JP5140185B2 - High-speed imaging device - Google Patents

Description

  The present invention relates to a high-speed imaging device, and more particularly to a high-speed imaging device capable of imaging at high speed using a pixel peripheral recording type imaging device.

  A pixel peripheral recording type imaging device has already been proposed as an imaging device capable of capturing an image of about 1 million frames per second, and is incorporated in an ultrahigh-speed imaging device and used in various fields (for example, Patent Documents). 1).

  However, the conventional high-speed imaging device to which the pixel peripheral recording type image sensor is applied has a performance of several hundred thousand even though the pixel peripheral recording type image sensor itself has a performance capable of imaging at one million frames / second. When photographing at a high speed of 1 million frames / second or more, there is a problem that the voltage of the drive signal applied to the image sensor is lowered and the image quality is deteriorated.

  FIG. 11 is a block diagram illustrating the configuration of a conventional high-speed imaging device. The conventional high-speed imaging device 110 converts a subject optical image into an analog electrical signal, and outputs from the photoelectric conversion unit 111. An analog electrical signal processing unit 112 that removes noise from the analog electrical signal to be converted into a digital electrical signal, and an image signal generation unit that processes the digital electrical signal output from the analog electrical signal processing unit 112 to generate an image signal 113, a control signal generation unit 114 that generates a control signal having a frequency corresponding to the imaging speed, and drive signals that drive the photoelectric conversion unit 111, the analog electric signal processing unit 112, and the image signal generation unit 113 based on the control signal. And a drive signal generation unit 115 for generation.

  FIG. 12 shows the output (solid line) of the drive signal generation unit 115 and the voltage waveform (broken line) actually applied to the photoelectric conversion unit 111. If the imaging speed (a) is 100,000 frames / sec, Although the output voltage of the drive signal generation unit 115 is applied as it is to the conversion unit 111, the amplitude of the voltage actually applied to the photoelectric conversion unit 111 at the imaging speed (b) of 1 million frames / second is the drive signal. It becomes smaller than the amplitude of the output voltage of the generator 115.

  FIG. 13 shows the maximum voltage Vreal_H, the minimum voltage Vreal_L, and the imaging speed of the voltage actually measured by the photoelectric conversion unit 111 (hereinafter referred to as the actual voltage Vreal) when the drive signal generation unit 115 outputs a rectangular wave. In the graph showing the relationship, the difference voltage between the maximum voltage Vreal_H and the minimum voltage Vreal_L gradually decreases at an imaging speed of 400,000 frames / second or more, and the maximum voltage Vreal_H at an imaging speed of several million frames / second or more. And the minimum voltage Vreal_L decreases, the signal-to-noise ratio (S / N) is extremely deteriorated, and imaging becomes impossible.

JP 2001-345441 A ([0032] to [0035], FIG. 2)

  The present invention has been made in order to solve the above-described problem, and uses an image recording device with a peripheral pixel recording so that an image without degradation of S / N even at a high speed of several hundred thousand to one million frames / second or more. An object of the present invention is to provide a high-speed imaging device capable of imaging the image.

  The high-speed imaging device of the present invention includes a photoelectric conversion unit that converts an optical image of a subject into an analog electric signal, and signal processing that removes noise from the analog electric signal output from the photoelectric conversion unit and converts the analog electric signal into a digital electric signal. An analog electrical signal processing unit to perform, an image signal generation unit for generating an image signal based on the digital electrical signal output from the analog electrical signal processing unit, and a control signal for generating a control signal having a frequency corresponding to the imaging speed A generation unit, a drive signal generation unit that generates an analog electric signal processing unit drive signal, an image signal generation unit drive signal, and a photoelectric conversion unit drive signal based on the control signal, and the photoelectric conversion as the frequency of the control signal increases And a duty ratio correction unit that corrects the duty ratio of the drive signal to be small.

  With this configuration, the charge discharging capability of the photodiode can be increased, and the charge transfer capability of the memory CCD can be increased.

  The present invention provides a drive signal generation unit that generates a photoelectric conversion unit drive signal in accordance with the frequency of the control signal, thereby using a pixel peripheral recording type image pickup device to achieve a high speed of several hundred thousand to one million frames / second or more. However, it is possible to provide a high-speed imaging device that has an effect of being able to capture an image without S / N degradation.

