JPS6317583A - Laser oscillating device - Google Patents

Abstract

PURPOSE:To make it possible to avoid an adverse effect caused by the dispersion of the oscillation characteristics by a method wherein the oscillation intensity of a laser diode is modified to the oscillation intensity in the set oscillation characteristics on the basis of oscillation characteristic information stored in a storage means. CONSTITUTION:A laser oscillating unit LO having a laser diode 1 is provided with an ROM 19 for storing correction data corresponding to the spread angle thetaV of a laser beam B which is generated from the laser diode 1 and a correcting means CM, which modifies the oscillation intensity of the laser diode 1 on the basis of the correction data in this ROM 19, is provided. Thereby, regardless of the dispersion of the oscillation characteristics between the individual laser diodes, the energy amount to be received in such objects as a photosensitive element or a light-receiving element, which ultimately receives the laser beam from this laser diode, can be made into one having no fluctuation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a laser diode in a recording device using a laser beam, such as a laser beam printer or a laser 00M system, or a measuring device using a laser beam. The present invention relates to a laser oscillation device used as a light source.

[Conventional technology]

The laser diodes used in the above-mentioned laser oscillation device have variations in oscillation wavelength of about [±20 nm] among the individual laser diodes. On the other hand, the photoreceptor or silver halide film on which a latent image is formed by irradiation with a laser beam in the above-mentioned recording device, or the light-receiving element that receives the laser beam in the above-mentioned measurement device, has sensitivity for each wavelength. It has variable spectral sensitivity characteristics.

Therefore, if the laser diode is changed, the amount of energy received by the photoreceptor or silver halide film in the recording device will change, and each time the laser diode is replaced for each recording device or even in the same recording device,
There is a risk that the resulting recorded images will have different densities.

Furthermore, in the above-mentioned measuring device, the amount of energy received by the light-receiving element changes as the laser diode changes, and as a result, in those that obtain measurement results based on the amount of light received by this light-receiving element, the measurement The results change with each measurement device or each time the laser diode is replaced.

On the other hand, since the laser beam from the laser diode propagates while expanding, a collimator lens is usually inserted immediately after the laser diode to shape the laser beam into parallel light. In particular, the spread angle of the laser beam between individuals in the direction perpendicular to the junction surface of the laser diode is [20d
eg] to CC55de], so if the laser diode changes, the amount of energy of the laser beam incident on the collimator lens will change.

Therefore, as in the case where there is variation in the oscillation wavelength described above, there is a possibility that the amount of energy received by the photoreceptor or the light receiving element may change depending on the device or each time the laser diode is replaced.

Therefore, conventionally, as laser diodes used in this type of laser oscillation device, the inconvenience caused by the variation in characteristics between individual laser diodes has been avoided by carefully selecting ones with little variation in oscillation wavelength and divergence angle. was measuring.

[Problem that the invention seeks to solve]

However, in such cases, the yield of laser diodes decreases and the cost of laser diodes increases, leading to a rise in the initial cost of recording and measuring equipment and a rise in running costs for replacing laser diodes. However, even if the laser diodes were carefully selected, it did not eliminate all the variations in oscillation characteristics among the individual laser diodes, and therefore did not eliminate all the negative effects caused by the variations.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned circumstances and to avoid adverse effects caused by variations in oscillation characteristics such as oscillation wavelength and divergence angle among individual laser diodes, and to reduce costs.

[Means for solving problems]

The characteristic configuration of the laser oscillation device according to the present invention includes a storage means for storing oscillation characteristic information of a laser diode, and an oscillation characteristic for setting the oscillation intensity of the laser diode based on the oscillation characteristic information stored in the storage means. This is because a correction means is provided for changing the oscillation intensity to .

[For production]

In other words, for example, in the photoreceptor or light receiving element that receives and receives the laser beam emitted from the laser diode,
The spectral sensitivity characteristic can be obtained by expressing the sensitivity at a wavelength other than the wavelength exhibiting a certain set sensitivity as a sensitivity ratio to the set sensitivity.

