JPH0661106B2 - Image information detection method that can automatically set effective image information area - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image information detecting method, and more specifically, it divides a projected image such as a color negative film into pixels and detects the maximum area of an image sensor. The present invention relates to an image information detecting method for setting effective image information area detection for actually extracting image information to be processed.

[Background of the Invention]

In this type of technology, for example, when printing a photo, the density of the original image on the color negative film must be measured in order to determine the exposure amount. Is the average transmission density over the entire area of the negative film, that is, LATD
(Large Area Transmittance Density) is measured. The image detection by measuring the LATD is to measure the density of the original image on an average, and is not to measure the image density of the original image accurately and over the entire screen. Therefore, the exposure amount cannot be determined reliably. There is. In addition, the original image is divided into screens by a two-dimensional image sensor using a CCD, image information for each pixel is detected, size information of the original image is obtained, and according to a predetermined effective image information detection area for each size. A method in which the image information is organized and the exposure amount is determined (for example, JP-A-60-177337), or a fixed size is determined according to the size information obtained with reference to a certain characteristic pixel. Setting the area (for example, JP-A-60-2
No. 20325). In these methods, the size of the effective image information detection layer that processes image information is patterned as size information, so the distance and angle between the image sensor and the original image change due to work accuracy (variation in mounting, etc.) or aging. If a deviation occurs due to such reasons, there is a problem that the size and position of the original image in the area where the image sensor receives light changes and proper image information cannot be obtained. In addition, there is a problem that it will be difficult to cope with the future when an original format of a new size appears.

In particular, Japanese Laid-Open Patent Publication No. 60-177337 discloses a method of determining an exposure amount in photographic printing, in which the area of the opening is obtained by detecting the density "0" which indicates that the image is sneak from the image information and obtaining the area. It is described that the size of the negative film can be discriminated as a result, and the exposure amount is determined. This is to detect the density “0” and obtain the area of the pixel group, It is a technology that determines the size of the negative film, arranges image information for each pixel according to the exposure amount determination area that is predetermined for each film size, and determines the exposure amount. Because it is predetermined,
If the distance or angle between the image sensor and the original image is misaligned, the size and position of the original image in the light receiving area of the image sensor will change and appropriate image information cannot be obtained. There is a problem that it is difficult to deal with the case where a size original picture format appears.

[Object of the Invention]

This invention was made as a result of considering the above points,
An image in which the effective image information detection area of the original image can be flexibly set from the maximum area received by the image sensor in response to various film formats and positional deviations, and thus appropriate image information can be obtained. It is an object to provide an information detection method.

[Structure of Invention]

The present invention is an image information detecting method for detecting image information on a color negative film, in which a projection image composed of an original image and a peripheral image is divided into a plurality of pixels so as to have a light intensity,
A characteristic value of at least one of transmittance and density is detected, a distribution of the detected characteristic value is obtained, and a pixel group forming the projection image is classified into a valid / invalid pixel group based on the distribution. A threshold of the characteristic value is determined, the pixels forming the projection image are classified into valid / invalid pixel groups based on the determined threshold, and an image information detection area is provided inside the valid pixel group. And image information used for determining the exposure amount or / and the exposure correction amount for the original image of the color negative film is obtained on the basis of the determined image information detection area. It is a detection method.

The original image in the present invention means a reflection image or a transmission image, and the reflection image includes a color print, an original image of an ordinary printed matter, etc., and the transmission image is an original image recorded on OHP, reversal film or negative film. and so on.

Image information uses reflected light or transmitted light of the original image,
For example, it can be read photoelectrically using an image sensor such as a CCD.

In the present invention, the exposure amount and / or the exposure correction amount is determined based on the image information. There are cases where the exposure amount is determined only by this image information and cases where the conventional LATD control method is used in combination.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. The examples described below are examples of the present invention and are not limited thereto.

The image information detection method of the present embodiment uses a color negative film, and by irradiating the color negative film with light, image information including the original image of the color negative film is divided into a plurality of pixels to divide the characteristic value into pixel units, that is, Here, the threshold value is set by detecting the light intensity and using the characteristic value function of the pixel group forming the screen, and the image information includes an effective image group including valid image information and an invalid image information. The pixel groups are classified into two pixel groups of invalid pixel groups, and an area where more effective image information can be obtained in the valid pixel groups is automatically set.

The characteristic value for each pixel, which is obtained by dividing the screen based on the image information obtained from the original image such as the negative film, can be detected by, for example, the method disclosed in JP-A-60-17733.

The characteristic value means the light intensity in this embodiment, but may be the transmittance or the density.

Next, the physical pixel group is classified into two valid / invalid pixel groups by setting a threshold value by a function of the characteristic value in the pixel groups that form the screen. Based on the obtained characteristic value for each pixel, a function of the characteristic value of the entire screen is obtained, and a threshold for classifying valid pixels and invalid pixels is obtained. Specifically, as shown in FIG. 1, the two-dimensional image information of the original image (for example, in the case of a 135 F size negative film) obtained by an image sensor such as a CCD is roughly classified to determine the exposure amount. There are an effective pixel group that may be used as information and an invalid pixel group that may not be used as image information.
Actually, the boundary part is not clear, and the position of the effective pixel group, due to the position shift of the image sensor and the original image,
The size and shape always change. Therefore, it is necessary that at least the area for obtaining appropriate image information is within the effective pixel group, and therefore, the effective pixel group needs to be first determined as a priori problem. Therefore, using a histogram (frequency distribution function) to represent the image shown in Fig. 2 (a) in a graph,
It becomes like (b). In this embodiment, since each pixel is represented by 8 bits, the light intensity in the histogram is 0-25.
It comes out as a value up to 5. By cutting this with a certain threshold value (for example, the value x shown by the alternate long and short dash line), two effective / ineffective pixel groups can be clearly classified. In this embodiment, the cumulative frequency distribution function (CDF) is preferably used as the characteristic value function for setting the threshold value, but a frequency distribution function can also be used.

FIG. 3 and FIG. 4 are graphs showing characteristic values at 135 F size and 110 size, for example, using the cumulative frequency distribution function. As shown in FIG. 3, in the case of 135 F size, the area of the effective pixel group is large and the frequency of values near the light intensity of 0 is low, but in the case of 110 size of FIG. It starts from where the value of is relatively high.

When the image sensor is zero-adjusted, that is, when the light intensity is 0 without light, the cumulative frequency distribution (CDF) shown in Figs. 3 and 4 is used. The graph shown can be used to classify valid / invalid pixel groups. However, sometimes the zero adjustment may go wrong due to the influence of noise in the circuit as shown in FIG. 5, but even in such a case, it is effective if the method of this embodiment described below is used. / Classification of invalid pixels is possible.

An example of actually using this cumulative frequency distribution function to obtain a threshold will be described below. First, the dynamic range (Dr) is determined. As shown in Fig. 5, the maximum value of light intensity (here, 24
0) and the minimum value (10 in this case) are taken and calculated by the following formula.

Dr = maximum value-minimum value (Dr = 240-10 = 230) Next, the values near the maximum and minimum values of the dynamic range are cut at a constant rate. This is generally performed in image information processing because valid information is often not included near the maximum and minimum values of the dynamic range. In the present embodiment, the following processing is performed by using a value obtained by cutting the fixed ratio by 5% each from the maximum value and the minimum value, but the ratio is not limited to this. The points after cutting are designated as P ₉₅ and P ₅ .

Then, take the CDF value from that point, and
Set (P ₉₅ ) → C ₁ and CDF (P ₅ ) → C ₂ .

The point X that internally divides C ₁ and C ₂ into m: n is obtained by the following formula. Here, although the optimum value of the m: n ratio varies depending on the imaging system, m: n = 7: 3 is preferably used in this embodiment.

Then, the inverse function of X, that is, the value of the light intensity at the value of X of CDF, CDF ^-1 (X), is used as a threshold value to classify the valid / invalid pixel group.

Based on the threshold value obtained as described above, a group of pixels having the light intensity or more is set as an effective pixel group. Further, an image information detection area, which is an area for actually obtaining image information, is set in the effective pixel group.

The image information detection area can be set in the following procedure, for example. The following method is an example, and the present invention is not limited to this.

As shown in FIG. 6, the area of the effective pixel group is first obtained by counting the effective pixels, and this is designated as A. Next, as shown in the figure of the image classified into valid / non-present pixels,
Each effective pixel is sequentially counted from the top to the bottom in the horizontal direction (X-axis direction) of the image, and the Y coordinate of the pixel whose accumulated area exceeds A / 2 is defined as Cy. . Next, the effective pixels are counted sequentially from left to right (or right to left) in the subordinate direction (Y axis direction), and the accumulated area exceeds A / 2. Pixel X
Let the coordinates be Cx. A pixel whose X and Y coordinates are Cx and Cy has a substantial center of gravity. The top and bottom are examined from the approximate center of gravity to detect the edge part. Set the top and bottom widths slightly inside, looking at the margin. This is to obtain a proper image information by taking a margin because the information near the edge has variations. The upper and lower edges of the upper and lower widths after the margin is taken are detected in the vertical direction from the substantial center of gravity, and the left and right edge portions are detected (the upper portion 2
Point, bottom 2 points in total 4 points) Compare the upper part and the lower part, and set the narrower width as the left and right width. Set the final left and right width to.

By the above work, the image information area in which appropriate image information can be taken in can be automatically set according to the actual original image regardless of the patterned size information. Therefore, even if an image sensor such as a CCD is displaced due to assembly or aging, and the position and size of the original image in the area where the image sensor receives light change, the image sensor can flexibly respond to the change and be appropriate. It is possible to obtain various image information. Further, since the size information is not patterned, it is possible to easily cope with the use of a new size original picture format in the future.

In this embodiment, in order to classify the effective pixel group and the invalid pixel group, an example in which the threshold value is set by using the cumulative frequency distribution function of the characteristic value is shown. However, as another method, for example, the function of the characteristic value is It is also possible to use one that involves line extraction processing. This is a method of taking an absolute value of a function obtained by differentiating or differentiating a function of a characteristic value, extracting a contour line of an image with a characteristic peak point as a reference, and setting a threshold value. As another method, a histogram of the image may be taken and the density of the minimum point (valley portion of the frequency distribution function) generated in the histogram may be set as the threshold value (see FIG. 2).

It should be noted that this embodiment can be configured so that the image information detection area is automatically set.

[Advantages of the Invention] As described above, when the image information detection method of the present invention is used, the effective image information detection area of the original image within the maximum light receiving area of the image sensor is set to various film sizes and optical axes of the image sensor. Since it is possible to flexibly set the position and the size of the image due to the positional deviation, it is possible to always obtain accurate image information.

[Brief description of drawings]

FIG. 1 is a diagram of image information of an original image obtained by an image sensor, and FIGS. 2 (a) and 2 (b) are diagrams showing a correspondence relationship between image information of an image sensor and a histogram for the image information, respectively. Fig. 3 (a) and (b) are 13
It is a figure which shows the graph of a cumulative frequency distribution function at the time of using 5F size, and the relationship between image information and FIG. 4 (a) (b).
FIG. 5 is a diagram showing the relationship between the graph of cumulative frequency distribution function and image information when 110 sizes are used. FIG. 5 shows a method of classifying effective / no-effect pixel groups using the cumulative frequency distribution function. FIG. 6 is an explanatory diagram, and FIG. 6 is an explanatory diagram of a method of setting an effective image information area from within an effective pixel group.

Claims (2)

[Claims] 1. An image information detecting method for detecting image information on a color negative film, wherein a projection image composed of an original image and a peripheral image is divided into a plurality of pixels, and at least one of light intensity, transmittance, or density is obtained. That characteristic value is detected, the distribution of the detected characteristic value is obtained, and the threshold value of the characteristic value for classifying the pixel group forming the projection image into the valid / invalid pixel group is determined based on the distribution. Pixels forming the projection image are classified into valid / invalid pixel groups based on the determined threshold value, an image information detection area is determined inside the valid pixel groups, and An image characterized in that image information used for determining an exposure amount and / or an exposure correction amount for an image is obtained based on the determined image information detection area. Multi-address detection method. 2. The image information detecting method according to claim 1, wherein the distribution of the characteristic values is represented by a frequency distribution function or a cumulative frequency distribution function.