JP5332447B2 - Imaging apparatus, endoscope apparatus, and control apparatus - Google Patents

Description

  The present invention relates to an imaging apparatus, an endoscope apparatus, and a control apparatus applied to these apparatuses.

  An imaging device including a CCD image sensor as a solid-state imaging device is known (see, for example, Patent Document 1). The surveillance camera as an imaging device of Patent Document 1 includes an optical system such as a lens and an imaging unit including a CCD image sensor. In addition, an AFE (analog front end) that converts an analog signal read from the imaging unit into a digital signal and a signal processing unit that processes the digital signal input from the AFE are provided.

JP 2008-85410 A

  At the time of AFE processing for converting an analog signal output from a CCD image sensor into a digital signal, sample / hold processing is performed at an appropriate timing on the signal waveform of an image (pixel) signal obtained from the CCD image sensor, It is important to convert it to a digital signal. This is because if the signal waveform from the CCD image sensor is not sampled / held at an appropriate timing, even if the CCD image sensor functions normally, it will not be properly converted into a digital signal by the AFE and output. This is because the image quality is degraded.

  The present invention has been made in view of such points, and an object of the present invention is to provide an imaging apparatus capable of improving the quality of an output image.

The invention according to claim 1 acquires a timing generator that generates various timing signals, a drive signal based on the timing signal generated by the timing generator, and outputs an image signal in accordance with the acquired drive signal An image signal processing unit that acquires a timing pulse based on a timing signal generated by the timing generation unit, and an image signal processing unit that processes an image signal output from the image sensor in accordance with the acquired timing pulse; Based on the timing signal generated by the timing generation unit, a phase adjustment unit that adjusts the phase between the image signal output from the image sensor and input to the image signal processing unit and the timing pulse input to the image signal processing unit ; anda control unit including the phase adjusting means and the timing generator and the image signal processing unit, the imaging device Is connected via a cable, it said phase adjusting means is interposed between said timing generator the imaging device advances the phase programmable control of the timing signal supplied from the timing generator The image signal is supplied to the image sensor as the drive signal that is a basis for outputting the image signal. An imaging apparatus characterized by calculating . Thereby, compared with the case where this invention is not employ | adopted, it can be set as the image signal of a desired timing.

According to a second aspect of the present invention, the imaging apparatus according to the first aspect is an endoscope apparatus that images a subject and outputs an image signal based on the acquired drive signal. As a result, the image signal input to the image signal processing unit and the timing pulse can be set to appropriate timing, and an endoscope apparatus with improved output image quality can be provided.

  The image signal and timing pulse input to the image signal processing unit can be set to appropriate timing, and an imaging apparatus and endoscope apparatus with improved output image quality can be provided.

  The best mode (embodiment) for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<Embodiment>
FIG. 1 is a diagram illustrating a schematic configuration of an imaging apparatus 100 according to the embodiment. The imaging apparatus 100 is used as an endoscope apparatus that performs observation or examination in a body cavity or a surveillance camera.

  As shown in FIG. 1, the imaging apparatus 100 includes a tip 10 having an optical system 11 such as a lens and a CCD image sensor 12 that is a solid-state imaging device. In addition, the imaging apparatus 100 includes a control unit 20 that processes an output signal from the CCD image sensor 12. In addition, the imaging apparatus 100 includes a coaxial cable 30 that connects the distal end portion 10 and the control unit 20 in a wired manner.

  The CCD image sensor 12 of the distal end portion 10 according to the embodiment is a device that converts an optical image of an object into an electrical signal and outputs it as a two-dimensional image, and a plurality of light receiving elements (photodiodes) that perform photoelectric conversion. Including a light receiving unit, a transfer gate, and a shift register (transfer unit).

  Each light receiving element of the light receiving unit generates and accumulates charges corresponding to the amount of light received. When the shift signal becomes active after a predetermined time required for charge accumulation has elapsed, the transfer gate is turned on. As a result, the stored charge, which is analog image data, is transferred to the shift register provided corresponding to each light receiving element via the transfer gate. The image (pixel) signal (accumulated charge) Vout transferred to each shift register is serially output from the CCD image sensor 12 based on H1 and H2 which are two-phase drive clocks (drive signals).

