JPH0443869Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a light source device for irradiating a strip area, and more specifically, to a light source device that has a simple structure and can accurately and stably control the amount of irradiated light. be.

[Prior Art] Conventionally, when forming images using light, in order to stably obtain the desired image density, a method has been adopted in which the amount of irradiated light is detected and the output of the light source is feedback-controlled accordingly. ing. In this case, the light amount detection element is usually arranged at the end or side of the irradiation area so as not to block the effective light beam involved in image formation.

Furthermore, in order to promote miniaturization of image forming apparatuses that utilize light, it is necessary to reduce the distance between the light source and the irradiation area as much as possible. Accordingly, the distance between the light source and the light amount detection element is also shortened, and relatively strong light is projected onto the light amount detection element. However, a light amount detection element such as a photodiode has a limit to the amount of light that it can receive due to its short circuit current-illuminance characteristics, and it is necessary to appropriately limit the amount of light that it can receive.
Therefore, a method is used in which the detection light is received through a light attenuating member such as a slit.

[Problems with the prior art] In the light amount detection method described above, the light amount detection element is placed within the irradiation area of the light source and at a position relatively close to the light source, so the placement accuracy has a large effect on the detected amount of light. . In other words, since the light is limited by the light attenuation member, the light intensity detection element is irradiated with a small number of strong light rays from a short distance, so for example, if one strong light ray comes off the light intensity detection element due to positional deviation. The effect on the total amount of light received is greater than when receiving a large number of weak light beams. Therefore,
Although it is required to accurately install the light amount detection element at a set position with respect to the light source, this work is difficult and causes an increase in the number of assembly steps. Furthermore, since a light attenuation member is required, it is difficult to arrange the device in a limited space, which increases the cost and further complicates assembly work.

[Purpose of the invention] The present invention was devised in view of the problems of the prior art described above, and provides a light source that can stably and accurately control the amount of irradiated light, is easy to assemble, and can promote miniaturization and cost reduction. The purpose is to provide equipment.

[Main Points of the Invention] In order to achieve the above object, the present invention provides a light source device for illuminating a band-shaped area, which includes a linear light source that extends along the band-shaped area and emits a band-shaped luminous flux over a predetermined range. a covering body covered with the linear light source and having a slit-shaped opening formed therein corresponding to the strip-shaped region to be irradiated; It is characterized by having a light amount detection element arranged at the position.

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

FIG. 1 is a front sectional view showing a light source device as an embodiment of the present invention, and FIGS. 2 and 3 show an optical writing head and a liquid crystal shutter (hereinafter referred to as LCS) to which the light source device is applied, respectively. ) type optical writing printer; FIG.

In FIG. 3, a photosensitive drum 1 is rotatably supported and driven to rotate at a predetermined speed in the direction of the arrow. The surface of the photoreceptor drum 1 is first charged with a charger 2.
The photosensitive drum 1 is uniformly charged to a predetermined polarity, and then information is written by the LCS type optical writing head 3 disposed on the downstream side along the rotational direction of the photosensitive drum 1. A recording control section 4 is installed inside the optical writing head 3, and this recording control section 4 controls the opening/closing timing of the LCS according to the input information to be recorded, and outputs an optical signal corresponding to the information. The surface of the photoreceptor drum 1 is irradiated to form an electrostatic latent image.
The configuration of this optical writing head 3 will be explained later.
Explain in detail. The electrostatic latent image formed in this manner is supplied with toner in the developing device 5 and is visualized. The toner image reaches the transfer position T where the next transfer charger 6 is disposed, and is transferred onto the transfer paper 7 conveyed from the appropriate position. Thereafter, the transfer paper 7 is conveyed to a fixing device (not shown), and the toner image is, for example, thermally fused, and then ejected from the machine to obtain a data paper on which information is recorded. On the other hand, toner that has not been transferred by the transfer charger 6 remains on the surface of the photoreceptor drum 1, and is removed from the surface of the photoreceptor drum 1 by, for example, a fur brush 8a, by a cleaner 8 disposed in sequence. . After the residual charge on the surface of the photosensitive drum 1 from which the residual toner has been removed is optically eliminated by an eraser 9 placed next, the drum 1 returns to the position where the charger 2 is disposed and is subjected to a new image forming process. .

