JPH03217161A - Image reading device - 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]

[Industrial Application Field] The present invention relates to an image reading device that reads transparent originals such as microfilm and 3Ev+m film and converts them into electrical signals, and in particular, the present invention relates to an image reading device that reads transparent originals such as microfilm and 3Ev+m film and converts them into electrical signals. Related to light amount control technology. [Prior Art] Conventionally, a negative film image is projected onto a platen glass using a projector (projection device), and the projected image of the film image is formed onto an image sensor using a mirror and a lens to read the film image. An image reading device called a film scanner or the like is provided, which illuminates a film and forms a transmitted image on an image sensor to read the image. These devices generally read images at a predetermined voltage level to correct overexposure and underexposure during shooting, and turn on the film illumination light source (hereinafter referred to as a lamp) depending on the output level of the signal at this time. The voltage was changed to obtain the optimal amount of light. [Problem to be Solved by the Invention] However, in the conventional example as described above, the range in which overexposure and underexposure can be corrected by changing the light intensity of the lamp is limited to at most overexposure with ISO 100 film, for example. The range is from +1.5 on the underexposure side to -2 on the underexposed side. On the other hand, silver halide photographs have exposure characteristics ranging from overexposed +3 to underexposed -2, so there were cases in which a print of a silver halide photograph could be visualized but could not be copied. . SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an image reading device that can make high-quality copies even from overexposed films of +1.5 or more, which were impossible to copy using conventional devices.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an image reading device having an image sensor including a solid-state image sensor that reads and scans a transmitted light image of a transparent original illuminated by a light source. Calculating means for calculating the optimum amount of light necessary for reading and scanning the transparent original from the image density level of the original, and light amount control means for controlling the amount of light emitted from the light source based on the optimum light amount calculated by the calculating means. The present invention is characterized by comprising an accumulation time control means for setting a longer charge accumulation time of the image sensor in response to the excess amount when it is determined that the optimum light amount exceeds the maximum light amount of the light source. Further, as an aspect of the present invention, when the accumulation time control means sets the charge accumulation time to a long time, the scanning speed control means controls to slow down the reading scanning speed of the image sensor in accordance with this. It is characterized by Further, as another aspect of the present invention, when the scanning speed control means slows down the reading scanning speed, the period of a write signal for storing the output signal from the image sensor in the image memory is lengthened accordingly, The present invention is characterized by having a memory control means for controlling the period of the read signal to be shorter than that of the write signal. Further, as another aspect of the present invention, when the accumulation time control means sets the charge accumulation time to be long, control is performed to set the recording scanning time of the recording device that records the image of the transparent original to be long in accordance with this. The present invention is characterized in that it has a recording speed control means for performing the following. [Function] In the present invention, prior to the operation of reading a projected image of a negative film, the output level of a plurality of pixels of the negative film is sampled, and the exposure status of the negative film image is determined based on the output level of the pixel. Based on the determination results, if the amount of light is insufficient even when the lamp is turned on at full capacity, the charge accumulation time of the image sensor is lengthened, so that the amount of light from the lamp is insufficient and copying is impossible with conventional equipment. +
Good quality copies can be made even from overexposed films of 1.5 or higher. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 shows the basic configuration of an embodiment of the present invention. In the figure, A is a light source, B is a transparent original, and C is an image sensor consisting of a solid-state image sensor that reads and scans a transmitted light image of the transparent original B illuminated by light source A. D is a calculation means for calculating the optimum light amount necessary for reading and scanning the transparent original B from the image density level of the transparent original B obtained from the output of the image sensor C. E is the light source A based on the optimum light amount calculated by the calculation means D.
This is a light amount control means for controlling the amount of light emitted by the light source. F is an accumulation time control means which, when it is determined that the optimum light quantity exceeds the maximum light quantity of the light source A, sets the charge accumulation time of the image sensor C to be longer in accordance with the excess quantity. Further, as an example, when the accumulation time control means F sets a long charge accumulation time, the image sensor C includes a scanning speed control means G that controls to slow down the reading scanning speed of the image sensor C in response to this setting. For example, when the scanning speed control means G slows down the reading scanning speed, the cycle of the write signal for storing the output signal from the image sensor C in the image memory K is lengthened accordingly, and the cycle of the read signal is increased. Shorter than the light signal《
It has a memory control means H that performs control. Further, as an example, when the accumulation time control means F sets a long charge accumulation time, a recording speed control means is configured to perform control to set a long recording scanning time of a recording apparatus that records an image of the transparent original B in response to this. has. Figure 2 shows the circuit configuration of an image reading device (film scanner) according to an embodiment (first embodiment) of the present invention. In the figure, 101 is a COD (charge-coupled device) line sensor for image input, and as shown in FIG. Color separation filters are applied to each pixel and arranged in a line. The CCD line sensor 101 receives a horizontal synchronizing signal (SH) generated by a CCD driver (drive circuit) 114.
) 115, clock signal (φIA, I1) 116,
．． By inputting (φ*h.m) 117, an output signal (OS) 118 proportional to the amount of incident light is output. The image signal output from the CCD line sensor 101 is sampled and held in a sample and hold circuit 102, and
/D (analog/digital) converter 103 G,
B is converted into each digital signal to become a time-series signal for the era line. 106 to 10g are the R, G,
A line memory that stores each data of H (hereinafter referred to as shading data) for each pixel, and RAM (
random access memory (hereinafter referred to as shedding RAM). When the digital signal from the A/D converter 103 is an image signal, 104 switches the output of the signal to the multiplier 105, and when the digital signal is a shading data signal, outputs the signal. This is a selector for switching to the shading RAMs 106-108. A switching signal to the selector 104 is supplied from an MPU (microprocessor unit) 111. FIG. 4 shows an example of the internal configuration of an image reading device (film scanner) according to an embodiment of the present invention. The shedding data is captured as follows. That is, when the original to be read is a color negative film, the CCD unit supporting the CCD line sensor 101 is moved by the reference numeral 3 in FIG.
14, set the base part of the negative film (film on which no image has been recorded, hereinafter referred to as base film) at the position shown by reference numeral 308 in FIG. 4, and set the illumination line 307 to the reference voltage . CC when lit and the base film is projected onto the platen glass 301
D One line of data is stored in the shading RAM mentioned above.
Written in 106-108. Further, in FIG. 2, the multiplier 105 performs calculation between the image signal and the shading data, and based on the calculation, corrects the output fluctuation of the image signal in the CCD main scanning direction and
, G, B White balance correction is performed. Specifically, when outputting an 8-bit correction signal using 8 bits of image signal (SL) and 8 bits of shading data (Ss), the corrected signal is called Sc (hereinafter referred to as normalized luminance signal). ), Sc is obtained by the following equation (1). Sc = 255 be able to. 109 is R corrected by the multiplier 105 as described above,
The G and B image signals are logarithmically converted to print colors Y (yellow), M (magenta), and so on. A logarithmic conversion table 110 performs masking correction, inking, OCR (undercolor removal), etc. on the Y, M, and C signals output from the logarithmic conversion table 109. This is a color processing circuit that performs color processing and generates Y, M, C, K (black) signals for an image output device such as a laser printer (not shown). The MPU 111 can directly access the shading RAMs 106 to 108, and executes an algorithm as shown in FIG.
Determine the lighting voltage. 112 is shading RAM
Shading data saving RAM that temporarily saves the shedding data stored in 106 to 108
It is. Further, 113 is a histogram RAM that stores a histogram created by an algorithm described later. Both RAM112, 113. Both MPU III
It is configured to be accessed with . Next, a method for determining the lighting voltage of the projector lamp 307 in the embodiment of the present invention will be explained. In general, the gradation recording characteristics of a color negative film are expressed by the following relational expression (2), where E is the amount of light incident on the film, and T is the transmittance of the 1 2 film after development processing. -ρolT = a + γn og E...
(2) Here, a is a predetermined constant, and γ is a positive constant (hereinafter referred to as "γ value") determined by the negative film used. Figure 5 shows the normalized density signal S of the above film incident light amount E.
This shows how it is converted to c. The relational expression (2) above corresponds to the linear region of the curve 401 in FIG. Now, for a negative film photographed with proper exposure, if the amount of light incident on the film corresponding to a black object is Ell+, and the amount of light corresponding to a white object is EWI, then the transmission density recorded on the negative film D (= β., T) are D+++ and Dw+, respectively. A curve 402 in FIG. 5 is a curve for converting film transmission density D into film transmission T, and the above transmission density [
] It can be seen that the transmittances corresponding to s+ and Dw+ are TIll and Tw+. When reading a film image with the configuration shown in Figure 4,
Signal F B output from CCD line sensor 101
I+PWl is proportional to the product of the light intensity ε of the projection lamp 307 and the film transmittance T++1, Twl. That is, α
Assuming that is a certain constant, P Bl=αTBIε, PWl=αTWIε・(
3). The signal PBIIPWI is (1
) is corrected by the multiplier 105, and the normalized luminance signal SBI, Sw+ is obtained. It is expressed by including the coefficient calculated by equation (1) in the constant α and further using equation (2). Now, assuming that the standardized luminance signals SRI and SWI are 8 bits, as is clear from FIG.
So that the value is 255 degrees. By setting the A/D converter 103 and setting the lamp light amount ε, efficient digital data can be obtained. The digital data obtained in this way is logarithmic conversion table 1.
09, it is logarithmically transformed according to the curve shown by the reference numeral 4fl5 in FIG. converted into a number. That is, the curve 405 is the conversion data executed by the logarithmic conversion table 109, and the reflection density of the subject is obtained. Next, consider a case where the read original film is not photographed with proper exposure. That is, it is assumed that the amount of film incident on the film at the time of photographing is larger than that at the time of proper exposure, and is the value shown by Emx and Ew* in FIG. 5, for example, with respect to the reference black and the reference white. In this case, if the projector lamp light intensity C is not changed, the standardized luminance signal S
ag, S■ becomes as follows from equation (4). Here, if l 5 is Eat/Eat = Ew+/Ew*, and this value is set as 1/k, ...(7) That is, Saw = 255, Swt = again in equation (7).
In order to make it Cp, it is sufficient to set the lamp light amount C to kε. This corresponds to replacing the straight line 403 in FIG. 5 with the straight line 404, and if the amount of light incident on the film at the time of shooting is k times the proper exposure, the amount of light from the projector lamp 307 will be changed. If k'YP1 is set, a normalized luminance signal in which the reference black is always 255 and the reference white is C is output, and furthermore, the density signal of the object can be obtained from the curve 405. However, since the exposure multiple at the time of shooting is actually unknown,
The image density on the film must be sampled to determine the lamp light intensity. Next, the procedure for determining the amount of lamp light will be explained with reference to the circuit configuration shown in FIG. 2 and the flowchart shown in FIG. 7. First, when the negative film reading mode is selected from an external device or console (not shown), the logarithmic conversion table 109 is switched from the curve 501 in FIG. 6 to the curve 405, and the color processing circuit 110 The settings of various parameters are switched (step Sl). Next, import the shading data. That is,
The unexposed part of the film used at position 308 in Figure 4 (
base film) or an equivalent filter (step S2), the projector lamp 307 is turned on at the reference voltage Va via the lamp power supply 121, and the selector 104
is switched to the shading RAMs 106, 107, and 108, the CCO sensor unit is moved to the center of the projected image area (step S3), and data for one line of the CCD is written to the shading RAMs 106 to 10g. When the capture of this shading data is completed, the CCD sensor unit is returned to a predetermined home position, and the projector lamp 307 is temporarily turned off (step S4). Next, the image film to be actually read is set at the position 308 in FIG. 4 (step S5), and sampling is performed to determine the exposure state of the film. Therefore, first of all,
MPUI the contents of shading RAM106 to 108
II, the shading data is saved to the shading data save RAM 112. Next, the projector lamp 307 is turned on at the above reference voltage Va (step S6) and moved to a predetermined position of the CCD sensor unit projection image section (step S7).
, R, G, in the shading RAMs 106 to 108.
Capture one line of image data of B (step s
g). In this way, shading RAM1 [16~10g
The multiplier 105 sequentially executes the correction calculation of formula (1) for each of R, G, and B for each pixel using the shading data that the MPU III saves in the shading save RAM 12. R, G, B normalized luminance signal values S* corrected to
, Sa, Sll are obtained (step S9), and only when the signal values S*, Sa, Sa satisfy the conditions described later, the histogram RAM1 of the address corresponding to S, l is calculated.
1 is added to the data of 13, and the process is repeated until the data for one line is completed (step S10). The projected image is read on multiple predetermined lines,
The arithmetic processing of steps S7 to SIO described above is repeated until all lines of the plurality of lines are completed. After reading all lines (step Sll)
), the contents of the above histogram RAM 113 are
11, and determines a lamp lighting voltage vl that provides the amount of light from the projection lamp necessary for properly reading the projected image. At this time, the CCD sensor unit (30
3, 304, 101) returns to the home page,
The projection lamp 307 is once turned off (step Sl2).
. In step Sl2, the lamp lighting voltage V, is determined as follows. That is, the histogram RAM 113 stores the frequency of occurrence of image signal values as shown in FIG. 8, and the signal value corresponding to the left end of the mountain in the histogram is
>> It is thought that the signal value corresponding to the right end of Sw++ in the equation corresponds to 81. Therefore, in order to eliminate the influence of noise, etc., as shown in FIG. Maximum value of degree H. If we cut the histogram by multiplying IIX by 1/l6, for example, and extract the signal value that gives the intersection with the histogram as Sm+n+Smax, we get 81.1
is the reference white level, and Sma++ is the value representing the reference black level. As already mentioned, S. ．． ．． =255,S. l. It is sufficient to determine the lamp lighting voltage V so that = CI - (8), but as shown in Figure 8, the histogram for a general color negative film image is is Sffiwa. Since the fall is steeper than the fall in the vicinity of , the Siltl value is less sensitive to the value that cuts the histogram, and a highly reliable value can be obtained. Therefore, the multiple β expressed by β==Cp/Smln (9) is determined, and the lighting voltage value V, which makes the amount of lamp light multiplied by β, becomes the value to be determined. It can be seen from FIG. 5 that in this case, 8■ automatically becomes 255. FIG. 9 is a graph showing the relative light amount ratio when the lighting voltage V is changed with respect to the lamp light amount when the reference lighting voltage v0 is used. This amount of light is approximately proportional to the voltage to the 3.5th power. The data of the curve shown in FIG. 9 may be stored in advance in the built-in ROM area of the MPU III, and the value of β in equation <9> may be converted to V and output. Here, ■ is a digital value, and this value is supplied to the variable voltage power supply 121 of the projector lamp 307 via a D/A converter (not shown), and the voltage V is applied to the projector lamp 307 at the start of the reading operation.
(volts) is applied. However, the output voltage of this variable voltage power supply 121 is finite. If the upper limit of this output voltage is 24V, and if the lamp 307 is not lit at a higher voltage, the amount of light from the lamp will be insufficient, in the case of a negative film, the lamp 307 is lit at 24V or less, and instead The charge accumulation time of the CCO line sensor 101 may be increased. The amount of light from the lamp 307 and the output voltage of the sensor 101 are in a proportional relationship, and the charge accumulation time of the sensor 101 and the output voltage of the sensor 101 are also in a proportional relationship. Therefore, by doubling the charge accumulation time of the sensor 101, the same effect as doubling the amount of light from the lamp 307 can be obtained. Next, a method for determining the above charge accumulation time will be explained. When the value of the multiple β obtained in the above step S12 is converted into a lighting voltage and is equal to or higher than the upper limit of 24V of the lamp power supply 121 (step S13), the MPU III sends an instruction signal 119 to the CCD to double the charge accumulation time. driver 114
The charge accumulation time of the COD line sensor 101 may be increased by outputting the charge to the COD line sensor 101 (step S14). For example, the reference lighting voltage is 18V, and the relative light amount ratio β at this time is 1. Let us now consider a case where the color negative film to be copied has a voltage of 26.7V and the amount of light is insufficient unless the lamp 307 is turned on. At this time, if the charge accumulation time is doubled as shown in FIG. 11 compared to the standard time (normal time) in FIG. 10, the relative light amount will be about % of that at 26.7V. The lighting voltage of the lamp 307 at this time is determined to be approximately 22V from FIG. 9 or by the following calculation (step Sl4). 26. 7V ÷ "J2 = 21.9V The above lamp lighting voltage is achieved by changing the output voltage of the lamp power supply 121 from 12V to 24V according to the instruction signal 120 of the MPU III. In the embodiment, the CCD line sensor 101 is used when the amount of light is insufficient for color negative film.
