JPS63138866A - Color film image reader - Google Patents

Abstract

PURPOSE:To obtain an image with high quality by obtaining a photoelectric conversion output corresponding to a photoelectric accumulating time in response to the separated color so as to decrease the setting of a gain of an amplifier lower and reducing the difference of gain between amplifiers. CONSTITUTION:When the drive of a stepping motor 6 is finished, a film mobil stage 3 is stopped and the accumulation of CCDs 9 - 11 for image read is attained. In giving an SH pulse to a R CCD 9, a G CCD 10 and a B CCD 11 to apply storage, and when the storage is finished sequentially, then the signal is read out. Analog switches 14a - 14c are turned on respectively, given to an A/D converter 16 at every photodetector via a sample/hold circuit 15, converted into a digital signal and stored in a memory circuit 18. The accumulating time corresponding to the color separation to CCDs 9 - 11 is controlled by a CPU circuit 20 to set the CCD accumulating time and a read timing properly. Thus, the proper adjustment taking the S/N into account is attained to amplifier circuits 13a - 13c.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color film image reading device that uses a plurality of one-dimensional image sensors such as CODs to read color-separated color film optical images.

(Prior Art) Conventionally, in a color film image reading device that optically reads a color film image and converts it into an electrical signal, a light image transmitted from a color film by a light source is passed through a color separation optical system to obtain, for example, a red image. , green, and blue,
A photoelectric conversion means provided for each color separation optical system, such as an image sensor such as a phototube or COD, converts it into an image signal, and an amplifier is provided independently for each output of each image sensor, and an image for each color obtained from the amplifier is used. The signals are processed by analog circuits.

In addition, for digital processing of image signals obtained from image sensors, an A/D converter is provided for each image sensor, and the amplified output of the image sensor is converted into a digital signal by the A/D converter and stored in a memory, etc. Predetermined image processing is performed under program control by a microcomputer.

(Problems to be Solved by the Invention) However, in such conventional color film image reading devices, the image sensor such as a CCD and the light source generally do not have flat spectral sensitivity characteristics in the visibility region. Therefore, when the image sensor's accumulation time is constant, the received light output will be at a different level depending on the color separation, and this sensitivity characteristic correction is done by adjusting the gain of the amplifier installed in the output stage of each image sensor to receive light for each color separation. You will need to adjust W4 for each color so that the levels are approximately the same, but since the output level of the image sensor is very small, if you adjust it for each separated color, the image sensor output of the separated color with low sensitivity will be very high. This requires setting the gain, which is disadvantageous in terms of S/N ratio, and noise in the image becomes noticeable.

On the other hand, in order to correct the spectral sensitivity characteristics of the image sensor, it is possible to offset the spectral output characteristics by giving the light source the opposite spectral output characteristics, but such a light source that corrects the spectral sensitivity characteristics of the image sensor consumes a lot of power and is expensive. There is also the problem that it becomes expensive.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and it is possible to increase the gain of an amplifier by obtaining a photoelectric conversion output based on a photocharge accumulation time corresponding to color separation. It is an object of the present invention to provide a color film image reading device that can obtain high-quality images regardless of the type of color separation by setting low settings and reducing the difference in gain between each amplifier.

In order to achieve this object, in the present invention, an optical image from a color film separated into a plurality of colors by a color separation optical system is incident on an image sensor such as a COD, and a control means sends an optical image to each image sensor for each separated color. In this case, different photocharge accumulation times are set.

(Function) According to the configuration of the present invention, even if the spectral sensitivity characteristics of the image sensor and the light source in the visibility range for color separation are not flat, the sensor output can be at approximately the same prescribed level. Since different accumulation times are set and read out depending on the color separation, the amplifier gain is also approximately the same, and the amplifier gain for color signals with low spectral sensitivity is set extremely high compared to others. Image signals with flat spectral sensitivity characteristics can be obtained without any problems.

