TSL235R inconsistent output

Other Hardware General Electronics
6

Condensed my code to the following however the issue still remains:

unsigned long period = 100000;
float area = 0.0092; // Sensing area of TSL25R device, in cm2

volatile unsigned long pulses = 0;
unsigned long lastPulseCount = 0;
unsigned long lastPulseOutputTime = 0;

void irq1()
{
  pulses++;
}

///////////////////////////////////////////////////////////////////
//
// SETUP
//
void setup() 
{
  Serial.begin(115200);
  Serial.println("START");
  pinMode(2, INPUT);
  digitalWrite(2, HIGH);
  attachInterrupt(0, irq1, RISING);
}

///////////////////////////////////////////////////////////////////
//
// MAIN LOOP
//
void loop()
{
  unsigned long elapsedTimeSincePulseCheck = micros() - lastPulseOutputTime;

  if (elapsedTimeSincePulseCheck >= period)
  {
    lastPulseOutputTime = micros();
    
    noInterrupts();
    unsigned long pulsesCopy = pulses;
    interrupts();
    
    unsigned long frequency = (pulsesCopy- lastPulseCount) * (1000000 / elapsedTimeSincePulseCheck);
    long irradiance = frequency / area;  // Calculate Irradiance (uW/cm2)
    
    Serial.println(frequency);
  
    lastPulseCount = pulsesCopy;
  }
}