JPH0827495B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to a function of selecting the interruption / continuation frequency of a voltage applied to a light source of the image reading device according to the operating state of the device. The present invention relates to an image reading device equipped with.

2. Description of the Related Art In recent years, image reading devices have been used in various fields. Among these image reading devices, there is one that reads an image recorded on a microfilm.

Microfilm has unique characteristics that are different from those of information recording media generally used in recent years, such as high-density information recording, semi-permanent storability, and readability. Therefore, it is used for still image files as an analog information recording medium in various fields that can make full use of this feature. The form of the microfilm is a roll form in which images are recorded sequentially, a unit form in which images are recorded flatly. However, in any form, since the image is recorded at high density on the microfilm,
An image reading device that retrieves the required image from this and displays this image on the screen as necessary, or projects it on a screen other than the screen to obtain a hard copy in order to electrically read this image is required. .

Such an image reading device is disclosed in, for example, JP-A-62-5.
Although there is one disclosed in Japanese Patent No. 764, this device uses a screen for enlarging and projecting an image recorded on a microfilm by an optical system, and an electrical system based on light from the optical system for projecting this image. And a photoelectric conversion unit that outputs the data to an external device such as a printer.

As described above, when the image is projected on the screen or when it is electrically read, it is performed by the light from the light source provided in the optical system. In this case, the light amount of the light source is the image on the screen. When projecting, it is sufficient that a person can easily recognize the image, but when electrically reading this image, a photoelectric conversion element such as a CCD, for example, even if the grayscale of the image to be read is different. It is necessary to change the brightness of the light source in multiple steps so that an appropriate amount of light is always incident on.

There are various methods for controlling the brightness of the light source in multiple stages, but as an image reading apparatus, the response speed of the photoelectric conversion element described above is very fast, and therefore the fluctuation with respect to the set illuminance is extremely large. A PWM control method that satisfies this requirement is used because a control method that is small and that can perform multi-step control is required.

There are various methods for performing this PWM control, but in the case of using a microcomputer, two counters are used, and the pulse width is controlled by making these counters alternately perform counting operation. There are many things like this.

A halogen lamp is generally used as the light source of the image reading device.However, in the case of the halogen lamp, when the PWM control frequency is 2.5 KHZ to 3 KHZ or more, the illuminance fluctuation with respect to the set illuminance is within the allowable range ( Since it is within 1 to 2%), the illuminance control of the halogen lamp is normally performed at a frequency of about 8 KH, in consideration of the required number of stages of illuminance adjustment and the performance of the device for PWM control.

Problems to be Solved by the Invention In such a conventional image reading apparatus, in order to supply an appropriate amount of light to the photoelectric conversion element, the halogen lamp, which is a light source, is PWM-controlled at a frequency of about 8 KH. Therefore, when the image reading device is used in a very quiet place, an oscillating sound having a constant frequency is emitted from the power source, and the oscillating sound may be harsh. This is because the frequency of the PWM control is in the audible range. To solve this problem, simply consider this frequency as a frequency outside the audible range, but it is required for the light source of the image reading device. The number of steps to adjust the illuminance is about 500 steps within the range of 0 to 100% (this can be achieved by changing the duty ratio of the pulse). Let's realize these 500 steps at frequencies outside the audible range. Then, the frequency of the counting operation of the counter described above is, for example, 20000 Hz for frequencies outside the audible range.
If set as, 20000HZ × 500 steps = 10000000HZ, but at present, it is not possible to use a microcomputer for counting operation at this frequency, and at present, a practical counting operation frequency is available. Since it is about 4 MHz, if you try to realize 500 adjustment stages at this frequency, the PWM frequency will be 8 KHZ, and under the present circumstances, the audible frequency is unavoidable, and the oscillation sound generated based on the PWM control is generated. It was difficult to control.

Further, in order to eliminate this oscillating sound, it is possible to control outside the audible range by using an external circuit, but the circuit for that becomes complicated, and there is a problem that the cost increases accordingly.

