JPH0783095B2 - Inspection method for solid-state image sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for inspecting a variation in sensitivity depending on a light receiving position in a solid-state image sensor including a large number of light receiving elements that photoelectrically convert incident light.

(Prior Art) Conventionally, a solid-state imaging device, as shown in FIG. 1, transmits light emitted from a light source 11 through an optical system such as a condenser lens 12, a filter 13, a pattern 14, a projection lens 15 and a diaphragm 16. While irradiating the irradiation area 17 with its intensity being uniform, the solid-state imaging device is arranged in this irradiation area 17 to irradiate the light receiving surface of the solid-state imaging device with the light having the uniform intensity, and the uniform light thus radiated respectively. The photoelectric conversion was performed by the light receiving element of and the variation was measured. That is, since the intensity of the irradiation light is uniform as described above, if the sensitivity of each light receiving element is uniform, the output after photoelectric conversion becomes uniform regardless of the light receiving element, while the sensitivity of the light receiving element varies. If there is, a difference occurs in the output depending on the light receiving position. Whether or not there is a difference in the output and the size thereof can be used to determine whether or not there is a variation due to the position of the light receiving surface of the solid-state image sensor.

(Problem to be Solved by the Invention) The above inspection method is based on the assumption that the intensity of the light flux illuminating the irradiation region 17 is truly uniform. However, the luminous flux that irradiates the irradiation area through the above optical system such as the condenser lens 12 is not a completely uniform luminous flux, and has a slight variation depending on its irradiation position, and it is about 3% depending on the irradiation position. The uneven strength could not be avoided.

Therefore, in the above inspection method, there is a limit to the measurement accuracy according to the intensity unevenness of the irradiation light flux, and for example, the measurement unevenness cannot be reduced below 3%.

The present invention has been made in view of such circumstances, and it is possible to measure the variation in sensitivity depending on the position of the light receiving surface of the solid-state image sensor with extremely high accuracy, even if a light source having intensity unevenness depending on the irradiation position is used. The purpose is to provide an inspection method.

(Means for Solving the Problem) That is, according to the present invention, the light receiving element surface of the solid-state image sensor is irradiated with illumination light of an inspection light source, and the output of the solid-state image sensor based on the illumination light is inspected to detect the light-receiving element. Assuming an inspection method to inspect the sensitivity, divide the irradiation surface irradiated by the illumination light into a large number of small irradiation areas of the same shape and the same area, prepare a reference solid-state image sensor, and receive the light-receiving element. The surface is divided into a large number of reference small inspection regions having the same shape and the same area as the small irradiation region, and each of the reference small inspection regions is arranged in each small illumination region. The corresponding solid-state imaging device is obtained by irradiating corresponding illumination light to obtain the output of the reference solid-state imaging device for each small illumination region, and changing the combination of the reference small inspection region and the small illumination region. By obtaining the output and calculating the average value of the output data thus obtained for each small illumination area, the output variation due to the difference in the reference small inspection area is eliminated and the output due to the difference in the small irradiation area is eliminated. The degree of variation is digitized and used as a correction value.The light receiving element surface of the solid-state image sensor to be inspected is irradiated with the illumination light of the inspection light source, and the output is obtained for each of the small illumination areas. It is characterized in that the output for each illumination area is corrected by the correction value and inspected.

In the present invention, since the reference solid-state image sensor is used to obtain the correction value by digitizing the degree of output variation due to the difference in the small irradiation area, the solid-state image sensor to be inspected as it is. Alternatively, a solid-state image sensor other than this may be used.

Further, as the small irradiation area, it is easy to divide and divide the irradiation surface, and in this case, by rotating the solid-state imaging device serving as a reference, the reference small inspection area and the small irradiation area are divided. It is possible to change the combination and obtain the output of the reference solid-state imaging device for all the combinations.

(Operation) According to the present invention, the irradiation surface irradiated with the illumination light is divided into a large number of small irradiation areas having the same shape and the same area, and a solid-state image sensor serving as a reference is prepared, and the light receiving element surface is Corresponding to the small irradiation area, it is divided into a large number of reference small inspection areas having the same shape and area, and each of the reference small inspection areas is arranged in each small illumination area. The output of the reference solid-state imaging device is obtained for each small illumination area by irradiating the corresponding illumination light, and the combination of the reference small inspection area and the small illumination area is changed, and all the combinations of the reference solid-state imaging element By obtaining the output and calculating the average value of the output data obtained in this way for each small illumination area, it is possible to eliminate the variation in the output due to the difference in the reference small inspection area and to determine the difference in the small illumination area. The degree of output variation is converted into a numerical value and is used as a correction value.The output for each small illumination area to be inspected is corrected by the above correction value and the inspection is performed. It is possible to selectively inspect only the sensitivity unevenness of the target solid-state imaging device.

(Example) Next, the Example of this invention is described with reference to drawings.

