JP3160906B2 - Film image reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film image reading apparatus that reads an image of, for example, a 35 mm film and performs image processing.

[Conventional technology]

FIG. 5 shows an example of a conventional film image reading apparatus used for reading an image on a 35 mm film original.

In this figure, a film original 2 stored in a film mount is held by a film holder 5.
This film original 2 is illuminated by a predetermined illuminating light source 1, and the transmitted light passes through an imaging lens 3 to form a line CCD.
An image of the film original 2 is formed on the light receiving surface of the image element 4 composed of the above. The film holder 5 can be translated in a direction intersecting the optical axis by a sub-scanning feed screw 6 rotated by a step motor 7. The image formed on the image element 4 is also moved in parallel by the parallel movement of the film holder 5, and the image element 4 is arranged so that its scanning direction is orthogonal to the moving direction of the formed image. . The transfer timing of the image element 4 is controlled by the control circuit 10 operating the timing generation circuit 12.

The image element 4 and the step motor 7 are controlled by the control circuit 10. The image signal output of the image element 4 is controlled in the form of digital data via the preamplifier 8 and the A / D converter 9 together with the position information of the step motor 7. Input to the circuit 10.

Here, the control circuit 10 operates the stepping motor 7 via the stepping motor driving circuit 11 to intermittently move the film holder 5 at regular intervals, and outputs the image signal output of the image element 4 at each movement. The data is converted into digital data by the / D converter 9 and imported.

The data received by the control circuit 10 is stored in the memory 13 and output to an external device through the interface 14 when necessary, and is used as image data according to the purpose.

[Problems to be solved by the invention]

By the way, the film original from which the image is read by these devices generally has a strong curvature, so that the film original is inserted into the film mount due to a problem in mounting work on the film mount and a subsequent change in temperature and humidity. It often has a certain amount of warpage even when it is in a squat state.

In the above-described conventional film reading apparatus, since the relative positional relationship between the film original 2, the imaging lens 3, and the image element 4 on the optical axis is fixed, an optical system is required to cope with the warpage of the film original 2. In general, a method is used in which the depth of focus is set deep so that even if there is a certain amount of warpage, the image is focused within the reading area.

This method will be described with reference to FIG. In the figure, 15
Denotes a film, 16 denotes a cross section of the film mount, and 18 denotes the depth of focus.

Here, the film 15 has a warp (curved) with respect to the film moving direction 17, but shows that the entire film 15 is within the depth of focus 18, and in this state, the film 15 Every position is in focus.

However, in this method, if the film 15 has a warp exceeding the depth of focus, there is a possibility that a portion that is out of focus may be generated depending on a reading range on the film 15.
FIG. 7 shows this state. Since the warp of the film 15 is larger than the depth of focus 18, the portion indicated by 19 of the film 15 is out of focus.

Furthermore, since increasing the depth of focus corresponds to darkening the optical system, it is necessary to take measures such as extending the accumulation time in order for the image sensor to obtain a sufficient amount of light,
As a result, there is a disadvantage that the S / N of the image signal is reduced.

The present invention has been proposed in view of the above problems, and has as its object to obtain a focused image at the time of image reading regardless of the warpage of the film, and to use a bright optical system. Accordingly, it is an object of the present invention to provide a film image reading apparatus capable of obtaining good image quality.

[Means for solving the problem]

According to a first aspect of the present invention, there is provided a film image reading apparatus for performing main scanning and sub scanning, reading an image on a film original, and performing image processing, wherein an optical system for forming an image on the film original on a light receiving surface of an image element is provided. Focus adjusting means for adjusting the focal position of the optical system, and detecting means for detecting the focal point of the film original, wherein the film original is within the depth of focus of the optical system when reading an image. Control means for controlling the focus adjusting means during scanning for reading the image is provided.

According to a second aspect of the present invention, there is provided a film image reading apparatus for performing main scanning and sub scanning, reading an image of a film original, and performing image processing, wherein an optical system for forming an image on the film original on a light receiving surface of an image element is provided. A focus position detecting means for detecting a focus position of the optical system at a plurality of predetermined positions on the film document; and an approximation means for approximating a straight line or a curve based on the detected focus positions. Based on the approximation result of the approximation means, focus adjustment means for adjusting the focus so that the optical system is in focus with respect to the film original, and at the film original position moving with the main scanning Control means for controlling the focus adjustment means so as to be in a focused state.

According to a third aspect of the present invention, in the film image reading device according to the second aspect, the focus position detecting means detects a focus position at three positions on the film document.

