JPH02277372A - Image reader - Google Patents

Abstract

PURPOSE:To perform focus adjustment with high accuracy and at high speed and also, easily by changing the light quantity of a lamp corresponding to the light and shade of an original (sample), or changing the light quantity by the operation of a filter before a focal point is found. CONSTITUTION:A lamp light quantity change means E changes the light quantity of the lamp of a light source J corresponding to the read value of the original (sample) I. A contrast evaluation quantity P is calculated sequentially by an arithmetic means D as moving an image pickup lens A from a start position to termination along an optical axis by a focus adjusting means H. A focal point position detecting means F detects a lens position at a time when the contrast evaluation quantity P obtained from the arithmetic means D becomes maximum within a range from the start position to the termination of the lens as a focal point position. A control means G performs control to move the image pickup lens A to the focal point position detected by the focal point position detecting means F via the focus adjusting means H.

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 (8F) mechanism for automatically adjusting the 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 lens varies within a range of several millimeters, manual focus adjustment is required each time an attempt is made to read an image without blur.

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

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. I was at 1.

[Problems to be Solved by the Invention] However, conventional flatbed film scanners that use solid-state imaging devices such as CCDs (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. However, there were drawbacks such as the need for laborious work, the generation of Newton's ring force (due to the film being sandwiched between glass plates), and the tendency for dust to adhere to the film.

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. I was supposed to read the image.

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, I am wondering if it would be possible to use the autofocus (automatic focus adjustment) technology used in cameras or microscopes in the image reading device for this transparent manuscript, and 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 a human-powered image signal from the sensor. This method is described in, for example, NHK Technical Research Vol.
This is disclosed in Publication No. 6, etc.

However, all of these conventional autofocus methods require complicated calculations, and therefore use complicated hardware configurations that can perform the complicated calculations.

However, even if the focal point is sufficiently detected for a bright film, i.e., a paper density sample, the focal point cannot be detected accurately for a dark film, i.e., a high density sample, making it difficult to read a blurred image. There was a drawback that it could be stored away.

It is best to use a microcomputer with a relatively simple hardware configuration as an autofocus mechanism to be incorporated into an image reading device for transparent originals. The drawback is that accurate detection is not possible, and it is not possible to easily determine the focal point position at high speed and with high precision.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading device that eliminates the above-mentioned drawbacks and allows accurate, high-speed, and easy focus adjustment.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an imaging lens that projects and forms an image of a document, and an imaging element that photoelectrically converts the image formed by the imaging lens into an electrical signal. , an analog-to-digital conversion means for converting the output signal of the image sensor into a digital signal, a calculation means for calculating the contrast evaluation amount P based on the output signal of the analog-to-digital conversion means using a predetermined contrast evaluation amount calculation formula, and a light source for illuminating the light source. A light source that
Lamp light amount changing means compares the output signal of the analog-to-digital converter with a threshold value and changes the lighting voltage of the light source based on the comparison result; and focus adjusting means moves the imaging lens from the starting end to the ending end along the optical axis. a focusing point position detecting means that sequentially calculates a contrast evaluation amount P by a calculating means and detects an in-focus point based on the calculated contrast evaluation amount P; and control means for moving the lens via focus adjustment means.

Further, the present invention is characterized in that it includes a filter control means that compares the output signal of the analog-to-digital conversion means with a threshold value and controls entry and exit of the filter of the imaging lens into and out of the optical path based on the comparison result.

Further, in the present invention, the calculation means is configured as a contrast evaluation M calculation formula (where P is a contrast evaluation amount, K is a normalization constant a,
b, j are constants, ×1 is the digital value of the first pixel, X
l-1 is the digital value of the i-1th pixel).

[Function] With the above configuration, the present invention changes the light intensity of the lamp depending on the brightness of the original (sample) or changes the light intensity by filter operation before determining the focused point P. Therefore, the in-focus point can be detected in an optimal state, and the in-focus point can be determined accurately and without failure.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention. In this figure, A is an imaging lens that projects and forms an image of the document I.

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.

Further, E is a lamp light amount changing means, which changes the lamp light amount of the light source J in accordance with the read value of the document (sample) (2). While the imaging lens A is moved along the optical axis from the starting end to the ending end by the focusing means H, the contrast evaluation amount P is sequentially calculated by the calculating means.

F is a focal point position detection means, which detects the lens position at which the contrast evaluation amount P obtained from the calculation means is maximum in the range from the starting position to the end of the lens as the focal point position. Reference numeral G denotes a control means that controls the imaging lens A to be moved via the focus adjustment means H to the focus position detected by the focus position pinching means.

In addition, the above-mentioned calculation means can be used as the above-mentioned contrast evaluation amount calculation formula, for example, (where P is the contrast evaluation amount, K is the normalization constant a,
b, j are constants, ×1 is the digital value of the first pixel, X
l-1 is the digital value of the i-1th pixel).

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 300.
This is an illumination optical system that converts the illumination light that passes through 2 into a parallel light beam.

3004 is a sub-scanning drive stand that moves the transparent original in the sub-scanning direction, 3005 is a rotary table that rotates the transparent original, 3006 is a film holder that stores the transparent original, and 3007 is a 35 m
It is a transparent original like 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
014 is a touch panel that manually controls the trimming area.

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 3010 into three colors of R, G, and B, and 3022, 3023, and 3024 are prisms, respectively. CCD using a CCD (charge-coupled device) array that photoelectrically converts the original image of each color separated by 3021.
It is a CD line sensor, and this CCD line sensor has a corresponding CCD alignment mechanism 3018.3019.3020.
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 (macenter), 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 minimum value detection circuit that detects the minimum value of the output signal of the lookup table 3031;
) Lookup table (LIT) to obtain the control amount of Nodame
), 3034 is a masking circuit that performs masking processing on the output signal of the lookup table 3031;
035 is an OCR 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. 3036
3037 is a density conversion circuit that converts the recording density of the output signal of the OCR circuit 3035 into a specified density, and 3037 is a scaling processing circuit that converts the output signal of the density conversion circuit 3036 to a specified scaling factor.

3038 is an interface circuit (I/F) that transmits signals between a precipitator (not shown) or an input/output terminal 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. It has a ROM (leat-on memory), a RAM (random access memory) used for data storage and a 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 3010, 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 is a trimming frame control unit that controls the trimming frame display 3015, and 3047 is a touch panel control unit that controls the touch panel 3016. 3048 is a rotary table rotation control unit that drives and controls the rotary table 3005; 3049 is a sub-scan control unit that controls scanning of the sub-scan drive table 3004; 3050 is a lamp light amount control circuit that controls the light amount of the light source (lamp) 3001; 3051; is a lamp position driving source that adjusts the position of the light source 3001 via the lamp holding member 3017.

3052 is a timing signal 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 output equipment; 3055 is a Synchronous signal line for output device,
and 3056 are communication lines.

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 mote (■), 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 CCD positioning mechanisms 3018 to 3020 each
This is for registering the CD line sensors 3022 to 3024 with the three-color separation prism 3021, and needs to be adjusted at least once. The analog circuit 3025 is composed of an amplifier and an A/D converter, and converts the signal amplified by the amplifier into the A/D converter in synchronization with the timing clock for A/D conversion output from the timing generator 3052. A/D conversion.

Next, R2O,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, the masking circuit 3034, the lookup table 3033, and the UC
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.
The M', C', and BK' signals 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 (e.g. Eva, personal computer) via a communication line 3056.

On the other hand, the lamp position driving source 3051 is connected to the lamp 300 of the light source.
This is for adjusting the lamp position when converting 1, and the lamp 3001 is positioned manually or automatically in accordance with the manual key operation on the operation unit 3041. Lamp light amount control section 3050 and lens aperture control section 3043
adjusts the amount of light received for images projected onto the CCD line sensors 3022 to 3024. In addition, the mirror drive unit 3045
controls the movable mirror 3008 to change the optical path for switching between guiding the image of the transparent original 3007 to the screen 3014 and 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 screen displayed on the screen 3014. 3015 , and a rich panel control unit 3047 controls a touch panel 3016 for inputting a trimming area.

Further, the lens distance ring control unit 3044 controls the imaging lens 3
Controlling the distance ring of 01O, the CCD line sensor 30
The images projected on 22 to 3024 and the screen 3014 are focused. The adjustment signal generation source 3026 generates a signal manually 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.

Preparatory operation: When a power switch (not shown) is turned on, the controller 3039 initializes each part (step Sl) and enters a state of waiting for a command manually 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 rotary table 3005, the light source 3001 illuminates the heat ray absorption filter 3006.
002, an illumination optical system 30 including a condenser lens, etc.
The image of the transparent original illuminated through the movable mirror 3
008 and projection lens 3011 and mirror 3012.3
013 and is projected onto the screen 3014.

