JPH02276364A - Image reader - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that scans a transparent original such as a photographic film to read an image, and particularly relates to an automatic focus adjustment technique for this image reading device.

[Prior Art] Conventionally, this type of apparatus for reading transparent originals such as 35 mm photographic film did not have an autofocus (CAF) mechanism for automatically adjusting focus.

However, reversal film (positive film) is generally stored one sheet at a time in a mount, but since the thickness of the mount is not constant, if you try to handle the film while it is mounted, it will not work in the optical axis direction of the film surface. Since the position of the subject varies within a range of several 111, manual focus adjustment is required each time if an attempt is made to read an image without blur.

Furthermore, since both mounted and unmounted films tend to curve under normal conditions, it is difficult to maintain a constant position of the film surface.

For this reason, in the past, the film was generally pasted on the glass surface or sandwiched between two pieces of glass to ensure that the film surfaces were always aligned and to prevent the film from curving. It was.

[Problems to be Solved by the Invention] However, conventional flatbed type film scanners that use solid-state imaging devices such as CC (charge-coupled devices) as imaging means have the following problems. there were.

In other words, as mentioned above, when the film is sandwiched between glasses to position the film surface and prevent the film from curving, there is no need to take out the mounted film from the mount and attach it to the glass. There are disadvantages such as requiring laborious work, creating Newton's rings when the film is sandwiched between glass, and making it easier for dust to adhere.

Furthermore, since the thickness of the above-mentioned mount is not constant, if you try to handle the film while it is mounted, the position of the film surface in the optical axis direction will vary within a range of several millimeters, so devices without an autofocus mechanism will produce blurred images. was supposed to be read.

In addition, it is cumbersome and time-consuming for humans to manually adjust the focus for each mount, and it is difficult to achieve accurate focusing.

On the other hand, due to various aberrations such as field curvature, astigmatism, and chromatic aberration of the imaging lens, the focal position for each point on the top surface of the film varies, for example, R (red), G (green), B (
The focal position of the color-separated image of the three colors (blue) was shifted, and the optimal focal position could not be determined.

Therefore, it came to mind that the autofocus (automatic focus adjustment) technology used in cameras or microscopes could be used in the image reading device for this transparent manuscript, but various types of autofocus technology have been proposed. .

Among these, an autofocus method that is particularly effective for image reading devices for transparent originals is one in which a CCD sensor (solid-state image sensor) for image reading is also used as a sensor for detecting the focal point of autofocus. There is an autofocus method that detects the in-focus position based on the contrast amount of the input image signal from the sensor. This method is described in, for example, NHK Technical Research Vol.
This is disclosed in Publication No. 6, etc.

In addition, as a control method for controlling the position of the lens system when detecting the focal point position, for example, as disclosed in Japanese Patent Publication No. 58-58868, the contrast evaluation amount is always maximized. A device that controls the lens system using a servo circuit. For example, as disclosed in Japanese Patent Publication No. 60-39203, the lens system is moved once over the entire area, the contrast evaluation amount is calculated, and the contrast evaluation that is the maximum value is performed. The contrast evaluation amount is memorized, and the contrast evaluation amount is calculated again when the lens system moves backward, and when the contrast evaluation amount becomes equal to the maximum value of the contrast evaluation amount calculated and memorized during the previous forward movement, the lens system There are things that control the system to stop.

However, with these control methods, all movement of the lens system is controlled while constantly obtaining the contrast evaluation amount, which requires a lot of calculation processing time and does not allow high-speed automatic focusing (autofocus). For devices such as film reading devices where the position of the copy object is limited to some extent, this results in unnecessary detection control.
Work efficiency was getting worse.

Furthermore, when a film holder normally holds a positive film in a slide mount and a negative film in a sleeve, the positive film and negative film are set at different positions, so both are commonly included. The focus detection range naturally becomes wider, and therefore, with conventional devices, it takes time to detect the position of the focus point, resulting in poor work efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus that solves the above-mentioned problems, detects the position of a focused point in a short time and without waste, and improves the efficiency of automatic focus adjustment work.

[Means for Solving the Problems] In order to achieve the above object, a first aspect of the present invention includes an imaging lens that projects and forms an image of a document, and a photoelectric converter that converts the image formed by the imaging lens into an electrical signal. An image sensor to be converted, an analog-to-digital converter to convert an output signal of the image sensor to a digital signal, and an arithmetic means to calculate a contrast evaluation amount P using a predetermined contrast evaluation amount calculation formula based on the output signal of the analog-to-digital conversion means. and a focused point detection means for detecting the focused point position of the imaging lens at which the maximum value of the contrast evaluation amount P calculated by the arithmetic means is obtained; The focus adjustment means moves along the optical axis, and while the focus adjustment means moves the imaging lens along the optical axis from the starting end to the ending end, when the calculating means calculates the contrast evaluation amount P, the starting point is the in-focus point detection range. The present invention is characterized by comprising a setting means for setting the value of the end and the end.

