JPS63238773A - Method for correcting picture element information - Google Patents

Abstract

PURPOSE:To correctly obtain the density information of an object by radiating a uniform light to respective picture elements, obtaining the correcting value of the output signal level of respective picture elements with the output signal level of one picture element as a reference and correcting the output signal level from respective picture elements at the time of the image pickup. CONSTITUTION:From E<2>PROM 63, address information to show a reference picture element part 55a and comparing picture element part 55b is fetched and the address information to show a memory means 55b is fetched to a memory means 69. A clock signal is supplied from a clock signal generating means 73 to an image pickup part 45. Simultaneously, the output signal of respective picture elements of a CCD sensor 55 is successively supplied to an A/D converter 61 at every pulse of the clock signal. After the information of the picture element of the reference picture element part 55a is A/D-converted 61, it is fetched into an arithmetic means 67. At the same time, a correcting value to correct the photoelectric converting performance of the picture element is read from the E<2>PROM 63 to the arithmetic means 67. At the arithmetic means 67, the dividng of the A/D-converted 61 value and the above-mentioned correcting value is executed, and the dividng result is stored into the prescribed position of the memory means 69 as the density information.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for correcting pixel information that can accurately obtain density information indicating the brightness and darkness of an object.

(Prior Art) In recent years, solid-state imaging devices have made remarkable progress, and image processing technology has also progressed rapidly.

Solid-state image sensors are used in various electronic devices, but
Cameras equipped with automatic focusing (AF) function (hereinafter referred to as AF)
It is sometimes abbreviated as a camera. ) also uses such an image sensor to determine focus.

Hereinafter, with reference to FIG. 2, how the image sensor in the AF camera is used and its operation will be briefly explained.

FIG. 2 is a block diagram showing the general structure of an AF camera.

In FIG. 2, 11 indicates a photographic lens, and 31 indicates a camera body to which the photographic lens 11 is attached.

The photographic lens 11 includes a lens system 15 including a lens 13 that is movable along the optical axis and contributes to focusing, and a camera body 31 for moving the movable lens 13 to a focusing position.
A clutch 17 that transmits force from a drive source (described later)
a, a driving force transmission mechanism 17 composed of a gear +7b, a helical screw 17c, etc., and a lens date ○M that stores aperture value information of the photographing lens, position information of the movable lens 13, etc.
+9, and a lens-side electrical contact group 21 for electrically connecting between the photographing lens 11 and the camera body 31.

On the other hand, the camera body 31 includes a main mirror 33, a sub mirror 35, a focusing plate 37, and a pentagonal prism 39.
, light receiving elements 41a and 41b for AE (automatic exposure photography), and a body-side electrical contact group 43 corresponding to the lens-side electrical contact group 21. In general, the camera body 31 includes an imaging section 45 having an imaging element made up of a plurality of pixels in order to receive a portion of the light from the subject that has passed through the lens system 15 and form an image. Roughly speaking, this camera body 31 has a movable lens 13 inside the photographic lens 11.
AF motor 47a, gear 47b, clutch 47c, and motor 4 configured with a DC motor, for example, to drive
A drive mechanism 47 having an encoder 47d for controlling the rotational speed of the motor 7a is provided. The driving force of the drive mechanism 47 is transmitted to the movable lens 13 via the body side clutch 47c, the lens side clutch 17a, etc., and as a result, this lens 13 is moved along the optical axis. Furthermore, this camera body 31 calculates an out-of-focus point indicating the amount of deviation from the in-focus position based on a signal from the imaging unit 45, drives the drive mechanism 47 based on this D, and performs automatic exposure. It includes a control section 49 that appropriately controls photographing and the like.

In a camera equipped with such an AF function, the out-of-focus Mli for the subject is determined, and if the value of this out-of-focus amount satisfies a certain standard, it is determined to be in focus, and if it is determined to be out of focus, Mli is determined. According to the amount, the movable lens 13 is moved to the in-focus position.

A method for determining this unfocused tV is called a phase opening method, and the above-mentioned imaging section 45 has the following structure to be suitable for this correlation method.

FIG. 3(A) is a diagram showing a schematic configuration of the imaging section 45 along with the correspondence relationship with other constituent components such as a photographing lens. Note that part of the light from the subject that has passed through the photographic lens 11 is guided to the imaging unit 45 by the sub-mirror 35 shown in FIG.
In this figure, this submirror is omitted.