As shown in FIG. 1, the optical system is the same as the conventional one. That is, the light emitted from the light source 11 illuminates the irradiation area through the optical system such as the condenser lens 12. Then, as shown in FIG.
A of the same shape and the same area at the position rotated by degrees,
It is divided into the four small irradiation areas B, C, and D.

Next, a light-receiving surface of a solid-state image sensor serving as a reference is arranged on the irradiation surface 17, and the light-receiving surface is made to correspond to the four small irradiation areas, and four reference small inspection areas a, b, c, and d. Divide into. As the reference solid-state image sensor, the solid-state image sensor to be inspected was used as it was. Further, the reference small inspection region a is associated with the small irradiation region A, b is similarly associated with B, c is associated with C, and d is associated with D.

Then, the output of each of the reference small inspection areas a, b, c, d is measured for each reference small inspection area, and this is measured as V _aA , V _bB , V _cC , V _dD.
And

Next, as shown in FIG. 2C, the solid-state imaging device is rotated 90 degrees about its center, the small irradiation pigment A is made to correspond to the reference small inspection region b, and similarly B is made to be c, C corresponds to d and D corresponds to a.

Then, the output of each of the reference small inspection areas a, b, c, d is measured for each reference small inspection area, and this is measured as V _bA , V _cB , V _dC , V _aD.
And

Then, this operation was repeated to measure V _cA , V _dB , V _aC , V _bD , and V _dA , V _aB , V _bC , and V _cD .

The output measured in this way is plotted on the horizontal axis as small irradiation areas A, B,
FIG. 3 shows a matrix display of C, D and vertical small inspection areas a, b, c, d.

As can be seen from FIG. 3, the small irradiation areas A, B,
The output was measured for all the combinations of C and D and the reference small inspection areas a, b, c, and d.

Next, in FIG. 3, along the vertical axis, V _aA , V _bA , V
The correction value V _A of the small irradiation area A was obtained by adding _cA and V _dA and dividing by the number 4 of the output data. And likewise, V _B ,
V _C and V _D were calculated.

Next, using the above-mentioned solid-state image sensor as a reference as a solid-state image sensor to be inspected, the sensitivity unevenness due to the position of this solid-state image sensor was calculated. That is, first, the output data V _aA obtained by associating the reference small inspection region a with the small irradiation region A was corrected by the correction value V _A to obtain the sensitivity V _a of the small inspection region a. Similarly, V _b , V _c and V _d were obtained.

Then, by comparing V _a , V _b , V _c, and V _dA thus obtained with each other, it was possible to accurately inspect the variation in sensitivity due to the position of the light receiving surface of the solid-state imaging device.

(Effect of the Invention) According to the present invention, it is possible to prevent variations in output due to differences in illumination areas and selectively inspect only the sensitivity unevenness of the solid-state image sensor to be inspected. Even if a certain light source is used, it is possible to measure the variation in sensitivity depending on the position of the light receiving surface of the solid-state image sensor with extremely high accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method for measuring the sensitivity of a solid-state image sensor.
FIG. 2A is an explanatory view showing the division of the irradiation surface, FIG. 2B is an explanatory view of the state where the division of the light receiving surface corresponds to the division of the irradiation surface, and FIG. 2C is the case where the light receiving surface is rotated. FIG. 3 is an explanatory diagram of a state in which the division of the light receiving surface corresponds to the division of the irradiation surface, and FIG. 3 is an explanatory diagram for explaining the calculation method of the output data. 11 …… Light source 12 …… Condenser lens 13 …… Filter 14 …… Pattern 15 …… Projection lens 16 …… Aperture 17 …… Irradiation surface

Claims (1)

[Claims] 1. An inspection method for irradiating the light-receiving element surface of a solid-state image sensor with illumination light from an inspection light source, and inspecting the output of the solid-state image sensor based on the illumination light to inspect the sensitivity of the light-receiving element. The irradiation surface irradiated with light is divided into a large number of small irradiation areas of the same shape and the same area, and a solid-state image sensor to serve as a reference is prepared, and the light-receiving element surface of the solid-state imaging element is divided into areas corresponding to the small irradiation areas. Each small illumination area is divided into a large number of reference small inspection areas of the same shape and the same area, and each of the reference small inspection areas is arranged in each small illumination area, and illumination light corresponding to these small illumination areas is irradiated. The output of the reference solid-state image sensor is calculated for each of the combinations, and the output of the reference solid-state image sensor is calculated for all the combinations. By calculating the average value of the data for each small illumination area, the variation in the output due to the difference in the reference small inspection area is removed, and the degree of the variation in the output due to the difference in the small illumination area is quantified. As the correction value, the light receiving element surface of the solid-state image sensor to be inspected is irradiated with the illumination light of the inspection light source to obtain the output for each of the small illumination areas, and the output for each of the small illumination areas to be inspected is the correction value. A method for inspecting a solid-state image sensor, comprising: