JPH0675434B2 - Light source - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a light source device of a latent image forming means such as a liquid crystal optical shutter for forming an electrostatic latent image on a photoconductor, and more specifically, to maintain a constant light amount of the light source. The present invention relates to a light amount control device for controlling as described above.

[Prior art]

In recent years, as a cold light source that does not dissipate heat, a light diffusing portion is formed along the longitudinal direction on the peripheral surface of a transparent light transmission rod, and light incident on one end surface of the rod is diffusely reflected by the light diffusing portion. Therefore, it is proposed that the light is emitted from the direction opposite to the light diffusion portion. Since such an illuminating device does not dissipate heat, it can be suitably used as a light source of a liquid crystal optical shutter whose operation characteristics change depending on temperature.

By the way, when a liquid crystal optical shutter is used in a recording device,
Since the latent image potential changes when the light quantity changes, the light source is required to have a constant light quantity. for that reason,
When the above-mentioned lighting device is used as a light source, the amount of light needs to be controlled to be constant although there is no heat dissipation. When controlling the light amount, the light amount emitted from the light source is detected, and the light emission amount of the light source is controlled based on the detected value.

Therefore, as a device for detecting the light amount of the illumination device using the above-mentioned rod, for example, the following device can be considered.

(1) As shown in FIG. 7, an optical sensor is provided below the rod 21.
23 is arranged at a position that does not block the effective irradiation area A of the liquid crystal optical shutter 22. In this case, the optical sensor 23 is a liquid crystal optical shutter.
One of the 23 effective irradiation areas A is arranged.

(2) As shown in FIG. 8, the optical sensor 23 is arranged below the end of the rod 21. Since the optical sensor 23 is located below the end of the rod 21, it does not block the light in the effective irradiation area of the liquid crystal optical shutter.

(3) As shown in FIG. 9, a mirror 24 is arranged at a position that does not block the effective irradiation area of the liquid crystal optical shutter.
The optical sensor 23 receives the light reflected from 24.

[Problems of conventional technology]

However, in any of the above-described devices shown in FIGS. 7 to 8, the rod 21 and the liquid crystal optical shutter which is the irradiation target are used.
If there is a sufficient distance to the liquid crystal display 22, there is no problem.
The effective irradiation area A may be blocked. Therefore, when mounting the optical sensor 23, high positional accuracy is required.
Similarly, in the structure shown in FIG. 9, the mirror 24 may block the effective irradiation area A of the liquid crystal optical shutter 22, and therefore a high positional accuracy of the mirror 24 is required.

In addition, if the distance between the rod 21 and the liquid crystal optical shutter 22 is short, the mounting position of the optical sensor 23 is restricted, which affects the optical structure of the light source device, which impairs the degree of freedom in design. Further, the amount of light received by the optical sensor 23 changes depending on the angle, and the amount of light received changes due to a slight change in the mounting position. Therefore, as shown in FIGS. 7 to 9, the change in the amount of received light due to the error in the mounting position and angle of the optical sensor 23 must be corrected by adjusting the gain of the amplifier that amplifies the output of the optical sensor 23. The light emitted from the rod 21 is several thousand to tens of thousands of lux, so
9 to 9 are all dimmed by the slits 25a of the plate 25 and irradiated on the optical sensor 23. But the slit
Since the amount of light received by the optical sensor 23 changes due to a slight error in 25a, it is necessary to adjust the gain of the amplifier as described above, and the adjustment range is 2 to 10 times.

[Object of the Invention]

In view of the above problems, the present invention can dramatically increase the degree of freedom in the design of the device, the accuracy of the mounting position of the optical sensor can be relatively low, and the dimming by the slit can be eliminated. An object is to provide a light source device.

[Main points of the invention]

In order to achieve the above-mentioned object, the present invention has an optical transmission body and a light diffusing portion formed along the longitudinal direction on the peripheral surface of the optical transmission body, and is incident from one end surface of the optical transmission body. In the light source device that diffuses and reflects the light of the light source that is emitted by the light diffusing unit and emits the light in the circumferential direction of the light transmitting body, the light diffusing unit that emits the light for light amount detection is formed in the light transmitting body. At the same time, a sensor for receiving the light emitted by the light diffusing unit is provided, and a control unit for controlling the light amount of the light source to a predetermined amount based on the output of the sensor is provided.

