JPS6020684A - Image pickup device - Google Patents

Abstract

PURPOSE:To eliminate the influence of irregularity of illumination by correcting shading generated on the surface of an object based on an image pickup signal photographed by two kinds of light outputted from an image pickup device. CONSTITUTION:An object 4 is photographed by a television camera 7 by the light of a wavelength which is relatively easily absorbed by the object and the light of a wavelength which is relatively difficult to be absorbed by the object 4. Shadow due to the irregularity of illumination by a lamp 1 is also present in an image pickup signal obtained by the light of a wavelength which is relatively easily absorbed by the object 4. On the other hand, in an image pickup signal obtained by the light of a wavelength which is relatively difficult to be absorbed by the object 4, the absorption of light by the object 4 hardly occurs, and accordingly, a part of the image pickup signal in which the light is absorbed is the shadow caused by the irregularity of illumination of the lamp 1. By determining (dividing) the ratio of image pickup signals obtained by the light of two kinds of wavelength, or by subtracting the two signals, the correction of shading is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an imaging apparatus, and more particularly to an image carrier in which shading correction is performed in an illumination system for carrying an image.

Background of the Invention For example, in the field of medical devices, when a subject is photographed with an imaging device, it is necessary to perform shading correction on the photographed image. This is because in these fields, it is necessary to obtain an accurate image of the subject, and if you leave the unevenness of the light shining on the subject as it is, the unevenness of light will be mixed into the photographed image, making it impossible to get an accurate image. This is because it cannot be used as material for judgment.

Therefore, as a shading correction in the conventional device,
The method used was to first photograph a standard subject before photographing the subject. This is done by adjusting the amplification degree of the Wi image device for each pixel of the screen obtained by shadowing a standard object, or by storing the image signal of the standard object in a memory. Then, the target subject is photographed, and the signal obtained by the image pickup tube and the image signal of the W single wave photographed object stored in the memory are processed to correct the shading of the photographed subject. was being carried out.

However, with the conventional methods described above, the uneven distribution of the amount of light to the subject due to the commonly seen fluctuations in the color of the irradiated light, in other words, the light irradiated from the light source to the subject changes over time. In this case, it was not possible to correct the shading caused by uneven illumination due to this temporal variation.

Furthermore, it has not been possible to correct subtle shadows that appear on the photographic screen due to the unevenness of the subject.

Let me explain with a specific example. Consider a case where the stained area and degree of staining of a living tissue that has just been stained is measured using an imaging device through a low-magnification microscope. In this case, for example, if the amount of light irradiated onto the subject from the light source used for photographing changes with im, the stained area and degree of staining of the subject will change in the photographed image. In fact, when observing the stained area and degree of staining of living tissues,
Changes in the staining state over time are one of the very important requirements. Therefore, it is a very important question whether the changes in the stained area and degree of staining in the captured images are actually changes in the staining state on the living tissue, or whether they are due to changes in the amount of light emitted from the light source. becomes.

In addition, if the surface of the biological tissue being photographed has irregularities,
When photographing and measuring this biological ffi tissue using a method similar to the method described above (so-called reflection-absorption method), even if a light source with uniform illumination is used for photographing, the unevenness of the surface of the subject , shading inevitably occurs on the surface of the object, and the brightness distribution on the surface of the object becomes uneven.

In this case too, 1iillI! The device had a drawback in that it was not possible to determine whether the brightness or darkness on the surface of the subject was due to the subject's own absorption of light or whether it was due to the unevenness of the subject's surface.

! i? Therefore, it is an object of the present invention to prevent the light from changing when the amount of light from a light source irradiating the subject changes over time or when there are irregularities on the surface of the subject. An object of the present invention is to provide an imaging device capable of performing shading correction so that shading that occurs does not appear on a photographic screen.

DESCRIPTION OF THE INVENTION The present invention is an imaging device including a light source, an imaging device, and a shading correction device. The light source generates two types of light: light with a wavelength that is relatively easy for the subject to absorb, and light with a wavelength that is relatively difficult to absorb. In addition, the shading correction means uses two scales of light output from the imaging means.
The shading that occurs on the surface of the subject is corrected based on the captured image signal.

