JPH10200796A - Member for picture element sensitivity spot correction and camera using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily correct the picture element sensitivity spot of an image sensor which is not affected by the type of an image pickup lens or the change of various image pickup environments by providing a function for irradiating the image sensor with the uniform illuminance of incident light. SOLUTION: For a sensitivity spot measuring cylinder 8, a light diffusion board 9 is fitted to the end face of a light source 10-side and plural light shielding lines 11 whose surfaces are treated into matting black are provided on the inner face of the measuring cylinder 8. The light shielding lines 11 are arranged at prescribed intervals and they are formed by a ring-like or spiral V shape groove part with the optical axis of the measuring cylinder 8 as a center. Light which is made incident on the measuring cylinder 8 is diffused by the light diffusion board 9 and light abutted on the inner face of the measuring cylinder 8 is shielded by the light shielding lines 11. They do not reach a linear CCD 2. The light shielding lines 11 guide light reflected on the inner face to a direction different from the direction of the CCD 2. Thus, the CCD 2 is uniformly illuminated and optimum sensitivity spot correction data are obtained with output data on the CCD 2 as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera for picking up an image by using an image sensor having pixels for performing photoelectric conversion, and more particularly, to a pixel sensitivity of an image sensor which is interchangeably mounted with an image pickup lens of the camera. The present invention relates to a spot correction member and a camera using the same.

[0002]

2. Description of the Related Art Conventionally, an image sensor using a CCD (charge coupled device) in which pixels for converting light into electric signals are arranged at a predetermined pitch has been used as an image pickup means for picking up an image pickup object as image data. What is used is common.

There are two types of CCD image sensors: CCD area image sensors in which pixels are arranged in a plane and CCD linear image sensors in which pixels are arranged in a line. 2. Description of the Related Art Digital imaging devices, such as so-called digital cameras, which include an image sensor and capture an image of an imaging target by using the image sensor, have been widely used.

For example, in the case of an imaging apparatus having the above-described CCD area image sensor, an image of an object to be imaged is guided onto the CCD area image sensor through an appropriate optical path, and imaging is performed. Then, the obtained image is displayed on the monitor, and the photographer adjusts the focus position and the imaging range while looking at the monitor. The captured image data is temporarily stored in a memory, read out as appropriate, displayed on a monitor, and a captured image is observed.

[0005] Each pixel of the CCD image sensor inherently has a sensitivity variation inherent to each pixel. However, when the imaging lens of a camera equipped with a CCD image sensor is replaceable, this variation in sensitivity between pixels may occur, for example, when the imaging lens attached to the camera body is replaced. Changes over time due to dust, dirt and scratches. Therefore, it is necessary to measure and correct the pixel sensitivity unevenness as needed. For this purpose, conventionally, a uniform illuminated reference plate having a constant reflectance is photographed through an imaging lens to obtain C
The pixel sensitivity unevenness of the CD image sensor was measured, and the pixel sensitivity unevenness was corrected based on the data.

[0006]

However, in the above-described method, it is not easy to uniformly illuminate the reference plate, for example, it is necessary to completely remove adhesion of dirt or the like that may be on the reference plate. . Also, since the pixel sensitivity unevenness is measured through the imaging lens, the uniformity of the illuminance on the CCD image sensor depends on the performance of the attached imaging lens, such as focus and brightness, and the shooting distance, aperture, and zoom position. Changes, every time the imaging environment changes, C
It is very troublesome to measure the pixel sensitivity unevenness of the CD image sensor, and it has not been possible to perform the optimum pixel sensitivity unevenness correction.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and means for easily correcting pixel sensitivity unevenness of an image sensor which is not affected by changes in the type of an imaging lens or various imaging environments. And a camera to which it can be attached.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image pickup device having an image sensor comprising pixels for performing photoelectric conversion, wherein a camera body to which an image pickup lens is replaceably mounted is provided. This is achieved by providing a pixel sensitivity unevenness correction member that can be attached instead and has a function of irradiating incident light to the image sensor with substantially uniform illuminance.