Further, the second aspect of the present invention is characterized in that the setting means sets the values of the starting end and the ending end in accordance with a detection signal from a detection means for detecting the type of film holder in which the document is stored.

Further, a third aspect of the present invention is characterized in that the setting means sets or changes the values of the starting end and the ending end in response to key input from the input means.

Further, a fourth aspect of the present invention is characterized in that the setting means changes the settings of the starting end and ending end values based on a change in the value of the contrast evaluation amount P calculated by the calculating means.

Furthermore, in a fifth aspect of the present invention, the calculation means calculates the contrast evaluation amount (where P is the contrast evaluation amount, K is a normalization constant, a, b, and j are constants, and Xi is the i-th The digital value of the th pixel, xl-1 is the digital value of the i-1th pixel).

[Function] With the above configuration, the present invention allows the starting end and the ending end of the lens to be arbitrarily set within the optimum minimum range when determining the in-focus point P, thereby eliminating unnecessary in-focus degree detection. This eliminates the need for additional processing, allowing the in-focus point detection processing to be executed in a short time and without failure, resulting in improved work efficiency.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the basic configuration of an embodiment of the present invention. In FIG. 1, A is an imaging lens that projects and forms an image of a document.

B is an imaging element that photoelectrically converts the image formed by the imaging lens A into an electrical signal. C is an analog-to-digital conversion means for converting the output signal of the image sensor B into a digital signal. D is a calculation means for calculating the contrast evaluation amount P based on the output signal of the analog-to-digital conversion means C using a predetermined contrast evaluation amount calculation formula. Reference numeral E denotes a focal point detection means for detecting the focal point position of the imaging lens A at which the contrast evaluation amount P calculated by the calculation means is the maximum value. F is a focus adjustment means for moving the imaging lens A along the optical axis to the focus position detected by the focus detection means E.

G is the in-focus point detection range between the starting end and the ending point when the imaging lens A is moved from the starting end to the ending end along the optical axis by the focusing means F and the contrast evaluation amount P is calculated by the calculation means. This is a setting means for setting values.

Further, the setting means G sets the values of the starting end and the ending end in accordance with the detection signal of the detecting means H, which detects, for example, the type of film holder in which the document is stored.

Further, the setting means G sets or changes the values of the starting end and the ending end in response to a key input from the input means (2), for example.

Further, the setting means G changes the settings of the values of the starting end and the ending end, based on the change in the value of the contrast evaluation amount P calculated by the calculation means, for example.

Furthermore, the calculation means is as follows: - As an example, the contrast evaluation amount calculation formula is as follows: (where P is the contrast evaluation amount, K is the normalization constant, a
, b, j are constants, xl is the digital value of the i-th pixel,
x, -1 is the digital value of the i-1th pixel) The following formula is used.

FIG. 2 shows a specific circuit configuration of an embodiment of the present invention.

In this figure, 3001 is a light source (lamp) for illuminating a transparent original, 3002 is a heat ray absorption filter that removes heat rays from the light rays from the light source 3001, and 3003 is a filter 30.
This is an illumination optical system that converts the illumination light that passes through 02 into a parallel light beam. 3004 is a sub-scanning drive table that moves the transparent original in the sub-scanning direction; 3005 is a rotating table that rotates the transparent original; 3006
3007 is a film holder for storing transparent originals, 35
It is a transparent original such as mm photographic film. 3008 is a movable mirror that switches the optical path of the light beam (original image) transmitted through the transparent original 3007, 3009 is a mirror that deflects the optical path of the original image, and 301O is an imaging lens that forms the original image that has passed through the mirror 3009.

3011 is a projection lens for projecting the original image reflected by the movable mirror 3008; 3012 is a mirror that deflects the optical path; 3013 is a mirror that deflects the same optical path; 3014
is a screen serving as a monitor on which the original image that has passed through the mirror 3013 is projected. 3015 is the screen 3014
3016 is the screen 3
This is a touch panel for inputting the trimming area integrated with 014.

3017 is a lamp holding member that supports the light source 3001. 3018, 3019, and 3020 are CCD positioning mechanisms, 3021 are three-color separation prisms that separate the transparent original image formed by the imaging lens 301O into three colors of R, G, and B, and 3022, 3023, and 3024 are prisms. This is a CCD line sensor using an ELL:D (charge coupled device) array that photoelectrically converts a document image of each color separated by 3021, and this CCD line sensor is connected to a corresponding CCD alignment mechanism 30L8.3019.302.
0 allows fine adjustment of the reading position.

3025 is CCD line sensor 3022.3023.3
3026 is an adjustment signal generation source that generates a standard signal for adjustment to the analog circuit 3025; 3027 is an analog circuit section 3025;
3028 is a shading correction circuit that performs shading correction on the output signal of the dark correction circuit 3027; 3029 is the output signal of the shading correction circuit 3028; A pixel shift correction circuit 3030 corrects pixel shift in the main scanning direction, and a pixel shift correction circuit 3030 converts the R, G, and B signals that have passed through the pixel shift correction circuit 3029 into Y (yellow), M (magenta), This is a color conversion circuit that converts into C (cyan) color signals. Further, 3031 is a lookup table (LIT) that performs LOG conversion and γ conversion of the signal.