1 is a block diagram of a high-speed imaging device according to a first embodiment of the present invention. The block diagram which shows the structure of the high-speed color imaging device to which the high-speed imaging device which concerns on this invention is applied. Structure diagram of pixel peripheral recording type image sensor used as red light photoelectric conversion unit The relationship between the maximum voltage Vd_H and the minimum voltage Vd_L of the red light photoelectric conversion unit drive signal Vd generated by the drive signal generation unit and the maximum voltage Vreal_H and the minimum voltage Vreal_L of the actual voltage Vreal applied to the red photoelectric conversion unit is shown. Graph Block diagram showing the connection relationship between the red photoelectric conversion unit and the drive signal generation unit Example of voltage correction circuit included in amplitude correction unit for red light photoelectric conversion unit Graph showing input and output waveforms of amplitude correction unit for red light photoelectric conversion unit The graph which shows the waveform of the red voltage photoelectric conversion part drive signal Vd, and the waveform of the actual voltage Vreal observed in the red color photoelectric conversion part A graph showing the maximum voltage Vreal_H and the minimum voltage Vreal_L of the actual voltage Vreal applied to the red light photoelectric conversion unit when the duty ratio is 50% and 25% The graph which shows the red voltage photoelectric conversion part drive signal Vd output from a duty ratio correction | amendment part, and the actual voltage Vreal applied to the red color photoelectric conversion part Block diagram showing the configuration of a conventional high-speed imaging device Graph showing output waveform of drive signal generator and voltage waveform actually applied to photoelectric converter A graph showing the relationship between the maximum voltage Vreal_H and the minimum voltage Vreal_L of the actual voltage Vreal and the imaging speed

  Hereinafter, embodiments of a high-speed imaging device according to the present invention will be described with reference to the drawings.

(First embodiment)
That is, the first embodiment of the high-speed imaging device 1 according to the present invention includes a photoelectric conversion unit 11 that converts an optical image of a subject into an analog electrical signal, and a photoelectric conversion unit 11 as shown in the block diagram of FIG. An analog electric signal processing unit 12 that performs signal processing to remove noise from the output analog electric signal and convert it to a digital electric signal, and generates an image signal based on the digital electric signal output from the analog electric signal processing unit 12 An image signal generation unit 13, a control signal generation unit 14 that generates a control signal having a frequency corresponding to the imaging speed, an analog electrical signal processing unit drive signal, an image signal generation unit drive signal, and a photoelectric conversion unit drive based on the control signal A drive signal generation unit 15 that generates a signal and an amplitude correction unit 16 that corrects the amplitude of the photoelectric conversion unit drive signal as the frequency of the control signal increases are included.

  FIG. 2 is a block diagram illustrating a configuration of a high-speed color imaging apparatus to which the high-speed imaging apparatus 1 according to the present invention is applied. The high-speed color imaging apparatus 2 includes a lens 27 that captures subject light, and incidence and interruption of subject light. A shutter mechanism 28 that controls the light, a spectral prism 29 that splits subject light incident on the high-speed color imaging device 2 via the shutter mechanism 28, and red light, green light, and blue light separated by the spectral prism 29 in analog form, respectively. Output from the red light photoelectric conversion unit 211, the green light photoelectric conversion unit 212, and the blue light photoelectric conversion unit 213, and the red light photoelectric conversion unit 211, the green light photoelectric conversion unit 212, and the blue light photoelectric conversion unit 213 that convert into electrical signals. Removes noise from red light analog electrical signal, green light analog electrical signal and blue light analog electrical signal, and red light digital A red light analog electrical signal processing unit 221, a green light analog electrical signal processing unit 222, and a blue light analog electrical signal processing unit 223 that perform electrical signal processing to convert an air signal, a green light digital electrical signal, and a blue light digital electrical signal; A color image signal generation unit 23 that generates a color image signal based on the red light digital electrical signal, the green light digital electrical signal, and the blue light digital electrical signal, and a control signal generation unit that generates a control signal having a frequency corresponding to the imaging speed 24, a drive signal generation unit 25 that generates an analog electrical signal processing unit drive signal, an image signal generation unit drive signal, and a photoelectric conversion unit drive signal based on the control signal, and a photoelectric conversion unit drive signal as the frequency of the control signal increases. And an amplitude correction unit 26 that greatly corrects the amplitude of.