According to a fourth aspect of the present invention, in the film image reading apparatus according to the third aspect, the three positions are substantially at both ends and substantially at the center of the reading range of the film document.

According to a fifth aspect of the present invention, in the film image reading apparatus according to the second aspect, the in-focus position detecting means detects a in-focus position by measuring a contrast.

According to a sixth aspect of the present invention, in the film image reading apparatus according to the second aspect, the control unit controls the focus adjustment unit so that the film original is always within the depth of focus of the optical system. And

[Action]

According to the first to sixth aspects of the present invention, when the image of the film original is scanned by the image element, the focal point of the film original is detected, and when the image is read, the control unit controls the focus adjusting unit. The focal position of the optical system is adjusted so that the film original is always within the depth of focus.

The control means may detect the focal point during the scanning of the image and adjust the focal position of the optical system in a timely manner, or may control the focal point at the time of image reading based on the focal point detected in advance.

〔Example〕

 Hereinafter, the present invention will be described with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment according to the first to sixth aspects of the present invention. The members denoted by the same reference numerals as those in FIG. 5 have the same functions as those of the conventional example.

In this device, the imaging lens 3 and the image element 4 are fixed at a fixed distance from each other by a connecting member 21. This is referred to as a focus adjustment block 22.

The focus adjustment block 22 has a structure that moves in the optical axis direction by the rotation of a step motor 23 controlled by the control circuit 10, and enables focus adjustment for the film original 2 (focus adjustment block 22). And step motor 23
(Not shown). Here, it is assumed that the focus adjustment by the step motor 23 is stepwise, and the amount of movement in one step is smaller than the focal depth of the optical system including the imaging lens 3 and the like.

Next, an example of means for detecting the focal point of the film document 2 will be described.

In this embodiment, a method is adopted in which the output contrast of each pixel corresponding to each position on the film original 2 is in the maximum state and the in-focus state is set at that position.

That is, in this embodiment, at an arbitrary film position, the focus adjustment block 22 is moved step by step, and the in-focus state is detected by measuring the contrast at each step. As means for measuring the contrast, the image element 4
Is used for a certain number of pixels of the CCD that constitutes the above, to obtain the sum of the differences between the outputs of adjacent pixels and the adjacent pixels.

Therefore, in the present embodiment, the contrast is measured for each reading area (one scan line) on the film original 2 as described above in accordance with the flowchart shown in FIG. The focal point can be set depending on the position.

Here, a simple approximation method is employed in this embodiment as a means for detecting the focal point position information corresponding to each position on the film document 2, and this will be described with reference to FIGS. 3 and 4. .

FIG. 3 is a schematic sectional view of the film original 2 and shows that the film 15 is warped with respect to the film moving direction 17. The points a and c on the film 15 indicate both ends of the range in which the image is read.
Point b is an intermediate point between them.

FIG. 4 is a flowchart showing an example of a focus detection operation at each position on the film original 2 in the apparatus having the configuration shown in FIG.

In this embodiment, before starting to read an image on the film original 2, points a and b on the film original 2 in FIG.
At each of the points c and c, the focal point is detected by the algorithm shown in FIG. Here, the detected focal points are stored as f (a), f (b), and f (c) in the memory 13, the control circuit 10, or other arithmetic circuits.

Then, from the obtained f (a), f (b), and f (c), the focal point at each position on the film original 2 is calculated.

That is, since it can be generally assumed that the film original 2 is uniformly along the entire surface, the points a and b and the point b
By approximating each of the points c and c as a straight line, the focal point (or the approximate position of the focal point) at each position therebetween can be easily calculated.

Here, since the film manuscript 2 has a gently curved warp, a slight error occurs when the approximate straight line is used as described above. However, if the focal depth of the optical system is set deeper than the expected error, This error has no effect on focusing. Needless to say, the depth of focus set here is extremely smaller than the conventional depth of focus for covering the entire film.

Next, in the case of performing image reading scanning, when the film original 2 is moved for each scanning line, the focus adjustment block 22 is operated so as to be at the in-focus position at the original position obtained by the above method. .

Until reading is completed, the focus adjustment is repeated each time the film document 2 moves, so that the in-focus state is always maintained at each position of the image film document.

In the present embodiment, the focus is first measured at three points of the document position, and then the focus between the points is complemented by linear approximation to simplify the detection of the focus. However, the present invention is not limited to this. Absent.