  The control unit 20 includes an AFE (analog front end) 21 that processes an image signal Vout that is an output signal from the CCD image sensor 12, and a digital signal processing unit 22 that performs digital signal processing on the output of the AFE 21. The control unit 20 generates drive clocks H1 and H2, which will be described later, which are control signals for the CCD image sensor 12, and generates various timing signals such as AFE drive pulses SHP, SHD, which will be described later, which are control signals for the AFE 21. A TG (Timing Generator) 23 is provided. The AFE (analog front end) 21, the digital signal processing unit 22, and the TG 23 are mounted on the same control board.

  The AFE 21 is a CDS (Correlated Double Sampling) 211 as an image signal processing unit that performs sample / hold processing while removing noise from the image signal (accumulated charge) Vout input from the CCD image sensor 12, and a sample. / PGA (Programmable Gain Amplifier) 212 for amplifying the image signal subjected to the hold process to a predetermined level. Further, the AFE 21 sends an A / D converter 213 that converts the analog image signal amplified by the PGA 212 into a digital signal, and the digital signal converted by the A / D converter 213 to the signal processing unit 22. And a latch part 214.

  The signal processing unit 22 performs processing on the digital signal output from the AFE 21 and performs imaging data processing required in the imaging apparatus 100. For example, the signal processing unit 22 performs video processing such as white balance and gamma correction, and encoding processing such as format processing and compression processing. The data subjected to the given processing by the signal processing unit 22 is displayed on a display unit (not shown), recorded on a recording medium (not shown), or output from a transmission unit (not shown). Or

  The TG 23 generates drive clocks H <b> 1 and H <b> 2 that are the basis of the image signal output of the CCD image sensor 12, and a reset gate pulse RG that is input to the gate of the CCD image sensor 12, and supplies it to the CCD image sensor 12. TG23 is a timing signal synchronized with control signals (timing signals) H1, H2 and RG for the CCD image sensor 12, and timing pulses SHP and SHD which are the basis of the sample / hold processing of the CDS 211 of the AFE 21. Is supplied to the AFE 21.

  Further, the control unit 20 corrects the phases of the drive clocks H1, H2 and the reset gate pulse RG, which are control signals output from the TG 23, and corrects the corrected drive clocks H1-a, H2-a and the corrected reset gate pulse RG-a. Is the same as TG23, AFE21, etc. so that PSC (Phase Shift Circuit) 50, which is a phase shift circuit for outputting to the CCD image sensor 12, is interposed (connected) between the TG 23 and the CCD image sensor 12. Is mounted on the control board.

In the imaging apparatus 100 according to the embodiment, the CCD image sensor 12 caused by the coaxial cable 30 is caused by advancing the phases of the control signals H1-a, H2-a, and RG-a with respect to the control signals H1, H2, and RG. This is to correct the delay of the image signal Vout from.

  Hereinafter, correction (adjustment) of the phases of the AFE drive pulses SHP and SHD by the PSC 50 will be described.

  If the AFE 21 performs a sample / hold process on the signal waveform of the pixel signal Vout obtained from the CCD image sensor 12 at an appropriate timing and does not perform A / D conversion, the AFE 21 is appropriate as captured image data that has undergone A / D conversion. Data is not available.

  FIG. 2 is a diagram showing timing waveforms of the sample / hold process performed in the CDS 211 of the AFE 21. For a signal waveform of an image signal for a certain pixel output from the CCD image sensor 12 shown as a waveform Vout, a point and a data level corresponding to a reference level (for example, a black level of the waveform) are used as a sample / hold process. Sampling of points corresponding to.

  The CDS 211 obtains the data level as a value with respect to the reference level by taking the difference between the signal value of the reference level and the signal value of the data level, and A / D converts the difference by the A / D converter 213. Thus, the AFE 21 acquires an appropriate data level based on the reference level as digital data.

  Then, the AFE drive pulse SHP at the timing shown in the figure is used for the sample level / sample processing of the reference level, and the AFE drive pulse SHD at the timing shown in the figure is used for the sample level / sample processing of the data level. .