The imaging unit 45 includes a condenser lens 51, a separator lens 53, a CCD sensor 55 as an imaging element, and the like. FIG. 3(B) is a perspective view showing the schematic structure of this CCD sensor 55. This CCD sensor 55 has a plurality of pixels, and these plurality of pixels are divided in advance into predetermined regions. The area indicated by 55a is called a reference pixel area, and includes, for example, the i-th to (i+n)-th pixels counted from one end of the CCD sensor 55, for example, the side indicated by X in FIG. 3(B). It is composed of (n+1) pixels (indicated by 56a to 56b in FIG. 3(B)). Further, the area indicated by 55b is called a comparison pixel area, and is spaced apart from the reference pixel area by a predetermined distance, and includes, for example, the j-th to (j+n+p)-th pixels counted from the pixel at one end of the CCD sensor 55. up to (n+1+
p) pixels (FIG. 3 CB) shown as 56c to 56d.

).

In an AF camera having such an imaging unit 45,
For example, the out-of-focus state of the subject can be calculated as follows.

Light from the subject obtained through the lens 13 is simultaneously imaged by the reference and comparison pixel sections 55a and 55b.

The brightness of the subject is photoelectrically converted by each pixel of these pixel units, and the output signal of each pixel is A/D converted by, for example, an A/D converter provided in the control unit 49 and sent to the control unit 4 as density information.
9 memory. These density information are compared and a correlation calculation is performed according to the following equation (1).

H(t)・Σ10(i+k)−D(4−t−II on j+
...(1) k=O Here, t selects the density information corresponding to consecutive (n+1) pixels by shifting it by one pixel from the memory of the comparison pixel section where the density information is stored. Indicates the amount of lateral shift. For example, when t=1, the CCD sensor 5
This means that the density information corresponding to (n+1) pixels from the jth to (j+n)th pixels counting from one end of 5 is selected, and when t is set to (p+1), Counting from one end of the CCD sensor 55 (j + p)
This means that density information corresponding to (n+1) pixels from the (j+n+p)th pixel is selected.

In the correlation method, it is determined whether the same image as the subject image captured in the reference pixel section 55a is captured in the (n+i) pixel regions for which the correlation calculation results have the minimum value among the plurality of pixels in the comparison pixel section 55b. judge. Roughly speaking, the position of this pixel area,
The amount of out-of-focus for the subject can be determined from the difference from a predetermined in-focus position.

(Problems to be Solved by the Invention) However, the COD sensor has a problem in that the photoelectric conversion performance of each pixel of the COD sensor is hardly uniform. In other words, if each pixel is irradiated with uniform light, the output signal level of each pixel should be the same, or in reality the output signal level of each pixel will vary. There was a problem.

Therefore, when correlation calculation is performed using the above-mentioned correlation method using such a COD sensor, the calculation result will include photoelectric conversion errors for each pixel, making it difficult to perform accurate automatic focusing. I can't do it.

The present invention has been made in view of these points, and therefore, an object of the present invention is to provide a method for correcting pixel information that can accurately obtain density information of a subject.

(Means for solving the problem) In order to achieve this object, according to the pixel information correction method of the present invention, when each pixel is irradiated with uniform light, one of the pixels is A correction i for the output signal level of each pixel is calculated based on the output signal level and stored in a memory, and the output signal level from each pixel is sent to the imaging section using the corresponding correction value read out from the memory. , is characterized by correction.

(Function) According to such a configuration, when the image sensor is, for example, a COD sensor, variations in the photoelectric conversion characteristics of the semiconductor elements constituting each pixel are corrected for each pixel.
The density information of the object obtained from the sensor accurately indicates the brightness and darkness of the object.

(Example) Hereinafter, an example of the pixel information correction method of the present invention will be described.

The pixel information correction method of the present invention is such that when each pixel of an image sensor having a plurality of pixels is irradiated with uniform light, the output of each pixel is calculated based on the output signal level of one of these pixels. Calculating a signal level correction value and storing it in memory, and then correcting the output signal level from each pixel when the object is actually imaged using the corresponding correction value read out from the memory. It is characterized by: Such a method of correcting pixel information can be applied to various devices equipped with an image sensor, and the method of the present invention will be explained below with specific application examples. The pixel information correction method of the present invention will be explained using an example in which it is applied to the AF camera described with reference to FIG.

Incidentally, in the following explanation, explanation of constituent components that are considered unnecessary for the explanation of the present invention among the constituent components already explained using FIG. 2 will be omitted.

In an AF camera like the one shown in Fig. 2, an image sensor having a plurality of pixels is used to obtain density information of the subject.
It can be constructed using the COD sensor 55 already explained using FIG. 3(8). Roughly, Figure 3 (A)%
By using the condenser lens 51, separator lens 53, etc., which have already been explained using
It is possible to have the D sensor take an image.

