imaging device, it is possible to compensate for the shortage of the imaging light amount by accumulating the signal charges in the photoelectric conversion unit of the imaging element.

On the other hand, in order to compensate for the shortage of the image pickup light amount in this way, a small amount of signal charge obtained by photoelectric conversion per certain image pickup cycle is once read out from the image pickup device and then A / D converted, Although it may be considered to integrate numerically, in such a method, noise of the output section of the image sensor, noise of an amplifier connected to the image sensor, etc. are added to the weak output signal, and these noise components are added. Is also added, and a circuit for numerical integration is also required, which complicates the device configuration and makes the device expensive, which is not appropriate.

On the other hand, according to the present invention, the noise of the output section of the image pickup device and the noise of the amplifier are not integrated, the apparatus is not complicated, and the S / N ratio is improved. it can.

Further, in the invention of claim 2, the control means controls the charge reading means or the illuminating means in accordance with the amount of signal charges accumulated in the photoelectric conversion section. Here, the amount of signal charges accumulated in the photoelectric conversion unit is the amount of illumination light generated from the illumination unit, the amount of light from the imaging target, or the magnitude of the output signal from the imaging element. Can be detected by measuring.

When the amount of accumulated signal charges is small, the control means increases the number of pulse illuminations within one image pickup cycle. Therefore, according to the present imaging device, for example, even when the amount of light output from the illumination unit changes, it is possible to automatically obtain a stable and optimum level image signal. Furthermore, no extra load is applied to the light source in the lighting means.

According to the inventions of claims 3 and 4,
Different from the inventions of claim 1 and claim 2, the image pickup object is emitted by the light emitting means, and the light generated from the image pickup object is incident on the image pickup element to perform image pickup.

The operation of the image pickup device and the light emission operation of the image pickup object by the light emitting means are controlled by the control means in the same manner as the image pickup device and the illumination means in the inventions of the first and second aspects. .

[0021]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the image pickup apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image pickup apparatus according to the present embodiment is an illumination light that illuminates an image pickup target 13. And a light emission control unit 12 for controlling the light emission unit.
An illumination device 10 including: an imaging device 15 that converts imaging light into an electrical signal; a control device 16 that controls driving of the illumination device 10 and the imaging device 15; and imaging optics that forms a subject image on the imaging device 15. A system 14 and a signal processing system 1 for performing constant signal processing on an image pickup signal obtained by the image pickup device 15.
7 and 7.

In the image pickup apparatus according to this embodiment having such a configuration, the illumination device 10 illuminates the image pickup object 13, and the image pickup optical system 14 forms an image of the image pickup object 13 on the image pickup device 15. To be done. The image is converted into an electric signal by the image pickup device 15, signal processing such as level adjustment is performed by the signal processing system 17, A / D converted, and then stored in a frame memory provided in the signal processing system 17. To be done.

The image signal is output to the monitor 18 for image display, or the computer 19
And numerical analysis is performed by various arithmetic processes. In addition, in the present device, as described later, the lighting device 10
Driving (generation of illumination light) is synchronized with driving of the image pickup device 15 (reading of signal charges).

The image pickup device 15 is an ITC D (interline transfer type charge coupled device) as shown in FIG.
It is composed by. As shown in the figure, the present imaging device includes a photoelectric conversion unit 31 that converts imaging light into electric charges, a vertical transfer path 32 and a horizontal transfer path 37 that sequentially transfer the electric charges,
It is composed of a light shielding film 36 which shields a portion other than the photoelectric conversion portion 31.

The signal charges obtained in the photoelectric conversion section 31 are transferred in parallel in the vertical direction by the vertical transfer path 32, and further transferred in the horizontal direction as a serial signal by the horizontal transfer path 37, and then output through the amplifier 35. It is read from 34.

FIG. 4 is an enlarged view of the light receiving portion shown in FIG. 3. As shown in FIG. 4, the photoelectric conversion portion 31 and the charge transfer path 32 are separated by the element isolation region 42, and the transfer electrode of the vertical transfer path is formed. 43 and 44 are provided. Opening 3 of the light shielding film
The image pickup light that has entered through 3 is converted into electric charges by the photoelectric conversion unit 31, and is transferred to the vertical transfer path 32. This transfer control is performed by the transfer gate MOS transistor 41, and the cycle of reading the signal charges from the photoelectric conversion unit 31 is variable.