Therefore, the spectral sensitivity characteristics of the photoreceptor and light receiving element are determined in advance in the manner described above, and based on these spectral sensitivity characteristics,
The intensity of the laser beam is changed by the correction means so that the intensity of the laser beam is multiplied by the reciprocal of the sensitivity ratio of the photoreceptor and the light receiving element at the oscillation wavelength of the laser diode, which is an example of the oscillation characteristics stored in the storage means. Regardless of the oscillation wavelength of the laser diode, the amount of energy received by the photoreceptor or photodetector can always be the same as when the photoreceptor or photodetector is irradiated with a laser beam of the set wavelength that indicates the set sensitivity.

In addition, the laser beam oscillated from this laser diode will not be eclipsed at all, for example, to a collimator lens, etc. By expressing the amount of incident light as a ratio of the amount of light to the set amount of light, it is possible to obtain the characteristics of the amount of light received by the photoreceptor or light receiving element according to the divergence angle of the laser beam.

Therefore, if the characteristics of the amount of light received by the photoreceptor or the light receiving element are known in advance in the manner described above, the divergence angle of the laser beam from the laser diode stored in the storage means is given as information, and this divergence angle can be determined. By changing the intensity of the laser beam using the correction means so as to be multiplied by the reciprocal of the light intensity ratio, the amount of energy received and taken by the photoreceptor and light receiving element can be constantly adjusted to the laser beam from the laser diode, regardless of the divergence angle. This is the same as when the photoreceptor or light receiving element is irradiated with a laser beam having a set divergence angle that enters a collimator lens or the like without vignetting.

In summary, by using information on the oscillation characteristics such as the oscillation wavelength and divergence angle described above stored in the storage means and changing the intensity of the laser beam by the correction means, the amount of energy received and taken by the photoreceptor and the light receiving element can be reduced. , it is possible to achieve the same result as when a laser diode with set oscillation characteristics such as the set wavelength or set divergence angle as described above is used, that is, it is not affected by variations in these oscillation characteristics between individual laser diodes. .

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 2 shows a schematic configuration of an irradiation optical system of a laser beam printer equipped with a laser oscillation device according to the present invention.

(1) is a laser diode, and a laser beam (B) directly modulated by a drive current according to image information is oscillated from this laser diode (1). This laser beam (B) is made into parallel light by a collimator lens (2), then reflected by a mirror (3), and reflected by a reflective surface (4a) with a polygon mirror (4) rotating at high speed.

The rotation of this polygon mirror (4) causes the laser beam (B
) changes, and accordingly, the reflected laser beam (B) is deflected and scanned in the longitudinal direction of the photoreceptor drum (8), which is an example of a photoreceptor. (This direction is the main scanning direction).

The laser beam after being reflected by the polygon mirror (4) is converged by the fθ lens (5) and then reflected by the mirror (6).
), the light passes through the window glass (7) and forms an image on the photoreceptor drum (8).

The surface of the photoreceptor drum (8) is uniformly charged, and a laser beam (B) modulated based on image information is focused on the surface and scanned, so that the photoreceptor drum (8) is charged according to its intensity. The surface charge potential is attenuated. By repeating this scanning with the rotation of the photoreceptor drum (8) at a constant speed (this rotation direction is the sub-scanning direction), an electrostatic latent image in pixel units is formed on the photoreceptor drum (8). It has become so.

In the figure, (9a) is a laser beam detection optical sensor for aligning the electrostatic latent image formation start position on the photosensitive drum (8) in the sub-scanning direction, and (9b) is a mirror.

Thereafter, although not shown, toner, which is a colored pigment, is selectively attached to this electrostatic latent image area and developed, and output paper is adhered to the toner image surface to transfer the toner image onto the pressing surface. By heating the toner, the toner is melted and fixed on the paper, producing an output image.

