KR100207471B1 - Dual sampling method and apparatus for improving sampling noise - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data sampling method and apparatus for an image processing system using a charge coupled device (CCD), and more particularly to a correlated double sampling method and apparatus for improving sampling noise. The present invention provides a pre-charge level sampling and holding process for sampling and holding a pre-charge level by an output signal of a charge coupled device, and a first data level for sampling and holding a data level in a signal by inputting an output of the charge coupled device. A sampling and hold process, an automatic gain adjustment process for amplifying the difference between the pre-charge level and the data level to constantly control the output, and inserting a blanking signal in an initial no-signal section of the output signal of the charge coupled device to remove noise. And a second data level sampling and holding step of sampling and holding an output of the removing and the output of the automatic gain adjusting process in the pre-charge level sampling section and the first data level sampling section. It is done. According to the present invention, after sampling the data of the charge-coupled device output signal after the automatic gain control, by holding and outputting the data, sampling noise can be eliminated and noise can be output without noise. There is an effect that can be eliminated.

Description

Correlated double sampling method and apparatus for improving sampling noise

1 is a flowchart of a correlated double sampling method for improving sampling noise according to the present invention.

2 is a flowchart of a dual sampling device for improving sampling noise according to the present invention.

3A to 3E show timing charts of a gate signal and a blanking signal with respect to the input signal shown in FIG.

4A to 4E show timing charts at internal node points of respective processes shown in FIG.

* Explanation of symbols for main parts of the drawings

2A: pre-charge level sampling and holding portion 2B: first data sampling and holding portion

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data sampling method and apparatus for an image processing system using a charge coupled device (CCD), and more particularly, to a correlated double sampling method and apparatus for improving sampling noise.

In general, the signal processing technology of the camera is widely used an image pickup device using a charge coupled device.

The charge coupled device performs a function of converting light energy due to the photoelectric effect into electrical energy and outputting the electrical energy. At this time, the signal converted into an electrical signal contains the necessary information and noise, which is an unwanted signal.

The technique of extracting the necessary information and removing unnecessary information is a correlated double sampling technique.

In the conventional correlated double sampling process, data is sampled and then held and proceeded in a sequential process according to timing. In the case of data sampling using analog technology, charge and discharge are performed by an internal capacitor during a sampling operation. As a result, noise is generated by a sudden current change, which is called sampling noise.

If the image is of normal brightness, the noise of the signal is relatively small, but there is no problem, but when inputting a dark image, the level becomes relatively difficult to ignore, and the gain is maximized by the automatic gain control circuit of the next block. And noise are amplified together to reduce image quality.

Therefore, there is a problem that should limit the camera imaging in the low light as possible.

Accordingly, an object of the present invention is to provide a correlated double sampling method and apparatus for improving sampling noise for selectively removing sampling noise in order to solve the above problems.

In order to achieve the above object, a correlated double sampling method for improving sampling noise according to the present invention is a correlated double sampling method for removing noise from a signal obtained by converting an image signal into an electrical signal using a charge coupled device. A pre-charge level sampling hold process of sampling and holding a pre-charge level among the output signals of the coupling element, and a first data level sampling hold for sampling and holding a data level among the input signals by inputting the output of the charge coupling element. A sampling synchronization step of sampling-holding and outputting the pre-charge level sampled and held in the first data level sampling and hold process at a new sampling timing, and outputting the sampled and held data level at a new sampling timing. The charge level and the data level An automatic gain adjustment step of amplifying the difference to constantly control the output, a step of removing noise by inserting a blanking signal in an initial no-signal section among the output signals of the charge coupled device, and outputting the output of the automatic gain adjustment step. The sampling noise may be reduced by including a second data level sampling and holding process of sampling and holding the battery in the charge level sampling section and the first data level sampling section.