3032 is a minimum value detection circuit that detects the minimum value of the output signal of the lookup table 3031; 3033 is a lookup table (3033) that obtains a control amount for under color removal (OCR) according to the detected value of the minimum value detection circuit 3032; LtlT)
, 3034 is a masking circuit that performs masking processing on the output signal of the lookup table 3031;
35 is an IIcR circuit (undercolor removal circuit) that performs undercolor removal processing on the output signal of the masking circuit 3034 based on the output value of the lookup table 3033.
Reference numeral 6 denotes a density conversion circuit that converts the recording density to a designated density for the output signal of the tlcR circuit 3035, and 3037 represents a scaling processing circuit that converts the output signal of the density conversion circuit 3036 to a designated scaling factor.

3038 is an interface circuit (1/F) that transmits signals between a printer or input/output terminal (not shown) and this device.
, 3039 is a controller that controls the entire device, and inside the controller 3039 there is a CPU (central processing unit) such as a microcomputer, and processing procedures as shown in FIGS. 3 and 9 are stored in program form. ROM (read-on memory), RAM (random access memory) used for data storage and work area, etc.

3040 is a peak detection circuit that detects the peak value of the output value inputted from the scaling processing circuit 3037 through the interface circuit 3038 and the controller 3039; 3041 is an operation unit that issues instructions to the controller 3039; 3042
is a display unit that displays the control status of the controller 3039 and the like.

3043 is a lens aperture control unit that controls the aperture of the imaging lens 301O, 3044 is a lens distance ring control unit that adjusts the focus of the imaging lens 3010, and 3045 is a mirror drive unit that drives the movable mirror 3008. 3046
3047 is a trimming frame control unit that controls the trimming frame display 3015 and a touch panel control unit that controls the touch panel 3016. 3048 is rotating table 3005
3049 is a sub-scanning control unit 3050 that controls scanning of the sub-scanning drive table 3004;
3051 is a lamp position drive source that adjusts the position of the light source 3001 via the lamp holding member 3017.

3052 is a timing generator that generates a timing signal (clock) based on the control of the controller 3039; 3053 is a bus that connects each of the above-mentioned control units and processing circuits with the controller 3039; 3054 is a data line for the output device; 3055 is an output Synchronization signal line for equipment,
and 305[1 is a communication line.

Next, the operation of each part will be explained.

The light source 3001 is a light source such as a halogen lamp, and the light emitted from the light source 3001 is passed through a heat absorption filter 30.
02 and an illumination optical system 3003 to illuminate a transparent original such as a 35 mm photographic film placed on a film holder 3006. The image of the transparent original is captured by a movable mirror 3008
By switching the optical path, ■ passing through the projection lens 3011 and mirrors 3012 and 3013 onto the screen 3014, or ■ passing through the mirror 3009, the imaging lens 3010, and the three-color separation prism 3021 onto the CCD line sensor 30.
22 to 3024.

In the case of the above-mentioned mode (■), the CCD line sensors 3022 to 3024 are connected to the timing generator 3052.
The output signals of each CCD line sensor are input to an analog circuit 3025. The CCO positioning mechanisms 3018-3020 are for registering each CCD line sensor 3022-3024 with respect to the three-color separation prism 3021, and need to be adjusted at least once. The analog circuit 3025 is composed of an amplifier and a ^10 converter, and converts the signal amplified by the amplifier to the ^/D converter in synchronization with the timing clock for ^/D conversion output from the timing generator 3052. /D conversion.

Next, RlG, B output from the analog circuit 3025
A dark processing circuit 3027 applies dark signal level correction to each digital signal, a shading correction circuit 3028 performs shading correction in the main scanning direction, and a pixel deviation correction circuit 3029 corrects pixel deviation in the main scanning direction. , for example, by shifting the write timing of a FIFO (first-in, first-out) buffer.

Next, in the color conversion circuit 3030, the color separation optical system 3021
R, G, etc., depending on the output device.

Convert B signal to Y, M, C color signals, Y.

It is converted into I and Q color signals. In the next lookup table 3031, the luminance linear signal is converted to LOG or arbitrary γ by referring to the table.

Reference numerals 3032 to 3037 constitute image processing circuits for outputting images in four colors, Y, M, C, and BK (black), which are mainly used in printers such as color laser copying machines. Here, the minimum value detection circuit 3032, masking circuit 3034, lookup table 3033, and υC
The combination of the R circuit 3035 performs printer masking and OCR (undercolor removal).

Next, the density conversion circuit 3036 performs table conversion of each density signal, and the scaling processing circuit 3037 roughly performs scaling processing in the main scanning direction.
Signals M', C', and B are sent to the printer of the output device via the interface circuit 3038.