(Embodiment) FIG. 1 is an explanatory diagram showing an embodiment of the present invention, taking digital image processing as an example.

First, the configuration will be described. Reference numeral 1 indicates a halogen lamp serving as an illumination light source, and 2 a condenser lens. The halogen lamp 1 and the condenser lens 2 constitute an illumination system.

Reference numeral 3 denotes a film moving stage, on which a film holder 4 is attached, and a color film 5 to be read is set on the film moving stage 3 by the film holder 4. The film moving stage 3 can be moved in six directions indicated by arrows by a stepping motor 6.

Reference numeral 7 designates a lens, in which the film image of the color film 5 set on the film movement stage 3 by the film holder 4 is incident on the three-color separation dichroic prism 8 through the lens 7, and the film image is converted into red (R) by the three-color separation dichroic prism 8. ＞, C0D-dimensional image sensor (hereinafter simply r
A film image is formed on a >9.10.11 light receiving section called CCDJ.

Furthermore, 12 is a COD drive circuit, which is controlled by the CPU circuit 20 and drives the CCDs 9, 10, and 11 independently.

13a, 13b, 13c are amplifier circuits, and CCD9,
It is provided every 10.11 and amplifies the output signal of the COD. Analog switches 14a and 14b are provided at the outputs of the amplifiers 13a to 13c, respectively.

14C is provided, one of the analog switches 14a to 14c is controlled to be turned on in response to a control pulse from the CPU circuit 20, and C0D9 to C0D9 corresponding to the switch ON are turned on.
Select one of the 11 sensor outputs.

Reference numeral 15 designates a sample and hold circuit to which the outputs of the analog switches 14a to 14c are commonly connected and input, and reference numeral 16 designates an A/D converter that converts the sensor output held by the sample and hold circuit 15 into a digital signal. The sample hold circuit 15 and the A/D converter 16 operate with pulses generated by the pulse generation circuit 17, and the pulse generation circuit 17
It is controlled by the PU circuit 20. Furthermore, the CPU circuit 20 is a 1at (t memo 1) circuit that stores image data digitally converted by the A/D converter 16, and the CPU circuit 20 performs predetermined 17I image processing based on the image data stored in the memory circuit 18. will begin to do this.

Furthermore, 19 is a motor drive circuit, which receives instructions from the CPU circuit 20 and applies drive pulses to the stepping motor 6.

Here, three image sensors 9.10.1 are operated by the COD drive circuit 12 based on the control by the CPU 20.
The principle of readout control based on the setting of the accumulation time of 1 will be explained.

First, the spectral sensitivity characteristics of C0D9-11 are as shown in FIG. 5, and the spectral output characteristics of halogen lamp 1 are as shown in
As shown in the figure.

That is, in the spectral sensitivity characteristics of the COD shown in FIG. 5, in the wavelength range of 400 to 700 nm, which is the visible sensitivity region, the longer the wavelength, that is, from blue to red, the higher the relative sensitivity of 9 degrees, It shows a peak value around 650 nm, which is in the red wavelength region, and as the wavelength becomes longer, the relative sensitivity decreases. Further, the spectral output characteristics of the halogen lamp 1 are approximately zero near the wavelength of 400 nm+1, which is violet, and as the wavelength becomes longer, the output increases approximately linearly.

As is clear from the spectral sensitivity characteristics of the COD and the spectral output characteristics of the light source shown in Figs.
9, 10, and 11, if the accumulation time of each C0D9-11 is equal, a large sensor output will be obtained in the order of R, G, and B.

Therefore, in the conventional device, the gain of the amplifier circuit is relatively increased for C0D9 to C0D11, into which the three-color separated images of R, G, and B are input, for B, which has the smallest spectral sensitivity characteristic. However, by increasing the gain, the S/N ratio worsens, resulting in a drop in image quality.

On the other hand, in the present invention, by increasing the accumulation time for COD in which a color separation image with low spectral sensitivity is incident, COD9 in which each color separation image of R, G, and B is incident.
Basically, the output levels of 11 to 11 are set to approximately the same level.