Example of Invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a light source device of the present invention. In this embodiment, a light source device of a liquid crystal optical shutter will be described as an example.

In FIG. 1, reference numeral 1 denotes an optical transmission body having a circular cross section, which is made of quartz glass, silicone resin or the like. Light from a light source such as a halogen lamp, which will be described later, is incident from one end surface of the light transmission body 1 through an optical fiber or the like.
Then, the light transmission body 1 functions to transmit the incident light to the other end side in the axial direction. Due to this function, the optical transmitter 1
In order to reduce transmission loss, it is desirable that the transparency is high and the light resistance is high. As shown in FIG. 2, a light diffusing portion 2 is formed on the outer peripheral surface of the light transmitting body 1 along the longitudinal direction, and diffuses and reflects the light incident from the light source. As the light diffusion portion 2, a transparent fine powder having a refractive index higher than that of the light transmission body 1 is used. For example, barium sulfate, magnesia or titania is preferably used.

The light incident on the light transmission body 1 is transmitted to the other end while repeating total reflection at the boundary surface, and is diffused and reflected in the light transmission body 1 by the light diffusing section 2 during the transmission. The reflected light is emitted with directivity in the direction opposite to the light diffusion portion 2 due to the lens effect of the light transmission body 1. The light transmission body 1 is provided in the central portion of the print head over the entire length of the liquid crystal light shutter 3, and the light emitted from the light transmission body 1 is projected on the liquid crystal light shutter 3. Further, a light diffusing section 4 for detecting the light quantity is formed on one side of the light transmitting body 1 (see FIG. 2), and the incident light is emitted in the opposite direction to the light diffusing section 4 in the same manner as described above. It is supposed to do. The light diffuser 4 for detecting the light amount is located outside the effective irradiation area so as not to block the light projected on the liquid crystal optical shutter 3. The light diffusely reflected by the light diffusing section 4 is transmitted by the optical transmission body 1.
The light is received by the optical sensor 6 on the drive unit 5 disposed on the side of the. The output of the optical sensor 6 is sent to the control unit 8 through the flexible connector 7, and the control unit 8 controls the light amount of the light source as described later to set the light amount emitted from the optical transmission body 1 to a predetermined amount. maintain. The light diffusing portion 4 for detecting the light amount may be formed on the side portion of the central portion of the optical transmission body 1, as shown in FIG. In this case as well, since the light diffusing section 4 is formed on the side of the optical transmission body 1, the irradiation of the effective irradiation area of the liquid crystal optical shutter 3 is not hindered.

The drive unit 5 drives the liquid crystal optical shutter and is arranged on both sides of the optical transmission body 1, and the optical sensor 6 is mounted on one side thereof as described above. That is, as shown in FIG.
A plurality of drive LSIs 10 are mounted on the printed board 9, and the optical sensor 6 is mounted on the end portion of the printed board 9. Optical sensor 6
The position of is a position facing the light diffusing portion 4 formed in the optical transmission body 1. Further, the drive LSI 10 selectively opens and closes each micro shutter of the liquid crystal optical shutter 3 according to the print data,
As a result, the light emitted from the light transmission body 1 is selectively transmitted by the micro shutter. This transmitted light is imaged by a lens on a photosensitive drum (not shown), and an electrostatic latent image is formed on the drum. As the optical sensor 6, a photodiode is used in this embodiment, but a photoelectric conversion element such as a phototransistor can also be used. In addition, the optical sensor 6
Is mounted on the printed circuit board 9 of the drive unit 5 by soldering, as shown in FIG. This mounting method is generally used, but as shown in FIG. 5 (b), the chip 6a of the optical sensor 6 may be directly attached to the printed board 9 and the surface thereof may be coated with resin or the like. Furthermore, drive LSI10
Similarly, a bare chip may be directly mounted on the printed circuit board 9. As shown in the table below, COB, COF
There are implementation methods such as.