In order to achieve the above object, the correlated double sampling device for improving sampling noise according to the present invention is a correlated double sampling device for removing noise from a signal obtained by converting an image signal into an electrical signal using a charge coupled device. Pre-charge level sampling and holding unit for inputting the output of the charge-coupled device, sampling and holding the pre-charge level (PRE-CHARGE LEVEL) by the first gating pulse in the signal, and inputting the output of the charge-coupled device. Inputs and outputs the first data level sampling and holding unit, the pre-charge level sampling and holding unit, and the first data level sampling and holding unit for sampling and holding a data level by a first gating pulse among the signals. An automatic gain control unit for amplifying and outputting the difference to a predetermined level, the automatic gain control unit A second data sampling and holding portion for inputting an output and sampling and holding a data level by a third gating pulse, and a first gating signal and a data level interval for sampling a pre-charge level interval from an output signal of the charge coupled device. And a gating pulse generator for generating a second gating signal for sampling the second gating pulse and a third gating pulse delayed by a predetermined time from the second gating signal.

The pre-charge level sampling and holding unit inputs the output of the charge coupling device to sample the first gating pulse and then holds and outputs the first sampling and holding unit and the second sampling pulse by inputting the output of the first sampling and holding unit. And a second sampling and holding portion for holding and outputting the sampled and held output after sampling, and a third sampling and holding portion for holding and outputting the sampled by the first gating pulse after inputting the output of the second sampling and holding portion. Sampling holding is effective.

The first data level sampling and holding unit inputs the output of the charge coupling device to sample the second gating pulse and then holds and outputs the fourth sampling and holding unit and the output of the fourth sampling and holding unit to obtain a first gating pulse. It is effective to sample and hold the data level, including a fifth sampling and holding portion for sampling and holding after outputting.

The pre-charge level sampling and holding portion and the first data level sampling and holding portion are effective to output in synchronization with a predetermined gating pulse.

A comparison unit for feeding back the output voltage of the pre-charge level sampling and holding unit and the first data level sampling and holding unit to the input of the pre-charge level sampling and holding unit; Reducing the DC Offset is effective.

Between the automatic gain adjusting unit and the second data level sampling and holding unit, a pre-blanking generation unit for generating a blanking signal in an initial signal-free period of the output signal of the charge coupled device reduces the effect of noise in the no signal. Is effective.

It is effective to reduce the level variation of the output of the charge coupling element by adding a clamp portion between the automatic gain adjusting portion and the second data level sampling and holding portion.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a correlated double sampling method for improving sampling noise according to the present invention.

Correlated double sampling method for improving the sampling noise of the present invention is a pre-charge level sampling and hold step 101 of sampling and holding the pre-charge level by the output signal of the charge-coupled device, the output of the charge-coupled device by inputting the signal A first data level sampling and holding process 102 for sampling and holding a data level among the two, a sampling synchronization process 103 for matching the sampling synchronization of both outputs, and an automatic gain adjusting process for amplifying the difference between the two inputs and outputting a constant level (104), a noise removing process 105 for removing noise by inserting a blanking signal in a non-signal section of the input signal, a second data level sampling hold for sampling and holding data in a section different from the sampling section of the sampling process above Process 106.

In the camera signal processing technology, the image data of the subject is scanned through the camera lens to the input terminal of the charge coupling device, and the charge coupling device is selectively separated by a filter attached to the outer surface to apply energy to the internal photodiode. At this time, a photoelectric effect of converting an optical signal into an electrical signal is generated in the charge coupling device, thereby sequentially generating an electrical signal from an external timing control circuit.

The generated charge coupled device output signal is a mixture of data components and noise components. In this case, a function of separating data and noise components and taking only data components to enable signal processing at a later stage is required.

In the above correlated double sampling method and apparatus, the dynamic range of input and output and the minimization of sampling noise dominate the performance.

The configuration of the output signal of the above charge coupled device can be divided into a signalless section T1, a reset noise section T2, a pre-charge section T3, and a data section T4 as shown in FIG. 2A.