The present invention has been made in view of the above-mentioned conventional problems, and the operating state of the image reading device is such that the mechanical system is not operating when the image is projected on the screen and the oscillating sound is easily heard. In the case of, the cutoff / continuation frequency of the voltage applied to the light source is out of the audible range, and the operating state of the image reading device is such that the mechanical system is operating during image hard copy or image reading, and the oscillating sound can be heard. It is an object of the present invention to provide an image reading apparatus having a function capable of setting a cutoff / continuation frequency of a voltage applied to a light source to outside the audible range when the light source is not present and obtaining a necessary adjustment step of the light source.

Means for Solving the Problems The present invention for achieving the above object provides an image reading apparatus for reading an image recorded on an information recording medium, and a light source for illuminating the image recorded on the information recording medium, and a light source. The screen on which the illuminated image is projected, and the light transmitted through the image recorded on the information recording medium are projected onto the screen. The first state and the light transmitted through the image recorded on the information recording medium are projected on other than the screen. The optical system capable of switching between the second state and the second state, and when the optical system is in the first state, a voltage intermittently applied at a first frequency outside the audible range is applied to the light source, and the optical system is in the second state. In this case, it has a voltage supply means for applying a voltage interrupted at the second frequency in the audible range to the light source.

With this configuration, the light source of the image reading device
Depending on the operating state, a voltage interrupted at a first frequency outside the audible range or a voltage interrupted at a second frequency outside the audible range is selectively applied, so that, for example, an operating sound is generated. When the mechanical system of the device to be operated is not in operation, the light source is applied with a voltage that is interrupted and interrupted at the first frequency outside the audible range, and the device sound is quiet, while the device sound is generated. When the system is in operation, the voltage applied to the light source at the second frequency in the audible range is interrupted / continuously applied, so that the number of adjustment stages required for the light source can be secured.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic block diagram of the image reading apparatus of the present invention.

As shown in the figure, a reflection mirror 2 is provided behind the halogen lamp 1 which is a light source, and a part of the light emitted from the halogen lamp 1 is reflected by the reflection mirror 2 to be emitted from the halogen lamp 1. The directly emitted light is focused by the condenser lens 3 and reflected by the reflection mirror 4, and the reflected light is movably held by the film carrier 6 via the condenser lens 5 on the information recording medium. The image recorded on a certain microfilm M is passed. A state in which the image reading device projects the image on the screen 11 (hereinafter, referred to as a reader).
In the case of, the second mirror 8 is at the position of the solid line position 8A in the figure, and the fourth mirror 9 is also set to the position of the solid line position 12A in the diagram, so at the time of the leader The light passing through the image is reflected in order of the second mirror 8, the fourth mirror 9, and the fifth mirror 10 through the magnifying lens 7, that is, the image of the microfilm M is displayed on the screen 11 by the optical path indicated by the points. To project. At the time of this reader, since the halogen lamp 1 is turned on and only the image is projected on the screen 11, there is no mechanical noise of the device.

Further, when the image reading device is in a state of electrically reading the image on the microfilm M (hereinafter, referred to as image reading), the fourth mirror 9 escapes to the position 9'in the figure, and the second mirror 8 and the third mirror 12 are 8 in the figure.
(A), 8 (B), 8 (C), 8 (D), 8 (A) and 12
(A), 12 (B), 12 (C), 12 (D), 12 (A) reciprocally move in synchronization in order, and at the time of image reading, the light passing through the image is reflected by the second mirror 8 and dimmed. The filter 13 and the third mirror 12 are sequentially reflected and dimmed to reach the CCD element 14 for photoelectric conversion. In other words, the light obtained by scanning the image on the microfilm M is applied to the CCD element 14 through the optical path indicated by the solid line, and the applied light is photoelectrically converted into image data. When reading this image, the second mirror 8 is mainly used.
Since the third mirror 12 reciprocates as described above, mechanical noise is generated.

