JP2987594B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image reading apparatus which projects a transparent original such as a film on a sensor and sequentially converts image information into an electric signal, and in particular, an automatic focusing apparatus which focuses on the original. Focus (A
F) An image reading device having a function.

<Prior Art> Conventionally, an image reading apparatus that converts image information of a transparent original such as a film into an electric signal has been known. Further, among these image reading apparatuses, there are also known image reading apparatuses having an AF function in order to cope with an out-of-focus state due to a warp of a film as a document or a difference in thickness of a slide mount for holding the film. .

FIG. 4 shows an example of these image reading devices. That is, the film F illuminated by the illumination optical system 2 in the apparatus main body 1 includes the reflection mirror 3, the projection lens 4, and the reflection mirror.
On the other hand, the image is projected onto the viewer 8 via 5, 6, and 7, and during the image reading operation, the optical path is switched by rotating the reflection mirror 11 from the solid line position in the figure to 45 ° indicated by the broken line, and the illumination is performed. The film F illuminated by the optical system 2 is projected onto a CCD line image sensor 15 via a reflection mirror 11, a projection lens 12, and reflection mirrors 13 and 14, and the line image sensor 15 is scanned in a direction indicated by an arrow. The image information of the film F is sequentially read.

<Problem to be Solved by the Invention> In the above-described conventional example, the film F illuminated by the illumination optical system 2 is warped during the AF operation or the actual reading operation, and the read image is out of focus. There is a problem.

Regarding the warpage of the film, as shown in FIG. 5, since the film F is composed of the base Fa and the emulsion Fb, if the film F is assumed to be a plane in FIG. As a result, the base Fa, as shown in FIG.
It has been experimentally and empirically known that the projection is warped to the side. On the other hand, the warping direction in the initial state of the film F is not constant, and there are various types such as a base Fa which is convex or a conversely a convex on the emulsion Fb side.
It has been experimentally and empirically known that the amount of warpage L in the finally stable state has little correlation with the warpage in the initial state of the film F, and is relatively stable. In other words, the film F whose initial warp direction is convex toward the emulsion side in the initial state changes to the base side by the lamp illumination, and the fluctuation of focus due to the warp is large. The change in the warp due to the lamp illumination is small, and the influence on the read image due to the change in focus is small.

Also, since the normal AF operation is performed prior to the reading operation, the state of the film warpage and the amount of warpage change between the AF operation and the reading operation, and as a result, there is a problem that the focus during the reading operation is out of focus. there were.

In order to solve these problems, it has been proposed to provide another sensor for detecting the film warpage and to issue a warning or the like based on the sensor output. Or the detection accuracy is insufficient.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems of the related art, and has as its object to provide an image reading apparatus that does not have an image focusing defect during an AF operation and during reading.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an illumination optical system for illuminating a transparent original and a projection optical system for guiding a light image from the original to a photoelectric conversion element by the illumination optical system. An image reading device for converting image information of the document into an electric signal; a focus detection unit for detecting whether the document is in focus; and refocusing based on a detection result of the focus detection unit. It has control means for controlling whether or not to perform a detection operation.

Further, it is preferable that the control unit determines the warpage of the document based on the detection result of the focus detection unit, and when the amount of warpage of the document is within a predetermined range, it is preferable to perform the focus detection operation again.

Further, the control means may determine the warpage of the document based on the detection result of the focus detecting means, and perform the focusing operation again when the warp direction of the document is a predetermined direction.

<Operation> The image reading apparatus having the above-described configuration can prevent a focus defect of a read image without providing any separate sensor by estimating the warpage of a transparent document such as a film from the detection result of the focus detection unit. it can.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows a projection lens for detecting whether the object is in focus or not.
FIG. 9 is a perspective view showing a lens driving unit that drives the lens 12 in the optical axis direction. Since the configuration other than the lens driving unit is the same as that of the conventional example shown in FIG. 4 described above, the same parts are denoted by the same reference numerals and description thereof will be omitted.

In the figure, 21 is a step motor for sliding the projection lens 12 in the optical axis direction via a lever or the like described later, 22 is a cam integrally provided on the output shaft of the step motor 21, and 23 is the step motor. A light shielding plate 24 provided integrally with the output shaft of the motor 22 is a photointerrupter.
21 initial positions (hereinafter referred to as HP) are detected. Reference numeral 25 denotes a first drive lever which comes into contact with the cam 22 and swings in the direction of the arrow in response to the rotation of the step motor 21. The first drive lever 25 comes into contact with the projection lens 12 at a projection 25a provided at one end thereof. The projection lens 12 is slid in the optical axis direction in response to the swing. Reference numeral 26 denotes a second drive lever for sliding the projection lens 4 in the optical axis direction. The second drive lever 26 is coupled to the drive lever 25 by a link 27 and swings in conjunction with the swing motion of the drive lever 25.

In the present embodiment having the above configuration, the step motor 21 is driven by the number of steps corresponding to the allowable depth of the lens from the HP position in order to detect the in-focus state. Projection lens 12
Slides in the direction of the optical axis of the lens according to the rotation angle of the step motor 21 via the cam 22 and the drive lever 25. Therefore,
The rotation angle of the step motor 21 and the position of the projection lens 12 correspond to each other, and the processing system described later can estimate the position (warpage) of the original film F based on the rotation angle of the step motor 21 determined to be in focus. It is possible.

FIG. 2 is a block diagram of a processing system for detecting the in-focus state corresponding to the lens driving unit having such a configuration.