Here, the structure of the LCS type optical writing head 3 will be explained. First, the light source device L installed in the optical writing head 3 will be explained based on FIG.

In FIG. 1, 10 is a halogen lamp as a light source, whereas in this example, an elliptical cold mirror 11 that selectively transmits infrared rays.
A part of the light emitted from the halogen lamp 10 is reflected in a predetermined direction along the optical axis _P1 . A light propagation rod 12 is disposed in front of the halogen lamp 10 in the light projection direction with its central axis aligned with the optical axis _P1 . The light propagation rod 12 in this example is made of highly transparent quartz glass (refractive index with respect to air: 1.46) and has a cylindrical shape with a diameter of 10 mm. In this example, on the outer peripheral surface of the light propagation rod 12, a diffusion band 13 for diffusing and reflecting the propagating light toward the inside is attached and formed in parallel to the central axis (optical axis P ₁ ) just above the figure. There is. Diffusion zone 13 in this example
The material is barium sulfate (refractive index: 1.51), which has a higher refractive index and better light resistance than the rod material quartz glass, and is formed into a band shape with a thickness of 0.15 mm and a width of 1.5 mm. In addition, the light propagation rod 12 and the diffusion band 13
The dimensions of each part are not limited to the above values, but should be set optimally depending on the application.

Therefore, the projected light from the halogen lamp 10 is
The light enters from one end surface 12a of the light propagation rod 12, and propagates in the axial direction toward the other end 12b while repeating total reflection on its circumferential surface (interface with air), but a diffusion band 13 is attached. The light incident on the surroundings is not totally reflected, but is diffusely reflected in the circumferential direction, and is emitted to the outside from the circumferential surface of the light propagation rod 12 that is approximately opposite to the circumferential surface to which the diffusion band 13 is attached.

The light propagation rod 12 configured as described above is housed and supported within a rod case 14 having an elongated housing shape. The rod case 14 of this example is extruded from aluminum, and the inner surface is not particularly processed. In order to hold the light propagation rod 12 at a predetermined position within the rod case 14, spacers 15a and 15b are interposed between both ends of the light propagation rod 12 and the rod case 14. The spacer 15a on the incident end side is made of a black resin material through which light does not pass. A holding hole 16 for holding the incident side end of the light propagation rod 12 is bored in the spacer 15a. The holding hole 16 has an inner diameter that changes in two steps, and the end of the light propagation rod 12 is inserted into the small diameter portion 16a. Note that a protrusion 12c and a recess 1 that can be fitted into each other are provided at the incident side end of the light propagation rod 12 and the spacer small diameter portion 16a, respectively.
6b, which are fitted together to prevent the rod 12 from shifting in the axial direction.

On the other hand, in the large diameter portion 16c of the above-mentioned insertion hole 16,
An IR cut filter 17 is installed to block the incidence of infrared rays, which serve as a heat source. This results in
The white light emitted from the halogen lamp 10 is passed through the cold mirror 11 and the IR cut filter 17.
Since infrared rays are excluded in this step, the inconvenience of the LCS, which is easily affected by heat as an irradiation target to be described later, being heated by the irradiation light is reliably prevented. Further, by using the spacer 15a as a holding member for the IR cut filter 17 in this way, there is no need to provide a separate holding member, which reduces the number of parts and contributes to cost reduction. Furthermore, since the IR cut filter 17 can be placed close to the rod entrance end face 12a, a smaller and cheaper filter can be used.

A holding hole is formed in the spacer 15b that holds the end of the light propagation rod 12 on the anti-incidence side, and a reflection plate 18 is provided between the bottom surface of the spacer 15b and the end surface 12b on the anti-incidence side of the rod.
is interposed. The light propagated to the anti-incidence side end face 12b is reflected to the incident side by this reflection plate 18, thereby achieving effective use of the light.

