JPS62277568A - Temperature characteristic correcting device for photodetector - Google Patents

Abstract

PURPOSE:To accurately correct the temperature characteristics of a photodetector receiving light from a light source element to be tested by calculating the difference between the signals of two photodetectors. CONSTITUTION:Luminous flux emitted by the light source element 31 of a correcting deice is split by a beam splitter 2 and its transmitted light reaches a photodetector 41 and the reflected light is repeatedly reflected in a light guide 1 to reach a photodetector 42. The output signals of those photodetectors 41 and 42 are supplied to the plus and minus input terminals of a differential amplifier 5. Here, a variable resistor VR is adjusted in a normal state and set so that the difference signal between the output signals of the photodetectors 41 and 42 is 0. Then if the outputs of the photodetectors in a temperature test tank and on a room temperature environment side change owing to the temperature variation in the temperature test tank, the output of the differential amplifier 5 varies, so this variation is added to the output signal of the photodetector for receiving the light of the light source element to be tested such as a laser, and consequently the temperature characteristics of the photodetector are corrected and only the temperature characteristics of the light source element to be tested are measurable.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a temperature characteristic correction device for a light receiving element used when measuring and evaluating the temperature characteristics of a laser diode, a light emitting diode, etc. It is related to.

(Prior Art) Conventionally, there has been no provision of a device capable of easily and accurately correcting temperature characteristics of this type.

(Problems to be Solved by the Invention) According to the present invention, the light source element, such as a laser diode or a light emitting diode whose temperature characteristics are to be measured and evaluated (hereinafter referred to as the light source element to be tested), is placed in a temperature test tank. The present invention provides a temperature characteristic correction device for a light receiving element that can accurately measure the temperature characteristics of a light source element under test by correcting the temperature characteristics of the light receiving element itself for receiving light from the element.

(Means for Solving the Problems) In order to achieve the above object, the present invention communicates the boundary between the inside of the temperature test chamber and the room temperature environment side with a glass rod-shaped light guide. A light receiving element is provided at the end,
A light receiving element and a light source element having the same temperature characteristics as the light receiving element are provided at the end of the light guide on the room temperature environment side through a beam splitter, and the light from the light source element is received by the two light receiving elements, and the temperature of both environments is adjusted. Differences in output signals due to changes are detected and used to correct the temperature characteristics of the light receiving element for use in measuring the temperature characteristics of the light source element under test.

(Function) With the above configuration, the present invention provides a differential amplifier that detects the difference between the two signals when a change in the output of each of the light receiving elements inside the chamber and on the room temperature environment side occurs due to a temperature change in the temperature test chamber. Since a change occurs in the output of the light source element under test, if this change is added to the output signal of the light receiving element for receiving light from the light source element under test, such as a laser, the temperature characteristics of this light receiving element will be corrected, and the light source element under test will change. Only the temperature characteristics of can be measured and evaluated.

(Example) A first example of the temperature characteristic correction device for a light receiving element of the present invention will be described below.
This will be explained using figures. FIG. 1 is a block diagram of one embodiment of the present invention. In the figure, 1 is a glass rod-shaped case,
(hereinafter abbreviated as light guide).

2 is a beam splitter, 3□ is a light source element consisting of a laser diode or light emitting diode (hereinafter referred to as a light source element), 41 and 4□ are light receiving elements with the same temperature characteristics, the boat is a differential amplifier, and Ro and R2 are resistors. , VR is a variable resistor,
vo represents the difference signal between the output signals of the light receiving elements 4□ and 42.

A beam splitter 2 is provided at one end of the light guide 1, a light source cable 3□ is provided on one side of the beam splitter 2, and a light receiving element 4□ is provided on the other side. Furthermore, a light receiving element 4□ is placed at the opposite end of the light guide 1 from the beam splitter 2.
A light-receiving element 4□ having the same temperature characteristics as that of the light-receiving element 4□ is provided, and a differential amplifier 5 is provided for determining the difference between the output signals of the light-receiving elements 4□ and 4□.

Next, the operation of the above embodiment will be explained. Light source element 3
The light beam emitted from the light receiving element 1 is split into transmitted light and reflected light by the beam splitter 2, and one of the light beams (here, the transmitted light) reaches the light receiving element 4□. The other light beam (reflected light) is repeatedly reflected within the light guide 1 and reaches the light receiving element 4□. The output signals of the two light receiving elements 4 and 4□ caused by the irradiation of light are connected to the input terminals ◯ and □ of the differential amplifier 5. By adjusting the variable resistor VR in the normal state (state 71 in which no temperature test is performed), the difference signal between the output signals of the two light receiving elements 4□ and 4□ is set to 0.