Transparent originals 3007 have image orientations of either vertical or horizontal orientation, but when the image is rotated and projected, the image is transferred from an external device via the interface circuit 3038 or from the operation unit 3041 to the controller 3039. When the rotation is instructed (step S2), the controller 303
9 sends a rotation control command to the rotary table rotation control unit 3048 via the bus 3053 to rotate the rotary 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 manner, when the transparent original 3007 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 3o47, and the touch panel control unit 3034 inputs the trimming information to the touch panel control unit 3034. The trimming information entered manually from the controller 3016 is taken into the controller 3o39 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 3o39 to start image reading via 038, image reading starts.
This is carried out according to the following procedure (step S6).

Optical path switching: First, the controller 3039 outputs a drive control signal to the mirror drive unit 3045 to move the movable mirror 3008, and the image of the transparent original 3007 is transferred to each CCT + -y-in sensor 302
The optical path is switched so that the optical path is guided above 2 to 3024 (step S7).

Dark correction signal set: Next, 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 of the CCD line sensors 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 3050 to
001 is turned on, and the dark correction circuit 3027, shading correction circuit 3028, pixel shift correction circuit 3029, color conversion circuit 3030, lookup table 3031, masking circuit 3034, UCR circuit 3035, density conversion circuit 3036, and scaling processing circuit 3037 are activated. The peak detection circuit 304 is controlled so that the mode is all through (input data is output as is) (step S9), and the raw data input manually to the controller 3039 via the interface circuit 3038 is processed while sub-scanning at high speed.
Beak detection is performed using 0 (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 3043 to change the aperture of the imaging lens 3010 (step 5
12).

AF (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 3010 (
Step 513).

Shading correction data set: Subsequently, each CCD line sensor 3022 to 3024 or illumination light
Step 514) of moving the sub-scanning drive base 3004 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
Shading correction data is manually set in the shading correction circuit 3028 using the dark-corrected signal in Step 515.

After the selection, a pixel shift correction amount is set in the pixel shift correction circuit 3029 (step 516). In addition, the color conversion circuit 3
Select the type of color conversion for 030, select the type of lookup table for lookup tables 3031 and 3033, select the type of masking for masking circuit 3034, and select the presence or absence of OCR for OCR circuit 3035. Then, the type of density conversion is selected for the density conversion circuit 3o36, 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. Start sub-scanning step S522),
An 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).

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
A CCD positioning mechanism for positioning the D line sensors 3061 to 3063, and 3065 to 3067 are drive signals output from the timing generator 3052 to drive the CCD line sensors 3061 to 3063, respectively. The other configurations are the same as the 2F previous embodiment.

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 306I to 3063 is capable of capturing R, G, and B color-separated images using respective on-depth 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-operation direction at 063, and is configured using, for example, several FIFO memories. The amount of delay for each color is set in advance by the controller 3039 according to the sub-operation 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 3010, 3070 is a deceleration mechanism that meshes with the distance ring 3069, and 3071 is a motor that rotates the distance ring 30δ9 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. Also, xp is the position of point P'' on the film 3007 in the optical axis direction, and xq is the imaging position (optical axis direction) of the image (qo) of point P''.
It is.

Furthermore, when the focal position of the imaging lens 3010 is changed by driving the motor 3071 by the controller 3039 via the distance ring control unit 3044 and moving the distance Nlf ring 3 [IB9 via the deceleration device 3070, This shows the imaging position of point P'.

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 AP (automatic focus adjustment) image reference area that is referred to when performing automatic focus adjustment. 3100' is an image area when the orientation of the transparent original 3007 is rotated by 90 degrees.

As shown in FIG. 7, when the image area 3100 of the subject document is trimmed and operated by the trimming area 3120 surrounded by two points P1 and P2, the effective image is within the trimming area. Most preferably, automatic focus control (AF) is performed within the crop area 3120. By doing this, even if the transparent original 3007 such as photographic film is tilted or warped with respect to the optical axis, it is possible to focus on the necessary image area with high precision. Ru.

Note that the 3-line sensor 3 as shown in FIGS. 4 and 5
061 to 3063 to find the focal position of each color, use both AF image reference areas 3101 (or 3
The CCD alignment mechanism 3064 moves the line sensors 3061 to 3063 in the sub-operation direction so that the line sensors 101') coincide with the film surface of the image area 3100 of the document.