Effect 2 of the Invention Since the second invention is configured as described above, shading that occurs on the surface of the subject due to changes over time in the light intensity of the light source, uneven irradiation, etc., and when the surface of the subject has unevenness, can be prevented. The above-mentioned features and effects of this invention are shown in the drawings. It will become clearer from the following description of the embodiments given below.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a block diagram of an embodiment of the present invention. The light emitted by the lamp 1 passes through either the optical filter 3a or 3b and reaches the half mirror 5.

The optical filter 3a is a filter that transmits only light having a wavelength that is relatively easily absorbed by the subject 4 out of the light emitted by the lamp '1. 1. : The optical filter 3b is a filter that transmits only light of a wavelength that is relatively difficult for the filter 4 to absorb out of the light emitted by the lamp 1. Further, for the optical filters 3a and 3b, among the lights having the respective characteristics described above, lights having wavelengths that are closest to each other are selected.

This is because if the wavelength difference between the eight lights is large, the way each light is scattered may be different, and in that case, correction by scattering is also required.

The half mirror 5 is 4
They are placed at a 5 degree angle. Half of the light emitted from the lamp 1 is reflected by the half mirror 5 and reaches a subject (object to be measured) 4.

When the subject 4 is a living tissue stained as described above, light is absorbed or reflected depending on the stained area and staining traces of the subject 4.

The reflected light from the object 4 travels from the object 4 to the half mirror 5, and half of the light passes through the half mirror 5 and is applied to the television camera 7, which is an example of an image conveying means, via a lens 6 or a low magnification microscope. It will be done.

The output signal of the television camera 7 is analog/digital (A
/D) It is converted into a digital signal by the converter 8 and stored in the frame memory 9.

The memory area of the frame memory 9 is shown in FIG. Second
As is clear from the figure, the frame memory 9 divides the signals conveyed by the television camera 7 and converted into digital signals into, for example, 11+1 pixels for each frame, and stores each pixel for each pixel. This frame memory 9 is
It is configured to be able to store data for each pixel for two frames.

In one memory, for example, a video signal imaged by Va image using light of a wavelength that is relatively easily absorbed by the subject 4 that is irradiated from the lamp 1 through the optical filter 3a is stored, and in the other memory, the image signal from the lamp 1 is stored. 1 to optical filter 3
A video signal captured by light having a vt length that is relatively difficult for the subject 4 to absorb through the light beam irradiated through the light source 4 is stored.

The stored data in each memory is controlled by a high speed processor 11 and divided by a divider 10. By this division, the above-mentioned shading correction is performed. This explanation will be detailed next.

The shading-corrected video signal is converted into an ablog signal by a digital/analog (D//', ) converter 12, and then sent to the monitor? It will be shown and published on L-V13.

In addition, the switching of the memory area for storing data for each frame in the frame memory 9 and the optical filters 3a and 3b are performed.
The switching between the filter support section 3 and the filter support section 3 (which is performed by the rotation of the filter support section 3 by the motor 2) is controlled in conjunction with the high speed processor 11.

Next, we will explain in detail how to perform shading correction using the imaging signal obtained by II imaging using light of two different crane wavelengths, together with its principle.

As described above, the subject 4 is exposed to Ia by the television camera 7 by light having a wavelength that is relatively difficult for the subject 4 to absorb and light having a wavelength that is relatively difficult to absorb.

In the case of am using light of two types of wavelengths in this way, in extreme terms, the 111 imaging problem can be seen as the division of the part of the subject 4 where light absorption occurs and the part where no light absorption occurs. By the way, in the case where the subject 4 is a biological tissue that has been stained as described above, the light is absorbed by the stained area and a shadow is generated in the imaging signal obtained using light at a wavelength that the subject 4 is relatively easy to absorb. In addition to this, there are also shadows that have nothing to do with dyeing, such as uneven irradiation from the lamp 1.

On the other hand, the imaging signal captured using light at a wavelength that is relatively difficult for the subject 4 to absorb is almost completely absorbed by the subject 4, so the portion of the m-image signal where the light is absorbed is due to the light being absorbed by the lamp 1. This is a shadow caused by uneven irradiation.

Therefore, shape ink correction can be performed by calculating the ratio (dividing) of the i-image (B@) obtained by the light of these two wavelengths or by subtracting the two signals. It becomes possible.