A laser beam (
B) propagates while expanding, and a collimator lens (2) is provided to shape this expanding laser beam (B) into parallel light. FIG. 3 shows the relationship between the collimator lens (2) and the laser beam (B).

The laser beam (B) from the laser diode (1) is
As shown in Fig. 4, the direction parallel to the joint surface (1a) (hereinafter referred to as the horizontal direction) and the direction perpendicular to the joint surface (1a) (hereinafter referred to as the vertical direction) are different. It has divergence angles (4) and (^). Note that the divergence angles (4,) and (Bv) in both of these directions are the values at which the output is half of the maximum output in the relationship between the radiation angle and relative optical output in the horizontal and vertical directions shown in Figure 5. It is defined by the radiation angle of the point.

The divergence angles 1) and (^) in both directions vary among individual laser diodes (1).

The vertical spread angle is [20 degl to []
There are variations within the range of 35 degrees. Further, the horizontal spread angle (to) is generally within a range of [20 degrees] or less.

In particular, since there is a large variation in the vertical divergence angle between individuals, the laser beam (B) is vignetted when it enters the collimator lens (2), resulting in light ftt.
The N loss (QL) differs between individual laser diodes (1). This light loss (OL) is determined by the following equation.

QL=exp[2・(a/D)”]xlOO(%)□■
Here, <a) is the aperture of the collimator lens (2), <D
> is the diameter of the laser beam (B) defined by the point where the intensity decreases by [8-”] times from the center value when it enters the collimator lens (2), and the focal length of the collimator lens (2) is Let <f>.

The vertical spread angle (^) of the laser beam (B) is <
It is obtained by the following equation, where e (deg) >.

D = 2・f-jan(e X 1.7/2)
□■The light loss (QL) determined by the above equation 0 is:
When the diameter of the laser beam (8) is about 1.7 times or more the diameter of the collimator lens (2), it becomes so small that it can be almost ignored, but when it is smaller than that, it becomes larger as it becomes smaller. Therefore, when the divergence angle (eV) changes and the diameter of the laser beam (B) changes, the collimator lens (
2) The amount of light incident on the photoreceptor drum (8) fluctuates and is received by the photosensitive drum (8): [The amount of energy also varies.

Therefore, a ROM (19) for storing correction data corresponding to the spread angle 1) of the laser beam (B) oscillated from the laser diode (1) is installed in the laser oscillation device (LO) having the laser diode (1). is provided. Based on the correction data in this ROM (19),
A correction means (leaf) for changing the oscillation intensity of the laser diode (1) is provided.

Next, a recording control device (PC) of a laser beam printer equipped with a laser oscillation device (LO) having the ROM (19) and a correction means (CM) will be described.

As shown in FIG. 1, this recording control device (PC) has an image memory (1 page) that stores image information for one page of recorded images.
0) exists. The capacity of this image memory (10) is
For example, 8 bits per dot, 4096 bits per page
Dot X: 4096 dots is 16 MB. Furthermore, the upper 12 bits of the address are set as a vertical address, and the lower 12 bits are set as a horizontal address.

In the figure, (PCLK) is a clock signal output from the pixel clock (11) and corresponds to each pixel, and (SO5) is a clock signal output from the laser beam detection optical sensor (9a) in Figure 2. This is the exposure start signal.

When entering the print cycle, the horizontal read counter (12)
and a vertical read counter (13) are both cleared and have an input of an exposure start signal (SO5). When the first exposure start signal (SO3) is input, the horizontal readout counter (12
) is reset and starts counting the clock signal (PCLK), and is counted up every time the clock signal (PCIJ) is input. In addition, a vertical read counter (13)
is configured to be counted up every time the exposure start signal (SO5) is input.

Horizontal read counter (12) and vertical read counter (13)
Both counter values are input to the image memory (10) as address setting signals, and the horizontal and vertical addresses of the image memory (10) are set. The clock signal (PCLK) is input to the image memory (10) as a strobe signal, and the clock signal (PCLK) is input to the image memory (10) as a strobe signal.
PCLK) is input, data at the corresponding address on the image memory (10) is sent to the DA converter (14).