FIG. 5 is a sectional view taken along the line AA 'of FIG.
On the semiconductor substrate 52, the transfer electrode 43, the transfer gate MOS transistor 41, and the opening 33 of the light shielding film.
And a photoelectric conversion part 31 are formed.

FIG. 6 is a timing chart showing the timing of illumination and the reading of signal charges in the present image pickup device. In FIG. 6, 6A is the timing of the illumination light generated by the illumination device 10 and 6B is the photoelectric conversion section. The charge transfer timing from 31 to the vertical transfer path 32, 6C the drive timing of the vertical transfer path 32, and 6D the image sensor 15
Shows the timing of reading the signal from, and the horizontal axis represents time.

Illumination light emits pulses at a high waveform portion of the illumination timing 6A, and the interval T is constant. The signal transfer is performed during the period when the waveform of the signal transfer timing 6B is high, that is, the signal charge is read from the photoelectric conversion unit 31.

In this device, as described above, the driving timing of the illuminating device 10 is synchronized with the driving timing of the image pickup device 15, and a reference time signal generator (not shown) provided in the control device 16 is provided. In the embodiment, the high-frequency signal of, for example, several MHz obtained by the crystal oscillator) is divided, the timing 6B of the transfer of the signal charge from the photoelectric conversion unit 31 to the vertical transfer path 32 is created, and the signal is generated. The frequency is further divided to create a vertical synchronizing signal of 30 Hz.

The timing 6A of illumination by the illumination device 10 is created by dividing the vertical synchronization signal by 3 (10 Hz), and the illumination light is generated and the photoelectric conversion unit 31 is used.
Signal 6 for signal transfer from the digital camera to the vertical transfer path 32
A and 6B are created by dividing the same reference time signal, the positional relationship between the two on the time axis is always constant, and both pulse signals 6A and 6B are synchronized.

Further, the pulses 6e, 6f, 6g are assumed to be generated at equal intervals in a normal state, and the intervals of 6B and 6A.
Although the intervals are set to the same period T, a plurality of illumination pulses of 6A may be generated at a regular interval of 6B.

In the apparatus of this embodiment, the control device 16
Thus, the pulse 6f of the transfer pulse of the signal charge from the photoelectric conversion unit 31 to the vertical transfer path 32 (driving pulse of the transfer gate MOS transistor 41) is stopped. As a result, the photoelectric conversion unit 31 is subjected to two pulse illuminations in one signal read cycle (imaging cycle), and the obtained signal charge is doubled as usual.

As described above, not only illumination is performed with two pulse illuminations in one imaging cycle, but also illumination is performed with three pulse illuminations in one imaging cycle by suspending 6f and 6g. It is possible to perform imaging with the pulsed illumination. Therefore, in this device, even when a sufficient image cannot be obtained because it is dark at the read intervals of 6e to 6g,
It is possible to obtain an image signal of an appropriate level by increasing the number of illumination pulses per one image pickup cycle (one read cycle).

Further, in this device, as shown in FIG. 6C, the signal charge transfer paths 32 and 37 are connected to the photoelectric conversion section 31.
It is always driven regardless of the presence or absence of the charge reading 6B. Therefore, as described above, the photoelectric conversion unit 31
When the pulse 6f for reading the charge from the image sensor 15 is stopped, the output signal 6 out of the signal 6D for reading the signal from the image sensor 15 is output.
h is a dark output signal of the vertical and horizontal transfer paths 32 and 37, not an image pickup signal. Since this dark output signal is unnecessary as an image signal, it is not taken into the frame memory in the signal processing system 17.

It is assumed that all the output signals of the image pickup device 15 are taken into the frame memory, and the effective image pickup signal 6i
Therefore, the dark output generated in the signal charge transfer paths 32 and 37 can be subtracted.

Further, as the image pickup device, an FTCCD (frame interline charge coupled device) can be used instead of the ITCCD (interline transfer type charge coupled device) shown in FIGS. 3 to 5. FIG. 7 shows the FTCC.
Although it is a schematic diagram showing the configuration of D, this FTCCD is provided with a vertical CCD 71 that vertically transfers signal charges and a horizontal CCD 72 that horizontally transfers signal charges. The charge transfer direction is indicated by an arrow.