Specifically, if T is the accumulation time of the CCD 9 which receives the color-separated image of red (R), which has the highest spectral sensitivity, then the accumulation time of C0DIO which receives the color-separated image of green (G), which has the next highest spectral sensitivity. Set the time to about 2 tones, and then set the blue color (which has the lowest spectral sensitivity
For CCDII that receives the color separation image of B), approximately 4
Set the accumulation time.

Of course, this accumulation time is appropriately set based on the spectral sensitivity characteristics of the image sensor actually used as shown in FIGS. 5 and 6 and the spectral output characteristics of the light source such as the halogen lamp 1. Furthermore, although FIG. 1 takes three color separations as an example, the number of color separations can be determined as appropriate.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to the time chart shown in FIG.

In the time chart of Figure 2, R3H, GSH, B
SH is a shift pulse for successive output given to CCD9, CCD10 and CCD11, respectively, and ROLI
T, GOLIT and BOtJT represent the waveforms of output signals read out from CCD9, CCD10 and CCD11 based on the shift pulses, respectively.

Furthermore, the on/off waveforms of the analog switch switches 14a to 14G are shown, and in this switch waveform, the H level is shown as the active level for switching on.

Furthermore, the driving period of the stepping motor 6 performed after reading C0D9 to C0D11 is shown.

First, if the period of the RS H pulse of CCD 9 corresponding to R, which has the highest spectral sensitivity characteristic, is T, then the CG corresponding to G
The accumulation time given by the period of the DIO GSH pulse is:
In this embodiment, it is approximately 2 kings, and the accumulation time given by the period of the B S H pulse of the CCD 11 corresponding to B, which has the lowest spectral sensitivity characteristic, is approximately 4 kings.

Here, the time required for successive output from COD following the shift pulse is set to be slightly shorter than the period T of the RS l-1 pulse. As a result, even if the ROUT signal is output from the C0D9, there is a period in which the signal level is zero in the GOUT output of the CCD 10 and the BOUT output of the CCD 11.

Therefore, the operation will be explained with reference to the time chart shown in FIG.

First, when the driving of the stepping motor 6 ends at time t1, the film moving stage 3 stops, so that it becomes possible to accumulate C0D9 to C0D11 for image reading.

In this embodiment, accumulation starts from time t2.

Since the B CCD 11 starts accumulating from time t2, a BSH pulse is output at time t2, and the charge accumulated in the CCD 11 up to that point is read out and discarded.

That is, the output BOut of the CCD 11 obtained by reading from time t2 is at this time the corresponding analog switch 14C.
Since the sample hold circuit 15 is in the off state, the sample hold circuit 15
The signals that are not output to the other side and continue to be output are simply discarded.

Subsequently, at time t3, the R CCD9 and the G CC
Give R8H pulse and GSH pulse for D10 and R
and G@start accumulation for reading.

Since the accumulation time of C0D9 of R is T, rf! g
When time t4 is reached, the accumulation of CCD9 is finished, and the next time &11
Reading of the CCD 9 is performed between t4 and t5.

At this time, since the analog switch 14a is on, the signal read from the CCD 9 is transmitted to the analog switch 1.
4a and is applied to the sample hold circuit 15,
Pixel data is held for each light-receiving pixel in a sample and hold circuit 15, converted into a digital signal by an A/D converter 16, and sequentially 1q pixel data is read back to a memory circuit 18.

At the next time 5, the accumulation of G CC010 (accumulation time 2T) is completed, and the G S t-t pulse is output and the C
Start reading from 0DIO. At the same time II 'j
5, the analog switch 14a is turned off, the analog switch 14b is turned on, and the signal from the CCD 10 passes through the analog switch 14b to the ripple hold circuit 15.
is converted into a digital signal by the A/D converter 16 for each light-receiving pixel and stored in the memory circuit 18.

Furthermore, at time 16, the accumulation of the B CCD 11 (open 4T during accumulation) is completed, and the BSH pulse is output and the CCDI
Start reading from I. At this time, the analog switch 14b is turned off and the analog switch 14C is turned on, so the signal read from the C0D11 is passed through the analog switch 14C and given to the sample and hold circuit 15, and is sent to the A/D converter 16 for each pixel. The signal is then converted into a digital signal and stored in the memory circuit 18.

On the other hand, since all C0D9 to C0D11 have been accumulated at time t6, there is no problem even if the film movement stage 3 is moved.
The driving of the stepping motor 6 is restarted at timing 7.

When reading from the CCDII of B is completed at time t8,
The analog switch 14c is turned off, the analog switch 14a is turned on again, the stepping motor 6 is driven until time t10 and stopped, the film moving stage 3 is moved to the next scanning position, and then from time t10 to time t1. - Repeat the same operation as shown in t8.

Therefore, the readout drive based on the set accumulation time of C0D9-11 becomes main scanning, and the movement of the film movement stage 3 at the end of COD output becomes sub-scanning, and by repeating this main scanning and sub-scanning alternately, the film Color film 5 attached to moving stage 3 with film hold 4
The image can be read.

As is clear from the above explanation of the operation, once the relationship between the accumulation times to obtain the same sensor output is determined from the spectral sensitivity characteristics of the color separation images for C0D~11 shown in Figures 5 and 6,
Based on this correlation of accumulation times, the CPU circuit 20
8H, GSI- (and BSI) pulses can be freely controlled, and the COD accumulation time and successive output timing can be set as appropriate.

Also, since the accumulation times of the three C0D9 to C0D11 are different, it is possible to
.about.11, the driving of the stepping motor 6 is stopped during the CCD accumulation period from time t2 to time t6. Since this stepping motor 6 can also be controlled by the CP circuit 20, COD accumulation control and motor drive timing control can be easily set.

FIG. 3 is a circuit block diagram showing an embodiment of a shift pulse control circuit that generates R3I(, GSt-, and BSI-(pulses) for COD reading shown in the time chart of FIG. 2.

In FIG. 3, 20 is the CPU circuit shown in FIG. 1, 22 is a shift pulse generation circuit that generates a shift pulse SH based on the υ control output of the CPtJ circuit 20, and 23
a to 23C are AND gates. This shift pulse generation circuit 22 and AND gates 23a to 23C are included in the CCDWI Alj1 circuit 12 in FIG.

The operation of the shift pulse control circuit shown in FIG. 3 will be explained with reference to the time chart shown in FIG. 4 as follows.

First, the shift pulse generation circuit 22 receives a command from the CPU circuit 20 and generates a shift pulse SH of a constant period. The generation cycle of the shift pulse SH can be arbitrarily set by using a programmable timer directly connected to the CPU bus.

On the other hand, from the CPU circuit 20, andoo 1-23 a~2
The control signals @RON, GON, and BON output to 3C are equal to the control signal RO when the period of the shift pulse SH is the king.
N is always kept at H level, and the control signal GON has a period T with a time delay of 1/2 with respect to the shift pulse SH.
The control signal BON is a signal that repeats L level and H level every time, and furthermore, the control signal BON goes to L level during the 3 kings with a time delay of T/2 with respect to the shift pulse SH, and goes to H level during the remaining kings.
This is a signal that repeats level inversion.

Therefore, when the shift pulse generation circuit 22 outputs the shift pulse SH at time 1, at this time, the control signals RON, G
Since they are at the ON and BONLtH level, the AND gates 23a to 23G are in the permissible state, and the shift pulse SH
passes through the AND gates 23a to 23C and becomes R3)-1,
Output as GSH and BSH pulses.

Next, at time t2, when T/2 has elapsed from time t1, the control signals GON and BON both go to L level, and the AND gates 23b and 23c are inhibited, and the shift that occurs at the next time t3 Pulse SH passes only through AND gate 23a and is output as R3l-1 pulse.