Further, the pixel sensitivity unevenness correcting member has a cylindrical shape, and has a light diffusing member on an end surface on a side where the incident light of the cylindrical shape is incident, and reflects light on an inner surface of the cylindrical shape. Prevention processing may be performed.

Further, the inner surface of the cylindrical form may be matte black, and a surface for reflecting light incident on the inner surface in a direction different from the direction toward the image sensor may be provided. For example, the inner surface has a plurality of Vs around the optical axis.
It has a shaped groove.

Further, in order to achieve the object of the present invention,
A pixel sensitivity unevenness correction member having an image pickup unit having an image sensor composed of pixels for performing photoelectric conversion and having a function of irradiating incident light to the image sensor with almost uniform illuminance is replaceably attached to an image pickup lens. A camera is provided.

Further, a camera to which the pixel sensitivity unevenness correcting member for mounting the object of the present invention can be attached is provided, wherein a plurality of pixels of the image pickup means which are sensitive to light irradiated with substantially uniform illuminance are provided. Correction means for making the signal levels substantially the same may be provided. This correction means, for example,
A calculating means for calculating a relative ratio of each output signal level from a plurality of pixels of the imaging means when the member for correcting pixel sensitivity is attached; and storing the ratio calculated by the calculating means. Storage means, and conversion means for converting each output signal level from a plurality of pixels of the imaging means when the imaging lens is mounted and imaged based on the relative ratio corresponding to each pixel And

The relative ratio is obtained, for example, by calculating the output signal levels from a plurality of pixels of the image sensor when the pixel sensitivity unevenness correction member is attached, by an average value of the output signal levels. This is the divided value.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the technical scope of the present invention is not limited to this embodiment.

FIG. 1 is a sectional view showing the configuration of a camera provided with an imaging lens. In the embodiment of the present invention, a CCD linear image sensor (hereinafter referred to as a linear C
2). Imaging lens 1 and linear C
An optical path switching mirror 4 for changing the optical path is arranged between the optical disc and the CD 2, and a focusing screen 5 is arranged at a focal position where the optical path is bent and moved by the optical path switching mirror 4.

For framing and focusing before imaging, an optical path switching mirror 4 is arranged so that a light beam forms an image on a focusing screen 5 and a focusing screen 5 is provided by a penta roof prism 6 and an eyepiece 7.
Observe and be done. During imaging, the light flux is linear C
An optical path switching mirror 4 is arranged so as to form an image on the CD 2.

In such a camera, the imaging lens 1 is exchangeable as described above, and the uniformity of the illuminance on the linear CCD 2 varies depending on the imaging distance, the type of the imaging lens, the aperture and the zoom position. I do. Therefore, it is not appropriate to correct the pixel sensitivity unevenness of the linear CCD 2 based on the output of the linear CCD 2 in a certain state. Therefore, the pixel sensitivity unevenness inherent to the linear CCD 2 and the linear CCD
In order to correct pixel sensitivity unevenness due to various environmental changes such as dirt adhering to the glass surface on 2, in the embodiment of the present invention, the imaging lens 1 is removed at the time of pixel sensitivity unevenness measurement, A sensitivity spot measuring tube 8 described below is attached to the camera body.

FIG. 2 is a sectional view showing the configuration of a camera in which the imaging lens 1 is detached and the sensitivity unevenness measuring tube 8 is mounted when measuring pixel sensitivity unevenness. The linear CCD 2 is moved to the center position of the sensitivity unevenness measuring cylinder 8 and is directed to an arbitrary light source 10 located sufficiently away from the mounting optical axis, and the linear CCD 2 photographs this arbitrary light source 10. .

FIG. 3 is an enlarged sectional view of the sensitivity unevenness measuring cylinder 8. The sensitivity unevenness measuring tube 8 is provided with a light diffusing plate 9
Further, the inner surface of the sensitivity unevenness measuring cylinder 8 has a plurality of light-shielding lines 11 which are surface-treated in matte black. The light-shielding lines 11 are arranged at predetermined intervals, and are formed of a ring-shaped or spiral V-shaped groove centered on the optical axis of the sensitivity spot measuring cylinder 8. The light incident on the sensitivity unevenness measuring tube 8 is diffused by the light diffusion plate 9, and the light hitting the inner surface of the sensitivity unevenness measuring tube 8 is shielded by the light shielding line 11,
Do not reach above.