The interface circuit 3038 includes a data line 3054 and a synchronization signal line 3055 for the output device, for example, R52.
A control command communication line such as 32C is connected.
It is also possible to communicate with a general computer (for example, a personal computer) via a communication line 3056.

On the other hand, the lamp position driving source 3051 is the lamp 305 as a light source.
This is for adjusting the lamp position when converting 1, and the lamp 3001 is positioned manually or automatically in accordance with key input operations on the operation unit 3041. Lamp light amount control section 3050 and lens aperture control section 3043
adjusts the amount of light received by the image projected onto the CCD line sensors 3022-3024. In addition, the mirror drive unit 304
5 controls the movable mirror 3008 to move the transparent original 3007
Optical path conversion is performed to switch between guiding the image to the screen 3014 or to the CCD line sensors 3022 to 3024.

In the case of mode (2) in which an image of the transparent original 3007 is projected onto the screen 3014, a trimming frame display controller 3046 displays a trimming area in order to instruct trimming of the image displayed on the screen 3014. 3015, and a touch panel control unit 3047 controls a touch panel 301B for inputting a trimming area.

In addition, the lens distance ring control unit 3o44 controls the imaging lens 3
Controlling the distance ring of 01O, the CCD line sensor 30
The images projected onto 22 to 3024 and the screen 3o14 are focused. The adjustment signal generation source 3o26 generates a signal to be input as a standard signal when adjusting the analog circuit 3025.

Next, the overall control operation of this apparatus will be explained with reference to the flowchart in FIG.

Note that the control procedure in this flowchart is based on the controller 3.
039 is stored in the internal ROM.

Preparation operation: When a power switch (not shown) is turned on, the controller 3039 initializes each part (step S1) and enters a state of waiting for a command input from an external device or from the operation unit 3041 via the interface circuit 3038. In this state, when the film holder 3006 with the transparent original 3007 mounted thereon is set on the rotating table 3005, the light source 3001 illuminates the heat ray absorption filter 300.
02, an illumination optical system 300 including a condenser lens, etc.
The image of the transparent original illuminated through the movable mirror 30
08 and projection lens 3011 and mirror 3012.30
13 and projected onto a screen 3014.

Transmission thickness 8% 3007 has images in vertical and horizontal orientations, but when the image is rotated and projected, it can be transmitted from an external device via the interface circuit 3038 or from the operation unit 3041 to the controller 3039. When the rotation of the image is instructed (step S2), the controller 30
39 is a rotary table rotation control unit 3048 via a bus 3053
A rotation control command is sent to the rotating table 3005 to rotate the rotating table 3005 (step S3). At this time, since the film holder 3006 is fixed to the rotating table 3005, it rotates together with the rotating table 3005. In this way, when the transmission thickness g43007 is rotated, the image projected onto the screen 3014 is also rotated.

Next, if you want to trim the image, use the operation section 3041.
or from an external device via the interface circuit 3038 (step S4), the controller 3039 sends a trimming information input command to the touch panel control unit 3047, and the touch panel control unit 3034 inputs the trimming information to the touch panel control unit 3034. The trimming information input from 3016 is taken into the controller 3039 via the bus 3053, and the controller 3039 sends trimming frame control information created based on the imported trimming information to the trimming frame display control unit 3046 via the bus 3053. Then, the trimming area is displayed (step S5).

Next, from the operation unit 3041 or the interface circuit 3
When the external device instructs the controller 3039 to start image reading via 038, image reading starts.
The following procedure is followed (step 56).

Optical path switching: ``First, the controller 3039 outputs a drive control signal to the mirror drive unit 3045 to move the movable mirror 3008, so that the image with a transmission thickness of 1f43007 is focused.

Each CCD line sensor 3022 is
The optical path is switched so that the optical path is guided above ~3024 (step S7).

Dark correction signal set secondary, dark correction circuit 3027
In order to set the dark correction information to
039, the lamp light amount control circuit 3050 is controlled to turn off the lamp, or the sub-scanning control unit 304
9 to move the sub-scanning drive stand 3004 to a light shielding position where each CCO line sensor 3022 to 3024 is shielded from light (before step S8). Next, the dark correction circuit 3027 is controlled by the controller 3039, and the dark correction circuit 3027 is controlled based on the signal that is converted into a digital signal and outputted via the analog circuit 3025.
A dark correction signal is set up (after step S8).

AE (automatic exposure adjustment): Next, controller 3039
controls the lamp light amount control circuit 305o to
001, dark correction circuit 3o27, shading correction circuit 3028, pixel shift correction circuit 3o29, color conversion circuit 3030, look-up tape, 3o31,
The masking circuit 3034, OCR circuit 3o35, density conversion circuit 3036, and variable magnification processing circuit 3037 are all through (
In step S9), the controller 3o39 is controlled via the interface circuit 3038 while performing sub-scanning at high speed.
The peak detection circuit 30
40 is used to detect peaks (step 510).