Here, let us explain the principle of this shading correction. It is well known that optical absorption of an object basically follows the Lambert-Beer law. This law can be expressed by the following formula.

i/’l-10””・(1) Here, i: Amount of light transmitted through the sample (subject) Amount of light incident on the garlic (subject) ε: molecular absorption coefficient C: Concentration of measurement substance (subject) [: The optical path length of the light passing through the sample (subject).

This equation (1) holds true for data and data for each pixel stored in the frame memory shown in FIG. Therefore, for any pixel, the above equation (1) can be expressed as wavelength λ, , A2
Considering the 8 lights, is(λ+) = 10
""" 1111 (/(+ >...(2)1+++
(A2) =10 ”” ■gl(A2)...(3
). Here l m to l,), 1w+ (A1)
, ε1+C+ij-+ is for light of wavelength λ, and 1
I11 (A2), IIl' (A2), ε2 R02, A
2 is a symbol representing each of the above-mentioned contents for light of wavelength λ2.

The ratio between equation (2) and equation (3) is as follows.

(ill (λ+) )/(12 > 1 in i m
−[(Im(λ+))/(Im(A2))]x 1 o
(2,c,mu,'-ExCyoIL) 0. ,(4)
In the above equation (4), the same l! for light of wavelength λ, , A2. In the i-element ■, 0 + -G z ``O* J1+'-L2-IL - Also, the ratio of the amount of incident light of both wavelengths (1m(λ+)/I
I (A12) ) is the wavelength characteristic of the light used ('m<lamp), and there is a constant relationship, so (Im(λ+)/I
It can be set as I(A2))-k (constant). Therefore, (4
) formula is as follows.

(in(λ+)/l R1(A12))-@,
1 o(Et-ε"n"', (5) In this equation (5), choose light with a wavelength that has the value of ε2#O, or ε2〉
〉If light with a wavelength of ε1 is selected, equation (5) becomes as follows.

(Is(λ heat /ia+(A21)−k ・10°
``ノ...(6) This formula (6) has the following meaning.

In other words, the image signal obtained by forming an AI image using light of two different wavelengths is calculated as follows by taking the ratio of the light amount of each pixel of both 1111z signals.
This means that an imaging signal that is independent of changes in the amount of incident light can be obtained. This means that image data that is not affected by non-uniform illumination of the light source can be obtained.

Therefore, as in one embodiment of the present invention, shape ink can be corrected by dividing image signals captured at two different wavelengths and finding the ratio for each pixel. Further, the calculation is not limited to division, but shading correction can also be performed by subtraction.

Note that although the Lambert-Beer law is explained using a transmission illumination method, it is not limited to this method, but also applies to a reflection-absorption method.

This invention is not limited to the embodiments described above, but
For example, a light source may simultaneously irradiate a subject with two different wavelengths of light, the two wavelengths of light reflected by the subject may be separated by a dichroic mirror and a filter, and then simultaneously transported by two image carriers (TV cameras). You can also do this.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. FIG. 2 is a diagram showing a memory area of the frame memory 9 shown in FIG. 1. In the figure, 1 is a lamp, 3a and 3b are optical filters, 4 is a subject, 7 is a television camera (imaging means), 9 is a frame memory, and 10 is a divider. Patent applicant Tateishi Electric Co., Ltd.

Claims (1)

[Scope of Claims] (1) A light source that generates 2N light of a wavelength that is relatively easy for a subject to absorb and a light that is a wavelength that is relatively difficult to absorb, the light source emitting light having different wavelengths; 2. Means for transporting the subject by the light of 2 f'J I, and means for correcting shading occurring on the surface of the subject based on the imaging signal m-imaged by two types of light output from the image carrying means. An imaging device, including: (2) The light source includes means for generating light with a broadband wavelength, and two types of filters that transmit light of a specific wavelength among the light generated by the generating means. The mm device according to claim 1. <3) The embroidery image drawing L according to claim 1 or 2, wherein the two types of light having different wavelengths are those having wavelengths that are closest to each other among the lights that satisfy the above conditions. 4) 8 of the wavelength is 2 (!9 of Class D), and the 1111 means is two, and a dichroic mirror is provided between the image carrying means and the subject; Imaging III according to claim 1, wherein each of the cylindrical means images the subject with light of the respective wavelengths. (5) The imaging signal output from the imaging means is ,
The shading correction means performs shading correction for each divided pixel unit, wherein the shading correction means performs shading correction for each divided pixel unit. An image transport device according to claim 1.