JPS6234468Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a linear light source for photoelectric reading in which a large number of light emitting elements are arranged in a straight line, and in particular a light source that can easily uniformize the entire illuminance distribution obtained from all the light emitting elements. It is related to the device.

Linear light sources for photoelectric reading in copying machines, facsimile machines, and the like must have uniform illuminance as a whole in order to improve reading accuracy. When trying to configure such a light source with a large number of light emitting elements arranged in a straight line, for example, light emitting diodes,
Since the current-brightness characteristics differ between individual light-emitting diodes, conventional methods measure the brightness of a large number of light-emitting diodes at a constant current value, carefully select those with a predetermined brightness, and then select only the selected light-emitting diodes. The sorting process is extremely time-consuming, resulting in poor productivity and high costs.

In order to eliminate the above-mentioned conventional drawbacks, the present invention has a large number of light emitting elements arranged in a straight line on a substrate with their light emitting surfaces facing upward, and a plurality of brightness adjustment resistors on the substrate. The light emitting element is divided into a plurality of blocks, the light emitting elements in each block are connected in series, and each block is connected in parallel with each other, and the resistor for each block is connected in series with the plurality of light emitting elements in each block. It is connected to
The purpose is to provide this type of light source device with uniform illuminance as a whole at low cost and in large quantities. The drawings will be described in detail below.

1 to 4 show a first embodiment of the present invention, in which 1 is a substrate, and 2 ₁ to 2 ₁₀₀ are substrates 1.
Above are light emitting diodes arranged in a straight line with their light emitting surfaces facing upward, 3a and 3y are discrete resistors for brightness adjustment, and 4 and 5 are power supply terminals. Light emitting diode 2 ₁ ~ 2 ₁₀₀ and resistor 3a ~ 3
y is the light emitting diode 2 ₁ to _{2 4} , 2 ₅ to _{2 8} , 2
₉ ~ 2 ₁₂ ... 4 each of 2 ₉₇ ~ 2 ₁₀₀ and resistors 3a, 3
It is divided into a plurality of blocks a, b, c, ... y, each consisting of one block b, 3c ... 3d,
The light emitting diodes and resistors in each block a to y are connected in series, and each block a to y is connected in series.
Both ends of the power supply terminals 4 and 5 are connected in parallel and in the same direction between the power supply terminals 4 and 5, respectively.

When a DC voltage E (V) is applied between power supply terminals 4 and 5 (E (V) is at least four times the forward drive voltage of the light emitting diode), each block a, b, c... The series circuit in y has currents Ia, Ib,
Ic, . . . Iy flow and the light emitting diodes 2 ₁ to 2 ₁₀₀ light up. At this time, if there are light emitting diodes in block b that have different current-brightness characteristics, for example, those that have lower brightness than normal, the overall illuminance distribution will be measured as shown in Figure 3, and block b will be different from other light emitting diodes. The illuminance is lower than that of the block. In such a case, the current Ib in block b can be reduced by replacing the low resistor 3b in block b with one with a smaller resistance value.
By increasing the brightness and brightness, it is possible to adjust to a uniform illuminance distribution as shown in FIG. If the illuminance is high, conversely, increase the resistance value and lower the current value.

According to the above embodiment, unevenness in the illuminance distribution due to differences in the luminance characteristics of the light emitting diodes can be adjusted by changing the resistance value of each block, and a uniform illuminance distribution can be achieved. No need, no hassle of sorting, and good productivity.

FIG. 5 shows a second embodiment of the present invention.
Discrete type resistor 3 in the first embodiment
Thick film printed low holes 6a to 6y are formed on the substrate 1 instead of a to 3y. According to this embodiment, the low resistance value can be adjusted by scraping off the printed resistors 6a to 6y with a knife or the like, resulting in even better productivity. Note that the other configurations, functions, and effects are the same as in the first embodiment.

As explained above, according to the present invention, a large number of light emitting elements are arranged on a substrate in a straight line with their light emitting surfaces facing upward, and a plurality of brightness adjustment resistors are provided on the substrate, The light emitting element is divided into a plurality of blocks, the light emitting elements in each block are connected in series, and each block is connected in parallel with each other, and the resistor for each block is connected in series with the plurality of light emitting elements in each block. Since the illuminance distribution is connected to the block, unevenness in the illuminance distribution due to differences in the luminance characteristics of the light emitting elements can be adjusted by changing the resistance value of the resistor for each block, and uniform illuminance distribution characteristics can be easily obtained as a whole. There is an advantage that it is possible to provide a photoelectric reading light source device that is inexpensive, mass-producible, and has uniform performance, without requiring the characteristics of the light emitting elements used to be the same as in the past, and without the trouble of selecting them. In particular, when used as a light source for reading a document such as a facsimile, the illumination light is uniform in the length direction, so there is no shading, and reading accuracy can be improved.

[Brief explanation of the drawing]

1 to 4 show a first embodiment of the present invention. FIG. 1 is a partially omitted perspective view showing the first embodiment of the photoelectric reading light source device of the present invention, and FIG.
1 is a circuit diagram of the apparatus shown in FIG. 1, FIGS. 3 and 4 are explanatory diagrams of illuminance distribution, and FIG. 5 is a partially omitted perspective view showing a second embodiment of the present invention. 2 ₁ ~ 2 ₁₀₀ ... Light emitting diode, 3a ~ 3y
...Daily type resistor, 6a to 6y...Thick film printed resistor.

Claims (1)

[Scope of utility model registration request] It has a large number of light emitting elements arranged in a straight line with the light emitting surface facing upward on a substrate, and a plurality of resistances for brightness adjustment arranged on the substrate, and the large number of light emitting elements are divided into a plurality of blocks. , the light emitting elements in each block are connected in series, the blocks are connected in parallel with each other, and the resistor for each block is connected in series with the plurality of light emitting elements in each block. Light source device for type reading.