Further, the magnifying lens 7 has a function of magnifying an image recorded on the microfilm M from several times to several tens of times,
Since the image has various shades, the illuminance of the halogen lamp 1 is controlled in multiple stages so that the CCD element 14 is always given a predetermined amount of light.

FIG. 2 shows a circuit diagram for controlling the voltage applied to the halogen lamp 1 and the interruption / continuation frequency thereof.

A voltage is supplied via an output buffer 22 and a resistor 23 to a CPU 21 as a voltage supply means for controlling the voltage value applied to the halogen lamp 1 (this voltage value is determined by the duty ratio) and its cut-off frequency. The gate of FET24 as a means is connected, and the gate of FET24 is turned on (when the output from CPU21 is H) and turned off (when the output from CPU21 is L) by the pulse signal output from CPU21. Become. The halogen lamp 1 is connected to the drain of the FET 24, and the source is grounded.
Since the drain and the source are connected when the gate is turned on, the halogen lamp 1 is turned on, and when the drain and the source are turned off, the halogen lamp 1 is turned off and the halogen lamp 1 is turned off. In addition, the diode 25 connected to both ends of the halogen lamp 1,
This is for absorbing the surge voltage generated when the halogen lamp 1 is interrupted in current.

The voltage applied to the halogen lamp 1 by the circuit configured as shown in FIG. 2 is controlled as follows by the flowchart shown in FIG.

This flowchart will be described below with reference to FIGS. 2 and 3.

When the program starts, CPU21 is initialized. That is, the value of the counter is set to 0 (step 1). Next, 50 values are input to each of the counter A and the counter B. This value is entered in the counter,
The frequency of the counting operation of counter A and counter B
If it is set to 2 MHZ, the FET 24 will be switched at 2 MHZ / 50 + 50 = 20000 HZ. In other words, CPU21
The H signal is output while the counter A is counting down, and the L signal is output while the counter B is counting down. Therefore, the halogen lamp 1 has a waveform as shown in FIG.
In KHZ, a voltage with a duty ratio of 0.5 is applied, and since this frequency is outside the audible range, the oscillating sound generated during PWM control cannot be heard.

In the above example, the values of 50 are input to each of the counter A and the counter B, but the values set in the counter A and the counter B are set by the operator on the operation panel. By operating the operating knob, the brightness of the projected image on the screen 11 can be set easily (however, in the range of A + B = 100).

(Step 2). Then, when the start button of the image reading device is pressed (step 3), 250 values are input to each of the counter A and the counter B. At this time, F
The ET24 is switched at 2MHZ / 250 + 250 = 4000HZ, and the halogen lamp 1 has an interruption / continuous frequency of 4K in the audible range.
A voltage with a duty ratio of 0.5 is applied in HZ, but since the mechanical system starts moving immediately after switching to this frequency, the oscillation sound during PWM control will be erased by the device sound from this mechanical system, There is no problem even if the frequency is lowered.
The reason for lowering the frequency during image reading is that it allows multiple adjustment steps. The illuminance of the halogen lamp 1 at this time is a predetermined value (a fixed value) because AE photometry described later is performed (step 4). At the time of image reading, the second mirror 8 and the third mirror 12 shown in FIG. 1 move forward, and the AE metering that determines the illuminance level of the halogen lamp 1 so that an appropriate amount of light is supplied to the CCD element 14 is performed. Done,
The data at the time of photometry is sampled (step 5).