This ODA converter (14) is supplied with the same clock signal (
PCLK) is input as a strobe signal, and the data is configured to be converted into an analog signal each time the clock signal (PCLK) is input. The converted analog signal is input to the division signal input terminal (X) of the divider (15).

A clock signal (PCLK) input as a strobe signal is input to the division signal input terminal (Y) of this divider (15).
A correction signal is input which is read out from the correction ROM (+9) in accordance with the strobe signal and converted into an analog signal by a DA converter (16) to which the same clock signal (PCIJ) is input as a strobe signal.

In the ROM (19), as correction data corresponding to the spread angle (^) of the laser beam (B) oscillated from the laser diode (1) described earlier, the laser that enters the collimator lens (2) without vignetting is stored. The beam incidence rate expressed in 10 bits for various divergence angles (0v) is written.

For example, if the focal length of the collimator lens (2) is [10,
6 mm], its aperture [10 mm], and the above-mentioned ■ for each value of the vertical spread angle (8v).

Using both equations (2), the light amount loss and the incident rate representing the remaining amount of incident light as shown in Table 1 below are determined.

Table 1 Note that the light amount loss (QL) determined by the formula 0 is rounded to [0%] when the divergence angle (^) is [16 degl]. Therefore, in the case of the example in Table 1, the laser diode (1) with a divergence angle of [16 deg] has the set divergence angle characteristic that gives the set light amount, and the incidence rate is The spread represents the ratio of the amount of incident light for each month.

Convert the incidence rate values in Table 1 to integers, add an address, and R
The state written in OM (19) is G as shown in Table 2 below.

As shown in Table 2 and Figure 1, the address line of this ROM (19) is connected to a decimal row read switch (17). This low re-dip switch (17)
At the time of shipment from the factory, a final check is performed to measure the vertical spread angle (^) of the laser beam (B) from the laser diode (1) for each individual, and based on the measurement results, the spread angle ( ROM (19
) is used to select the address. That is, the rotary dip inch (17) is connected to the storage means (M) for storing the oscillation wavelength information of the laser diode (1).
).

For example, if the measured divergence angle (^) is [23 degrees], by setting the rotary dip switch (17) to [3] corresponding to the last digit, the ROM (1
Address [23] of 9) is selected.

Then, the data [9711 stored at this address is transferred to the ROM (1) according to the clock signal (PCLK).
9), converted into an analog signal, and input to the divider (15).

This divider (15) has a division signal input terminal (X
) is divided by the signal input from the removal signal input terminal (Y). That is, the reciprocal of the incidence rate to the collimator lens (2) is multiplied, and as a result, the output terminal (
The signal output from the collimator lens (2) is preliminarily added with an amount corresponding to a light amount loss (QL) when entering the collimator lens (2).

The output signal from the divider (15) is input to a laser diode drive circuit (20), and the output of the laser diode (1) is modulated accordingly.

Therefore, when the modulated laser beam (B) oscillated from the laser diode (1) is modulated by the output signal from the divider (15), when it enters the collimator lens (2), it is The amount of light is lost due to vignetting, and when it reaches the photoreceptor drum (8), the influence of the variation in the divergence angle of each individual laser diode (1) has been removed. It is.

As a result, even if the device changes, the laser diode (1)
Even if the laser oscillation device (LO) containing the LO is replaced, a recorded image with the same density can always be obtained. That is, the correction means (CM) is composed of the DA converter (16), the divider (15), and the like.

The output of the modulation signal based on one line of image information is completed,
When the next exposure start signal (SO5) is input, the vertical read counter (13) is counted up and the image memory (
10), a vertical address corresponding to the next line is set. And the clock signal (PCLK)
The configuration is such that the image data of the next line is read out in accordance with the image data of the next line.

