JP3208620B2 - Vertical register transfer degradation measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical register transfer deterioration measuring method capable of accurately measuring a color bar defect occurring in, for example, a CCD imager having an on-chip color filter.

[0002]

2. Description of the Related Art As is well known, a solid-state imaging device is a device in which a photoelectric conversion unit and a scanning unit are formed on a single silicon chip, and a two-dimensional imaging device using a CCD (charge coupled device). There are many. In recent years, a color filter is formed on a chip for colorization, and is integrated with a two-dimensional image sensor. Such a solid-state imaging device is used, for example, as a camera-integrated VTR, and while miniaturization is progressing, a device having a larger number of pixels has been developed. The response to is also being done.

In a two-dimensional image pickup device using a CCD, light receiving elements are arranged in a matrix to form each pixel, and signal charges of these light receiving elements are sequentially read out by the CCD. That is, the CCD operates as a so-called shift register, and vertically reads and transfers signal charges corresponding to pixel columns in the vertical direction sequentially.
D and horizontal CCDs which read and transfer signal pixels of odd and even columns among the signal charges read by the vertical CCDs, respectively. Of the signal charges transferred by the horizontal CCD, odd-numbered signal charges form an odd-numbered field, and even-numbered signal charges form an even-numbered field.

Incidentally, the above-mentioned vertical CCD is also called a vertical register, and it is known that a color stick defect occurs when transfer deterioration occurs in the vertical register. Transfer deterioration refers to a phenomenon in which a part of the charge is left behind when the charge is transferred from one potential well forming the CCD to the next potential well. Such a phenomenon is caused by charge trapping at the interface state.

Conventionally, transfer deterioration (color bars) of a vertical register is measured by, for example, displaying an output of a two-dimensional image sensor as an image and checking a color bar defect appearing in this image by visual inspection. There is a method in which the output signal of the vertical register is measured by an oscilloscope or the like in the first even field of the vertical blanking period, and the transfer deterioration of the vertical register is determined from the remaining amount of trapped charge.

[0006]

However, in the above-described visual inspection, transfer deterioration cannot be treated as a quantitative value, and the inspection result has an artificial effect due to individual differences among inspectors. Therefore, there is a problem that color bar defects cannot be measured accurately. In addition, the method of measuring the output signal of the vertical register with an oscilloscope or the like has a problem that the signal level is weak, and it is not possible to determine which pixel corresponds to the transfer deterioration, and the measurement accuracy cannot be obtained. is there. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vertical register transfer deterioration measuring method capable of accurately measuring a color stick defect.

[0007]

In order to achieve the above object, a vertical register transfer deterioration measuring method according to the present invention comprises: laying a color filter on a plurality of pixels arranged in a matrix; In a solid-state imaging device including a vertical register for sequentially reading and transferring signal charges corresponding to vertical pixel columns, the plurality of pixels are irradiated with monochromatic light, and charges are accumulated according to the spectral characteristics of the color filters. A first step of generating a pixel that does not accumulate and a pixel that does not accumulate, and extracting a signal level of a pixel that does not accumulate the signal charge from an output signal transferred from the vertical register in response to a field readout. And a second step of judging the transfer deterioration of the vertical register according to In a preferred embodiment, the first step is performed when irradiating red light.
The pixels corresponding to the cyan and green filters do not accumulate charges, while the pixels corresponding to the yellow and green filters do not accumulate charges when irradiated with blue light.

[0008]

According to the present invention, when a solid-state imaging device is irradiated with monochromatic light of red or blue, pixels in which electric charge is accumulated and pixels in which electric charge is not accumulated are generated according to the spectral characteristics of the color filter, and transferred according to the field readout. Only a signal corresponding to a pixel in which no charge is accumulated in the output signal is extracted, and transfer deterioration (color stick defect) of the vertical register is determined from the signal level. Therefore, it is possible to measure the color stick defect with higher accuracy than the conventional visual inspection or measurement using an oscilloscope.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A transfer deterioration measuring method according to an embodiment of the present invention will be described below with reference to the drawings. This embodiment is applied to transfer deterioration measurement of a vertical register in a CCD imager.

First, FIG. 1 is a view showing the structure of a color filter F integrally formed on a CCD imager (two-dimensional image sensor). The color filter F is formed of a complementary color filter obtained by dividing a pixel area of a CCD imager into four in the vertical and horizontal directions. That is, in the first row L1 of the color filters F, the magenta filters Mg and the green filters G are alternately arranged, and in the second and fourth rows L2 and L4, the yellow filters Ye and the cyan filters Cy are alternately arranged. . In the third row L3, the green filters G and the magenta filters Mg are alternately arranged opposite to the first row L1.

In a CCD imager provided with a color filter F having such a complementary color arrangement, when a monochromatic red light is irradiated, a yellow filter Y based on the spectral characteristics of the filter is used.
e and the signal charge is accumulated only in the pixel corresponding to the magenta filter Mg. Further, when blue monochromatic light is irradiated, the cyan filter Cy and the magenta filter Mg
Is stored only in the pixel corresponding to.

By the way, when the field of the CCD imager is read out, as shown in FIG.
, The signal charges of the pixels corresponding to the complementary color arrangement are sequentially read. That is, an odd field formed from the pixels in the odd columns L1 and L3 and an even field formed from the pixels in the even columns L2 and L4 are generated. Here, the odd field and the even field are, as shown in FIG.
Since they have the same complementary color relationship, and the even fields are only shifted by one line with respect to the odd fields, there is no apparent difference between the two.