Then, the brightness of the light source 3001 is changed by controlling the lamp light amount control circuit 3050 so that the detected peak value approaches a certain level (step 5ll), or
Alternatively, the amount of light to the CCD line sensors 3022 to 3024 is adjusted by controlling the lens aperture control unit 3o43 and changing the aperture of the first most image lens 301O (step 512).

AE (autofocus) secondary, dark correction circuit 30
The signal subjected to dark correction by 27 is input to the controller 3039 via the interface circuit 3038 with the subsequent processing circuit set to through mode, and the lens distance ring control unit 304 uses the information of the input signal.
4 to focus the imaging lens 301O (
Step 513).

Shading correction data set: Subsequently, each CCD line sensor 3022-3024 is 100
Step 514) of moving the sub-scanning drive stand 3o04 to the exposure position where % exposure is to be performed, the lamp light amount control circuit 3050 adjusts the lamp light amount to an appropriate brightness, and the dark correction circuit 30
While inputting the dark-corrected signal in step 27, shading correction data is set in the shading correction circuit 3028 (step 515).

Selection: Next, a pixel shift correction amount is set in the pixel shift correction circuit 3029 (step 516). In addition, the color conversion circuit 3
Select a color conversion type for 030, select a lookup table type for lookup tables 3031 and 3033, select a masking type for masking circuit 3034, and select tlcR for uCR circuit 3035.
, the type of density conversion is selected for the density conversion circuit 303B, and the type of scaling and sharpness is selected for the scaling processing circuit 3037 (step 517). Furthermore, the lamp light intensity is controlled to be optimal via the lamp light intensity control circuit 3050, and the sub-scanning speed and trimming information are sent to the sub-scanning control unit 3049 to move the transparent original 3007 to the sub-scanning start position and put it on standby. (Step 518)
.

Data output A: In an operation based on a read start command from the operation unit 3041 (step 519), a start command is issued to an output device (not shown) via the interface circuit 3038 (step 520), based on a synchronization signal from the output device. Sub-scanning is started (step 522), and the image is captured while being synchronized with the output device, and the processed image data is output via the interface circuit 3038 (step 523).

Data output B: In the reading operation based on the reading start command via the interface circuit 3038 (step 519
), reports the completion of preparation to the output device (not shown) via the interface circuit 3038 (step 521), starts sub-scanning based on the synchronization signal from the output device (step 522), captures images while being synchronized with the output device Then, the processed image data is output via the interface circuit 3038 (step 523).

(Hereafter, extra white) FIG. 4 shows another circuit configuration of the embodiment of the present invention.

In this figure, 3059 is the pixel shift correction circuit 3 of FIG.
029 is a corresponding buffer memory, 3060 is the entire image sensor, 3061 is a CCD line sensor with an R color separation filter, and 3062 is a CCD line sensor with a G color separation filter.
CD line sensor 3063 is a CCD line sensor having a B color separation filter. Also, 3064 is CC
CCD positioning mechanism for positioning D line sensors 3061 to 3063; 3065 to 3067 are CCDs;
This is a drive signal output from the timing generator 3052 to drive each of the line sensors 3061 to 3063. The rest of the structure is the same as that of the previous embodiment shown in FIG.

The image sensor 3060 is a 3-line line sensor 3061~
3063, each line sensor 3061 to 30
63 are independently driven by drive signals 3065 to 3067 output from the timing generator 3052. Furthermore, each of the line sensors 3061 to 3063 is capable of capturing R, G, and B color-separated images using respective on-chip color filters.

The buffer memory 3059 stores each line sensor 3061 to 3.
This is a delay memory for correcting positional deviation in the sub-scanning direction in 063, and is configured using several FIFO memories, for example. The amount of delay for each color is set in advance by the controller 3039 according to the sub-scanning speed.

FIG. 5 shows the configuration of a control system for performing automatic focus adjustment in the embodiment of FIG. 4. In this figure, 3069 is a distance ring attached to the outer periphery of the imaging lens 301O, 3070 is a deceleration mechanism that meshes with the distance ring 3069, and 3071 is a motor that rotates the distance ring 3069 via the deceleration mechanism 3070. 3073 is an image processing section, which includes the dark correction circuit 3027 to the conversion processing circuit 3037 shown in FIG. In addition, Xp is the position of point P° on the film 3001 in the optical axis direction, and Xq is the imaging position (optical axis direction) of the image (Qo) of point P°.
It is.

Sarani Q" drives the motor 3071 via the range ring control unit 3044 with the controller 3039, and moves the range ring 3069 via the deceleration device 3070, thereby changing the focal position of the imaging lens 3010 at point P. This shows the imaging position in °.

Further, 3081 is a detection means for detecting the type of film holder 3006 that accommodates the transparent original 3007.

As this detection means 3081, the film holder 30
A photointerrupter or the like is used to detect a cut groove, protrusion, or through hole formed in advance at a predetermined position of 06 corresponding to the above type.

Note that, except for the image sensor 3060, the configuration of automatic focus adjustment in the embodiment shown in FIG. 2 is also the same as that in FIG. 5.