  Therefore, in order to obtain appropriate captured image data from the AFE 21, the AFE drive pulses SHP and SHD at the above timing must be in an appropriate phase state with respect to the image signal Vout from the CCD image sensor 12. If the mutual phases of the AFE drive pulses SHP and SHD and the image signal Vout are not appropriate, sampling cannot be performed at the timing of the reference level and the data level of the image signal Vout, and the A / D converted captured image data The value is not appropriate. That is, if the phase of the AFE drive pulses SHP and SHD with respect to the image signal Vout from the CCD image sensor 12 is not appropriate, the quality of the image is degraded.

  On the other hand, when the tip 10 having the CCD image sensor 12 and the control unit 20 having the AFE 21 and the PSC 50 are connected by the coaxial cable 30 as in the imaging apparatus 100 according to the embodiment, the coaxial cable 30 is used. When a signal is transmitted, a transmission delay occurs. In particular, when the PSC 50 and the AFE 21 are mounted on the same control board and the distance between the PSC 50 and the AFE 21 is several millimeters or several centimeters, the length of the coaxial cable 30 is several meters. Transmission delay appears remarkably.

  FIG. 3 is a timing chart in an imaging apparatus having a configuration in which the PSC 50 is omitted from the imaging apparatus 100 according to the embodiment. In FIG. 3, CK is a clock signal at the operating frequency of the TG 23, and the drive clocks H1 and H2 and the reset gate pulse RG are output by dividing the clock signal by a frequency division ratio of 2. H1-1, H2-1, and RG-1 are control signals when H1, H2, and RG output from the TG 23 reach the CCD image sensor 12.

  FIG. 2 is also a timing chart when it is assumed that no transmission delay occurs between the CCD image sensor 12 and the control unit 20, and the state of FIG. 2 is compared with the state of FIG.

  As shown in FIG. 3, since transmission delay occurs in the coaxial cable 30, the control signals H 1, H 2 and RG output from the TG 23 reach the CCD image sensor 12 via the coaxial cable 30 from the TG 23. A time d1 (sec) that is longer than the time required for the output control signals SHP and SHD to reach the AFE 21 (the separation distance between the TG 23 and the AFE 21 is several mm or several centimeters and is substantially 0 (sec)) elapses. Further, a time d2 elapses until the image signal Vout output from the CCD image sensor 12 reaches the AFE 21 via the coaxial cable 30.

Here, the transmission delay time S (sec) of the coaxial cable 30 can be calculated using the following equation (1).
S = L / Vp (sec) (1)
Here, L (m) is the length of the coaxial cable 30, and Vp (m / sec) is the transmission speed of the coaxial cable 30. Vp (m / sec) can be calculated using the following equation (2).
Here, C is the speed of light (2.999725 × 10 ⁸ (m / sec)), μr is the relative permeability, and εr is the relative permittivity.

In the case of the coaxial cable 30, the relative permeability μr = 1 and the relative dielectric constant εr = 2.4. Therefore, when these values are input to the equation (2), Vp = 1.94 × 10 ⁸ (m / sec) It is.
Therefore, for example, when the coaxial cable 30 with L = 1 (m) is used, the transmission delay time S (sec) is S = 1 / (1.94 × 10 ⁸ ) ≈5.2 (nsec).
Further, since the calculated delay time S corresponds to d1 (forward path) and d2 (return path) in the timing chart shown in FIG. 3, the transmission delay time in the entire imaging apparatus 1 is d1 + d2 = 2 × S = 10. .4 (nsec).

  When the maximum operating frequency of the TG 23 is 50 MHz, the periods of the drive clocks H1 and H2 and the AFE drive pulses SHP and SHD are 40 (nsec). Therefore, when a coaxial cable having a length of 1 (m) is used as the coaxial cable 30 of the imaging apparatus 1, only a delay time caused by the coaxial cable 30 is 25% of the phase compared to normal image data. Deviation occurs.

  Therefore, in the imaging apparatus 100 according to the present embodiment, the drive clocks H1, H2, which are control signals output from the TG 23, and the PSC 50 as the phase adjusting means are interposed between the TG 23 and the CCD image sensor 12. Corrected drive clocks H1-a, H2-a and corrected reset gate pulse RG-a, in which the phase of the reset gate pulse RG is corrected at an appropriate timing, are output to the CCD image sensor 12.

  Therefore, as the PSC 50, a phase control (shift) circuit that can perform phase control in a programmable manner and outputs at least one clock signal whose phase is advanced with the highest resolution (delay difference) N with respect to the input signal. Is used. Since the highest resolution is N, the phase can be advanced in units of 1 / (f × N) (sec) when the frequency f (Hz) (period 1 / f (sec)) is input.

  For example, when a phase shift circuit having a maximum resolution of 32 is taken as an example as the PSC 50, the maximum operating frequency of the TG 23 is 50 (MHz), and the frequencies of the drive clocks H1 and H2 and the reset gate pulse RG are 25 (MHz). In this case, the phase can be advanced in units of 1 / (25 (MHz) × 32) = 1.25 (nsec).

  Therefore, when it is desired to obtain a phase shift amount corresponding to the delay time in order to correct the delay time 10.4 (nsec) due to the coaxial cable 30 having a length of 1 (m), the shift amount 8 (/ 32 ). As a result, the signals H1-a, H2-a, and RG-a that reach the CCD image sensor 12 from the PSC 50 are 10 (nsec) for the signals H1, H2, and RG output from the TG 23 toward the PSC 50 (= 1.25 (nsec) × 8) is advanced and correction is possible.

  FIG. 4 is a timing chart when a phase shift circuit having a maximum resolution of 32 is used as the PSC 50 of the imaging apparatus 100 according to the embodiment and the shift amount is programmed to 8. The length of the coaxial cable 30 is 1 (m).

  Due to the coaxial cable 30, it takes 10.4 (= d1 + d2) (nsec) from the output of the control signals H1, H2, RG by the TG 23 to the arrival of the image signal Vout output from the CCD image sensor 12 to the AFE 21. On the other hand, the signals H1-a, H2-a, and RG-a corrected by the PSC 50 with respect to the outputs of the signals H1, H2, and RG by the TG 23 are advanced by 10 (nsec). As a result, as shown in FIG. 4, the AFE drive pulses SHP and SHD have an appropriate timing with respect to the image signal Vout, so that the sample / hold processing is appropriately performed in the CDS 211, and appropriate imaging from the AFE 21 is performed. Image data is obtained.

  In the above description, the length of the coaxial cable 30 is assumed to be 1 (m) and the shift amount of the PSC 24 having the maximum resolution of 32 is programmed to 8. However, depending on the length of the coaxial cable 30 It is preferable to adjust the shift amount. For example, when the length of the coaxial cable 30 is 2 (m), it is preferable to program the shift amount of the PSC 50 to 16.

  In addition, the example of the PSC 50 having the maximum resolution of 32 has been illustrated. For example, when the maximum resolution is 16, the shift amount of the PSC 50 is programmed to 4 when the length of the coaxial cable 30 is 1 (m). It is preferable to do.

  In addition, it is indispensable that the imaging apparatus applied to the endoscope apparatus or the monitoring camera includes the AFE 21, the digital signal processing unit 22, the TG 23, and the PSC 50 in the imaging apparatus 100 according to the above-described embodiment separately for each part. Instead, they may have functions equivalent to these regardless of the shape.

  That is, a timing generation unit that generates various timing signals, an imaging device that acquires a drive signal based on the timing signal generated by the timing generation unit, and outputs an image signal according to the acquired drive signal, and a timing generation unit Based on the timing signal generated by the timing generation unit and the image signal processing unit that acquires the timing pulse based on the timing signal generated, and processes the image signal output from the image sensor according to the acquired timing pulse The image pickup apparatus preferably includes an image signal output from the image sensor and input to the image signal processing unit, and a phase adjusting unit that adjusts the phase of the timing pulse input to the image signal processing unit.