Further, in this embodiment, the control section 49 shown in FIG. 2 is as follows. FIG. 1 is a block diagram mainly showing the internal configuration of the control section 49, mainly showing the parts related to the present invention.

In FIG. 1, 61 is a CCD sensor 55 of the imaging section 45.
shows an A/D converter to which the output signal of each pixel is input,
63 is 62F ROM (Electrically
rasable & Proqrammable RO
M) @indicates, 65 indicates comparison means, 67 indicates calculation means,
Reference numeral 69 indicates memory means, 71 indicates an input/output port, and 73 indicates clock generation means.

In the control circuit 49 having such a configuration, in order to make the photoelectric conversion performance of each pixel of the COD sensor 55 the same, a correction value for correcting the level of the output signal of each of the plurality of pixels of the COD sensor 55 is stored. Memory tE2 PR
It can be configured with OM of 63%. In addition, the calculation means 6 is a means for correcting the output signal from each pixel during imaging using the correction value read out from the E2FROM 63.
7 can be mainly configured.

Note that the correction value for correcting the output signal of each pixel can be obtained, for example, as follows.

First, when each pixel of the COD sensor 55 is irradiated with uniform light, the level of the output signal of each pixel is determined. If the output signal levels vary, the pixel that shows the lowest output signal among these output signals is used as a reference pixel, and the output signal of this reference pixel is used to determine the output signal of each pixel other than this reference pixel.

Normalize each pixel and correct the reference pixel for each pixel @
Find in advance. The correction values for each pixel obtained in this manner are stored in predetermined memory locations of the 62FROM 63, respectively.

In addition, this E2P date 0M63, in addition to the above-mentioned correction value,
f! Among these types of information, some of the information related to this invention is as described below.

First, address information indicating the reference pixel portions 55a and 55b among the plurality of pixels of the COD sensor 55 is stored. The reason for this is as follows. COD sensor 55
Does it have a plurality of pixels? Among these plural pixels, the pixels used for focus judgment are the plural pixels belonging to the reference pixel section 55a explained using FIG. 3 CB) and the comparison pixel section 55b. A plurality of pixels belong to the plurality of pixels. Therefore, calculation processing time is reduced and memory usage is reduced! In terms of reducing l, C
Among the output signals of the plurality of pixels of the OD sensor, the signals to be taken into the control section 49 are preferably the signals of each pixel of the reference pixel section 55a and the signal of each pixel of the comparison pixel section. In this manner, address information indicating the pixel portions of the EzP day ○M63 (both pixels) is stored and utilized when taking in information (details will be described later).

Second, the imaging unit 45 collects information on each pixel indicating the brightness and darkness of the subject.
A program for executing a series of processes from to storage in the memory means of the control unit 49 is stored.

100' Positive 5 Tongue 8 Next, a method for correcting pixel information in the AF camera of the embodiment will be explained with reference to FIGS. 1 and 4. Furthermore, the fourth
The figure is a flowchart showing the operation of the correction method in this AF camera, and a program for executing such operation is stored in the E2FROM 63.

Address information (details will be described later) indicating the reference pixel section 55a and comparison pixel section 55b is loaded from the Snake 2PROM 63 into the memory means 69 (step 101). on the other hand,
An integration start signal of the COD sensor is supplied to the imaging unit 45 (step 103). When the integration time of the COD sensor reaches a predetermined time, a clock signal is supplied from the clock signal generating means 73 to the imaging section 45 in response to this.

In the case of this embodiment, at the same time as the clock signal is supplied, the output signal of each pixel from the pixel at one end to the pixel at the other end, indicated by /D converter 61 sequentially (
Step +05), L/ However, the A/D converter 61 does not perform A/D until the output signal of a predetermined pixel is supplied.
No conversion is performed. Further, the control section starts counting the clock signal at the same time as the supply of the clock signal starts (step +07). Here, the address information indicating the reference pixel section and the comparison pixel section stored in the E2FROM is added to the clock signal. It shall be kept as a numerical value corresponding to the count number.

Further, as already explained using FIG. 3 CB), the reference pixel section 55a in this case is the (i+n)th pixel from the i-th pixel counting from one end of the COD sensor 55.
1) In such a case, when the cumulative number of pulses of the clock signal matches the number i indicating the leading value M of the reference pixel section (step 109 ), starting from this pixel (n+1
) It operates to sequentially A/D convert the information of the pixels up to the pixel and sequentially supply it to the control section. This operation will be explained in detail as follows.