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 (XJ-XJ-1)2
(1) J=a (However, XJ is the output level of the first pixel in the main operation direction,
a and b are the numbers of the second pixel from the beginning and the last pixel in the main operation direction of the F image reference area 3101. ) FIG. 8 shows the contrast evaluation amount (hereinafter, focus This figure shows an example of a change in the value of P (referred to as degree). 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 Δx0 is the in-focus position.

In the embodiment of the present invention, before calculating the contrast evaluation amount P, the amount of lamp light is changed in the following manner according to the read value of the area of the sample (original) 3007 where the in-focus point is to be detected.

(2) The lamp voltage when determining the shading correction data in step S15 in FIG. (hereinafter referred to as reference voltage LO) through the lamp light amount control circuit 3050.
Light source) 3001 is turned on.

■Next, the sensor output of the image sensor 3060 of the color to be referenced is A/D converted, and the maximum value c of the converted digital data is
Find m.

(2) Next, the magnitude relationship between the maximum value cm and a predetermined threshold value S0 is compared, and when the maximum value Cn is smaller than the threshold value S, the light amount of the lamp 3001 is changed as described later.

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, the shoulder 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 531, stage control (2) is executed. In this stage control (2), control is performed to move the stage (sub-scanning drive stand) 3004 to the area where focus point detection is desired via the sub-scanning control unit 3049.

Subsequently, in step S32, lens control (2) is executed. In this lens control (2), the lens distance ring 3069 is controlled to be moved to the in-focus point detection start position via the distance ring control section 3044.

Next, in step S33, lamp control (2) is executed. This lamp control ■ uses the reference voltage. lamp 300
The voltage of the lamp 3001 is controlled from the controller 3039 via the lamp light amount control circuit 3050 so that the lamp 3001 is turned on.

Next, in step S34, data reading (2) is executed. In this data reading process (2), a digital signal Xj obtained by digitally converting an output signal from an image sensor 3060 consisting of a CCD is read, and the maximum value Cm of the digital signals x and H is determined.

Next, in step 535, a threshold value S is set in advance, where the maximum value Cn is set in advance. Determine whether it is larger or smaller than. If the maximum value Cm is larger than the threshold value S0, the process proceeds to step 538, and if it is smaller, the process proceeds to step 53B.

The maximum value Cm is the threshold value S. If it is smaller than , proceed to step 536. In step S36, the lamp light amount L' when performing in-focus point detection is calculated using the following equation.

L' = C, .Lo/Cm Next, in step S37, lamp control (2) is executed. In this control (2), the controller 30 controls the lamp light intensity through the lamp light intensity control circuit 3050 so that the above lamp light intensity L' is achieved.
The lamp 3001 is turned on from 039.

Next, in step 538, lens control (2) is executed. Step 538 may be executed by skipping steps 536 and S37 depending on the execution result of step S35. Lens control in step 538 ■ The lens distance ring 3069 is adjusted by a certain amount Δ via the distance ring control unit 3044.
Performs control to move by ρ.

Next, it is shown in the above formula (2).

Performs calculation processing. When this calculation is completed, the calculation result is stored in the internal memory (RAM) of the controller 3039.

Next, the process moves to step S40, and it is determined whether the lens distance ring 3069 has reached the final position. If it has not reached the final position yet, the above-described steps 538 and 539 are repeated.

Thereafter, when the lens distance ring 3069 reaches the terminal position, the calculation is terminated (step 540), and the next step 54
1, the maximum value P of the degree of focus P from the result obtained in step S39 described above. Loud lens extension amount ΔX,
Detect.

Next, in step S42, lens control (2) is executed.

In this lens control ■, the maximum value P of the degree of focus P. The lens distance ring m ring 3069 is controlled to be moved via the lens distance ring control unit 3044 to the position of the desired lens extension amount ΔXo.

Finally, in step S43, stage control (2) is executed.゛In this stage control■, stage 3004
The sub-scanning control unit 304 returns the
Stage 3004 is moved via 9.

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
This is figure 0.

Other examples FIG. 11 shows the configuration of another embodiment of the present invention.

In this embodiment and the embodiment shown in FIG.
200. The difference is that it includes a filter control section 3201, and the other parts are the same. This filter 32
00 is, for example, a cyan color correction filter or an ND filter, and several types are prepared. For example, when a color negative film is targeted, a cyan color correction filter is used.

Here, the cyan filter cuts out the orange base portion of the color negative film and adjusts the color balance of the color sensor to which the R, G, and B filters are attached.

If the film is other than color negative film, use an ND filter.