In the pre-charge level sampling and hold process 101, a pre-charge level is sampled from an output signal of an input charge coupled device and then held and output. That is, a function of holding the signal after sampling the signal in the pre-charge period shown in FIG. 3A is performed.

In the first data level sampling and holding process 102, a data level is sampled and held in an output signal of an input charge coupled device to be output. That is, the function of holding the signal after sampling the signal in the data section shown in FIG.

The sampling synchronization process 103 is a process for reducing sampling noise by matching the sampling timing of the pre-charge level sampling hold process 101 with the sampling timing of the first data level sampling hold process 102.

That is, after the sampling hold of the pre-charge level and the sampling hold of the data level are completed, the sampling timing can be matched by sampling and holding the above held signals.

The automatic gain adjustment process 104 performs a function of amplifying and outputting the difference between the pre-charge level and the data level of the held signal through the sampling synchronization process 103 with an amplification proportional to the illuminance of the input signal.

The noise removing process 105 performs a function to reduce the influence on the noise in the no-signal section T1 of FIG. 3A. That is, in this section, the influence of the noise is reduced by ignoring the input signal by the blanking pulse shown in FIG. 3e.

The second data level sampling and hold process 106 performs a function of sampling the sampling and held data output which has performed the noise elimination process 105 once again.

At this time, the sampling timing is different from the sampling timing performed in the pre-charge level sampling hold process 101, the first data level sampling hold process 102, and the sampling synchronization process 103.

Sampling noise is generated when sampling in front of the automatic gain adjustment process 104, and the sampling noise is also amplified and output together with the data through the automatic gain adjustment process 104.

Therefore, the amplification degree in the automatic gain adjustment process 104 at low light becomes large on the screen of normal brightness, and thus is greatly affected by sampling noise.

The reason for sampling and holding data again as above is that the data level is increased by the automatic gain adjustment process 104. When the data level of this signal is sampled again, sampling noise is generated even in this case. This is because the level is relatively low to reduce the influence of sampling noise.

2 is a configuration diagram of a correlated double sampling device for improving sampling noise of the present invention.

3A to 3E show timing charts of a gate signal and a blanking signal with respect to the input signal shown in FIG.

4A to 4E show timing charts at internal node points of respective processes shown in FIG.

The correlated double sampling device for improving sampling noise according to the present invention includes a first sampling and holding unit 201 for holding and outputting an input signal according to a sampling gating signal and then holding the sampled signal according to the sampling gating signal. The second sampling and holding unit 202 to output, the sampling signal after holding the input signal in accordance with the sampling gating signal, the third sampling and holding unit 203 for outputting, after holding the sample after the input signal in accordance with the sampling gating signal A fourth sampling and holding unit 204, a fifth sampling and holding unit 205 for holding and outputting an input signal after sampling the input signal according to the sampling gating signal, and an automatic gain for automatically adjusting and outputting a gain according to an automatic gain control signal The adjusting unit 206, the clamp unit 207 for limiting the range of the voltage of the input signal to a predetermined range, the scene of the predetermined section of the input signal Pre-blanking unit 208 for ignoring and outputting the second data level sampling and holding unit 209 for holding and outputting an input signal after sampling the input signal according to the sampling gating signal, and for comparing the input signal and outputting a difference. 210, a gate signal generator 211 for generating a gating signal for sampling.

The gate signal generator 211 may include a first gating pulse for sampling the pre-charge level shown in FIG. 3a, a second gating pulse for sampling the data level, and a second gating pulse among the output signal configurations of the charge coupling device. Outputs a third gating pulse with a predetermined time delay and is used to sample the input signal at each sampling and holding unit.

The output of the charge coupled device is input to the first sampling and holding portion 201 and the fourth sampling and holding portion 204 after the DC voltage is blocked by the capacitors C1 and C2, respectively.