FIG. 8 is a sectional view taken along the line BB ′ of FIG. 7. This FTCCD is the ITCCD shown in FIGS. 3 to 5.
Unlike the above, the photoelectric conversion part does not exist independently, two layers of electrodes are provided, and the vertical transfer path and the horizontal transfer path are formed by the embedded channel type CCD.
A diffusion layer 84 having a conductivity type different from that of No. 3 is formed. Then, the voltage applied to the electrodes 81, 82 causes the electrodes 81, 82 to
A potential well is formed under 82 to store and transfer signal charges.

In the case of using this FTCCD, in this embodiment, the image pickup light is made incident from the back surface of the CCD, but the image pickup light entering the semiconductor substrate produces electrons and holes.
Depending on the conductivity type of the substrate 83 and the voltage of the electrodes 81 and 82, one charge is accumulated in the potential well below the electrode, and this accumulated charge serves as an imaging signal. In this way, this CCD
Since the image signal transfer section and the charge storage section by photoelectric conversion are the same part, the pixel size, which is the minimum unit for performing photoelectric conversion, can be made smaller than the ITCCD, and the spatial resolution can be improved. Can be raised.

By the way, unlike the ITCCD, such an FTCCD does not have a transfer gate MOS transistor for controlling whether or not the signal charges converted by the photoelectric conversion section are transferred to the vertical transfer path. The method is different from the IT CCD.

Therefore, this driving method will be described with reference to FIG. In the figure, 9A shows the timing of generation of illumination light from the lighting device, 9B shows the timing of driving the charge transfer path, 9C shows the timing of reading signals from the elements, and the horizontal axis represents time. At the illumination timing 9A, the illumination light emits pulses in a high waveform portion as in FIG. 6, and the interval T is constant.

When the present image pickup device is used, signal charges are transferred at a higher speed compared with the timing of illumination and in synchronization with the illumination, and 9d to 9f in the figure schematically show how drive pulses are generated. Is shown in.

Here, for example, by suspending a series of drive pulses 9e in a state synchronized with the illumination timing 9A, signal charges for two illumination light pulses are accumulated in the potential well of the vertical CCD in FIG. This image signal is obtained as the output 9g in FIG.

As described above, the FTCC is used as the image pickup device.
The image pickup apparatus of the present invention can be configured by using D.

Further, similarly, as the image pickup device, F
It is also possible to use an ITCD (frame interline transfer type charge coupled device) or an XY address type image pickup device represented by a MOS type image pickup device.

Further, the present image pickup apparatus is provided with a device for measuring the amount of illumination light generated from the illumination device, the amount of light from the image pickup object, the magnitude of the output signal from the image pickup device, etc. The device may determine the amount of signal charge accumulated in the photoelectric conversion unit based on a detection signal from the device, and control the driving of the image pickup device (reading of the charge) according to the amount. it can.

With this configuration, when the amount of signal charges accumulated in the photoelectric conversion unit of the image pickup device is small, the number of pulse illuminations within one image pickup cycle is increased to automatically stabilize the signal. It is possible to obtain the optimum level image signal.

FIG. 2 is a block diagram showing the arrangement of an image pickup apparatus according to the second embodiment of the present invention. The image pickup apparatus according to the present embodiment includes a light emitting unit 21 that emits illumination light that illuminates an image pickup target 23 and a light emission control unit 22 that controls the light emitting unit 21, as in the image pickup apparatus according to the first embodiment. And an image pickup device 25 for converting image pickup light into an electric signal.
A control device 26 for controlling the drive of the illumination device 20 and the image pickup device 25, an image pickup optical system 24 for forming a subject image on the image pickup device 25, and a constant signal with respect to the image pickup signal obtained by the image pickup device 25. And a signal processing system 27 for processing.

On the other hand, in the image pickup apparatus of the present embodiment, as described above, the driving of the illuminating apparatus (generation of illumination light) is synchronized with the driving of the image pickup element (reading of the signal charge). On the contrary, unlike the imaging device, the imaging device 25 is driven in synchronization with the driving of the illumination device 20.