FIG. 6 shows a specific example of the image reference area for automatic focus adjustment in the embodiment of the present invention. In this figure, 310
0 is an image area of the transparent original 3007, and 3101 is an image reference area for AF (automatic focus adjustment) that is referred to when performing automatic focus adjustment. 3100° is an image area obtained by rotating the orientation of the transparent original 3007 by 90°.

As shown in FIG. 7, when the image area 3100 of the subject document is trimmed and scanned with the trimming area 3120 surrounded by two points P+ and P2, the effective image is within the trimming area. It is most desirable to perform automatic focus control (AF) within the trimming region 312θ. By doing this, even if the transparent original 3007, such as a photographic film, is tilted or warped with respect to the optical axis, it is possible to focus on the required image area with high accuracy.

Note that the 3-line sensor 3 as shown in FIGS. 4 and 5
061 to 30113 to find the focal position of each color, the CCO alignment mechanism 3064 is used to align both image reference areas 3101 (or 3101') for AF of each color on the film surface of the image area 3100 of the original. The line sensors 3061 to 3063 are moved in the sub-scanning direction.

Next, an automatic focus detection mechanism according to an embodiment of the present invention using the contrast evaluation amount disclosed in US Pat. No. 3,364,815 will be described.

The contrast evaluation amount P described above is given by the following equation (1).

P=Σ (X'-Xj-+)'
(1) J*a (where Xj is the output level of the j-th pixel in the main scanning direction,
a and b are the numbers of the second pixel from the beginning and the last pixel in the AF image reference area 3101 in the main scanning direction.

FIG. 8 shows the distance 1 [ji3069
is moved by the lens distance ring control unit 3044, thereby changing the lens aperture amount ΔX of the lens 3010 and changing the focal position. It is something that Here, the degree of focus P is calculated using the above equation (1).

In this way, the degree of focus P obtained is maximum P. The lens extension position Δ×. is the focal point position.

In the embodiment of the present invention, before calculating the contrast evaluation mP described above, the imaging lens 301 is
The starting end (movement start position) and end (movement end position) of 0 are determined, for example, as follows.

(2) The above-mentioned starting end and ending end are determined in response to a detection signal from a detection means 3081 that detects the type of film holder 3006.

(2) If it is desired to change the starting end and ending end, press a specific key on the touch panel 3016 or the operation unit 3041 to change the starting end and ending end values.

In the embodiment of the present invention, when determining the in-focus point P, the degree of focus P is determined by the microcomputer of the controller 3039 according to the control procedure shown in the flowchart of FIG.
The maximum value P of the degree of focus P. Shouting lens extension amount Δx
0 and detect the in-focus position.

The degree of focus P used in the embodiments of the present invention is given by the following equation (2).

(However, stone is averaged data, and K is a normalization constant.) Note that the square value in the above equation (2) may be an integer power such as the third power.

Next, the operation of the control system shown in FIG. 5 will be explained with reference to the flowchart shown in FIG.

Note that the control procedure in this flowchart is based on the controller 3.
039 is stored in the internal ROM.

First, in step S31, the process of stage control (2) is executed. In this stage control (2), the stage (
Performs control to move the sub-scanning drive stand) 3004.

Next, in step S33, the process of lamp control (2) is executed. In this lamp control, at reference voltage L0, lamp 3
The voltage of the lamp 3001 is controlled by the controller 3039 via the lamp light amount control circuit 3050 so as to turn on the lamp 0θ1.

Next, in step S34, the process of reading the detection signal from the film holder detection means 3081 is executed. In this reading, the film holder detection means 3081
The detection signal from the camera is read, and based on the detection signal, it is determined whether the film holder 3006 is, for example, a sleeve film holder or a slide film holder.

Next, in step 535, the process (2) of determining the starting end and ending end of the imaging lens 301O is executed. In this decision ■, the film holder 3 is
When it is determined that the type 006 is a sleeve film holder, the position data of the starting end and the ending end of the imaging lens 301O are determined as follows: starting end=As, ending end=BS. Furthermore, when the type of film holder 3006 is identified as a slide mount film holder, the position data of the starting end and ending end of the imaging lens 3010 are determined to be starting end=^2 and ending end=[lv, respectively. . In addition, these data 8.

The values of B,, A,, B, are set in advance by controller 3.
039 is stored in the internal ROM or RAM.

Next, in step 53B, the values of the starting end and ending end of the imaging lens are displayed on the display screen of the display unit 3042 at the first O.
Display as shown in the figure and wait for 5 to be input to the key described later.

At this time, the user is determined by the controller 3039,
If the user wishes to modify the starting and ending values displayed on the display section 3042, the user presses 4 on the key Kl~ shown in FIG.
37), change the starting and ending values above.