Further, at time t4, the control signal GON becomes H level, and the next generated shift pulse is output from the AND gate 23a.
, 23b and are output as R3H and GSH pulses. Furthermore, at time t5, which is four times after time t1, the BSH pulse is output in addition to the R5H and GSH pulses from the second layer where the control signal BON is at the H level, and this process is repeated thereafter. It becomes like this.

In this way, by using the simple shift pulse generation circuit shown in FIG. 3, the accumulation time and readout timing of the three CODs 9 to 11 shown in FIG. analog switch 1
Since one corresponding to the reading of C0Ds 48 to 14C is turned on, even if a plurality of C0Ds 9 to 11 are used, only one expensive A/D converter 15 is required. Furthermore, the amplifier circuit 13
Since a to 13C have appropriate →reference adjustment in consideration of the S/N ratio, noise components will not increase for a particular separated color, and high-quality image reading can be performed with a small circuit scale. can.

FIG. 7 is a block diagram showing another embodiment of the successive control circuit used for read-out control of C0D9 to C0D11 in FIG. Fine control of accumulation time can be performed.

In FIG. 7, 20 is a CPU circuit, 25 is a shift pulse generation circuit, 26, 27, and 28 are programmable timers directly connected to the CPU bus, and 29a.

29b and 29c are AND gates.

As the COD driven by the embodiment shown in FIG. 7, a COD equipped with a sensor reset terminal is used. Accumulation of signal charges due to charge conversion is prevented over the period of time.

Therefore, the operation according to the embodiment shown in FIG. 7 will be explained with reference to the time chart shown in FIG. 8.

First, the shift pulse generation circuit 25 generates a shift pulse SH of a constant period under the control of the CPU circuit 20. Further, the CPU circuit 20 is similar to the embodiment shown in FIG.
R8)l by control signals RON, GON and BON;
GSH, BS) Controls the pulse. However, in this embodiment, the periods of the R3H, GSH, and BSH pulses are the same, and the COD read period is set to be shorter than the period of the shift pulse SH.

First, from time t1 to t5, reset pulse RR3
Since is at H level, R CCD9 is in the reset state,
It has stopped accumulating charge. When the reset pulse RR3 goes to L level at time t5, accumulation in the CCD 9 starts. When the R3H pulse is output at time t7 during this accumulation, reading out of the signal charges accumulated in the CCD 9 is started. CCD10 corresponding to G and C0 corresponding to B
Similarly for D11, reset pulses GR8, BR
Accumulation starts from the time when the 8IfiL level is reached (times t6 and t4), and readout of signal charges starts at the timing when a predetermined accumulation time ends (times t8 and t9) due to the GSH and BSH pulses.

In this way, in the embodiment of FIG. 7, the accumulation time of C0D9 to C0D11 can be controlled by the reset pulses RR3, GR3, BR3, and
3 is generated by programmable timers 26 to 28, so that the accumulation time can be set in a delicate manner up to the period of the reference clock provided from the CPU circuit 20 (on the order of microseconds).

As a result, the COD data obtained by A/D conversion is
The U circuit 20 calculates shift pulses S)t, fbll, W signal RON, so that the output of COD becomes the same level.
GON, BON and reset pulses RR3, GR8, B
By controlling R3, automatic setting control of the COD accumulation time becomes possible.

As described above, in this embodiment, the optical image signals from the color film separated into three colors by the color separation optical system are photoelectrically converted by the three image sensors, and one of the amplified outputs of each image sensor is selected. A switch means is provided for each image sensor, and a control means sets a different photocharge accumulation time for each separated color in each image sensor, and each time the set time is reached, one of the corresponding switch means is sequentially activated. It is turned on and the image sensor output is read out to the outside.