  Furthermore, the amplitude correction unit 26 includes a red light photoelectric conversion unit amplitude correction unit 261, a green light photoelectric conversion unit amplitude correction unit 262, and a blue light photoelectric conversion unit amplitude correction unit 263.

  Red light photoelectric conversion unit 211, green light photoelectric conversion unit 212 and blue light photoelectric conversion unit 213, red light analog electric signal processing unit 221, green light analog electric signal processing unit 222 and blue light analog electric signal processing unit 223, and red Since the photoelectric correction unit amplitude correction unit 261, the green light photoelectric conversion unit amplitude correction unit 262, and the blue light photoelectric conversion unit amplitude correction unit 263 have the same configuration, the red photoelectric conversion unit 211, red The configuration and operation of the optical analog electric signal processing unit 221 and the red light photoelectric conversion unit amplitude correction unit 261 will be described.

  FIG. 3 is a structural diagram of the pixel peripheral recording type image pickup device 3 used as the red light photoelectric conversion unit 211. A photodiode 31 for converting the intensity of red light into an analog electric signal extends downward by about 100. A stage memory CCD 32 (area surrounded by a thick solid line) is provided. The photodiode 31 generates a charge proportional to the amount of light received at each exposure and sequentially transfers it to the memory CCD 32.

  The charges accumulated in the memory CCD 32 are output to the red light analog electrical signal processing unit 221 via the vertical read transfer path 33 (area surrounded by a thick broken line) and the horizontal read transfer path 34 (area surrounded by a thick dashed line). Is done.

  The red light analog electrical signal processing unit 221 is a correlated double sampling (CDS) circuit that performs signal processing for removing noise generated in the red light photoelectric conversion unit 211 and an analog / digital conversion that converts the analog electrical signal into a digital electrical signal. A red light digital electric signal by removing noise from the red light analog electric signal.

  The color image signal generation unit 23 is configured by, for example, a digital signal processor (DSP), and generates, for example, a color image signal of the NTSC standard from the red light digital electrical signal, the green light digital electrical signal, and the blue light digital electrical signal.

  The control signal generator 24 generates a control signal having a frequency corresponding to the imaging speed.

  The drive signal generation unit 25 is configured using, for example, a field programmable gate array (FPGA), and an analog electric signal processing unit drive signal, an image signal generation unit drive signal, and a photoelectric conversion unit drive signal based on the control signal. Is generated.

  The red light photoelectric conversion unit amplitude correction unit 261 corrects the amplitude of the photoelectric conversion unit drive signal to a greater extent as the frequency of the control signal increases.

  FIG. 4 shows the maximum voltage Vd_H and the minimum voltage Vd_L of the red light photoelectric conversion unit drive signal Vd generated by the red light photoelectric conversion unit amplitude correction unit 261 and the actual voltage Vreal applied to the red light photoelectric conversion unit 211. It is a graph which shows the relationship between the maximum voltage Vreal_H and the minimum voltage Vreal_L.

  As can be seen from this graph, in order to maintain the difference between the maximum voltage Vreal_H and the minimum voltage Vreal_L of the actual voltage Vreal applied to the red light photoelectric conversion unit 211 at 12 volts, the amplitude correction unit for the red light photoelectric conversion unit It is necessary for H.261 to increase the maximum voltage Vd_H of the red photoelectric conversion unit drive signal Vd as the frequency of the control signal increases and to decrease the minimum voltage Vd_L as the frequency of the control signal increases.

  The red light photoelectric conversion unit amplitude correction unit 261 corrects all the pulses that drive the red light photoelectric conversion unit 211.

  FIG. 5 is a block diagram showing the connection relationship between the red light photoelectric conversion unit 211 and the red light photoelectric conversion unit amplitude correction unit 261, and shows a case where the memory CCD 32 of the red light photoelectric conversion unit 211 is driven in four phases. . Here, the red light photoelectric conversion unit amplitude correction unit 261 includes the first amplitude correction unit 261a, the second amplitude correction unit 261b, the third amplitude correction unit 261c, the fourth amplitude correction unit 261d, and the fifth. The amplitude correction unit 261e is included.