In the previous embodiment, after converting the image data stored in the image memory (10) into an analog signal, the ROM (10)
9) Divide the correction data based on the oscillation characteristics of the laser diode (1) stored in the internal memory by the analog converted data, and use the signal after this division to convert the laser diode (1).
A method of directly modulating the laser beam (B) from the laser beam (B) was explained.

Instead, as a correction means (CM), an optical modulator such as a PLZT element whose transmittance changes depending on the applied voltage is interposed between the laser diode (1) and the collimator lens (2), The intensity of the laser beam (B) can be changed by changing the voltage applied to this optical modulator based on the data in the ROM (19) selected by a set of rotary dip switches (17). You can.

In addition, in the previous embodiment, data on the incidence rate for each divergence angle 1) is used as the oscillation characteristic information of the laser diode (1).
The oscillation characteristic information of each individual laser diode (1) is stored in the OM (19) and set by setting the rotary dip switch (17). Instead, a separate memory may be provided to store the data of the spread angle (^) for each individual.

In this case, this memory becomes the storage means (M).

When configured in this way, the data stored in this memory may indicate the address of the ROM (19).

Furthermore, as mentioned above, if a memory is provided to store the data of the spread angle (8) for each individual,
ROM (19) is omitted, and the correction means (CM) contains 0
It may be configured to include a calculation unit that calculates the incidence rate from the calculation of the equations and 0 equations and the light amount loss.

Furthermore, in the previous embodiment, the configuration was such that only the divergence angle (8v) of the laser beam (B) oscillated from the laser diode (1) was corrected for variations in its characteristics between individuals. However, instead of, or in addition to, data on the oscillation wavelength of the laser diode (1) is stored in another memory, while the correction means (
A memory for storing the spectral sensitivity characteristics of the photoreceptor drum (8) is further provided in the CM), and according to the spectral sensitivity characteristics information in this memory, the photosensitive drum (1) is stored with a The oscillation intensity of the laser beam (B) from the laser diode (1) is changed so that the amount of energy received by the photoreceptor drum (8) is always constant by compensating for the sensitivity of the photoreceptor drum (8). Good too.

The laser oscillation device (LO) according to the present invention is applicable to a laser beam printer that stores a visible image on a recording paper as described in the previous embodiment, as well as a laser COM system that imprints a micro image on a micro film. It can be applied to recording devices using Furthermore, the laser oscillation device according to the present invention can also be used in measurement devices using laser beams.

〔Effect of the invention〕

As described above, the laser oscillation device according to the present invention changes the oscillation intensity between individual laser diodes by changing the oscillation intensity of the laser diode based on the oscillation characteristic information such as the oscillation wavelength and divergence angle of the laser diode. Regardless of variations in the oscillation characteristics of the laser diode, the laser beam emitted from the laser diode can ultimately reach the target object, such as the irradiator or photodetector, by keeping the amount of energy absorbed by the receiver constant. It has become possible to tolerate variations in the oscillation characteristics of laser diodes while reducing density differences in recorded images that occur, for example, in laser beam printers due to changes in laser diodes.

As a result, it has become possible to increase the yield of laser diodes and reduce equipment costs while maintaining high gradation reproducibility in recording devices and high reliability in measuring devices. Ta.

[Brief explanation of the drawing]

The drawings show an embodiment of the laser oscillation device according to the present invention, FIG. 1 is a block diagram of the recording control device of the laser beam printer, FIG. 2 is a schematic diagram of the irradiation optical system of the laser beam printer, and FIG. A side view showing the relationship between the diode and the collimator lens, Fig. 4 is a perspective view showing the laser beam emitted from the laser diode, and Fig. 5 shows the relationship between the radiation angle and relative optical output of the laser beam emitted from the laser diode. This is a graph showing. (1)... Laser diode, (M)...
...Storage means, (CM)...Correction means.

Claims (1)

[Claims] A storage means for storing oscillation characteristic information of the laser diode, and a correction means for changing the oscillation intensity of the laser diode to the oscillation intensity in the set oscillation characteristic based on the oscillation characteristic information stored in the storage means. A laser oscillation device.