The light-shielding line 11 has a function of guiding the light reflected on the inner surface in a direction different from the direction of the linear CCD 2. Accordingly, the light-shielding line 11 is not limited to the V-shaped groove as long as the light reflected by the inner surface of the sensitivity measuring tube 8 does not reach the linear CCD. For example, a protrusion made of a plurality of pyramids may be formed on the inner surface. It may be provided.

Although the sensitivity spot measuring cylinder 8 shown in FIG. 3 is cylindrical, it may be shaped like, for example, a square cylinder having an inner surface that does not allow reflected light to reach the linear CCD.

As a result, the linear CCD 2 can be uniformly illuminated, and optimum sensitivity unevenness correction data can be obtained based on the output data of the linear CCD 2 at this time.
In addition, since the image forming optical system is not used, delicate adhesion of the light diffusing plate 9 has no effect. The pixel sensitivity unevenness of the linear CCD 2 can be appropriately corrected by the correction data thus obtained. Hereinafter, a method of correcting the pixel sensitivity unevenness will be described.

FIG. 4 is a block diagram of a linear CCD pixel sensitivity unevenness correction circuit. This linear CCD pixel sensitivity unevenness correction circuit is provided, for example, in a microcomputer which is a camera control means incorporated in the camera body. Further, a so-called external correction device may be connectable to a camera.

The output signal of the linear CCD 2 is digitally converted by an A / D conversion circuit 12. When the pixel sensitivity unevenness is measured, the digital output digital output value of the linear CCD 2 is output to an arithmetic circuit 18. The arithmetic circuit 18 calculates optimal pixel sensitivity unevenness correction data. It is memorized.

Specifically, for example, first, a linear CCD
The average of the two effective pixel outputs is calculated. Then, the output value of each pixel is divided by the average value. By this arithmetic processing, the correction data of each pixel becomes 1 when the output value of each pixel is equal to the average value, becomes 1 or more when the pixel has an average sensitivity or more, and further becomes 1 when the pixel has an average sensitivity or less. The value is 1 or less. That is, the correction data is stored in the nonvolatile memory 16 via the switch 20 as the ratio of the deviation from the average value for each pixel.

Next, when imaging is performed, the linear CC
The output signal from D2 is supplied to the A / D conversion circuit 12 as described above.
The digital output value is input to the division circuit 13 by the operation of the switch 19.

On the other hand, a linear C that drives the linear CCD 2
The output of the CD drive circuit 14 is also input to the address counter 15. At this time, the switch 20 selects the signal from the address counter 15 and synchronizes with the output of the linear CCD 2 to divide the pixel sensitivity unevenness correction data corresponding to each pixel address stored in the nonvolatile memory 16 into the division circuit 13.
Is output to

Then, in the division circuit 13, the digital output value of each pixel of the linear CCD 2 is divided in synchronism therewith by the correction data corresponding to each pixel address read from the nonvolatile memory 16. . As a result, the output value of the linear CCD 2 is appropriately corrected.

That is, for example, the correction data obtained as described above for two pixels A and B having different sensitivities are each 1.1.
And 0.9, that is, in comparison with the average output value,
If there is a deviation of ± 10%, when the two pixels A and B receive the same amount of light, different output values will be output. At this time, the output value can be converted into an output value at the average sensitivity by dividing the output value by the respective correction data 1.1 and 0.9. Thus, the variation in the sensitivity of the pixels on the linear CCD 2 is corrected.

The corrected image data is stored in the buffer memory 17.