The CPU 21 calculates constants α and β for determining the duty ratio based on the data sampled in step 5. Here, the sum of the constant α and the constant β is set to 500 in order to set the interruption / continuation frequency of the voltage applied to the halogen lamp 1 to 4 KHZ. 500
The reason is that the number of steps for adjusting the illuminance of the halogen lamp 1 is set to 500 (step 6). The calculated constant α and constant β are used as counter A and counter B.
(Step 7). Assuming that the constant α and the constant β calculated by this AE photometry are α = 400 and β = 100, respectively, they have a waveform as shown in FIG. 3 (b), and the disconnection / continuation frequency is 4KHZ and the duty ratio is 0.8. When a voltage is applied to the halogen lamp 1 and α = 300 and β = 200, the halogen lamp 1 has a waveform as shown in FIG. 3 (c), and a voltage with a duty cycle of 4KHZ and a duty ratio of 0.6. , And α = 200, β = 300, it has a waveform as shown in Fig. 3 (d), and the duty ratio is 4KHZ at disconnection / continuation frequency.
A voltage of 0.4 is applied to the halogen lamp 1, and the disconnection / continuation frequency is constant at 4 KHZ, but voltages of waveforms with different duty ratios are applied to the halogen lamp 1.
As a result, the halogen lamp 1 is turned on with different illuminance. Next, the second mirror 8 and the third mirror 12 shown in FIG. 1 are moved back, and the image reading device performs photoelectric conversion based on the optical signal applied to the CCD element 14 under the determined illuminance. Then, the image is output as an electric signal to an external device (step 8). Then, when the reading of the respective mirrors is completed and the reading is completed, the process returns to step 1, and the halogen lamp 1 is turned on by the voltage of which the interruption / continuation frequency is 20 KHZ and the duty ratio is 0.5 (step 9). .

As described above, when the reader of the image reading device does not generate the device sound, the applied voltage of the halogen lamp 1 is set to 20 KHZ which is a frequency outside the audible range to eliminate the oscillating sound, and the mechanical system of the image reading device operates. When reading an image, the oscillating sound is canceled by the operating sound of the mechanical system and becomes unpleasant to the ear, and a low interruption / continuity frequency is required to adjust the illuminance in more stages. The frequency of interruption and continuation of voltage is 4KHZ, which is the frequency in the audible range.

In this embodiment, the counter frequency is specifically set to 2 MHz, but the interruption / continuation frequency of the voltage applied to the halogen lamp 1 is set outside the audible range at the time of reading, and at the time of image reading. If the condition that the frequency is in the audible range to the extent that the necessary adjustment of the illuminance of the halogen lamp 1 is obtained is satisfied, the disconnection / continuous frequency of the voltage applied to the halogen lamp 1 at the time of the reader and the image reading is not particularly limited. Of course not.

Effects of the Invention As is clear from the above description, according to the present invention,
Depending on the operating state of the image reading device, either the voltage interrupted / interrupted at the first frequency outside the audible range or the voltage interrupted at the second frequency outside the audible range is selectively applied to the optical system. Is applied to the light source constituting the above, it is possible to prevent the oscillating sound that is harsh to the ear and to obtain the stage of adjusting the illuminance of the light source that does not hinder the image reading.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image reading apparatus according to the present invention,
FIG. 2 is a circuit diagram for controlling the voltage applied to the halogen lamp and its disconnection / continuation frequency, FIG. 3 is a diagram showing an example of the output waveform of the circuit shown in FIG. 2, and FIG. 3 is an operation flowchart of the circuit shown in FIG. 1 ... Halogen lamp (light source), 11 ... Screen, 14
... CCD, 21 ... CPU (voltage supply means), 24 ... FET (voltage supply means), M ... microfilm.

Claims (1)

[Claims] 1. An image reading apparatus for reading an image recorded on an information recording medium, a light source for illuminating the image recorded on the information recording medium, a screen onto which the image illuminated by the light source is projected, and an information recording medium. An optical system capable of switching between a first state in which light transmitted through the image recorded on the screen is projected onto a screen and a second state in which light transmitted through the image recorded on the information recording medium is projected outside the screen; A voltage interrupted at a first frequency outside the audible range is applied to the light source when the optical system is in the first state, and a voltage interrupted at the second frequency in the audible range when the optical system is in the second state. And a voltage supply means for applying a light source to the light source.