To explain the operation method for this change, in Fig. 10,
When the user wants to increase the value of the starting end ^5, he presses the key 1 up to the number of times corresponding to the increment, and when he wants to decrease the value, he presses the key 2 in the same way. On the other hand, if the user wants to increase the value of the terminal B5, he presses the 3 key, and if he wants to decrease the value, he presses the 4 key. In this way, when the modification of the values of the starting end ^8 and the ending end O5 is completed, the user presses the 5 key to notify the controller 3039 that the modification has been completed.
tell.

In addition, if the user does not want to change the numerical value, press 1 on the key.
．． 2. K3. Press only 5 on the key without pressing K4. In response to the input of 5 to the key (step 536), the controller 303S proceeds to the next step 538.

In step 538, lens control processing (2) is executed. In this lens control ■, the lens distance ring control section 30
44, the lens distance ring 3069 is controlled to be moved to the above-mentioned starting end position.

Next, in step S39, lens control processing (2) is executed. In this lens control ■, the lens distance l! ! The lens distance ring 3069 is adjusted by a certain amount Δ via the ring control unit 3044.
Perform control to move only L.

Next, in step 540, the arithmetic processing of the above equation (2) is performed using the averaged data of the pixel signals from the image processing section 3073. When this calculation is completed, the calculation result is stored in the internal memory (RAM) of the controller 3039.

Next, in step 541, the lens distance ring 3069
It is determined whether or not the end point has reached the above-mentioned end position, and if it has not reached the above-mentioned end position yet, the above-mentioned step S39. After repeating the process in step 540, if it is determined that the terminal position has been reached, the arithmetic process is finished and the next step S
Move to 42.

In step S42, the maximum value P0 of the degree of focus P and the lens extension amount ΔXo corresponding to the maximum value P0 are detected. That is, in this process, the lens extension amount Δx0 that provides the maximum value P0 of the degree of focus P is detected from the calculation result obtained in step 54G described above.

Next, in step S43, lens control processing (2) is executed. In this lens control ■, the maximum value P0 of the degree of focus P
The lens distance ring m ring 3069 is controlled via the lens distance ring control unit 3044 to move to the position of the lens extension amount ΔXO.

Finally, in step 544, the process of stage control (2) is executed. In this stage control ■, stage 30
The stage 3004 is directed via the sub-scanning control unit 3049 so as to return the stage 3004 to the home position.

An example of the result obtained by the control operation described above is the focusing degree P
The relationship between the lens extension amount ΔX and the lens extension amount ΔX is the first
Figure 1. Although FIG. 11 shows an example of the case of a film holder for a sleeve, almost the same tendency is shown in the case of a film holder for a slide.

Another Embodiment FIG. 12 shows a control procedure of another embodiment of the present invention. In this embodiment, the degree of focus P is determined according to the control procedure shown in FIG. 12, and the maximum value P of the degree of focus P is determined. Shouting lens extension amount Δ
The in-focus point is detected by determining xo. In the control procedure of FIG. 12, the steps with the same step numbers as those in FIG. 9 are the same as the control contents explained in FIG. 9, so detailed explanation thereof will be omitted.

First, in step S31, stage control is performed to move the stage 3004 to the nine in-focus point detection area.

Next, in step S33, the lamp 300 is
Execute lamp control (■) to turn on 1.

Next, in step S34, the film holder 300
Execute holder detection reading ■ to identify the type of 6.

Next, in step S35, the film holder 30
Determining the starting and ending positions of the lens distance ring 30F+9 according to the type of lens distance ring 30F+9 is executed.

Next, in step 538, the lens distance ring 3069
Execute lens control ■ to move the lens to the starting end position.

Next, in step S39, the lens distance ring 3069
Execute lens control ■ to move the lens by a fixed amount Δ1.

Next, in step S40, the following calculation is performed using the output data of the image processing section 3073.

Next, in step 550, the previously calculated value of the degree of focus P and the currently calculated value are compared. Based on this comparison result, if the currently calculated value is greater than or equal to the previously calculated value, the process moves to the next step S51, otherwise the process moves to step S54.

In step 551, the internal counter CN is reset. This counter reset is a control that writes a "0" value into the counter.

Next, in step S52, it is determined whether the imaging lens 3010 is at the end position. That is, in this judgment, it is determined whether the imaging lens 301O is at the end position, and if it is at the end position, the next step S5 is performed.
In 3, change the terminal value by a certain amount in the increasing direction,
Return to step S39. Further, if the imaging lens 301O is not at the end position, the process returns to step S39 without doing anything.

On the other hand, in step S54, the above-mentioned internal counter CN is counted up. This count up increases the value of count CN by "1".

Next, in step 555, it is determined whether there is a monotonous decrease. This determination is made if the counter CN has never been reset and the counter value exceeds a predetermined threshold value, then it is determined that the process moves to step 558; otherwise, the process moves to step 557.

In step S58, processing is executed to change the value of the starting end in the direction of decreasing it by a certain amount. Then, the process returns to step 338.

Further, in step S57, it is determined whether the value of the counter CN exceeds the above threshold value, and if it exceeds the above threshold value,
The process moves to step S42, and if it does not exceed the limit, step 53
Return to 9.