When the first pixel of the reference pixel section 55a, in this case the i-th pixel counted from one end of the COD sensor, is reached, the information of this pixel is A10 converted by the A/D converter 61 and then taken into the calculation means 67. At the same time, a correction value for correcting the photoelectric conversion '1 ability of this i-th pixel is read from the E2 PROM 63 into this calculation means. The calculation means divides the A/D converted value by this correction value (step 113), and stores the division result in a predetermined location of the memory means 69 as density information (step 115). (n+1
．． ) It is checked whether the processing of steps 113 to 115 has been completed for all pixels (step 11).
7).

If the process has not been completed, A/D conversion of the information of the pixel, correction calculation, and storage of the calculation result in the memo 1 means are performed in sequence (steps +19. +13 to +15).
).

When the acquisition of the density information from the reference pixel section 55a is completed, it is checked whether the cumulative number of pulses of the clock signal has reached a value indicating the leading value M of the comparison pixel section (steps 119, 121').

As already explained using FIG. 3 CB), the comparison pixel section 55b in this case is the (n
+1+p) pixels. In such a case, this AF camera calculates the (n+1+p)th pixel starting from this pixel when the cumulative number of pulses of the clock signal reaches the number (aj) indicating the starting position of the reference pixel section (step 121). Sequentially A/D the information of pixels up to
After conversion and correction calculation, the data are sequentially stored in predetermined locations in the memory means 69. This series of operations is performed in the same manner as steps 111 to 119 already described, and the explanation thereof will be omitted (steps 123 to +31').

When the processes in steps 123 to 127 are completed for all (n+1+p) pixels of the comparison pixel section 55b, the brightness and darkness of the subject obtained from the reference pixel section 55a and the comparison pixel section 55b are stored in a predetermined area of the memory means. Density information indicating the density information is stored in a state in which variations in the photoelectric conversion ability of each pixel have been corrected.

Furthermore, since A/D conversion and correction calculations are performed only on the pixel information of the reference pixel section and comparison pixel section, it is possible to reduce power consumption, calculation time, and memory usage.

Note that this invention is not limited to the above-described embodiments.

For example, in this embodiment, the correction value stored in the E2PROM is suitable for division, but the correction value is not limited to this. For example, the reference value may be the maximum value or average value of the output signal levels from each pixel, or any output signal level may be used as the reference value.

In addition, in the above embodiment, the memory for storing correction values is E2.
The explanation is given using an example configured using FROM. E2FR
The reason for using OM is to take into account that each correction value varies depending on the image sensor, and by doing so, it is possible to adjust the correction value according to the image sensor included in each camera during the camera assembly process. This is because writing can be performed easily. However, it is of course possible to use something other than the 22PROM as the memo 1 section for storing correction values.

(Effects of the Invention) As is clear from the above description, according to the pixel information correction method of the present invention, variations in the photoelectric conversion characteristics of each pixel of an image sensor are corrected for each pixel, so that this image pickup The density information of the object obtained from the element accurately indicates the brightness and darkness of the object.

[Brief explanation of drawings]

FIG. 1 shows an A to which the pixel information correction method of the present invention is applied.
FIG. 2 is a block diagram schematically showing the configuration of the AF camera according to the present invention; FIG. FIG. 3(B) is a perspective view schematically showing the imaging section equipped with the AF camera according to the present invention, and FIG. is a flowchart showing the operation of the correction method according to the embodiment of the present invention. DESCRIPTION OF SYMBOLS 11...Photographing lens, 13...Movable lens 15...Lens system, 17...Driving force transmission mechanism 17a...Lens side clutch! 7b... Kise, 17c... Helicoid screw 19... Lens ROM, 21... Lens side electrical contact group 31... Camera body, 43... Body side electrical contact group 45... Imaging section , 47・
...Drive mechanism 47a...AF motor, 47b...
・Gear 47c...Body side clutch 47d...Encoder, 49-...Control unit 51.
...Condenser lens, 53...Separator lens 5
5... CCD sensor, 55a... Reference pixel section 5
5b...Comparison pixel section, 61.-A/D converter 63...Mi2PROM, 65...Comparison means 67
...Arithmetic means, 69...Memory means, 71
. . . Input/output coupler door 3 . . . Clock signal generation means. Patent applicant: Asahi Optical Industry Co., Ltd. Figure 3

Claims (1)

[Claims] (1) When each pixel is irradiated with uniform light, a correction value for the output signal level of each pixel is calculated using the output signal level of one of these pixels as a reference and stored in memory, and when capturing an image. A method for correcting pixel information, comprising correcting an output signal level from each pixel using the corresponding correction value read from the memory.