(The need for adjustment using the variable resistor VR is such that the ratio of transmitted light and reflected light by the beam splitter 2 is not necessarily 1:1.
This is because it is not necessarily the case. ,) Next, referring to FIG. 2, a description will be given of an apparatus according to an embodiment of the present invention shown in FIG. 1, which is used for a temperature characteristic evaluation test of a light source element under test consisting of a laser diode or a light emitting diode.

FIG. 2 is a configuration diagram of the apparatus for the temperature characteristic evaluation test.

In the same figure, the numbers attached to the temperature characteristic correction device of the light-receiving element according to an embodiment of the present invention.

The symbols and their names are the same as in Figure 1. 3□ is a light source element to be tested consisting of a laser diode or a light emitting diode; 4. is a light receiving element that receives the light from the light source element to be tested 3□, 6 is a temperature test tank, R1, R4 and R
5 represents a resistor, vo and 2 represent output signals.

In the apparatus according to the embodiment of the present invention shown in FIG. 1, one light receiving element 4□ is placed inside a temperature test chamber 6 through a light guide 1, and one light receiving element 4□ and the light source element 31 are placed in a room temperature environment. put. Furthermore, a light source element to be tested 3□ consisting of a laser diode or a light emitting diode, and a light receiving element 4 that receives the light. are placed in a pair inside the temperature test tank 6. If the temperature inside the temperature test tank 6 is changed in this state, the amount of light emitted by the light source element 3□ under test will change, and at the same time, the light receiving element 4 will change.
．． And 4□ itself also causes a change in sensitivity (corresponding to output). Therefore, the light receiving element 4. The output signal V is the output signal difference V between the light receiving elements 41 and 4□. If you add , the signal ■
. is a correction of the temperature difference output of the light receiving elements 41 and 4□, so the signal V2 of V + V, = V2 is the correction of the temperature difference output of the light receiving elements 4. becomes the output signal. Therefore, the signal v
By measuring 2, it is possible to accurately measure the change in the amount of light emitted by the light source element 3□ under test. Here, the increase or decrease of the signal is adjusted by selecting and setting the resistance values of each of the resistors □ to R5 and the variable resistor VR shown in FIGS. 1 and 2.

Signal amplification is expressed by the following equation using the respective resistance values (represented by the same symbols) of each resistor.

FIG. 3 is a diagram showing an example of the relationship between the relative output of the light receiving elements (4□, 4□, 4.) with respect to the ambient temperature. Since both voltage (V) and current (I) have such temperature characteristics, by using the apparatus shown in FIG. temperature characteristics can be corrected accurately.

(Effects of the Invention) According to the present invention, when performing a temperature characteristic evaluation test of a light source element such as a laser diode or a light emitting diode, it is possible to accurately correct the temperature characteristic of a light receiving element used therein.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a temperature characteristic correction device for a light-receiving element in an embodiment of the present invention, Figure 2 is a configuration diagram of an apparatus for temperature characteristic evaluation testing of a light source element, and Figure 3 is a diagram showing how the ambient temperature of the light-receiving element is adjusted. FIG. 3 is a diagram showing a relationship between relative outputs. 1...Light guide, 2...Beam splitter, 3...Light source element such as a laser diode (31, 3□
same), 4... light receiving element (41, 4□, 4.
), 5...Differential amplifier, 6...Temperature test tank. Patent applicant Matsushita Electric Industrial Co., Ltd. Fig. 1 ρ2 Fig. 2 6, -; fmJt c double tank

Claims (1)

[Claims] In a temperature characteristic correction device for a light receiving element that receives light from a light source element under test whose temperature characteristics are to be measured and evaluated, a light receiving element is provided at one end of a glass rod-shaped light guide, and a beam splitter is provided at the other end of the light guide. A light receiving element having the same temperature characteristics as the light receiving element is provided on one side, and a light source element is provided on the other side, and the luminous flux of this light source element is distributed to each of the two light receiving elements by reflection and transmission by the beam splitter. A temperature characteristic correction device for a light receiving element, characterized in that the difference between the signals of the two light receiving elements is determined by a differential amplifier, and the difference is used to correct the temperature characteristics of the light receiving element that receives light from the light source element under test. .