Therefore, as described above, when field reading is performed while irradiating the CCD imager with red monochromatic light, signal charges are not accumulated only in pixels corresponding to the combination of (Cyan Cy + Green G) in odd fields. Become. Therefore, FIG.
As shown in (2), only the signal charge of the pixel corresponding to the combination of (Cyan Cy + Magenta Mg) is set, and as a result, the register transfers the comb-shaped output signal to the outside.
When blue monochromatic light is applied, no signal charge is stored in the pixel corresponding to (yellow Ye + green G) in the vertical register, and only the signal charge of the pixel corresponding to (yellow Ye + magenta Mg) is set. Is done.

If the vertical register is an ideal one in which transfer deterioration does not exist, as shown in FIG. 5A, an appropriate transfer output is generated in which the level of a region where there is no signal charge is "0". However, when the transfer is deteriorated, a part of the signal charge is trapped as shown in FIG. When the trapped charges are discharged to a region where there is no signal at the time of transfer, a transfer output as shown in FIG. 3C is obtained, and the discharged signal charges cause a color stick.

As is apparent from the above, by measuring the output level of the portion where the signal charge is not actually stored, it is possible to accurately measure the color stick defect (transfer deterioration). That is, when the CCD imager is irradiated with monochromatic red light, the color bar defect can be accurately determined by measuring the output of the portion corresponding to the (Cyan Cy + Green G) pixel among the transfer outputs of the vertical register in the odd field. Good detection becomes possible. Further, when blue monochromatic light is irradiated, a color bar defect can be similarly detected by measuring the output of the portion corresponding to the above-mentioned (yellow Ye + green G) pixel. That is, as is apparent from the waveform example shown in FIG. 4, the monochromatic light illuminating the CCD imager is changed to “red”.
Since the registers in which the color bars are generated are different by replacing with “blue”, the transfer deterioration (color bars) of all the registers can be measured by using these two monochromatic lights.

In an actual measurement, a signal of a pixel portion where no signal charge is accumulated is transferred to a portion far from the horizontal register, for example,
It is extracted from the area where the transfer is most deteriorated at the lower part of the screen, such as the inspection area shown in FIG. Then, after removing the point defect from the median value, all the extracted lines are added to each of the vertical registers provided on the left and right sides to emphasize the signal amount L (see FIG. 7) and to determine whether there is a color stick defect. Is determined.

Then, as shown in FIG.
The average value of the transfer output quantity L _L from the right side of the vertical register transfer output quantity L _R and the left vertical register (L _R + L _L / 2)
The subtraction to determine the average difference _{P (P = L- (L R} + L L / 2)), by taking the maximum value, to measure the absolute amount of Irobo remove the shading present in the horizontal direction, The transfer deterioration of the vertical register is detected.

As described above, according to the above-described embodiment, C
When red or blue monochromatic light is applied to the CD imager, pixels in which electric charge is accumulated and pixels in which electric charge is not accumulated are generated according to the spectral characteristics of the on-chip color filter. Since only the signal corresponding to the pixel in which the charge is not accumulated is extracted and the transfer deterioration (color stick defect) of the vertical register is determined from the signal level, the color stick defect can be measured with high accuracy. In addition, the above-described measurement method can be similarly applied to a two-dimensional image sensor having a line-sequential color filter. Further, since the transfer deterioration measuring method according to the present invention utilizes the spectral characteristics of the on-chip color filter, the transfer deterioration of the vertical register can be easily determined in-process, and the transfer deterioration can be easily determined by using the production selection of the imaging device itself. This can be an effective method.

[0019]

As described above, according to the present invention,
When a solid-state image sensor is irradiated with monochromatic red or blue light, pixels that accumulate electric charges and pixels that do not accumulate occur according to the spectral characteristics of the color filters. Since only the signals corresponding to the pixels for which no data is accumulated are extracted and the transfer deterioration (color stick defect) of the vertical register is determined from the signal level, the transfer deterioration (color Rod defect) can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color filter F applied to one embodiment of a vertical register transfer deterioration measuring method according to the present invention.

FIG. 2 is a diagram for explaining a field readout mode corresponding to a complementary color array of a color filter F of the embodiment.

FIG. 3 is a diagram for explaining a reading mode of an odd field and an even field of the embodiment.

FIG. 4 is a diagram for explaining a state of signal charges in an odd field.

FIG. 5 is a signal waveform diagram for explaining transfer deterioration of a vertical register.

FIG. 6 is a diagram for explaining a measurement mode of the example.

FIG. 7 is a diagram for explaining a measurement mode of the example.

[Explanation of symbols]

 F: color filter Mg: magenta filter G: green filter Ye: yellow filter Cy: cyan filter L1 to L4: first to fourth rows

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/04-9/11 H04N 5/335 H04N 17/00-17/06

Claims (2)

(57) [Claims] 1. A solid state device comprising: a color filter laid on a plurality of pixels arranged in a matrix, and a vertical register for sequentially reading and transferring signal charges corresponding to a vertical pixel column among the plurality of pixels. A first step of irradiating the plurality of pixels with monochromatic light to generate a pixel in which electric charges are accumulated and a pixel in which electric charges are not accumulated according to the spectral characteristics of the color filter; and Extracting a signal level of a pixel in which the signal charge is not accumulated from output signals transferred from the vertical register, and determining transfer deterioration of the vertical register according to the signal level. Characteristic method of measuring transfer deterioration of vertical register. 2. The method according to claim 1, wherein the pixels corresponding to the cyan and green filters do not accumulate charge when illuminated with red light, while the pixels corresponding to the yellow and green filters illuminate with blue light. 2. The method according to claim 1, wherein the pixels do not accumulate charges.