That is, red light photoelectric conversion unit for amplitude correction unit 261, the first amplitude corrector 261a for generating a photo-gate pulse phi _PG for controlling the photodiode 31 of the red light photoelectric conversion unit 211, the first cell of the memory CCD32 321, the fifth cell 325, the ninth cell 329..., The second amplitude correction unit 261 b that generates the first phase pulse φ ₁ that controls the second cell 322, the sixth cell 326 of the memory CCD 32. third amplitude correction unit 261c for generating a second phase pulse phi ₂ for controlling ..., the third cell 323 of the memory CCD 32, a third phase pulse phi ₃ for controlling the seventh cell 327 ... of resulting fourth amplitude correction section 261 d, a fifth of the amplitude correction unit 261e to generate a fourth phase pulse phi ₄ for controlling the fourth cell 324, cell 328 of the eighth ... memory CCD 32.

  FIG. 6 shows an example of a voltage correction circuit included in the amplitude correction unit 261 for the red light photoelectric conversion unit, which is configured by a discrete element. The input signal is a photoelectric conversion unit drive signal Vc having the same frequency as the control signal, and the maximum voltage Vd_H. The red light photoelectric conversion unit drive signal Vd that is the minimum voltage Vd_L and is an output signal is supplied to the red light photoelectric conversion unit 211.

  FIG. 7 is a graph showing the input and output waveforms of the amplitude correcting unit 261 for the red light photoelectric conversion unit, and an input signal (photoelectric conversion unit drive signal Vc) and an output signal (red light photoelectric conversion unit drive signal Vd). However, the waveform is not distorted, and the rectangular-wave red light photoelectric conversion unit drive signal Vd can be supplied to the red light photoelectric conversion unit 211.

  The drive signal generation unit 25 may be configured with a programmable element such as an FPGA.

  Hereinafter, the operation of the high-speed color imaging device 2 will be described.

  That is, the light emitted from the subject forms an image in the high-speed color imaging device 2 through the lens 27.

  The subject image is split into red light, green light, and blue light by the spectral prism 29, and is converted into an electric signal by the red light photoelectric conversion unit 211, the green light photoelectric conversion unit 212, and the blue light photoelectric conversion unit 213. For the sake of simplicity, the red light processing will be described below.

  When the high-speed color imaging device 2 captures an image at 1 million frames / second, the drive signal generation unit 25 generates a photoelectric conversion unit drive signal Vc with a duty ratio of 50% based on a control signal having a frequency of 1 MHz, and the red color The photoelectric conversion unit drive signal Vc is output to the photoelectric correction unit amplitude correction unit 261. The photoelectric conversion unit drive signal Vc has a constant amplitude, for example, the maximum voltage Vc_H is 12 volts and the minimum voltage Vc_L is 0 volts.

  The drive signal generation unit 25 generates an analog electrical signal processing unit drive signal and an image signal generation unit drive signal based on a control signal having a frequency of 1 MHz, and generates a red light analog electrical signal processing unit 221 and a color image signal generation, respectively. To the unit 23.

  Also, the red light photoelectric conversion unit amplitude correction unit 261 sets the maximum voltage Vreal_H of the actual voltage Vreal to 12 volts, and the minimum voltage Vreal_L to 0 volts. The red light photoelectric conversion unit drive signal Vd having the maximum voltage Vd_H of 16 volts, the minimum voltage Vd_L of −4 volts, and the amplitude of 20 volts is generated by correction.

  FIG. 8 is a graph showing the waveform of the red light photoelectric conversion unit drive signal Vd generated by the red light photoelectric conversion unit amplitude correction unit 261 and the waveform of the actual voltage Vreal observed by the red light photoelectric conversion unit 211. The red photoelectric conversion unit 211 also has an amplitude of 12 volts, and it can be seen that, for example, a clear image can be captured even at 1 million frames / second.

Note that the red photoelectric conversion unit drive signal Vd includes five pulses of a photogate pulse φ _PG , a first phase pulse φ ₁ , a second phase pulse φ ₂ , a third phase pulse φ ₃ , and a fourth phase pulse φ _4. Including.

Each time the _photogate pulse _φPG reaches the maximum voltage, the red light photoelectric conversion unit 211 generates a charge proportional to the amount of received light, and sequentially transfers it to the first cell 321 of the memory CCD.

  Then, the charge transferred to the first cell 321 is sequentially transferred to the second cell 322, the third cell 323,... And stored in the cell.

  When the imaging is completed, the charges stored in the memory CCD 32 are sent to the red light analog electrical signal processing unit 221 via the vertical readout transfer path 33 and the horizontal readout transfer path 34.