A slit 14a serving as a light irradiation opening is provided at the bottom of the rod case 14, that is, at a portion facing the circumferential surface of the light propagation rod 12 opposite to the circumferential surface to which the diffusion band ₁₃ is attached. The holes are drilled parallel to each other over a predetermined range. Therefore, as shown in FIG. 2, of the light emitted from the light propagation rod 12, only the light directed toward the slit 14a is emitted to the outside of the rod case 14 to form a band-shaped light beam for LCS irradiation, which will be described later. The emitted light is diffusely reflected by the inner surface of the rod case 14, which is not optically smooth.
The band-shaped light flux emitted from the rod case 14 and passed through the light propagation rod 12 has a characteristic that the amount of light locally increases at the incident side end in the light distribution in the longitudinal direction.

A photodiode 19 as a light amount detection element is disposed at a position on the upper wall 14b of the rod case 14 corresponding to the incident end of the slit 14a. Photodiode 19
is held by a holder 20 and directly connected to a recording control board 4a that is spaced apart along the upper surface of the upper wall 14b, and the output of the halogen lamp 10 is feedback-controlled in accordance with the amount of light detected by the photodiode 19. , the amount of light emitted from the light propagation rod 12 is maintained at the desired set level.

Only the scattered light that has been diffusely reflected on the inner surface of the rod case 14 is projected onto the photodiode 19 provided at the above position. Furthermore, these scattered lights reach the photodiode 19 while being repeatedly diffused and reflected on the inner surface of the rod case 14, and their intensity is considerably attenuated and weakened.
That is, the rod case 14 becomes a light integrating box, and a large number of scattered lights of low intensity are projected onto the photodiode 19 from all directions. Therefore,
Even if the relative mounting positions of the light propagation rod 12, halogen lamp 10, and photodiode 19 vary somewhat, the effect on the amount of light detected by the photodiode 19 is extremely small and can be ignored.
Therefore, feedback control of the amount of light can be stably performed by accurate light amount detection without setting the mounting precision of each of the optical members to be high, and assembly is facilitated, reducing the number of work steps. Further, even if dust or the like adheres to the detection surface of the photodiode 19, the amount of light can be detected stably and accurately without being affected by it. Furthermore, since scattered light with low intensity is detected, a light attenuation member is not required, and the structure is simplified. In addition, since the photodiode 19 is directly connected to the recording control board 4a, it is less affected by noise than when both are far apart, and the amount of light can be detected more accurately. In this example, the photodiode 19 is provided corresponding to the incident side end where the peak of the light distribution occurs in the emitted band-shaped light beam, and the photodiode 19 is
Although the configuration is such that the decrease in the amount of emitted light distribution due to the provision of the light beam 9 cancels out the peak of the light distribution, this does not apply in cases where the decrease in the amount of light or the peak of the light distribution can be ignored. Incidentally, a diffusing material such as magnesium oxide may be applied to the inner surface of the rod case 14 to improve diffusivity.

As shown in FIG. 2, the light source device L constructed as described above is installed on a head base 21 from which the irradiation light e is formed to protrude. In this case, shelf surfaces 21a extending on both sides of the head base 21,
Both sides of the LCS panel 22 to be irradiated are placed on the LCS panel 21a, and the legs 14c, 14c on both sides of the rod case 14 are placed and connected via the flexible printed circuit 23 connected to both sides. LCS
Each end of the panel 22 and the flexible printed circuit 23 is sandwiched between the rod case leg 14c and the head base shelf surface 21a to maintain electrical connection therebetween.

The LCS panel 22 roughly consists of two glass substrates 2
A liquid crystal agent (not shown) is sealed between 2a and 22b, and a large number of microshutters (not shown) corresponding to one pixel are arranged in an array along the longitudinal direction of the liquid crystal agent, and the light propagation is It is held so as to extend parallel to the longitudinal center axis (optical axis P ₁ ) of the rod 12 .
Lower glass substrate 2 on both sides of this LCS panel 22
A large number of signal electrodes (not shown) are extended on 2a to correspond to the microshutters, and these signal electrodes are arranged on both sides of the write head 3 by the above-mentioned flexible printed circuits 23, 23. The shutter drive boards 24, 24 are connected to the shutter drive boards 24, 24, respectively.
Each shutter drive board 24 is connected to the recording control board 4a described above, and the transmission of the irradiated light from the light source device L is controlled by opening and closing each microshutter in accordance with the input information signal. to form an optical signal.