For example, a method of measuring the focal point at three or more points to complement more accurately and a method of complementing using a curve instead of a straight line (for example, a pseudo curve better matched to the warpage of the film original 2) may be used. Even if a complementary method is used, the gist of the present invention is not deviated. In addition, instead of approximation using these straight lines and curves, the in-focus state of each line on the film original 2 is stored. The image may be read by adjusting the adjustment block 22.

On the other hand, in this embodiment, the method of using the contrast of the video output is used to detect the focal point. However, another method may be adopted. For example, by providing a unique optical means or the like for focus detection and detecting by a method such as a phase difference detection method, a simple actual measurement method, a curved state of the film 15 using a physical measurement sensor, and the like. The in-focus state or the like resulting therefrom may be measured.

Further, the focus adjusting mechanism of the present embodiment adopts a method of fixing the relative positional relationship between the optical system 3 and the image element 4 and simultaneously moving the optical system 3 and the image element 4 to adjust the focal position of the optical system. There is an advantage that the magnification is kept constant without change. However, focus adjustment is not limited to this method,
Other methods may be adopted.

In addition, the present invention does not deal only with the warpage of the film 15; for example, the thickness (especially, the thickness) of the film mount on which the film original 2 is placed varies due to unevenness and non-uniformity, and furthermore, the difference of the manufacturer. Thus, there is an advantage that it is possible to cope with a case where the focal position changes when a different film document 2 is used.

〔The invention's effect〕

As described above, according to the first to sixth aspects of the present invention, in a film image reading apparatus, even when a target film is deformed, an image which is always in focus at each film original position during image reading is obtained. Is obtained.

Furthermore, unlike the conventional case, it is not necessary to increase the depth of focus, and it is possible to eliminate the adverse effect on image quality caused by darkening the optical system and increasing the accumulation time, and conversely, reducing the depth of focus compared to the conventional case. This makes it possible to easily obtain a clearer and brighter image.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment according to claims 1 to 6 of the present invention. FIG. 2 is a flowchart for detecting the focal point of the film in the film image reading apparatus of FIG. FIG. 3 is an explanatory diagram showing the relationship between the image reading position and the in-focus position in the film image reading device of FIG. FIG. 4 is a flow chart showing the operation of an example of the focus detection means in the film image reading apparatus of FIG. FIG. 5 is an explanatory view showing an example of a conventional film image reading apparatus. 6 and 7 are schematic sectional views showing an example of a warped state of the film original. [Description of Signs of Main Parts] 1 ... irradiation light source, 2 ... film original, 3 ... imaging lens (optical system), 4 ... image element, 7 ... step motor, 10 ... control circuit (control) Means), 11 ... Step motor drive circuit for moving original, 12 ... Timing generation circuit for image element, 15 ... Film, 20 ... Step motor drive circuit for focus adjustment, 23 ... Step motor (focus adjustment means) .

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G03B 13/36 H04N 1/00 H04N 1/19

Claims (6)

(57) [Claims] 1. A film image reading device for performing main scanning and sub scanning to read an image of a film document and perform image processing, wherein: an optical system for forming an image on the film document on a light receiving surface of an image element; Focus adjusting means for adjusting a focal position of an optical system; and detecting means for detecting a focal point of the film original, wherein the focus adjustment is performed so that the film original is within the focal depth of the optical system when reading an image. A film image reading apparatus, further comprising control means for controlling the means during sub-scanning of image reading. 2. A film image reading device for performing main scanning and sub scanning to read an image of a film document and perform image processing, comprising: an optical system for forming an image on the film document on a light receiving surface of an image element; Focusing position detecting means for detecting a focusing position of the optical system at a plurality of predetermined positions of a film document, and approximating means for approximating as a straight line or a curve based on the detected plurality of focusing positions, Focus adjusting means for adjusting the focus so that the optical system is in focus with respect to the film document based on the approximation result of the approximating means; and focusing at the film document position moving with the main scanning Control means for controlling the focus adjustment means so as to be in a state. 3. The film image reading device according to claim 2, wherein said focus position detecting means detects a focus position at three positions on said film document. 4. The film image reading apparatus according to claim 3, wherein the three positions are substantially both ends and a center of a reading range of the film document. 5. The film image reading apparatus according to claim 2, wherein said focus position detecting means detects a focus position by measuring a contrast. 6. A film image reading apparatus according to claim 2, wherein said control means controls said focus adjusting means such that said film original is always within the depth of focus of said optical system. Film image reader.