In step S42, the maximum value P of the degree of focus P is determined.

Detection of the lens extension amount ΔX0 is performed.

Next, in step S43, the feeding amount ΔXo
Lens control to move the lens distance ring 3o69 to the position ■
Execute.

Next, in step S44, stage control (2) is executed to return the stage 3004 to the home position.

13(A) and 13(B) show an example of the operation performed in the control procedure of FIG. 12 in terms of the relationship between the focused point P and the lens extension amount ΔX.

If the focusing degree shown in FIG. 13(A) is obtained at the starting end and the ending end of the lens determined in step 535 described above, after the calculation of the focusing degree PB obtained at the end position is completed, 5
, steps S51 and S52 are executed, and the process moves to step 553. At this time, the value of the counter is 0, and the terminal value is changed in step 553 as shown in FIG.
), and the in-focus point detection control operation continues.

For example, the degree of focus P shown in FIG. 3(B). If the value is obtained, the counter value becomes "4", which is equal to or higher than a preset threshold value (for example, "4"), and the in-focus point detection is completed before reaching the end point.

[Effects of the Invention] As explained above, according to the present invention, when determining the degree of focus P, it is possible to arbitrarily and freely set the starting end and the ending end of the lens within the optimum minimum range. There is no need to perform unnecessary focus detection processing, the focus detection processing can be executed in a short time without failure, and work efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing a specific circuit configuration of an embodiment of the present invention, and FIG. 3 is an overall diagram of the embodiment of FIG. 2. Flowchart showing the control procedure, FIG. 4 is a block diagram showing the circuit configuration of another embodiment of the present invention, FIG. 5 is a block diagram showing the main part configuration of the embodiment of the invention shown in FIG. 4, FIG. FIG. 7 is a plan view showing a specific example of the image reference area for automatic focus adjustment in the embodiment of the present invention. FIG. 7 is a plan view showing an example of the relationship between the trimming region and the reference region in the embodiment of the present invention. FIG. A diagram showing the relationship between the degree of focus P and the lens aperture amount ΔX in the embodiment, FIG. 9 is a flowchart showing the control procedure for focusing point detection control in the embodiment of the present invention, and FIG. 1O is a starting point in the embodiment of the present invention. FIG. 11 is a plan view showing an example of display of the end and the end; FIG. 11 is a diagram showing a specific example of the control result according to the control procedure shown in FIG. 9 in terms of the relationship between focus degree P and lens extension amount ΔX; FIG. Flowchart showing the control procedure of focused point detection control in another embodiment, FIG. 13(A),
(B) is a diagram showing the relationship between the focusing degree P and the lens extension amount ΔX in a specific example of the control operation according to the control procedure of FIG. 12. 3006... Film holder 3007... Transparent original (film), 301O...
Imaging lens, 3025...Analog circuit, 3039...Controller, 3041...Operation unit, 3042...Display unit, 3044...Lens distance ring control unit, 3049...Sub-scanning control unit, 3060 ...Entire image sensor, 3061, 3062.3063...CCD3069.
... Lens distance 121 [T! J, 3071...Motor, 3073...Image processing unit, 3081...Film holder detection means, 3101...
・Image reference area for F. Line sensor, 1... Light source, 3005... Rotating table (stage), △X. Shinsu No. 1 East Exit Type △

Claims (1)

[Scope of Claims] 1) An imaging lens that projects and forms an image of a document, an imaging device that photoelectrically converts the image formed by the imaging lens into an electrical signal, and an output signal of the imaging device that converts an output signal into a digital signal. An analog-to-digital conversion means for converting, a calculation means for calculating a contrast evaluation amount P based on a predetermined contrast evaluation amount calculation formula based on an output signal of the analog-to-digital conversion means, and a calculation means for calculating a contrast evaluation amount P calculated by the calculation means. a focal point detection means for detecting a focal point position of the imaging lens that has a maximum value; a focal point adjustment means for moving the imaging lens along an optical axis to the focal point position detected by the focal point detection means; While moving the imaging lens from the starting end to the ending end along the optical axis by the focus adjusting means, when calculating the contrast evaluation amount P by the calculating means, the values at the starting end and the ending end, which are the in-focus point detection range, are calculated. An image reading device comprising a setting means for setting. 2) The setting means sets the values of the starting end and the ending end according to a detection signal from a detection means for detecting the type of film holder in which the document is stored. Image reading device. 3) The image reading device according to claim 1, wherein the setting means sets or changes the values of the starting end and the ending end in response to a key input from an input means. 4) The setting means changes the settings of the starting end and the ending end based on a change in the value of the contrast evaluation amount P calculated by the calculating means. The image reading device according to any one of the above. 5) The calculation means may be a mathematical formula, a chemical formula, a table, etc. as the contrast evaluation amount calculation formula (where P is the contrast evaluation amount, K is a normalization constant, and a
, b and j are constants, x_i is the digital value of the i-th pixel, and x_i_-_1 is the digital value of the i-1th pixel). The image reading device described in .