As described above, even if the image pickup device 25 is driven in synchronization with the drive of the illumination device 20, an image pickup device which can always obtain an image signal of a constant level is provided as in the image pickup device of the first embodiment. Can be configured.

Further, in the first and second embodiments, the illuminating device is provided, and the illuminating device illuminates the object to be imaged to take an image. However, instead of the illuminating device, the imaging is performed. A light emitting device that emits light from the object itself may be provided. In this case, by driving the light emitting device in the same manner as driving the lighting device, it is possible to always obtain a stable and optimum level image signal, as in the first and second embodiments. it can.

In this image pickup apparatus, the image pickup element can be used even at room temperature (about 20 ° C.), but when the illuminance of illumination light is low or the image pickup optical system is dark, the image pickup object is illuminated. When the amount of light incident on the image sensor is small, such as when the amount of light absorbed is large, the photoelectric conversion unit accumulates the signal charge for a long time, or as shown in FIG. 9, the signal charge inside the image sensor is increased. When the driving of the transfer path and the signal charge reading means is stopped, it is desirable to cool the image sensor and reduce the dark current (current due to the thermally excited charges).

Further, in the image pickup device shown in FIG. 3, the light shielding film is provided, but the image pickup light does not enter (the illumination light does not emit) during the signal charge transfer period and the signal charge read period. By setting the timing, it is possible to omit the light-shielding film, which simplifies the manufacturing of the image pickup device and further increases the area of the photoelectric conversion unit to improve the sensitivity of the device. .

[0054]

As described in detail above, according to the image pickup apparatus of the present invention, a stable and optimum level image signal is always output and a high-quality image having no unevenness in each image field can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image pickup apparatus according to a second embodiment of the present invention.

FIG. 3 is a plan view schematically showing a part of the configuration of the image pickup device provided in the image pickup apparatus of the first embodiment of the present invention.

FIG. 4 is a plan view showing an enlarged part of a light receiving portion of the image pickup device of FIG.

5 is a cross-sectional view taken along the line AA ′ of FIG.

FIG. 6 is a diagram showing a drive timing of the image pickup apparatus of the first embodiment.

FIG. 7 is a plan view schematically showing a part of the configuration of another image sensor used as the image sensor of the image pickup apparatus of the first embodiment.

8 is a cross-sectional view taken along the line BB ′ of FIG.

FIG. 9 is a diagram showing a drive timing when another image pickup device is used as the image pickup device of the image pickup apparatus of the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Illumination device 11 Light emission part 12 Light emission control part 13 Imaging target object 14 Imaging optical system 15 Imaging device 16 Control device 17 Signal processing system 18 Monitor 19 Computer 31 Photoelectric conversion part 32,71 Vertical transfer path 33 Opening part 34,74 Output terminal 35, 73 Amplifier 36 Light-shielding film 37, 72 Horizontal transfer path 41 Transfer gate MOS transistor 42 Element isolation region 43, 44, 81, 82 Electrode 51 Photoelectric conversion part diffusion region 52, 83 Semiconductor substrate 53, 84 Embedded CCD diffusion region In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] 1. A photoelectric conversion unit for converting light from an object to be imaged into an electric charge, and an image pickup device having a charge reading unit for reading out the electric charge obtained by the photoelectric conversion unit; and a pulse for illuminating the object to be imaged for a certain period of time. And a driving means for controlling the charge reading means or the illuminating means so that at least one pulsed illuminating light is generated within one cycle of reading charges from the photoelectric conversion unit. An image pickup apparatus comprising: a control unit. 2. The image pickup apparatus according to claim 1, wherein the control unit controls the charge reading unit or the illumination unit according to an amount of signal charges accumulated in the photoelectric conversion unit. 3. An image sensor having a photoelectric conversion unit for converting light from an object to be imaged into an electric charge, and a charge reading unit for reading out the electric charge obtained by the photoelectric conversion unit, and light emission for causing the object to be imaged to emit light for a certain period of time. And a control unit that controls the drive of the charge reading unit or the light emitting unit so that the imaging target emits light at least once within one cycle of reading the charge from the photoelectric conversion unit. apparatus. 4. The image pickup apparatus according to claim 3, wherein the control unit controls the charge reading unit or the light emitting unit according to an amount of signal charges accumulated in the photoelectric conversion unit.