  The timing generation unit supplies the generated timing signal to the image sensor as a drive signal, while the phase adjustment unit is interposed between the timing generation unit and the image signal processing unit and is supplied from the timing generation unit. It is preferable to delay the phase of the timing signal synchronized with the drive signal and supply it to the image signal processing unit as a timing pulse that is a basis for processing the image signal.

  Alternatively, the timing generation unit supplies the generated timing signal to the image signal processing unit as a timing pulse, while the phase adjustment unit is interposed between the timing generation unit and the image sensor and is supplied from the timing generation unit. It is preferable that the phase of the timing signal synchronized with the timing pulse is advanced and supplied to the image sensor as a drive signal that is a basis for outputting an image signal.

  When the timing generation unit, the image signal processing unit, the control unit including the phase adjustment unit, and the imaging device are connected via a cable, the phase adjustment unit adjusts the phase of the image signal and the timing pulse. The amount is preferably an amount corresponding to the length of the cable.

  The control unit 10 applied to the imaging apparatus generates a timing signal, supplies a driving signal based on the generated timing signal to the imaging element, and an image signal output from the imaging element in accordance with the driving signal. And a phase adjustment unit that adjusts the phase between the image signal output from the image sensor and the timing pulse based on the generated timing signal. Is preferred.

  While the generated timing signal is supplied to the image sensor as a drive signal, the phase adjustment unit delays the phase of the generated timing signal in synchronization with the drive signal and supplies it as a timing pulse that is a basis for processing the image signal. It is preferable to do.

  Alternatively, while the generated timing signal is used as a timing pulse for image signal processing, the phase adjustment unit can supply a signal obtained by advancing the phase of the timing signal generated in synchronization with the timing pulse as a drive signal to the image sensor. Is preferred.

  The amount of adjustment of the phase between the image signal and the timing pulse by the phase adjusting means is preferably an amount corresponding to the length of the cable that transmits the drive signal to the image sensor.

  In the above-described embodiment, the CCD image sensor 12 is configured to serially output the image signal (accumulated charge) Vout transferred to each shift register based on the drive clocks (drive signals) H1 and H2. The PSC 50 was applied to the imaging apparatus 100 provided. However, the control unit 10 including the PSC 50 or the PSC 50 may be applied to an imaging apparatus including a CCD image sensor other than the CCD image sensor 12 of this aspect.

1 is a diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment. It is a figure which shows the timing waveform of the sample / hold process performed by CDS of AFE. 5 is a timing chart in an imaging apparatus having a configuration in which a PSC interposed between TG and AFE is omitted from the imaging apparatus according to the embodiment. 6 is a timing chart in the imaging apparatus according to the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Imaging device, 10 ... Tip part, 11 ... Optical system, 12 ... CCD image sensor, 20 ... Control part, 21 ... AFE, 22 ... Signal processing part, 23 ... TG, 50 ... PSC, 211 ... CDS, 212 ... PGA, 213 ... A / D converter, 214 ... latch part

Claims (2)

A timing generator for generating various timing signals;
An image sensor that acquires a drive signal based on the timing signal generated by the timing generation unit and outputs an image signal according to the acquired drive signal;
An image signal processing unit that acquires a timing pulse based on the timing signal generated by the timing generation unit, and processes an image signal output from the imaging device according to the acquired timing pulse;
Phase adjusting means for adjusting the phase of the image signal output from the image sensor and input to the image signal processing unit and the timing pulse input to the image signal processing unit based on the timing signal generated by the timing generating unit; Including ,
The timing generation unit, the image signal processing unit, the control unit including the phase adjustment unit, and the imaging element are connected via a cable,
The phase adjusting unit is interposed between the timing generation unit and the imaging device, and is a group that outputs the image signal by advancing the phase of the timing signal supplied from the timing generation unit by programmable control. An image pickup apparatus that is supplied to the image pickup device as a drive signal, and an adjustment amount of a phase between the image signal and the timing pulse is calculated based on a length, a magnetic permeability, and a dielectric constant of the cable .   The imaging apparatus according to claim 1, wherein the imaging apparatus images an object and outputs an image signal based on the acquired drive signal.