In the figure, reference numeral 31 denotes a control unit which controls each unit, and controls the step motor 21 and the line image sensor 15 of the lens driving unit, detects the in-focus state, and the like. Reference numeral 32 denotes a drive control unit that drives the step motor 21 according to a control signal from the control unit 31, reference numeral 33 denotes a driver that drives the line image sensor 15 according to the control signal from the control unit 31, and reference numeral 34 denotes an output of the line image sensor 15. An amplification unit for amplifying, an A / D converter for sequentially performing analog / digital conversion on the output signal of the line image sensor 15 amplified by the amplifying unit, and a predetermined evaluation of an output from the A / D converter A processing unit that performs arithmetic processing based on a function. The calculation process evaluates the contrast of the image. Specifically, assuming that the evaluation function is Q and the output of the i-th pixel of the line image sensor 15 is Ai, Q = Σ (A _i −A _{i + 1} ) ² Those represented by are typical.

The evaluation function Q is calculated each time the step motor 21 is driven by a predetermined number of steps, and the position of the lens corresponding to the maximum value of the evaluation function Q is the lens position in the focused state. Since the warpage occurs at the center of the film, it is desirable to calculate using the output of the line image sensor 15 corresponding to the center of the film and an appropriate amount.

FIG. 3 shows the position of the projection lens 12 in the optical axis direction and the evaluation function Q.
FIG. 4 is a characteristic diagram showing the relationship of FIG. In the figure, it can be seen that the evaluation function Q corresponding to the lens position driven by the above-described lens driving unit changes, and the evaluation function Q takes a maximum value at a certain lens position. The lens position corresponding to the maximum value of the evaluation function Q is determined as the focal point, and the projection lens 12 is driven to this position for the actual reading operation.

The position of the lens that can take the maximum value of the evaluation function Q is convex on the emulsion side in the left area in the figure (the curve shown by a dashed line in the figure), and the base side in the right area (the curve shown by the solid line in the figure). Is convex. In view of the above-described film warpage characteristics, the control unit 31 detects the in-focus state and determines that the film F
Is determined to be convex on the emulsion side, control is performed to perform the focus detection operation again, and when it is determined that the film F is convex on the base side, an image reading operation is performed.

Further, when it is determined that the image is convex on the emulsion side and the focus detection operation is performed again to prevent a focus defect of the read image, the value is experimentally 90% or more in a normal use state and the remaining 10%. % Or less, it has been confirmed that the warp state of the film F changes over a long time thereafter. Therefore, when it is determined that the projection is convex toward the emulsion side, it can be said that the sequence of performing the focus detection operation is almost satisfied practically once.

In the above-described embodiment, the evaluation function Q for evaluating the contrast of the image and the lens position are used to determine the warping state of the film. However, the evaluation function Q and the lens for the center part and the peripheral part of the film are used. It is also possible to make a determination based on the position.

Specifically, this means sets the lens position at which the maximum value of the evaluation function Q can be obtained at the center of the film to P _C , and the lens positions at which the maximum value of the evaluation function Q can be obtained at both ends of the film to P _A and P respectively. and _B, for example when the evaluation amount is a, a = using the _{(P a + P B) /} 2-P C, it is possible to determine the warp direction of the film by the positive and negative evaluation value a.

In this case, the warp state of the film is determined from the focus state of the center part and the peripheral part of the film, so that not only the warp state of the film can be determined, but also such as a film put in a slide mount having various thicknesses. Even if the absolute position of the film is changed, the warped state of the film can be accurately determined.

<Effect of the Invention> As described above, the present invention provides a focus detection unit for detecting a focus state of a film original, a film warpage state based on a detection result of the focus detection unit, and a control unit. By controlling whether or not the focus detection operation is performed again, the image reading operation can be performed in a state where the film warpage is stable, and the film warpage state differs between the focus detection operation and the reading operation. This has the effect that blurring of the read image can be easily prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view of a lens driving unit of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a processing system of the image reading apparatus, and FIG. 3 shows a relationship between a lens position and an evaluation function. FIG. 4 is a perspective view of a conventional image reading apparatus, and FIGS. 5 (a) and 5 (b) are explanatory views showing film warpage. Reference numeral 1 denotes an apparatus main body, 2 denotes an illumination optical system, 4 denotes a projection lens (for a viewer), 12 denotes a projection lens (for reading), and 1
1,13,14 ... reflection mirror, 15 ... line image sensor, 21 ... step motor, 24 ... photo interrupter, 31 ... control unit, 32 ... drive control unit, 36 ... processing unit
F: Film (transparent original), Fa: Base, Fb: Emulsion.

Claims (3)

(57) [Claims] 1. An image reading apparatus comprising: an illumination optical system for illuminating a transparent original; and a projection optical system for guiding a light image from the original to a photoelectric conversion element by the illumination optical system, and for converting image information of the original into an electric signal. The apparatus includes a focus detection unit that detects whether the document is in focus, and a control unit that controls whether to perform the focus detection operation again based on the detection result of the focus detection unit. An image reading device characterized by the above-mentioned. And a controller for determining whether the original is warped based on a detection result of the focus detector, and performing an in-focus detection operation again when the amount of warpage of the original is within a predetermined range. The image reading device according to claim 1, wherein: 3. The apparatus according to claim 2, wherein the control means determines the warpage of the document based on the detection result of the focus detecting means, and performs the focusing operation again when the warp direction of the document is a predetermined direction. Item 2. The image reading device according to Item 1.