In this embodiment, when determining the focus degree P, the controller 3
The degree of focus P is determined by the microcomputer No. 039 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
The in-focus position is detected by determining o.

Next, the operation of the control system shown in FIG. 11 will be explained with reference to the flowchart shown in FIG. 12. Note that, in the following, parts that are different from the control procedure in the flowchart of FIG. 9 will be explained in detail, and detailed explanations of parts that are the same will be omitted.

First, in step 531, stage control (2) is executed without moving the stage 3004 to the focused point detection area.

Next, in step S32, the lens distance ring 3069
Execute lens control ■ to move the lens to the in-focus point detection start position.

Next, in step S33, the reference voltage is increased. Execute lamp control (2) to turn on the lamp 3001.

Next, in step 550, filter control (2) is executed. In this filter control ■, if the document 3007 is a color negative film, a cyan color correction filter is applied.
If the film is not a color negative film, an ND filter is set in the filter 3200 by the controller 3039 via the filter control unit 3201. The type of film is determined by a dedicated sensor output or manually from the operation section 3041.

Next, in step S34, the maximum value Cm of the digital data is determined. Execute data reading■.

Next, in step S35, if the maximum value Cm is larger than a preset threshold value, step 53
The process moves to step 8, and if it is smaller, the process moves to step 551.

In step 551, filter control (2) is executed. This filter control (1) is to control to remove the filter 3200 from the optical path, and the controller 3
039, the filter 3100 is moved out of the optical path via the filter control unit 3101.

Next, in step S52, the lamp light amount L'' is switched.

This switching is performed based on the following formula % formula % (where ΔL is a predetermined constant), and is the standard light amount. A certain amount ΔL than
Set the increased lamp light intensity.

Next, in step S53, lamp control (2) is executed. In this lamp control (2), the voltage of the lamp 3001 is controlled by the controller 3039 via the lamp light amount control circuit 3050 so that the lamp 3001 is turned on so that the lamp light amount is L''.

Next, in step 538, the lens distance ring 3069
Execute lens control ■ that moves the lens by a fixed amount Δ℃.

Next, the calculation in step 539 is performed, steps 540, 541 . S42. S
Moving on to 43.

[Effects of the Invention] As explained above, according to the present invention, before determining the focal point P, the light intensity of the lamp is changed depending on the brightness of the original (sample), or the light intensity is changed by filter operation. As a result, the in-focus point can be detected in an optimal state, and the in-focus point can be determined accurately and without failure.

[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. 1θ is the control procedure in FIG. 9. 11 is a block diagram showing the main part configuration of another embodiment of the present invention, and FIG. 12 is a diagram showing the relationship between the focusing degree P and the lens extension amount ΔX. 12 is a flowchart showing a control procedure for focus point detection control in another embodiment of the present invention. 1... Light source, 3005... Rotating table (stage), 3006... Film holder 3007... Transparent original (film), 3010...
Imaging lens, 3025...Analog circuit, 3039...Controller, 3044...Lens distance ring control section, 3049...Sub-scanning control section, 3050...Lamp light amount control circuit, 3060...Imaging device Overall, 3061, 3062.3063... CCD line sensor, 3069... Lens distance ring, 3071... Motor, 3073... Image processing unit, 3101... Image reference area for AF, 3200... Filter 3201...filter control unit. Sign spread flat

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 converts the output signal of the imaging device into a digital signal. an analog-to-digital converter for converting the analog-to-digital converter into an analog-to-digital converter; an arithmetic unit for calculating a contrast evaluation amount P using a predetermined contrast evaluation amount calculation formula based on the output signal of the analog-to-digital converter; a light source for illuminating the light source; lamp light intensity changing means for comparing the output signal of the converting means with a threshold value and changing the lighting voltage of the light source according to the comparison result; and focusing means for moving the imaging lens from a starting end to a terminal end along the optical axis. and a focused point position detection means for sequentially calculating the contrast evaluation amount P by the calculation means and detecting the focused point based on the calculated contrast evaluation amount P; and the focused point detected by the focused point position detection means. An image reading device comprising: a control means for moving the imaging lens to a position via the focus adjustment means. 2) A filter control means for comparing the output signal of the analog-to-digital conversion means with a threshold value and controlling entrance/exit of the filter of the imaging lens into and out of the optical path based on the comparison result. The image reading device described in . 3) 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 the normalization constant a,
b, j are constants, x_i is the digital value of the i-th pixel,
3. The image reading apparatus according to claim 1, wherein x_i_-_1 is a digital value of the i-1th pixel.