In the case of COF mounting, the flexible connector (first
(See the drawing) can be eliminated, and at this time, the drive unit 5 and the control unit 8 can be integrally configured. Further, as described above, when the chip 6a of the optical sensor 6 is directly mounted on the printed board 9, the peripheral circuit of the optical sensor 6 can also be mounted on the same board. In this case, noise resistance can be improved.

FIG. 6 shows a specific example of the control circuit for controlling the light emitted from the optical transmission body 1.

Reference numeral 11 in the figure denotes a current / voltage conversion unit, which converts the output of the optical sensor 6 into a voltage. The photocurrent of the optical sensor 6 changes according to the amount of light received, and therefore the output voltage of the current / voltage converter 11 changes according to the amount of light received by the optical sensor 6. Current /
The output of the voltage conversion unit 11 is sent to the differential amplifier Q ₂ , and the amplifier Q ₂ compares and amplifies with the set voltage Er set by the resistors R ₅ , R ₆ , and R ₇ at the non-inverting terminal. The output of the differential amplifier Q ₂ is current-amplified by the transistor Q ₃ , and its output is input to the transistor Q ₄ . When the amount of light incident on the optical sensor 6 is small, the collector current of the transistor Q ₄ increases and the light source
Power supply to 12 increases. When the amount of light incident on the optical sensor 6 increases, the collector current of the transistor Q ₄ decreases, and the power supplied to the light source 12 also decreases. In this way, the power supplied to the light source 12 is maintained at the set value by the resistors R _{5 to} R ₆ , and thus the light transmitter 1 that emits the light of the light source 12
The light amount of is also maintained at a predetermined value. In the figure, numeral 13 is a blinking switch of the light source 12.

〔The invention's effect〕

As described above, according to the present invention, the light diffusing portion for detecting the light amount is formed in the optical transmission member, and the reflected light is received by the optical sensor. Therefore, the optical path from the optical transmission member to the irradiated object is set. Since it is not necessary to dispose the optical sensor therein, it is possible to solve the problem that the optical sensor has to be mounted with high accuracy as in the conventional case. Further, since the light diffuser reflects off the light sensor, it is only necessary to provide the light sensor so as to face the position where the light diffuser is formed, which can dramatically increase the degree of freedom in designing. This is effective when installing a sensor. Furthermore, the amount of diffusely reflected light can be adjusted by changing the size, film thickness, material, etc. of the light diffusion part.
It is possible to eliminate the need for dimming by the slit. Therefore, since there is no slit, it is not necessary to perform correction due to an error in the size of the slit, which is advantageous in manufacturing.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a perspective view showing a main part of the present invention, FIG. 3 is a perspective view showing another example, and FIG. FIG. 5 (a) is a sectional view showing a mounted state of the optical sensor, FIG. 5 (b) is a sectional view showing another mounting example of the optical sensor, and FIG. FIG. 7, FIG. 8, FIG. 9, and FIG. 9 are light source control circuit diagrams of the above-described embodiment, respectively, which are configuration diagrams showing a light amount detecting device of a conventional example. 1 ... Optical transmitter, 2 ... Light diffusing unit, 3 ... Liquid crystal light shutter, 4 ... Light diffusing unit (for detecting light amount) 5 ... Driving unit, 6 ... Optical sensor, 11 ... Current / voltage Converter, 12 ... Light source.

Claims (1)

[Claims] 1. A light transmission body, and a light diffusing portion formed along a longitudinal direction on a peripheral surface of the light transmission body, wherein light from a light source incident from one end surface of the light transmission body is provided. In a light source device that diffuses and reflects by a light diffusing section and emits light in the circumferential direction of the light transmitting body, a light diffusing section that emits light for detecting a light amount is formed in the light transmitting body, and the light diffusing section is used. A light source device comprising a sensor for receiving emitted light, and a controller for controlling the light amount of the light source to a predetermined amount based on the output of the sensor.