The first sampling hold unit 201 samples the pre-charge level among the output signals of the charge coupled device input by the first gating pulse shown in FIG. 2b output from the gate signal generator 211 and then performs the next sampling. Hold and output until pulse input.

The output of the first sampling and holding portion 201 is input to the second sampling and holding portion 202 and is sampled by the second gating pulse shown in FIG. 3c output from the gate signal generator 211, but is already pre-charged. Since the level is being held after sampling, the sampling timing is only changed by sampling and holding the pre-charge level again.

The output of the second sampling and holding unit 102 is input to the third sampling and holding unit 103 and is sampled by the first gating pulse output from the gate signal generating unit 111, but is already held after sampling the pre-charge level. Since the pre-charge level being held is sampled and held again, it is output as shown in FIG. 3a, and only the sampling timing is changed.

The fourth sampling and holding unit 204 samples the data level among the output signals of the charge coupled device input by the second gating pulse output from the gate signal generator 211, and then holds and outputs the data level until the next sampling pulse input. .

The output of the fourth sampling and holding section 204 is input to the fifth sampling and holding section 205 and is sampled by the first gating pulse output from the gate signal generating section 211, but is already held after sampling the data level. Since the data level being held is again sampled and held, and output as shown in FIG. 4B, only the sampling timing is changed.

Therefore, the third sampling and holding unit 203 samples and holds the pre-charge level in the output signal of the charge-coupled device, and outputs it. The fifth sampling and hold unit 205 samples the data level in the signal of the charge-coupled device. It is then held and output, and these outputs are held after being sampled in accordance with sampling synchronization with the first gating pulse of the gate signal generator 211.

The output of the third sampling and holding unit 203 and the output of the fifth sampling and holding unit 205 are input to the comparator 210 to control the comparator 210 during the high period of the clamp pulse controlling the comparator 210. The reference level of the image signal is kept constant in synchronization with the black level of and is output to the first sampling and holding unit 201 and the fourth sampling and holding unit 204.

The output of the third sampling and holding section 203 and the output of the fifth sampling and holding section 205 are input to the automatic gain adjusting section 206 to execute control for keeping the output level constant.

The problem here is that the timing charts of FIGS. 4A and 4B show instantaneous noise in the sampling period.

Of course, the output of the third sampling and holding section 203 and the output of the fifth sampling and holding section 205 are synchronized by the first gating pulse, and then, by the automatic gain control section 206, a minute difference in the phase and magnitude of the noise. When the input signal is small, the amplification is increased, so the sampling noise is also amplified.

The amplification degree of the automatic gain control unit 206 is controlled to be amplified to within 6 dB in the normal brightness screen, but is controlled to amplify up to about 35 dB in the dark screen.

In general, the output of the charge coupling device of 200mVpp ~ 220mVpp (based on the data component) is generated on the screen of normal brightness, the output of the charge coupling device is reduced from 8mVpp to 20mVpp in the dark screen, the noise of the automatic gain control unit 206 Due to amplifier amplification, the signal is relatively weak on a dark screen.

The automatic gain control unit 206 is input to the clamp unit 207 to fix the signal at a constant level for each clamping pulse section of the horizontal period, thereby limiting and outputting the signal.

The output of the clamp unit 207 is input to the pre-blanking unit 208 to output a signal-free period during the horizontal period as an internal DC voltage value to prevent noise.

The output of the pre-blanking unit 208 is inputted to the second data level sampling and holding unit 209 to generate noise by the third gating pulse shown in FIG. 4d among the output signals of the automatic gain control unit 206 above. After sampling at the part where does not occur, hold and output it.

In the case of sampling by the third gating pulse in the second data level sampling and holding unit 209, sampling noise is generated as in the case of sampling by the first gating pulse and the second gating pulse. Since it is more than 400mVpp, the noise effect is relatively insignificant, and a negligible signal can be obtained.