FIG. 5 is a flowchart of the measurement and correction of the linear CCD pixel sensitivity unevenness. In step S1, for example, when periodic sensitivity unevenness correction is performed, the sensitivity unevenness measurement tube 8 is mounted on the camera body instead of the imaging lens 1 (step S2), and an arbitrary light source is imaged (step S3). Then, the calculation and storage of the correction data described above are performed (step S4).

When the correction data is updated, the imaging lens 1 is mounted on the camera body in place of the sensitivity spot measuring tube 8 (step S5), and a desired image is taken. The correction is performed based on the correction data (step S6).

In the present invention, a CCD area image sensor may be used instead of the linear CCD 2 described in the present embodiment.

The camera to which the above-described sensitivity spot measuring cylinder 8 is attached may not be provided with the linear CCD pixel sensitivity spot correction circuit, and may be used only for measuring variations in illuminance.

[0035]

As described above, according to the present invention,
Variations in sensitivity among the pixels of the image sensor can be easily corrected at any time according to changes in the imaging environment or aging such as contamination of the pixels of the image sensor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a camera to which an imaging lens is attached.

FIG. 2 is a cross-sectional configuration diagram of a camera equipped with a sensitivity spot measurement tube 8 instead of the imaging lens 1 when measuring pixel sensitivity spots.

FIG. 3 is an enlarged sectional view of a sensitivity unevenness measuring cylinder 8.

FIG. 4 is a block diagram of a circuit for measuring and correcting linear CCD pixel sensitivity unevenness.

FIG. 5 is a flowchart of measurement and correction of linear CCD pixel sensitivity unevenness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image pickup lens 2 Linear CCD 3 Linear CCD scanning mechanism 4 Optical path switching mirror 8 Sensitivity unevenness measuring cylinder 9 Light diffusion plate 10 Light source 11 Light-shielding line with matte black surface treatment 13 Division circuit 15 Address counter 16 Nonvolatile memory 18 Arithmetic circuit

Claims (9)

[Claims] 1. An image pickup device comprising an image sensor comprising pixels for performing photoelectric conversion, the image pickup means being attachable to a camera body to which an image pickup lens is exchangeably mounted, in place of the image pickup lens. A pixel sensitivity unevenness correction member having a function of irradiating an image sensor with substantially uniform illuminance. 2. A cylindrical form, wherein a light diffusing member is provided on an end surface on a side where the incident light of the cylindrical form is incident, and an inner surface of the cylindrical form is subjected to a light reflection preventing treatment. The member for correcting pixel sensitivity unevenness according to claim 1. 3. An anti-reflection treatment of the inner surface of the cylindrical form,
The pixel sensitivity unevenness correction member according to claim 2, wherein the member is matte black. 4. The cylindrical inner surface is provided with a surface for reflecting light incident on the inner surface in a direction different from the direction toward the image sensor. Pixel sensitivity unevenness correction member. 5. The member for correcting unevenness in pixel sensitivity according to claim 4, wherein the inner surface has a plurality of V-shaped grooves around the optical axis. 6. The apparatus according to claim 1, further comprising correction means for making output signal levels of a plurality of pixels included in said imaging means, which are sensitive to light irradiated with substantially uniform illuminance, substantially the same. A camera to which any one of the pixel sensitivity unevenness correction members according to any one of the above is attached. 7. A calculating means for calculating a relative ratio of each output signal level from a plurality of pixels of the image pickup means when the pixel sensitivity spot correcting member is attached, and Storage means for storing the ratio calculated by the calculation means; and the output signal levels from a plurality of pixels of the imaging means when the imaging lens is attached and imaged, the relative signal levels corresponding to the respective pixels being 7. The camera according to claim 6, further comprising a conversion unit configured to perform conversion based on a ratio. 8. The relative ratio is obtained by dividing each output signal level from a plurality of pixels of the imaging means when the pixel sensitivity correcting member is attached by an average value of the output signal levels. The camera according to claim 7, wherein the value is a value. 9. A pixel sensitivity unevenness correction member having image pickup means having an image sensor comprising pixels for performing photoelectric conversion, and having a function of irradiating incident light to the image sensor with substantially uniform illuminance. A camera which is interchangeably mounted.