In the irradiation port e of the head base 21 located on the output side of the LCS panel 22, an imaging lens is formed by arranging short focus imaging elements in an array in correspondence with the microshutter array of the LCS panel 22 described above. Array 25 is attached. Therefore, the signal light emitted from the LCS panel 22 passes through the imaging lens array 25 and is imaged as pixels on the circumferential surface of the photosensitive drum, thereby performing optical writing of information. In this case, the band-shaped luminous flux irradiated from the light source device L is accurately and stably controlled to the set light amount as described above, and therefore the photoreceptor drum 1
The contrast of the electrostatic latent image formed thereon is also always kept constant, and an image with a desired density can be stably obtained.

It should be noted that the present invention is not limited to the preferred embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, an appropriate wavelength selection filter is attached to the light receiving surface of a normal light amount detection element in order to obtain the required sensitivity (in the above embodiment, the sensitivity is equivalent to the sensitivity of the photosensitive layer on the surface of the photosensitive drum 1). However, by matching the wavelength selection characteristic of the IR cut filter 17 in the above embodiment to the sensitivity of the photosensitive layer of the photoreceptor drum 1, there is no need to add a wavelength selection function to the light amount detection element, and the cost can be reduced accordingly. or,
The linear light source is not limited to a light source device that uses a light propagation rod, but a fluorescent lamp or the like may be used to directly emit a band-shaped light beam, but in this case, the peripheral surface of the fluorescent lamp may be covered with aluminum foil, etc. It is necessary to form an aperture using the same method to give directivity to the emitted light. Furthermore, the present invention can be widely applied not only to LCS printers but also to image forming apparatuses that utilize various types of light, such as electrophotographic copying machines. In addition, photodiode 1
9 may be provided not only on the reflection side of the slit 14a but also on the side wall 14d of the rod case 14 where the light emitted from the light propagation rod 12 is not directly irradiated.

[Effects of the invention] As described above in detail, according to the invention, each optical member is It is possible to prevent the occurrence of inconveniences in which the amount of detected light changes due to changes in the mounting position of the sensor, dirt on the light receiving surface of the light amount detection element, etc. Therefore, by accurately and stably detecting the amount of light and controlling the output of the light source based on this feedback, it is possible to always stably illuminate a strip area with the desired amount of light, making it suitable for use in light sources of image forming devices. In this way, the desired image density can be stably obtained. In addition, since a certain tolerance can be assumed for the mounting accuracy of the optical components, assembly becomes easy, and since a light reduction member is not required, it is possible to significantly reduce the cost of the light source device. .

[Brief explanation of the drawing]

Figure 1 shows a light source device L as an embodiment of the present invention.
FIG. 2 is a schematic front sectional view showing the light source device L.
A schematic cross-sectional view showing an optical writing head 3 using
FIG. 3 is a schematic diagram showing the general structure of an LCS type optical writing printer equipped with the optical writing head 3 described above. 4a... Recording control board, 10... Halogen lamp, 12... Light propagation rod, 13... Diffusion band, 1
4... Rod case, 14a... Slit, 15
a, 15b...Spacer, 17...IR cut filter, 19...Photodiode, 21...Head base, 22...LCS panel, 25...Imaging lens array.

Claims (1)

[Scope of utility model registration request] A light source device for illuminating a strip-shaped area includes a linear light source that extends along the strip-shaped area and emits a strip-shaped luminous flux over a predetermined range; It is characterized by having a covering body in which a slit-shaped opening is bored corresponding to a strip-shaped area, and a light amount detection element disposed in a position outside the light emission range of the linear light source in the covering body. Light source device.