That is, in this embodiment, by making the accumulation time different for each color, the signals are read out not simultaneously but in time series, so that the outputs of the switch means can be commonly connected and input to the A/D converter. One A/D converter is required regardless of the number of color separations, and as a result, the circuit configuration is simple, the equipment cost is low, and the amplifier gain can be set to an appropriate value considering the S/N ratio. It is possible to obtain high quality images.

In addition, although the above embodiment takes as an example a case where an image of a color film is color-separated and the image is read using a plurality of CODs, the present invention is not limited to this, and it is possible to read the image from a suitable medium. It can be directly applied to a device that separates and reads an optical image. For example, it is suitable as an image reading device for a system that separates an optical image from a color film and transmits the image using a communication line.

Furthermore, in the embodiment shown in FIG. 1, the configuration is shown in which the signals of each color are sequentially read out using the difference in the photoelectric charge accumulation time of each color, but the configuration is not limited to this, and the signal of each color can be read out simultaneously. It's okay. In that case, of course, the analog switch 14
a, 14b, and 14c are removed, and the sample and hold circuit 15
, A/D converter 16 is configured to be provided for each color.

Furthermore, in this embodiment, the outputs of the analog switches 14a to 14C) are converted into digital signals by the A/D converter 16, but the outputs of the analog switches 14 are supplied to an analog processing circuit to perform predetermined image processing. You can also do it.

(Effects of the Invention) As described above, according to the present invention, an optical image from a color film or the like that has been separated into a plurality of colors by a color separation optical system is incident on an image sensor such as a COD, and each image is Since different accumulation times are set on the sensor for each separated color, even if the spectral sensitivity and spectral output characteristics of the image sensor and light source in the visibility region are not flat, the sensor output can be kept at approximately the same level and the spectral sensitivity is flat. This makes it possible to suppress extreme level differences in image sensor output caused by the spectral sensitivity characteristics of the image sensor and the spectral output characteristics of the light source.

Therefore, there is no need to adjust the gain of the amplifier that amplifies the output of the image sensor to an extremely different value for each image sensor, and the S/N ratio of the output signal of each image sensor can be suppressed to approximately the same specified value to reduce noise. It is possible to obtain high-quality scanned images with a small number of images.

Furthermore, since COD storage, readout, and stepping motor drive can be freely controlled, the image reading speed can be varied over a wide range.This allows the speed required by the device that receives and receives the read image data to be easily adjusted. It can be easily combined with a suitable device for processing the read image data.

Furthermore, in the digital processing of this embodiment, one A
Since only a /D converter is required, the circuit configuration becomes simple and the device cost can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, FIG. 2 is a time chart showing the operation of FIG. 1, and FIG. 3 is a pulse diagram for COD driving used in the embodiment of FIG. 1. A circuit block diagram showing an embodiment of the II control circuit, FIG. 4 is a time chart showing the operation of FIG. 3, FIG. 5 is a graph showing the spectral sensitivity characteristics of the COD image sensor, and FIG. A graph showing the spectral output characteristics of a halogen lamp, FIG. 7 is a circuit block diagram showing another embodiment of the pulse control circuit for COD driving used in the present invention, and FIG. 8 shows the operation of FIG. 7. This is a time chart shown. 1: Halogen lamp 2: Condenser lens 3: Film moving stage 4: Film holder 5: Color film 6: Stepping motor 7: Lens 8: 3-color division dichroic prism 9.10, 11: CCD-dimensional image sensor 12
: CCD drive circuits 13a to 13C: Amplification circuits 14a to 14C; Analog switch 15: Sample hold circuit 16: A/D converter 17: Pulse generation circuit 18: Memory circuit 19: Motor drive circuit 20: CPIJ circuit

Claims (1)

[Claims] A color separation optical system that separates an optical image obtained from a color film into a plurality of colors; a plurality of image sensors that receive the optical image color-separated by the optical system and generate a light reception output according to the light reception accumulation time; 1. A color film image reading device comprising: control means for controlling accumulation time so that the output of each image sensor reaches a prescribed level.