As described above, according to the present invention, after sampling the data of the charge-coupled device output signal after the automatic gain control, by holding and outputting the sampling noise, sampling noise can be eliminated and the image can be output without noise even in low light conditions. There is an effect that can eliminate the inconvenience to be limited.

Claims (8)

A correlated double sampling method for removing noise from a signal obtained by converting an image signal into an electrical signal using a charge coupled device, comprising: a pre-charge level sampling hold for sampling and holding a pre-charge level among an output signal of the charge coupled device; process; A first data level sampling and holding step of inputting an output of the charge coupling device to sample and hold a data level among the input signals; A sampling synchronization step of sampling-holding and outputting the pre-charge level sampled and held in the pre-charge level sampling and holding process and the data level sampled and held in the first data level sampling and holding process at new sampling timings; An automatic gain adjustment process of amplifying a difference between the pre-charge level and the data level to constantly control an output; Removing noise by inserting a blanking signal in an initial no-signal period among the output signals of the charge coupling device; And a second data level sampling and holding step of sampling and holding the output of the automatic gain adjustment process outside the pre-charge level sampling interval and the first data level sampling interval. Correlated double sampling method to improve noise. A correlated double sampling device for removing noise from a signal obtained by converting an image signal into an electrical signal using a charge coupled device, wherein the output of the charge coupled device is input to sample a pre-charge level by a first gating pulse among signals. A pre-charge level sampling and holding unit for holding and outputting the same; A first data level sampling and holding unit configured to input an output of the charge coupling device to sample a data level by a first gating pulse among the signals, and then hold and output the data level; An automatic gain adjusting unit configured to input outputs of the pre-charge level sampling and holding unit and the first data level sampling and holding unit to amplify and output a difference between the two inputs to a predetermined level; A second data level sampling and holding unit configured to input the output of the automatic gain control unit to sample-hold and output the data level by a third gating pulse; And generating a first gating signal for sampling a pre-charge level section, a second gating signal for sampling a data level section, and a third gating pulse delayed by a predetermined time from the second gating signal. And a sampling pulse generator for reducing the sampling noise. 3. The apparatus of claim 2, wherein the pre-charge level sampling and holding unit comprises: a first sampling and holding unit configured to input an output of the charge coupled device and to hold the sample after first sampling by a first gating pulse; A second sampling and holding unit for inputting the output of the first sampling and holding unit, sampling and holding the sample by a second gating pulse, and then holding and outputting the sample; And a third sampling and holding portion for inputting the output of the second sampling and holding portion to be sampled by a first gating pulse, and then holding and outputting the sample. Dual sampling device. 3. The display device of claim 2, wherein the first data level sampling and holding unit comprises: a fourth sampling and holding unit configured to input an output of the charge coupled device, sample the second gated pulse, and hold and output the sample; A correlated double sampling device for sampling the data level, comprising a fifth sampling and holding portion for inputting the output of the fourth sampling and holding portion to be sampled by a first gating pulse and then holding and outputting the sample; . 3. The correlated double sampling apparatus of claim 2, wherein the pre-charge level sampling and holding portion and the first data level sampling and holding portion output in synchronization with a predetermined gating pulse. 3. The method of claim 2, wherein the output voltage obtained by comparing the output of the pre-charge level sampling and holding unit with the first data level sampling and holding unit is input to the pre-charge level sampling and holding unit and the first data level sampling and holding unit. A correlated double sampling device for improving sampling noise characterized by reducing a DC offset by adding a feedback comparing unit. 3. The non-signal of claim 2, wherein a pre-blanking generator is provided between the automatic gain control unit and the second data level sampling and hold unit to generate a blanking signal in an initial signal-free period of an output signal of the charge coupled device. Correlated double sampling device for improving the sampling noise, characterized in that to reduce the effect of noise. 3. The correlated double sampling according to claim 2, wherein a clamp portion is added between the automatic gain adjusting portion and the second data level sampling and holding portion to reduce the level variation of the output of the charge coupled device. Device.