  As described above, according to the first embodiment, the amplitude of the photoelectric conversion unit drive signal for driving the photoelectric conversion unit is increased according to the imaging speed, thereby increasing the speed from several hundred thousand to one million frames / second or more. It is possible to take images with

(Second Embodiment)
In the first embodiment, the amplitude of the photoelectric conversion unit drive signal is increased in accordance with the imaging speed. However, when the imaging speed is increased, the charge accumulated in the photodiode of the photoelectric conversion unit in the reset operation is completely reduced. This is to prevent blooming from occurring due to inability to discharge.

  Therefore, if the charge discharging capability in the reset operation can be increased, high-speed imaging can be performed without increasing the amplitude of the photoelectric conversion unit drive signal in accordance with the imaging speed.

  In order to increase the charge discharging capability in the reset operation, it is necessary to lengthen the time during which the photoelectric conversion unit drive signal maintains the minimum voltage.

  Therefore, in the second embodiment, the duty ratio of the photoelectric conversion unit drive signal Vc having the maximum voltage of 12 volts and the minimum voltage of 0 volts is changed according to the imaging speed.

  FIG. 9 is a graph showing the maximum voltage Vreal_H and the minimum voltage Vreal_L of the actual voltage Vreal applied to the red light photoelectric conversion unit 211 when the duty ratio is 50% and 25%.

  If the duty ratio is 50%, the center voltage of the actual voltage Vreal is 6 volts, and if the imaging speed is several hundred thousand frames / second or more, the dynamic range of the image is lowered.

  On the other hand, if the duty ratio is 25%, the center voltage decreases to 3 volts and the charge discharging capability in the reset operation increases, so that charges can be transferred even if the imaging speed is several hundred thousand frames / second. .

  Therefore, in the second embodiment, the high-speed color imaging device 2 to which the high-speed imaging device 1 is applied has the duty ratio correction unit 17 in which the duty ratio correction characteristic is incorporated.

  FIG. 10 is a graph showing the red light photoelectric conversion unit drive signal Vd output from the duty ratio correction unit 17 and the actual voltage Vreal applied to the red light photoelectric conversion unit 211, where the duty ratio is 50%. (A) and (b) when the duty ratio is 25% are shown.

  As can be seen from this graph, when the duty ratio is 50%, the actual voltage Vreal applied to the red-light photoelectric conversion unit 211 is the center voltage = 6 volts, and the charge overflows during transfer and blooming occurs. become.

  When the duty ratio is 25%, the actual voltage Vreal applied to the red light photoelectric conversion unit 211 is the maximum voltage Vreal_H = 6 volts and the minimum voltage Vreal_L = 1 volt, so that blooming is unlikely to occur.

  Since the configuration and operation of the second embodiment other than those described above are the same as those of the first embodiment, description thereof will be omitted. The high-speed color imaging device 2 may include the duty ratio correction unit 17 alone, or may include the amplitude correction unit 26 and the duty ratio correction unit 17 at the same time.

  As described above, according to the second embodiment, the duty ratio of the photoelectric conversion unit drive signal applied to the photoelectric conversion unit is reduced according to the imaging speed, so that it is several hundred thousand to million frames / second or more. High-speed imaging is possible.

  As described above, the high-speed imaging device according to the present invention has an effect that the pixel peripheral recording type imaging device can be driven at a high speed of several hundred thousand to one million frames / second or more, and is effective as an imaging device or the like. It is.

DESCRIPTION OF SYMBOLS 1 High-speed imaging device 11 Photoelectric conversion part 12 Analog electric signal processing part 13 Image signal generation part 14 Control signal generation part 15 Drive signal generation part 16 Amplitude correction part 17 Duty ratio correction part

Claims (1)

A photoelectric conversion unit that converts an optical image of a subject into an analog electrical signal;
An analog electrical signal processing unit that performs signal processing to remove noise from the analog electrical signal output from the photoelectric conversion unit and convert it to a digital electrical signal;
An image signal generator for generating an image signal based on the digital electric signal output from the analog electric signal processor;
A control signal generation unit that generates a control signal having a frequency according to the imaging speed;
A drive signal generator that generates an analog electrical signal processor drive signal, an image signal generator drive signal, and a photoelectric converter drive signal based on the control signal;
A high-speed imaging device including a duty ratio correction unit that corrects the duty ratio of the photoelectric conversion unit drive signal to be smaller as the frequency of the control signal is higher.

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