Although the explanation has been given using an example in which the charge accumulation time is doubled, it goes without saying that the present invention is not limited to this doubling. Furthermore, in the case of the configuration shown in FIG. 4, the CCD line sensor 101
reads the image of the color negative film projected onto the platen glass 301 while moving in the arrow direction (sub-scanning direction) in the figure along with the lenses 303 and 304.
If the charge accumulation time is increased, the resolution of the read image may gradually deteriorate. To prevent this inconvenience, the scanning speed of the CCD sensor unit may be slowed down in accordance with the lengthening of the charge accumulation time. That is, when the charge accumulation time is doubled, the MPU III performs control to keep the scanning speed of image reading constant. 2 3 In this case, the printer connected to this film image scanner must synchronize with this and reduce its recording scanning speed. Depending on the type of printer, it is very difficult to change the recording speed (for example, an electrophotographic printer). If the image data is read out at a faster clock frequency than the clock frequency used when writing and printed, substantially the same effect as when the printer speed is changed to a lower speed can be obtained. [Effects of the Invention] As explained above, according to the present invention, prior to the operation of reading a projected image of a negative film, the output levels of a plurality of pixels of the negative film are sampled, and the output level of the pixels is sampled. The exposure status of the negative film image is determined, and based on the determination results, if the amount of light is insufficient even if the lamp is turned on at full capacity, the charge accumulation time of the image sensor is lengthened, so that the amount of light from the lamp is insufficient. As a result, it is possible to obtain high-quality copies even from overexposed films of +1.5 or more, which were impossible to copy using the conventional apparatus.

[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 the circuit configuration of an image reading device (film image scanner) according to an embodiment of the present invention. FIG. 4 is a cross-sectional view of essential parts showing the arrangement of the optical system of an image reading device according to an embodiment of the present invention, and FIG. 5 is a plan view showing the configuration of a three-color color separation CCD line sensor. Graph illustrating conversion to a density signal. Figure 6 is a graph showing the relationship between the normalized luminance signal and density signal when converting the output of the CCD line sensor to a density signal. Figure 7 is an example of the present invention. Figure 8 is a graph showing an example of the histogram of the image signal, Figure 9 is a graph showing the relationship between the light intensity of the projection lamp and the lighting voltage, and Figure lθ is the graph when the light intensity of the projection lamp is sufficient. A timing chart showing the timing of the CCD drive signal and the CCD output signal. Fig. 11 is a timing chart showing the timing of the CCD drive signal and the CCO output signal when the charge accumulation time is lengthened due to insufficient light intensity of the projection lamp. . ...CCD line sensor, ...sample hold circuit, ...A/D converter, ...selector, ...multiplier, ~108...line memory, ...logarithmic conversion table, ・...color processing circuit, ...MPU, ...shading data saving RAM...histogram RAM, ...CCD driver, ...projection lamp. -421- JP-A-3 217161 (15) JP-A-3 217161 (16)

Claims (1)

[Scope of Claims] 1) In an image reading device having an image sensor including a solid-state image sensor that reads and scans a transmitted light image of a transparent original illuminated by a light source, an image of the transparent original obtained from the output of the image sensor. Calculating means for calculating the optimum amount of light necessary for reading and scanning the transparent original from the density level; Light amount control means for controlling the amount of light emitted from the light source based on the optimum amount of light calculated by the calculating means; and the optimum amount of light. an image reading device comprising: an accumulation time control means for setting a charge accumulation time of the image sensor to be longer in accordance with the excess amount when it is determined that the amount of light exceeds the maximum amount of light of the light source. 2) According to claim 1, further comprising scanning speed control means for controlling the reading scanning speed of the image sensor to be slowed down when the accumulation time control means sets the charge accumulation time to be long. The image reading device described. 3) When the scanning speed control means slows down the reading scanning speed, the cycle of the write signal for storing the output signal from the image sensor in the image memory is lengthened accordingly, and the cycle of the read signal is made shorter than the write signal. 3. The image reading apparatus according to claim 2, further comprising memory control means for performing control to shorten the length of the image reading apparatus. 4) When the accumulation time control means sets the charge accumulation time to a long time, the recording speed control means controls to set a long recording scanning time of the recording device that records an image of the transparent original in accordance with this. Claim 1 characterized by
The image reading device described in .